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 Colour CCTV camera, 8mm lens, 1.2ghz wireless receiver Fully
12vdc200m a 582X628 Res 380 lines cased audio and video 1.2ghz
Automatic aperture lens Mirror function wirelessreceiver190x140x30mm,
PAL Back Light Comp MLR, metal case, 4 channel, 12vdc
100x40x40mm ref EE2 £75.90 Adjustable time delay, 4s, 8s, 12s,
16s. £49.50 Ref EE20
Built in Audio .15lux CCD camera 12vdc
200ma 480 lines s/n ratio >48 db 1v P-P The smallest PMR446 radios currently available
output 110x60x50mm ref EE1 £108.90 (54x87x37mm). These tiny handheld PMR radios look
great, user friendly & packed with features including VOX,
Scan & Dual Watch. Priced at £59.99 PER PAIR they are
Metal CCTV camera housings for internal or excellent value for money. Our new favourite PMR radios!
external use. Made from aluminium and Standby: - 35 hours Includes:- 2 x Radios, 2x Belt Clips &
plastic they are suitable for mounting body 2 x Carry Strap £59.95 Ref ALAN1 Or supplied with 2 sets
cameras in.Available in two sizes 1- of rechargeable batteries and two mains chargers £93.49
100x70x170mm and 2- 100x70x280mm Ref Ref Alan2
EE6 £22 EE7 £26 Multi position brackets Ref The TENS mini Microprocessors offer six
EE8 £8.80 types of automatic programme for shoulder Ultra-compact, lightweight, easy to use and comfortable to hold,
pain, back/neck pain, aching joints, the new NVMT is unique for a night scope in offering a tactile,
Rheumatic pain, migraines headaches, suregrip plastic bodyshell and, for extra protection/grip, partialrubber
sports injuries, period pain. In fact all over armouring. Currently the top of the range model, the NVMT G2+
body treatment. Will not interfere with features a 'commercial' grade* Gen 2+ Image Intensifier Tube (IIT).
existing medication. Not suitable for anyone The NVMT has a built-in, powerful Infrared (IR) Illuminator for use
with a heart pacemaker. Batteries supplied. in very low light/total darkness. Power for the scope and IR is
£21.95Ref TEN327 Spare pack of provided by 1 x 3V Lithium CR123A battery (not supplied). A green
electrodes £6.59 Ref TEN327X LED next to the viewfinder indicates when the Image Intensifier
Self cocking pistol plcr002
Dummy CCTV cameras These motorised Tube is switched on while a red LED indicates when the IR
Excellent quality multi purposeTV/ crossbow with metal body.· cameras will work either on 2 AA batteries or Illuminator is switched on.Type Gen Weight Size Lens Mag 2x,
TFT screen, works as just a LCD Selfcocking for precise string with a standard DC adapter (not supplied) Weight 400g, 125x82x35mm angle of view 30 deg, built in infra red,
colour monitor with any of our CCTV alignment Aluminium alloy They have a built in movement detector that rang 3 - 400m, supplied with batteries £849 ref COB24023.
cameras or as a conventional TV construction High tec fibre will activate the camera if movement is
ideal for use in boats and caravans glass limbs Automatic safety 55 - 200 WATT INFRA RED TORCHS
detected causing the camera to ‘pan’ Good Search guard 1 infrared torch Plastic
49.75mhz-91.75mhz VHF channels catch Supplied with three deterrent. Camera measures 20cm high,
1-5, 168.25mhz-222.75mhz VHF bolts Track style for greater bodied waterproof infrared
supplied with fixing screws. Camera also has rechargeable lamp. 100mm diameter
channels 6-12, 471.25mhz- accuracy Adjustable rear a flashing red led. £10.95 Ref CAMERAB
869.75mhz, Cable channels sight 50lb draw weight 150ft lens, 200mm body length. 55 watt
INFRA RED FILM 6" square piece of flexible bulb, 1,000,000 candle power (used
112.325mhz-166.75mhz Z1-Z7, sec velocity Break action 17"
infra red film that will only allow IR light through. as an indication of relative power)
Cable channels 224.25mhz- string 30m range £23.84 Ref
Perfect for converting ordinary torches, lights, Supplied complete with a 12v car
446.75mhz Z8-Z35 5" colour PLCR002
headlights etc to infrared output using standard lighter socket lead/charger and a 240v
screen,Audio output
light bulbs Easily cut to shape. 6" square mains plug in charger. £49 REF
150mW,Connections, external
£16.50 ref IRF2 or a 12" sq for £34.07 IRF2A sguard 1. Also available, 70watt @
aerial, earphone jack, audio/video
input,12vdc or mains, Accessories THE TIDE CLOCK These clocks indicate £59, 100 watt @£79, 200watt @ £99.
supplied Power supply Remote the state of the tide,Most areas in the world AIR RIFLES FROM £24.70
control Cigar lead power supply have two high tides and two low tides a day,
Headphone Stand/bracket. 5" Fully cased IR light source so the tide clock has been specially designed
model £139 Ref EE9, to rotate twice each lunar day (every 12 hours
suitable for CCTV applications.
and 25 minutes) giving you a quick and easy
The unit measures
indication of high and low water. The Quartz
10x10x150mm, is mains
tide clock will always stay calibrated to the
operated and contains 54 infra
moon. £23.10 REF TIDEC B2 AIR RIFLE AvaIlable In.177 and .22• 19" Tapered Rifled Barrel•
red LEDs. Designed to mount
LINEAR ACCTUATORS 12-36VDC BUILT IN Adjustable Rear Sight• Full Length Wooden Stock• Overall Length
on a standard CCTV camera
ADJUSTABLE LIMIT SWITCHES POWDER 43" approxBarrel Locking Lever • Also available in CARBINE
bracket. The unit also contains
COATED 18" THROW UP TO 1,000 LB THRUST Grooved for Telescopic Sight model with 14" barrel - no front sight
a daylight sensor that will only
(400LB RECOMMENDED LOAD) SUPPLIED WITH for use with scope. Weight approximately 6lbs Extremely Powerful
activate the infra red lamp when
Colour CCTV Camera measures MOUNTING BRACKETS DESIGNED FOR .22 £28.90, .177 £24.70, pellets (500) £2.55, sights 4x20 £6.80,
the light level drops below a
60x45mm and has a built in light OUTDOOR USE These brackets originally made for 4x28 £15.32 Other models available up to £250 www.airpistol.co.uk
preset level. The infrared lamp
level detector and 12 IR leds .2 lux moving very large satellite dishes are possibly more
is suitable for indoor or exterior 12V SOLAR PANELS AND
12 IR leds 12vdc Bracket Easy suitable for closing gates, mechanical machinery,
use, typical useage would be to REGULATORS
connect leads £75.90 Ref EE15 robot wars etc. Our first sale was to a company
provide additional IR 9 WATT £58.75
building solar panels that track the sun! Two sizes
illumination for CCTV cameras. 15 WATT £84.25
available, 12" and 18" throw. £32.95 REF ACT12,
£53.90 ref EE11 22 WATT £126.70
Regulator up to 60 watt £21.25
Samarium magnets are 57mm x 20mm and Regulators up to 135 watt £38.25
have a hole (5/16th UNF) in the centre and a The combination of multi-crystal cells and a high-reliability module
magnetic strength of 2.2 gauss. We have tested structure make this series of solar panels the ideal solar module.
these on a steel beam running through the For large-scale power generation hundreds or even thousands of
A high quality external colour CCTV
offices and found that they will take more than modules can be connected in series to meet the desired electric
camera with built in Infra red LEDs 3km Long range video 170lbs (77kgs) in weight before being pulled off. power requirements. They have a high output, and highly efficient,
measuring 60x60x60mm Easy and audio link complete with With keeper. £21.95 REF MAG77 extremely reliable and designed for ease of maintenance. Separate
connect leads colour Waterproof
transmitter, receiver, 12.5m New transmitter, receiver and camera positive negative junction boxes and dual by-pass diodes are a few
PAL 1/4" CCD542x588 pixels 420
cables with pre fitted kit. £69.00 examples of some of its outstanding features. Supplied with an 8
lines .05 lux 3.6mm F2 78 deg lens
connectors and aerials. Kit contains four channel switchable metre cable. Perfect for caravans, boats, etc. Toughened glass.
12vdc 400ma Built in light level
Acheive up to 3km. Cameras camera with built in audio, six IR leds
sensor. £108.90 Ref EE13
and transmitter, four channel switchable
not included Ideal for stables,
receiver, 2 power supplies, cables,
remote buildings etc. Mains
connectors and mounting bracket.
power required £299 £69.00 Wireless Transmitter Black and
white camera (75x50x55mm) Builtin 4
channel transmitter (switchable) Audio built in 6 IR Leds Bracket/ LOCK PICK SETS 16, 32 AND 60 PIECE SETS
stand Power supply 30 m range Wireless Receiver 4 channel This set is deluxe in every way! It includes a nice assortment of
(switchable) Audio/video leads and scart adapter Power supply balls, rakes, hooks, diamonds, two double ended picks, a broken
and Manual £69.00 ref COP24 key extractor, and three tension wrenches. And just how do you top
A small colour CCTV camera off a set like this? Package it in a top grain leather zippered case.
just 35x28x30mm Supplied with This miniature Stirling Cycle Engine
Part: LP005 - Price £45.00
bracket, easy connect leads. measures 7" x 4-1/4" and comes complete
This 32 piece set includes a variety of hooks, rakes, diamonds,
Built in audio. Colour 380 line Complete wireless CCTV sytem with built-in alcohol burner. Red flywheels
balls, extractors, tension tools ... and comes housed in a zippered
res, PAL 0.2 lux +18db sensitivity with video. Kit comprises and chassis mounted on a green base, these
top grain leather case. If you like choices, go for this one!
Effective pixels 628x582 6-12vdc pinhole colour camera with all-metal beauties silently running at speeds
Part: LP006 - Price £65.00
Power 200mw £39.60 Ref EE16 simple battery connection and in excess of 1,000 RPM attract attention and
If your wants run toward the biggest pick set you can find, here it is.
a receiver with video output. 380 create awe wherever displayed. This model
This sixty piece set includes an array of hooks, rakes, diamonds,
lines colour 2.4ghz 3 lux 6-12vdc comes completely assembled and ready to
balls, broken key extractors, tension wrenches, and even includes
manual tuning Available in two run. £106.70 REF SOL1
a warded pick set! And the zippered case is made, of course, of the
versions, pinhole and High-power modules using 125mm square multi -
finest top grain leather. First Class!
standard.£79 (pinhole) Ref crystal silicon solar cells with bypass diode Anti
Part: LP007 - Price £99.00
Peltier module. Each module is EE17, £86.90 (standard) Ref reflection coating and BSF structure to improve
Mamod steam roller, supplied with fuel and
supplied with a comprehensive EE18 cell conversion efficiency: 14%. Using white
everything you need (apart from water and a
18 page Peltier design manual tempered glass, EVA resin, and a weatherproof
film along with an aluminum frame for extended match!) £85 REF 1312 more models at
featuring circuit designs, design www.mamodspares.co.uk
information etc etc. The Peltier outdoor use. system Lead wire with waterproof
manual is also available connector. 80 watt 12v 500x1200 £315.17, 123w Mamod steam roller, supplied with
separately Maximum watts 56.2 12vdc 1499x662x46 £482.90
fuel and everything you need (apart
40x40mm Imax 5.5A Vmax 165 w 24v 1575x826x46mm £652.30
from water and a match!) £130
16.7 Tmax (c- dry N2) 72 £32.95
(inc manual) REF PELT1, just BULL GROUP LTD REF 1318 more models at
www.mamodspares.co.uk
manual £4.40 ref PELT2 UNIT D HENFIELD BUSINESS PARK PEANUT RIDER STIRLING ENGINE This
GASTON SEALED LEAD HENFIELD SUSSEX BN5 9SL all metal, black and brass engine with red
ACID BATTERIES TERMS: CASH, PO, CHEQUE PRICES+VAT flywheel is mounted on a solid hardwood
1.3AH 12V @ £5.50 GT1213 platform. comes complete with an alcohol
3.4AH 12V @ £8.80 GT1234 WITH ORDER PLUS £5.50 P&P (UK) PLUS VAT.
fuel cell, extra wick, allen wrenches, and
7AH 12V @ £8.80 GT127 24 HOUR SERVICE £7.50 (UK) PLUS VAT. Owner’s Manual.Specifications: Base is
17AH 12V @ £19.80 GT1217 OVERSEAS ORDERS AT COST PLUS £3.50 5-1/4" x 5-1/4", 4" width x 9" height, 3/4"
COMPAQ 1000mA 12vdc power All new and boxed, bargain Tel: 0870 7707520 Fax 01273491813 stroke, 3-1/2" flywheel £141.90
supplies, new and boxed. 2 metre
lead DC power plug 2.4mmx10mm
prices. Good quality sealed lead
acid batteries Sales@bullnet.co.uk SHOP ONLINE
£5.25 each, 25+ £3.50 100+£2.50
FAX 01273 323077
www.bullnet.co.uk WWW.BULLNET.CO.UK
 ISSN 0262 3617
PROJECTS . . . THEORY . . . NEWS . . .
COMMENTS . . . POPULAR FEATURES . . .

VOL. 34. No. 8 AUGUST 2005

Cover illustration: Mehau Kulyk/Science Photo Library
www.epemag.co.uk
EPE Online: www.epemag.com

Projects and Circuits

AUDIO SYSTEM – COMMUNICATIONS by Raymond Haigh 532
A preamp with a.g.c. and a power amp with switched filtering for
communications and surveillance
MOTOR AMPLIFIER by Ken Ginn 549
The power with which this unit can drive a heavy-duty motor is astonishing!
PAIN MONITOR by John Becker 561
A patient welfare logger that also has other event logging applications
as in sailing, golfing or wildlife watching, for example
INGENUITY UNLIMITED – Sharing your ideas with others 570
Helix Thermostat; Meter Identifier; The Terminator
BACK TO BASICS – 5 Kitchen Timer and Room Thermometer 576
by Bart Trepak
Simple, easy-to-build circuits based on one or two CMOS logic chips

Series and Features

TECHNO TALK by Mark Nelson 540
How buses communicate with bus-shelter time-to-wait displays
PIC N’ MIX by John Becker 545
How to get the DS1307 RTC chip working with PICs
INTERFACE by Robert Penfold 558
Using a PC-controlled DAC as an ADC
NET WORK – THE INTERNET PAGE surfed by Alan Winstanley 568
The delight of upgrading to ADSL!
CIRCUIT SURGERY by Alan Winstanley and Ian Bell 581
More code examples for using CompactFlash cards with PICs

Regulars and Services

BACK ISSUE CD-ROMS single-source shopping for issues you’ve missed 526
BACK ISSUES Did you miss these? 527
EDITORIAL 531
NEWS – Barry Fox highlights technology’s leading edge 542
Plus everyday news from the world of electronics
PIC PROJECTS VOL 1 CD-ROM 548
A pletora of 20 “hand-PICked” EPE past projects
READOUT John Becker addresses general points arising 555
CD-ROMS FOR ELECTRONICS 573
A wide range of CD-ROMs for hobbyists, students and engineers
SHOPTALK with David Barrington 583
The essential guide to component buying for EPE projects
PLEASE TAKE NOTE 583
Crossword Solver; Cybervox; Toolkit TK3 update V3.05
DIRECT BOOK SERVICE 584
A wide range of technical books available by mail order, plus more CD-ROMs
PIC RESOURCES CD-ROM 588
Invaluable to all PICkers
PRINTED CIRCUIT BOARD AND SOFTWARE SERVICE 589
PCBs for EPE projects. Plus EPE project software
© Wimborne Publishing Ltd 2005. Copyright in all
drawings, photographs and articles published in ELECTRONICS MANUALS 590
EVERYDAY PRACTICAL ELECTRONICS is fully CD-ROM reference works for hobbyists, students and service engineers
protected, and reproduction or imitations in whole or
in part are expressly forbidden. ADVERTISERS INDEX 592
Our September 2005 issue will be published on Thursday,
11 August 2005. See page 523 for details Readers Services • Editorial and Advertisement Departments 531

Everyday Practical Electronics, August 2005 521

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HP 182T with 8557A 10kHz-350MHz . . . . . . . . . . . .£300-£400 HP 8165A Programmable Signal Source HP 5316A Universal Counter 0-100MHz HPIB . . . . . . . . . . . . .£95
OSCILLOSCOPES HP 140T with 8555A 10MHz-18GHz . . . . . . . . . . . . . . . . .£500 1MHz-50MHz (Pulse/ Function) . . . . . . . . . . . . . . . . . . .£325 THANDAR TF810 Frequency Counter 5Hz-200MHz Battery . .£60
ADVANTEST TR4131 10kHz-3.5GHz . . . . . . . . . . . . . . . . .£950 HP 3325A Synthesised Function Gen 21MHz . . . . . . . . .£350 THANDAR TF200 Frequency Meter 10Hz-200MHz 8 digit . . . .£40
TEKTRONIX 2247A 4 Channel 100MHz WAYNE KERR SSA1000A 150kHz-1GHz . . . . . . . . . . . . .£950 HP 3312A Function Gen 0.1Hz-13MHz AM/FM BLACK STAR Meteor 100 Counter 5Hz-100MHz . . . . . . . . . .£50
Counter/Timer/ Voltmeter . . . . . . . . . . . . . . . . . . . . . . . .£275 MARCONI 2382 200Hz-400MHz High Resolution . . . . . .£1250 Sleep/Tri/Burst etc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .£200 BLACK STAR 1325 Counter Timer 1300MHz . . . . . . . . . . . . .£150
TEKTRONIX 2335 Dual Trace 100MHz Delay Sweep . . .£125 MARCONI 2370 30Hz-110MHz . . . . . . . . . . . . . . . . . . . . .£500 WAVETEK 21 Stabilised Function Gen 11MHz . . . . . . . .£225 BECKMAN UC10A Universal Counter 120MHz . . . . . . . . . . . .£60
TEKTRONIX 485 Dual Trace 350MHz Delay Sweep . . . .£300 HP 8754A Network Analyser 4-1300MHz . . . . . . . . . . . . . .£500 WAVETEK 23 Synthesised Function Gen 12MHz . . . . . .£275 LEADER LDC9043 Digital Counter 100MHz . . . . . . . . . . . . .£125
IWATSU SS5711 4 Channel 100MHz Delay Sweep . . . .£150 MARCONI 6500A Amplitude Analyser with head . . . . . . . .£750 EXACT 529 AM/FM Function Gen 20MHz . . . . . . . . . . .£150
PHILIPS 3065 2+1 Channel 100MHz Dual TB/Delay – Autoset £200 HP 334A DIstortion Analyser 5Hz-600kHz . . . . . . . . . . . . .£100 ANALOGUE 2030 Synthesised Multi Function Waveform £250
PHILIPS 3055 2+1 Channel 60MHz Dual TB/Delay – Autoset £150 THANDER TG503 Pulse/Function Gen 5MHz . . . . . . . . .£195 DIGITAL MULTIMETERS ETC
PHILIPS PM3217 Dual Trace 50MHz Delay Sweep . . . .£125 THANDER TG502 Sweep/Function Gen 5MHz . . . . . . . .£195
KIKUSUI COS6100 5 Trace 100MHz Delay . . . . . . . . . .£150 SIGNAL GENERATORS KRON-HITE 5200A Sweep Func Gen 0.00003Hz-3MHz £150 SOLARTRON 7150 6½ digit True RMS IEEE . . . . . . . . . . . . . £75
TEKTRONIX 475A Dual Trace 250MHz Delay Sweep . . .£175 HP 3310B Info as 3310A + etc. . . . . . . . . . . . . . . . . . . .£120 SOLARTRON 7150Plus As Above + Temp Measurement. . . £100
TEKTRONIX 475 Dual Trace 200MHz Delay Sweep . . . .£150 HP 8350B Sweeper with 83592B 10MHz-20GHz . . . . . . .£1500 HP 3310A Func Gen 0.005Hz-5MHz Sine/Sq/Tri/Ramp/Pulse .£80 DATRON 1065 5½ digit Autocal AC/DC Resistance IEEE . . . . £95
TEKTRONIX 465B Dual Trace 100MHz Delay Sweep . . .£125 HP 8350A Sweeper with 83592A 10MHz-20GHz . . . . . . .£1250 PHILIPS PM5132 Function Gen 0.1Hz-2MHz . . . . . . . . . . . . . .£95 FLUKE 77 3½ digit Handheld. . . . . . . . . . . . . . . . . . . . . . . . . £35
TEKTRONIX 465 Dual Trace 100MHz Delay Sweep . . . . .£95 HP 8350B Main Frame Only . . . . . . . . . . . . . . . . . . . . . . . .£125 PHILIPS PM5131 Function Gen 0.1Hz-2MHz . . . . . . . . . . . . . .£75 FLUKE 77 Series 2 3½ digit Handheld. . . . . . . . . . . . . . . . . . £45
PHILIPS PM3209 Dual Trace 40MHz Delay . . . . . . . . . .£125 HP 83525B RF Plug-in for 8350 0.01-8.4GHz . . . . . . . . . . .£500 FEEDBACK FG601 Func Gen 0.001Hz-1MHz . . . . . . . . . . . . .£60 FLUKE 8060A 4½ digit True RMS Handheld . . . . . . . . . . . . . £75
PHILIPS PM3215 Dual Trace 50MHz . . . . . . . . . . . . . . . .£75 HP 83590A RF Plug-in for 8350 2-20GHz . . . . . . . . . . . . . .£800 HP 8112A Pulse Gen 50MHz . . . . . . . . . . . . . . . . . . . . . . . . .£750 BECKMAN HD110 3½ digit Handheld in Carry Case . . . . . . . £30
KENWOOD CS4035 Dual Trace 40MHz . . . . . . . . . . . . . .£50 HP 8660C Sig Gen 1.3GHz . . . . . . . . . . . . . . . . . . . . . . . .£450 HP 8111A Pulse Generator 20MHz . . . . . . . . . . . . . . . . . . . . .£400 TTI 1905A 5½ digit Bench . . . . . . . . . . . . . . . . . . . . . . . . . . . £60
PANASONIC VP5564A Dual Trace 40MHz . . . . . . . . . . . .£50 HP 8660C Sig Gen 2.6GHz . . . . . . . . . . . . . . . . . . . . . . . .£750 LYONS PG73N Pulse Gen 20MHz . . . . . . . . . . . . . . . . . . . . . .£50 SOLARTRON 7045 4½ digit Bench . . . . . . . . . . . . . . . . . . . . £30
HITACHI V525 Dual Trace 50MHz Cusors . . . . . . . . . . . . .£95 HP 86603A RF Plug-in for 8660C 1-2600MHz . . . . . . . . . .£....... LEADER LAG120B Sine/Sq Audio Generator 10Hz-1MHz . . .£60 AVO DA116 3½ digit with Batteries & Leads. . . . . . . . . . . . . . £20
HITACHI V523 Dual Trace 50MHz Delay . . . . . . . . . . . . . .£80 HP86631B Axillary Section for 8660C . . . . . . . . . . . . . . . .£....... FARNELL LFM4 Sine/Sq Osc. 10Hz-1MHz Low Distortion, AVO 8 Mk6 in Ever Ready Case with Leads etc . . . . . . . . . . . £75
HITACHI V425 Dual Trace 40MHz Cursors . . . . . . . . . . . .£75 HP86632B Modulation Section for 8660C . . . . . . . . . . . . .£....... TTL Output, Amplitutde Meter . . . . . . . . . . . . . . . . . . . . . . . . . .£60 AVO 8 Mk5 with Leads etc . . . . . . . . . . . . . . . . . . . . . . . . . . . £50
HITACHI V422 Dual Trace 40MHz . . . . . . . . . . . . . . . . . .£60 MARCONI 2017 0.01-124MHz Low Phase Noise . . . . . . . .£500 GOULD J3B Sine/Sq Osc 10Hz-100kHz Low Distortion . .£50-£75 RACAL 9301A True RMS RF Millivoltmeter . . . . . . . . . . . . . £125
HITACHI V223 Dual Trace 20MHz Delay . . . . . . . . . . . . . .£60 MARCONI 2019 Synthesised AM/FM 80kHz-1040MHz . . .£325 FARNELL LF1 Sine/Sq Oscillator 10Hz-1MHz . . . . . . . . . . . . .£50 RACAL 9300 True RMS Millivoltmeter 5Hz-20MHz
HITACHI V222 Dual Trace 20MHz . . . . . . . . . . . . . . . . . .£50 FLUKE 6060B AM/FM Syn Sig Gen 10kHz-1050MMHz . . .£300 MARCONI SANDERS 6055C Signal Source 850-2000MHz .£125 usable to 60MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . £30
HITACHI V212 Dual Trace 20MHz . . . . . . . . . . . . . . . . . .£50 LEADER LSG221B Sig Gen 25-950MHz . . . . . . . . . . . . . .£200 MARCONI SANDERS 6055B Signal Source 850-2150MHz .£125 RACAL 9300B as 9300 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . £45
FARNELL DTV12-14 Dual Trace 12MHz . . . . . . . . . . . . .£40 HP 8656B Synthesised 0.1-990MHz . . . . . . . . . . . . . . . . . .£500 MARCONI SANDERS 6056B Signal Source 2-4GHz . . . . . .£125 GOODWILL GVT427 Dual Chan AC Millivoltmeter 10mV in
HP 8656A Synthesised 0.1-990MHz . . . . . . . . . . . . . . . . . .£400 MARCONI SANDERS 6057B Signal Source 4.5-8.5GHz . . .£125 12 ranges 10Hz-1MHz Unused. . . . . . . . . . . . . . . . . . . . . . . . £75
STORAGE HP 8640A AM/FM 500kHz-512MHz . . . . . . . . . . . . . . . . . .£150 MARCONI SANDERS 6059A Signal Source 12-18GHz . . . .£125 KENWOOD VT176 Dual Chan Millivoltmeter. . . . . . . . . . . . . . £40
PHILIPS PM3320 Dual Trace 200MHz 250Ms/S . . . . . . .£300 HP 8620C Sweep Osc with 86290B 2-18.6GHz . . . . . . . . .£500 MARCONI SANDERS 6070A Signal Source 400-1200MHz .£125
LECROY 9400 Dual Trace 125MHz . . . . . . . . . . . . . . . .£325 HP8620C Sweep Osc with 86222B 0.01-2.4GHz . . . . . . . .£400 FLUKE 6011A Synthesised 11MHz . . . . . . . . . . . . . . . . . . . .£125
TEKTRONIX 468 Dual Trace 100MHz Delay Sweep Digital HP8620C/B/A with any of the following plug-ins . . . . .£150-£200 PHILIPS 5514V Colour Bar Generator Video . . . . . . . . . . . . .£195 POWER SUPPLIES
Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .£200 HP 86220A Plug in 10-1300MHz BLACK STAR ORION Colour Bar Gen . . . . . . . . . . . . . . . . . . .£50
VELLEMAN HPS5 1MHz 5MHz Sampling. Handheld Unused £60 HP 86230B Plug in 1.5-4GHz BLACK STAR ORION Later Version Metal Case . . . . . . . . . . .£75 FARNELL XA35.2T 0-35V 0-2A Twice Digital . . . . . . . . . . . . . £95
HP 86235A Plug in 1.7-4.3GHz FARNELL LT30-2 0-30V 0-2A Twice. . . . . . . . . . . . . . . . . . . £110
HP 86240A Plug in 2-8.5GHz FARNELL B30/20 30V 20A Variable No Meters . . . . . . . . . . £110
ANALYSERS HP 86240C Plug in 3-6-8.6GHz FREQUENCY COUNTERS/TIMERS FARNELL B30/10 30V 10A Variable No Meters . . . . . . . . . . . £55
HP 86245A Plug in 5.9-12.4GHz FARNELL LT30-1 0-30V 0-1A Twice. . . . . . . . . . . . . . . . . . . . £75
ADVANTEST R3265A 100Hz-8GHz . . . . . . . . . . . . . . . . .£4500 HP86250B Plug in 8-12.4GHz EIP 371 Source Locking Microwave Counter 10Hz-18GHz . . .£325 FARNELL L30.2 0-30V 0-2A . . . . . . . . . . . . . . . . . . . . . . . . . £55
TEKTRONIX 492P 50kHz-21GHz . . . . . . . . . . . . . . . . . . .£2250 HP 86250D Plug in 8-12.4GHz EIP 331 Autohet Microwave Counter 825MHz-18GHz . . . . . .£195 FARNELL L30.1 0-30V 0-1A . . . . . . . . . . . . . . . . . . . . . . . . . £40
HP8560A 50Hz-2.9GHz Built In Tracking Gen . . . . . . . . . .£3250 HP 86260A Plug in 12.4-18GHz HP 5386A Counter 10Hz-3GHz . . . . . . . . . . . . . . . . . . . . . . . .£350 FARNELL E350 0-350V 0-200mA . . . . . . . . . . . . . . . . . . . . £125
HP 8560A 50Hz-2.9GHz . . . . . . . . . . . . . . . . . . . . . . . . . .£2950 MARCONI TF2015 AM/FM 10-520MHz . . . . . . . . . . . . . . . .£95 FEEDBACK SC230 Counter 1.3GHz . . . . . . . . . . . . . . . . . . . .£75 FARNELL D30-2T 0-30V 0-2A Twice Digital . . . . . . . . . . . . . . £95
HP 8569A 10MHz-22GHz . . . . . . . . . . . . . . . . . . . . . . . . . .£950 MARCONI TF2016 AM/FM 10kHz-120MHz . . . . . . . . . . . . .£95 RACAL 9916 Counter 10Hz-520MHz . . . . . . . . . . . . . . . . . . . .£75 THURLBY PL330 0-32V 0-3A Digital (Kenwood badged) . . . . £75
HP 8565A 10MHz-22GHz . . . . . . . . . . . . . . . . . . . . . . . . . .£750 PHILIPS PM5328 100kHz-180MHz with RACAL 9906 Universal Counter 200MHz . . . . . . . . . . . . . . . . .£95 THURLBY TS3021S 0-30V 0-2A LCD . . . . . . . . . . . . . . . . . . £65
HP 853A with 8559A 100kHz-21GHz . . . . . . . . . . . . . . .£1100 200MHz Freq Counter IEEE . . . . . . . . . . . . . . . . . . . . . .£225 RACAL 9904 Counter Timer 50MHz . . . . . . . . . . . . . . . . . . . . .£50 THURLBY PL320 0-30V 0-2A Digital . . . . . . . . . . . . . . . . . . . £55
HP 182T with 8559A 100kHz-21GHz . . . . . . . . . . . . . . . . .£750 PANASONIC VP8117A AM/FM 100kHz-110MHz RACAL 1991 Counter/Timer 160MHz 9 digit . . . . . . . . . . . . .£195 TAKASAGO GMO35-3 0-35V 0-3A 2 Meters . . . . . . . . . . . . . £45
HP182T with 8558B 100kHz-1500MHz . . . . . . . . . . . . . . .£600 FM 0-100kHz Digital Display etc. Unused . . . . . . . . . . . .£225 MARCONI 2431A Frequency Meter 200MHz . . . . . . . . . . . . . .£50 TAKASAGO TMO35-2 0-35V 0-2A 2 Meters. . . . . . . . . . . . . . £35
MARCONI 2437 Counter/Timer 100MHz . . . . . . . . . . . . . . . . .£75 ISOLATING TRANSFORMER - Yellow - 500VA with
STEWART of READING HP 5340A Automet Microwave Counter 10Hz-18GHz . . . . . .£250 13Amp Socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . £35

17A King Street, Mortimer, Near Reading RG7 3RS Used Equipment – GUARANTEED. Manuals supplied
Telephone: (0118) 933 1111. Fax: (0118) 933 2375 This is a VERY SMALL SAMPLE OF STOCK. SAE or Telephone for lists.
www.stewart-of-reading.co.uk Please check availability before ordering.
Open 9am-5.00pm Monday to Friday (other times by arrangement) CARRIAGE all units £16. VAT to be added to Total of Goods and Carriage

522 Everyday Practical Electronics, August 2005

 NEXT MONTH
SNOOKER AND DARTS
SCOREBOARD
This Snooker and Darts Scoreboard was suggested by a
reader – so standby your cues and arrows ready for next
month's issue!
Score data is entered via a 4 x 4 matrixed data keypad,
processed to suit the game type by a PIC microcontroller.
The resulting data values are output to a matrixed 8-digit
7-segment l.e.d. array, suitable for viewing by a small audi-
ence, and an alphanumeric l.c.d. display module for the ben-
efit of the scorer (adjudicator). The l.e.d. digits are basically
50mm size, although larger ones can be used.
In snooker mode, each player’s frame score is shown, MULTICORE CABLE TESTER
together with the current break count, the value of the balls
left on the table, and the number of frames won by each The number of fairly complex multicore cables in the home
player, and fouls can be awarded. and workshop is is steadily increasing, and whether you buy
In darts mode, each player’s leg score is shown and the or make them, so too is the chance that they may develop a
number of legs won.The starting leg value can be set for any fault. This unit is designed to test cables of up to eight cores,
between 101 and 1001, in steps of 100. In both games adju- with cables having more than eight conductors being split
dicator errors in data entry can be amended. into groups of tests.
The unit can be used with leads for Ethernet, audio, SCART,
keyboard, mouse, computer monitor, modem, USB etc. It
CONTROLLING MODEL RAILWAY identifies a cable, checks continuity of all cores and identifies
a “crossover” type. It outputs testing results via l.e.d.s and
SIGNALS beeps from a buzzer.
In modern railways semaphore signals have mostly given
way to coloured-light signals, or no signals at all, at least ALL BAND RADIO
those at the side of the track. But in the model railway world
there is a desire to include semaphore signals since part of One might call this a “dog” of a radio. It doesn’t pretend to
the attraction of the hobby is the ability to show the way any finesse and it doesn’t have high fidelity sound. However,
things were. it has good coverage, and good sensitivity. Moreover, it is a
This article follows on from that by the late Andy Flind, PIC robust design that, unlike many others, does not depend on
Quickstep of June ’04, which gave a very good introduction daintily wound coils, obscure parts, or a carefully construct-
to stepper motors and the means of testing them. Here a ed antenna.
specific application for stepper motors is described, using Built in Cape Town, the prototype brought in a good many
them to control the movement of semaphore signal arms. stations from all around the world – loud and clear. This
A number of matters are covered which will need to be con- included the BBC, the Voice of America, Radio China, Radio
sidered for any stepper motor application. Even if a reader is Iran, the Deutsche Welle, and many more besides.
not interested in model railway signals, the solutions adopt- Well into the night, it even picked up local Australian stations
ed here may be a useful guide. on the medium waves.
This is a regenerative set and has sharper tuning and
greater sensitivity than many other tuned radio frequency
PLUS BACK TO BASICS – 6 (t.r.f.) sets. On the medium waves, it works well even without
an external antenna or earth, although an aerial may be
ɀ Daily Reminder attached to very good effect. Also, while its volume is mod-
est, it is strong enough to serve as a bedside radio, or in a
ɀ Whistle Switch small workshop.

NO ONE DOES IT BETTER

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ORDER NOW!
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SEPTEMBER 2005 ISSUE ON SALE THURSDAY, AUGUST 11

Everyday Practical Electronics, August 2005 523
 Quasar Electronics Limited Postage & Packing Options (Up to 2kg gross weight): UK standard 3-7 Day
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Helping you make the right connections!

ABC Maxi AVR Development Board NEW! DTMF Telephone Relay Switcher
PIC & ATMEL Programmers The ABC Maxi board Call your phone number
has an open architec- using a DTMF phone from
We have a wide range of low cost PIC and ture design based on anywhere in the world
ATMEL Programmers. Complete range and Atmel’s AVR and remotely turn on/off
documentation available from our web site. AT90S8535 RISC any of the 4 relays as
Programmer Accessories: microcontroller and is desired. User settable
40-pin Wide ZIF socket (ZIF40W) £15.00 ideal for developing new designs. Security Password, Anti-Tamper, Rings to
Features: Answer, Auto Hang-up and Lockout.
18VDC Power supply (PSU010) £19.95
8Kb of In-System Programmable Flash Includes plastic case. 130 x 110 x 30mm.
Leads: Parallel (LDC136) £4.95 / Serial
(1000 write/erase cycles) • 512 bytes Power: 12VDC.
(LDC441) £4.95 / USB (LDC644) £2.95
internal SRAM • 512 bytes EEPROM Kit Order Code: 3140KT – £39.95
• 8 analogue inputs (range 0-5V) Assembled Order Code: AS3140 – £59.95
• 4 Opto-isolated Inputs (I/Os are
NEW! USB ‘Flash’ PIC Programmer bi-directional with internal pull-up resistors) Serial Port Isolated I/O Module
USB PIC programmer for most • Output buffers can sink 20mA current Computer controlled
‘Flash’ devices. No external (direct l.e.d. drive) • 4 x 12A open drain 8-channel relay
power supply making it truly MOSFET outputs • RS485 network board. 5A mains
portable. Supplied with box connector • 2-16 LCD Connector rated relay outputs
and Windows Software. ZIF • 3·5mm Speaker Phone Jack and 4 opto-isolated
Socket and USB Plug A-B lead • Supply: 9-12VDC. digital inputs (for
not incl. The ABC Maxi STARTER PACK includes monitoring switch
Kit Order Code: 3128KT – £34.95 one assembled Maxi Board, parallel and states, etc). Useful in a variety of control
Assembled Order Code: AS3128 – £39.95 serial cables, and Windows software and sensing applications. Programmed via
CD-ROM featuring an Assembler, serial port (use our new Windows interface,
BASIC compiler and in-system terminal emulator or batch files). Serial
“PICALL” ISP PIC Programmer programmer. cable can be up to 35m long. Includes
“PICALL” will program Order Code ABCMAXISP – £89.95 plastic case 130 x 100 x 30mm. Power:
virtually all 8 to 40 The ABC Maxi boards only can also be 12VDC/500mA.
pin serial-mode* AND purchased separately at £69.95 each. Kit Order Code: 3108KT – £49.95
parallel-mode Assembled Order Code: AS3108 – £59.95
(PIC16C5x family)*
Programmed PIC Controllers & Loggers Infra-red RC 12-Channel Relay Board
micro controllers. Control 12 on-board relays
Free fully functional Here are just a few of the controller and data with included infra-red
software. Blank chip auto detect for super acquisition and control units we have. remote control unit. Toggle
fast bulk programming. Parallel port connec- See website for full details. Suitable PSU for or momentary. 15m+ range.
tion. Supply: 16-18V dc. all units: Order Code PSU445 – £8.95 112 x 122mm.
Assembled Order Code: AS3117 – £39.95 Supply: 12VDC/0·5A.
Kit Order Code: 3142KT – £39.95
Rolling Code 4-Channel UHF Remote Assembled Order Code: AS3142 – £49.95
ATMEL 89xxx Programmer
Uses serial port and any State-of-the-Art. High security.
4 channels. Momentary or PC Data Acquisition & Control Unit
standard terminal comms
latching relay output. Range Monitor and log a
program. 4 LEDs display
up to 40m. Up to 15 TXs can mixture of analogue
the status. ZIF sockets
be learned by one Rx (kit and digital inputs
not included. Supply:
includes one Tx but more and control external
16VDC.
available separately). devices via the ana-
Kit Order Code: 3123KT – £29.95
4 indicator LEDs. logue and digital
Rx: PCB 77x85mm, 12VDC/6mA (standby). outputs. Monitor
NEW! USB & Serial Port PIC Programmer Two & Ten Channel versions also available. pressure, tempera-
USB/Serial connection. Kit Order Code: 3180KIT – £39.95 ture, light intensity, weight, switch state,
Header cable for ICSP. Free Assembled Order Code: AS3180 – £47.95 movement, relays, etc. with the apropriate
Windows software. See web- sensors (not supplied). Data can be
site for PICs supported. ZIF Computer Temperature Data Logger processed, stored and the results used to
Socket and USB Plug A-B Serial port 4-channel tem- control devices such as motors, sirens,
lead extra. 18VDC. perature logger. °C or °F. relays, servo motors (up to 11) and two
Kit Order Code: 3149KT – £34.95 Continuously logs up to 4 stepper motors.
Assembled Order Code: AS3149 – £49.95 separate sensors located
200m+ from board. Wide Features
range of free software appli-
11 Analogue Inputs – 0·5V, 10 bit (5mV/step)
USB Flash ICSP PIC Programmer
16 Digital Inputs – 20V max. Protection 1K in
Fully assembled version of cations for storing/using data.
PCB just 38x38mm. Powered series, 5·1V Zener
our 3128 USB Flasher
by PC. Includes one DS1820 sensor and
1 Analogue Output – 0-2·5V or 0-10V. 8 bit
PIC Programmer but (20mV/step)
four header cables.
WITHOUT the pre-
Kit Order Code: 3145KT – £16.95
8 Digital Outputs – Open collector, 500mA, 33V
gramming socket. It max
just has 5-pin ICSP Assembled Order Code: AS3145 – £23.95
Custom box (140 x 110 x 35mm) with printed
header (GND, VCC, Additional DS1820 Sensors – £3.95 each front & rear panels
CLK, DAT, VPP) and
Windows software utilities (3·1 to XP) and
cable. No external programming examples
PSU required. Free
Supply: 12V DC (Order Code PSU203)
Windows software. Most items are available in kit form (KT suffix)
or pre-assembled and ready for use (AS prefix). Kit Order Code: 3093KT – £64.95
Order Code: AS3182 – £37.95 Assembled Order Code: AS3093 – £94.95
Hot New Kits This Summer! FM Bugs & Transmitters
Here are a few of the most recent kits Our extensive range goes from discreet
CREDIT
added to our range. See website or join our surveillance bugs to powerful FM broadcast CARD
email Newsletter for all the latest news. transmitters. Here are a few examples. All
can be received on a standard FM radio SALES
and have adjustable transmitting frequency.
NEW! EPE Ultrasonic Wind Speed Meter 0871
Solid-state design
wind speed meter MMTX’ Micro-Miniature 9V FM Room Bug 717
(anemometer) that Our best selling bug! Good
uses ultrasonic performance. Just 25 x 15mm.
7168
techniques and has Sold to detective agencies
no moving parts worldwide. Small enough to Helping you make the right connections!
and does not need hide just about anywhere.
calibrating. It is intended for sports-type Operates at the ‘less busy’ top
activities, such as track events, sailing,
end of the commercial FM waveband and Electronic Project Labs
hang-gliding, kites and model aircraft flying, Great introduction to the world of electron-
to name but a few. It can even be used to also up into the more private Air band.
Range: 500m. Supply: PP3 battery. ics. Ideal gift for budding electronics expert!
monitor conditions in your garden. The probe
is pointed in the direction from which the Kit Order Code: 3051KT – £8.95
wind is blowing and the speed is displayed Assembled Order Code: AS3051 – £14.95 500-in-1 Electronic Project Lab
on an LCD display. This is the top of the range
HPTX’ High Power FM Room Bug and is a complete electronics
Specifications Our most power- course taking you from

Units of display: metres per second, feet per beginner to ‘A’ level standard
ful room bug.
second, kilometres per hour and miles per hour and beyond! It contains all
Very Impressive
• Resolution: Nearest tenth of a metre the parts and instruc-
• Range: Zero to 50mph approx. performance. Clear and stable output signal
thanks to the extra circuitry employed. tions to assemble 500
Based on the project published in Everyday Range: 1000m @ 9V. Supply: 6-12V DC (9V projects. You get three
Practical Electronics, Jan 2003. We have comprehensive course books
PP3 battery clip suppied). 70 x 15mm.
made a few minor design changes (see web (total 368 pages) – Hardware Entry Course,
Kit Order Code: 3032KT – £9.95 Hardware Advanced Course and a micro-
site for full details). Power: 9VDC (PP3 bat- Assembled Order Code: AS3032 – £17.95
tery or Order Code PSU345). computer based Software Programming
Main PCB: 50 x 83mm. Course. Each book has individual circuit
MTTX’ Miniature Telephone Transmitter explanations, schematic and assembly dia-
Kit Order Code: 3168KT – £34.95 Attach anywhere grams. Suitable for age 12 and above.
along phone line. Order Code EPL500 – £149.95
NEW! Audio DTMF Decoder and Display
Tune a radio into the 30, 130, 200 and 300-in-1 project labs also
Detects DTMF
tones via an signal and hear available – see website for details.
on-board electret exactly what both parties are saying.
microphone or Transmits only when phone is used. Clear,
direct from the stable signal. Powered from phone line so Number 1 for Kits!
phone lines through completely maintenance free once installed.
Requires no aerial wire – uses phone line as With over 300 projects in our range we are
the onboard audio
transformer. The antenna. Suitable for any phone system the UK’s number 1 electronic kit specialist.
numbers are displayed on a 16-character, worldwide. Range: 300m. 20 x 45mm. Here are a few other kits from our range.
single line display as they are received. Up Kit Order Code: 3016KT – £7.95
to 32 numbers can be displayed by scrolling Assembled Order Code: AS3016 – £13.95
the display left and right. There is also a 1046KT – 25W Stereo Car Booster £29.95
serial output for sending the detected tones 3087KT – 1W Stereo Amplifier £6.95
3 Watt FM Transmitter
to a PC via the serial port. The unit will not 3105KT – 18W BTL mono Amplifier £9.95
Small, powerful FM
detect numbers dialled using pulse dialling. transmitter. Audio 3106KT – 50W Mono Hi-fi Amplifier £23.95
Circuit is microcontroller based. preamp stage and 3143KT – 10W Stereo Amplifier £10.95
Supply: 9-12V DC (Order Code PSU345). three RF stages 1011-12KT – Motorbike Alarm £12.95
Main PCB: 55 x 95mm. 1019KT – Car Alarm System £12.95
deliver 3 watts of RF
Kit Order Code: 3153KT – £17.95 1048KT – Electronic Thermostat £9.95
Assembled Order Code: AS3153 – £29.95 power. Can be used
with the electret 1080KT – Liquid Level Sensor £6.95
microphone supplied or any line level audio 3003KT – LED Dice £7.95
NEW! EPE PIC Controlled LED Flasher source (e.g. CD or tape OUT, mixer, sound 3006KT – LED Roulette Wheel £9.95
This versatile card, etc). Aerial can be an open dipole or 3074KT – 8-Ch PC Relay Board £24.95
PIC-based LED Ground Plane. Ideal project for the novice 3082KT – 2-Ch UHF Relay £30.95
or filament bulb wishing to get started in the fascinating 3126KT – Sound-Activated Relay £8.95
flasher can be world of FM broadcasting. 45 x 145mm. 3063KT – One Chip AM Radio £11.95
used to flash Kit Order Code: 1028KT – £23.95 3102KT – 4-Ch Servo Motor Driver £15.95
from 1 to 160 Assembled Order Code: AS1028 – £31.95 3155KT – Stereo Tone Controls £11.95
LEDs. The user arranges the LEDs in any
pattern they wish. The kit comes with 8 1096KT – 3-30V, 5A Stabilised PSU £32.95
25 Watt FM Transmitter 3029KT – Combination Lock £7.95
superbright red LEDs and 8 green LEDs. Four transistor based stages with a Philips
Based on the Versatile PIC Flasher by Steve 3049KT – Ultrasonic Detector £14.95
BLY89 (or equivalent) in the final stage.
Challinor, EPE Magazine Dec ’02. See web- 3130KT – Infra-red Security Beam £13.95
Delivers a mighty 25 Watts of RF power.
site for full details. Board Supply: 9-12V DC. Accepts any line level audio source (input SG01MKT – Train Sounds £6.95
LED supply: 9-45V DC (depending on SG10 MKT – Animal Sounds £5.95
sensitivity is adjustable). Antenna can be an
number of LED used). PCB: 43 x 54mm. 1131KT – Robot Voice Effect £9.95
Kit Order Code: 3169KT – £11.95 open dipole, ground plane, 5/8, J, or YAGI
configuration. Supply 12-14V DC, 5A. 3007KT – 3V FM Room Bug £6.95
Supplied fully assembled and aligned – just 3028KT – Voice-Activated FM Bug £11.95
connect the aerial, power and audio input. 3033KT – Telephone Recording Adpt £8.95
Most items are available in kit form (KT suffix) 70 x 220mm. 3112KT – PC Data Logger/Sampler £18.95
or assembled and ready for use (AS prefix) Order Code: AS1031 – £134.95 3118KT – 12-bit Data Acquisition Unit £49.95
3101KT – 20MHz Function Generator £69.95

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Club/Maestro
EXTRA ARTICLES – ON ALL VOLUMES
BASIC SOLDERING GUIDE – Alan Winstanley’s internationally £ ...............................................
acclaimed fully illustrated guide. UNDERSTANDING PASSIVE COMPO-
NENTS – Introduction to the basic principles of passive components. Card No. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
HOW TO USE INTELLIGENT L.C.Ds, by Julyan Ilett – An utterly practi-
cal guide to interfacing and programming intelligent liquid crystal display Card Security Code . . . . . . . . . . (The last 3 digits on or just under
modules. PhyzzyB COMPUTERS BONUS ARTICLE 1 – Signed and the signature strip)
Unsigned Binary Numbers. By Clive “Max” Maxfield and Alvin Brown.
PhyzzyB COMPUTERS BONUS ARTICLE 2 – Creating an Event Valid From . . . . . . . . . .Expiry Date . . . . . . . . .
Counter. By Clive “Max” Maxfield and Alvin Brown. INTERGRAPH
COMPUTER SYSTEMS 3D GRAPHICS – A chapter from Intergraph’s Maestro Issue No. . . . . . . . . . . . . .
book that explains computer graphics technology. FROM RUSSIA WITH SEND TO: Everyday Practical Electronics,
LOVE, by Barry Fox – Russian rockets launching American Satellites. Wimborne Publishing Ltd.,
PC ENGINES, by Ernest Flint – The evolution of Intel’s microprocessors. 408 Wimborne Road East, Ferndown, Dorset BH22 9ND.
THE END TO ALL DISEASE, by Aubrey Scoon – The original work of
Tel: 01202 873872. Fax: 01202 874562.
Rife. COLLECTING AND RESTORING VINTAGE RADIOS, by Paul
Stenning. THE LIFE & WORKS OF KONRAD ZUSE – a brilliant pioneer
E-mail: orders@epemag.wimborne.co.uk
in the evolution of computers. A bonus article on his life and work written Payments must be by card or in £ Sterling – cheque or bank
by his eldest son, including many previously unpublished photographs. draft drawn on a UK bank.
Normally supplied within seven days of receipt of order.
Note: Some of the EXTRA ARTICLES require WinZip to unzip them.

526 Everyday Practical Electronics, August 2005

 BACK ISSUES
We can supply back issues of EPE by post, most issues from the past three years are available. An EPE index for the last five years is also available at
www.epemag.co.uk or see order form below. Alternatively, indexes are published in the December issue for that year. Where we are unable to provide a
back issue a photocopy of any one article (or one part of a series) can be purchased for the same price. Issues from Nov. 98 are available on CD-ROM –
see next page – and issues from the last six months are also available to download from www.epemag.com.
Please make sure all components are still available before commencing any project from a back-dated issue.
DID YOU MISS THESE?
APRIL ’04 APR ’05
PROJECTS ɀ EPE Experimental Seismograph PROJECTS ɀ Spontaflex Radio Receiver ɀ
Logger 1 ɀ Infra-Guard Monitor ɀ Loft Light Alarm Safety Interface ɀ Fridge/Freezer Door Alarm ɀ
ɀ PIC Moon Clock. Smart Karts - 7.
FEATURES ɀ USB To PIC Interface ɀ Ingenuity FEATURES ɀ Back To Logic Basics - 1 ɀ Circuit
Unlimited ɀ Teach-In 2004 Part 6 ɀ Interface ɀ Surgery ɀ Ingenuity Unlimited ɀ Interface ɀ PIC18F
Techno Talk ɀ Circuit Surgery ɀ New Technology Microcontroller Family Introduction ɀ Techno Talk ɀ
Update ɀ Net Work – The Internet Page ɀ Pull-Out – Net Work – The Internet Page
Semiconductor Classification Data.
MAY ’05
MAY ’04 PROJECTS ɀ Crossword Solver ɀ DAB Radio
PROJECTS ɀ Beat Balance Metal Detector ɀ In-Car Aerial ɀ 20W Amplifier Module ɀ Smart Karts - 8
Laptop PSU ɀ Low-Frequency Wien Oscillator ɀ ɀ Water Level Detector ɀ Burglar Alarm
EPE Experimental Seismograph Logger–2. FEATURES ɀ Back To Logic Basics - 2 ɀ Circuit
FEATURES ɀ Coping With Lead-Free Solder Surgery ɀ Ingenuity Unlimited ɀ Passive Component
ɀ Teach-In 2004 – Part 7 ɀ Ingenuity Unlimited DEC ’04 Photocopies only Testing ɀ Practically Speaking ɀ Techno Talk ɀ Net
ɀ Techno Talk ɀ Circuit Surgery ɀ Practically PROJECTS ɀ Super Vibration Switch ɀ Versatile Work – The Internet Page
Speaking ɀ Pic-N’-Mix ɀ Net Work – The Internet PIC Flasher ɀ Wind Direction Indicator ɀ Smart
Page. Karts - 3.
FEATURES ɀ Light Emitting Diodes-4 ɀ Ingenuity
JUNE ’04 Photocopies only Unlimited ɀ Circuit Surgery ɀ Interface ɀ PIC ‘N’ Mix
PROJECTS ɀ PIC Quickstep ɀ Crafty Cooling ɀ ɀ Techno Talk ɀ Net Work – The Internet Page ɀ
MIDI Synchronome ɀ Body Detector Mk2. INDEX Vol. 33.
FEATURES ɀ Clinical Electrotherapy ɀ Ingenuity
Unlimited ɀ Teach-In 2004 – Part 8 ɀ Interface JAN ’05
ɀ Circuit Surgery ɀ Techno Talk ɀ PIC-N’-Mix ɀ Net PROJECTS ɀ Speed Camera Watch ɀ Gate Alarm
Work – The Internet Page. ɀ Light Detector ɀ Smart Karts - 4.
FEATURES ɀ Practially Speaking ɀ 32-Bit Signed
Integer Maths for PICs ɀ Ingenuity Unlimited ɀ
Circuit Surgery ɀ Techo Talk ɀ PIC ‘N’ Mix ɀ
Picoscope 3205 Review ɀ Net Work – The Internet
Page

FEB ’05 JUNE ’05

PROJECTS ɀ PIC Electric MK2 Pt1 ɀ Sneaky ɀ PROJECTS ɀ PIC Ultrasonic Radar ɀ Radio
Sound Card Mixer ɀ Smart Karts - 5. Control Model Switcher ɀ Super-Ear Audio
FEATURES ɀ Interface ɀ Circuit Surgery ɀ Ingenuity Telescope ɀ Electronic Scarecrow ɀ Digital Lock
Unlimited ɀ Techno Talk ɀ PIC ‘N’ Mix ɀ E-Blocks and FEATURES ɀ Catch the Wave (Tsunami) ɀ Back To
Basics – 3 ɀ Digital TV Switchover ɀ Programming
Flowcode V2.0 Reviews ɀ Net Work – The Internet PIC 18F Interrupts ɀ Circuit Surgery ɀ Interface ɀ
Page Ingenuity Unlimited ɀ Net Work – The Internet Page

JULY ’04 Photocopies only MAR ’05 JULY ’05

PROJECTS ɀ Portable Mini Alarm ɀ Bongo Box ɀ PROJECTS ɀ Cat Flap ɀ Stereo Headphone Monitor PROJECTS ɀ Cybervox ɀ LF and VLF Converter
Hard Drive Warbler ɀ EPE PIC Magnetometry ɀ PIC Electric Mk2 Pt2 ɀ Smart Karts - 6 ɀ Bingo Box. ɀ Multi-Clap Switch ɀ Doorchime ɀ Electronic Dice
Logger–1. FEATURES ɀ TK3 Simulator and PIC18F Upgrade FEATURES ɀ Discovering PICs Reviewed ɀ Back
FEATURES ɀ Making Front Panel Overlays ɀ ɀ Circuit Surgery ɀ Ingenuity Unlimited ɀ Techno To Basics – 4 ɀ Digital TV Switchover ɀ Practically
Practically Speaking ɀ Teach-In 2004 – Part 9 ɀ Talk ɀ PIC ‘N’ Mix ɀ Practically Speaking ɀ Net Work Speaking ɀ Circuit Surgery ɀ Interface – The
Ingenuity Unlimited ɀ Circuit Surgery ɀ Techno Talk – The Internet Page Internet Page
ɀ PIC-N’-Mix ɀ Net Work – The Internet Page.

AUG ’04 BACK ISSUES ONLY £3.80 each inc. UK p&p.

PROJECTS ɀ EPE Scorer ɀ Keyring L.E.D. Torch ɀ Overseas prices £4.50 each surface mail, £5.50 each airmail.
Simple F.M. Radio ɀ EPE PIC Magnetometry We can also supply issues from earlier years: 2000 (except Feb., Mar., July, Oct.), 2001 (except Feb., May, Aug., to
Logger – 2.
FEATURES ɀ PIC To PS/2 Mouse and Keyboard Nov.), 2002 (except Feb., June, Aug. to Nov.), 2003 (except June), 2004 (except June, July, Oct. and Dec). Where
Interfacing ɀ Techno Talk ɀ Circuit Surgery ɀ Teach- we do not have an issue a photocopy of any one article or one part of a series can be provided at the same price.
In 2004 – Part 10 ɀ Interface ɀ Ingenuity Unlimited
ɀ PIC-N’-Mix ɀ Net Work – The Internet Page. ORDER FORM – BACK ISSUES – PHOTOCOPIES– INDEXES
SEPT ’04 អ Send back issues dated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PROJECTS ɀ EPE Wart Zapper ɀ Radio Control អ Send photocopies of (article title and issue date) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Failsafe ɀ Rainbow Lighting Control ɀ Alphamouse
Game. អ Send copies of last five years indexes (£3.80 for five inc. p&p – Overseas £4.50 surface, £5.50 airmail)
FEATURES ɀ Light Emitting Diodes – Part 1 ɀ High
Speed Binary-To-Decimal For PICs ɀ Practically Name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Speaking ɀ Ingenuity Unlimited ɀ Techno-Talk ɀ
Circuit Surgery ɀ PIC-N’-Mix ɀ Network – The Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Internet Page
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Tel: . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OCT ’04 Photocopies only អ I enclose cheque/P.O./bank draft to the value of £ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

PROJECTS ɀ EPE Theremin ɀ Smart Karts – Part អ Please charge my Visa/Mastercard/Amex/Diners Club/Switch £ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 ɀ Volts Checker ɀ Moon and Tide Clock Calendar.
FEATURES ɀ Light Emitting Diodes – 2 ɀ Circuit ......................................................................... Switch Issue No.
Surgery ɀ Interface ɀ Ingenuity Unlimited ɀ Techno
Talk ɀ PIC-N’-Mix ɀ Network – The Internet Page ɀ Card No. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ROBOTS – Special Supplement
Valid From . . . . . . . . . . . . . . . . .Card Expiry Date . . . . . . . . . . . . Card Security Code . . . . . . . . . .
(The last 3 digits on or just under the signature strip)
NOV ’04
SEND TO: Everyday Practical Electronics, Wimborne Publishing Ltd., 408 Wimborne Road East, Ferndown, Dorset BH22 9ND.
PROJECTS ɀ Thunderstorm Monitor ɀ M.W.
Tel: 01202 873872. Fax: 01202 874562.
Amplitude Modulator ɀ Logic Probe ɀ Smart Karts - 2.
E-mail: orders@epemag.wimborne.co.uk On-line Shop: www.epemag.wimborne.co.uk/shopdoor.htm
FEATURES ɀ Light Emitting Diodes-3 ɀ Floating
Payments must be in £ sterling – cheque or bank draft drawn on a UK bank. Normally supplied within seven days of receipt of order.
Point Maths for PICs ɀ Ingenuity Unlimited ɀ PE
40th Anniversary ɀ Circuit Surgery ɀ Techno Talk ɀ Send a copy of this form, or order by letter if you do not wish to cut your issue.
M08/05
PIC-N’-Mix ɀ Net Work – The Internet Page.

Everyday Practical Electronics, August 2005 527

 EE276 135 Hunter Street, Burton-on-Trent, Staffs. DE14 2ST
Tel 01283 565435 Fax 546932
http://www.magenta2000.co.uk
E-mail: sales@magenta2000.co.uk
All Prices include V.A.T. ADD £3.00 PER ORDER P&P. £6.99 next day

MAIL ORDER ONLY • CALLERS BY APPOINTMENT

PIC PIPE DESCALER
EPE PROJECT PICS
Programmed PICs for *EPE Projects

SIMPLE TO BUILD

HIGH POWER OUTPUT

SWEPT
FREQUENCY
EPE
12C508/9 – £3.90; 16F627/8 – £4.90
16C84/16F84/16C71 – £5.90
16F876/877 – £10.00

AUDIO & VISUAL MONITORING
An affordable circuit which sweeps
the incoming water supply with
TEACH-IN
All inc. VAT and Postage
(*Some projects are copyright)
variable frequency electromagnetic
signals. May reduce scale formation,
dissolve existing scale and improve
lathering ability by altering the way
2000
salts in the water behave. Full set of top quality NEW
EPE MICROCONTROLLER Kit includes case, P.C.B., coupling components for this educa-
P.I. TREASURE HUNTER
coil and all components. tional series. All parts as
High coil current ensures maximum specified by EPE. Kit includes
The latest MAGENTA DESIGN – highly effect. L.E.D. monitor.
stable & sensitive – with I.C. control of all breadboard, wire, croc clips,
timing functions and advanced pulse KIT 868 ....... £22.95 POWER UNIT......£3.99 pins and all components for
separation techniques. experiments, as listed in

High stability
drift cancelling MICRO PEsT introduction to Part 1.
*Batteries and tools not included.

Easy to build
& use
SCARER

No ground Our latest design – The ultimate TEACH-IN 2000 -
effect, works scarer for the garden. Uses
in seawater special microchip to give random KIT 879 £44.95
delay and pulse time. Easy to
build reliable circuit. Keeps pets/
pests away from newly sown areas,
MULTIMETER £14.45
play areas, etc. uses power source
from 9 to 24 volts.

EE

RANDOM PULSES SPACEWRITER

PP

Detects gold,

RO
NOM C

HIGH POWER An innovative and exciting project.

W HIP
silver, ferrous & Wave the wand through the air and

W &

DUAL OPTION Plug-in power supply £4.99

IT S
non-ferrous

H O
your message appears. Programmable

PI FT
metals to hold any message up to 16 digits long.

C1 W
KIT 867. . . . . . . . . . . . . . . . . . . . . . . . . . . . .£19.99

6C AR
Comes pre-loaded with “MERRY XMAS”. Kit

84 E

Efficient quartz controlled includes PCB, all components & tube plus
microcontroller pulse generation. KIT + SLAVE UNIT. . . . . . . . . . . . . . . . . . . .£32.50

DI
instructions for message loading.

SK

Full kit with headphones & all
hardware WINDICATOR KIT 849 . . . . . . . . . . . .£16.99
KIT 847 . . . . . . . . .£63.95 A novel wind speed indicator with LED readout. Kit comes
complete with sensor cups, and weatherproof sensing head.
Mains power unit £5.99 extra. 12V EPROM ERASER
A safe low cost eraser for up to 4 EPROMS at a
DEVELOPMENT KIT 856. . . . . . . . . . . . . . . . . . . . . . . . . . . . .£28.00
68000 time in less than 20 minutes. Operates from a
12V supply (400mA). Used extensively for mobile

TENS UNIT

TRAINING KIT work - updating equipment in the field etc. Also in
educational situations where mains supplies are

NEW PCB DESIGN not allowed. Safety interlock prevents contact

8MHz 68000 16-BIT BUS with UV.

MANUAL AND SOFTWARE

2 SERIAL PORTS DUAL OUTPUT TENS UNIT Set of KIT 790 . . . . . . . . . . . .£29.90

PIT AND I/O PORT OPTIONS As featured in March ’97 issue. 4 spare

12C PORT OPTIONS electrodes
Magenta have prepared a FULL KIT for this.
excellent new project. All components, PCB,
£6.50 SUPER BAT
hardware and electrodes are included. DETECTOR
KIT 621 Designed for simple assembly and testing and
providing high level dual output drive. 1 WATT O/P, BUILT IN
£99.95 KIT 866. . Full kit including four electrodes £32.90 SPEAKER, COMPACT CASE

ON BOARD 20kHz-140kHz
5V REGULATOR NEW DESIGN WITH 40kHz MIC.

PSU £6.99 1000V & 500V INSULATION A new circuit using a

SERIAL LEAD £3.99
TESTER ‘full-bridge’ audio
amplifier i.c., internal
Superb new design. Regulated speaker, and
headphone/tape socket.
output, efficient circuit. Dual-scale The latest sensitive
Stepping Motors meter, compact case. Reads up to transducer, and ‘double
200 Megohms. balanced mixer’ give a
MD100..Std 100 step..£9.99 Kit includes wound coil, cut-out stable, high perfor-
case, meter scale, PCB & ALL mance superheterodyne design.
MD200...200 step...£12.99
MD24...Large 200 step...£22.95
components. KIT 861 . . . . . . . . . . .£34.99
KIT 848. . . . . . . . . . . . £32.95 ALSO AVAILABLE Built & Tested. . . £48.99

ULTRASONIC PEsT SCARER

MOSFET MkII VARIABLE BENCH SIMPLE PIC
Keep pets/pests away from newly
POWER SUPPLY 0-25V 2·5A sown areas, fruit, vegetable and PROGRAMMER
Based on our Mk1 design and flower beds, children’s play areas,
preserving all the features, but patios etc. This project produces KIT 857... £12.99
now with switching pre- intense pulses of ultrasound which
regulator for much higher effi- deter visiting animals.
ciency. Panel meters indicate Includes PIC16F84 chip
Volts and Amps. Fully variable
KIT INCLUDES ALL disk, lead, plug, p.c.b.,
down to zero. Toroidal mains COMPONENTS, PCB & CASE
transformer. Kit includes
EFFICIENT 100V
UP TO 4 METRES
all components and
punched and printed case and TRANSDUCER OUTPUT RANGE instructions
all parts. As featured in April
COMPLETELY INAUDIBLE
LOW CURRENT
1994 EPE. An essential piece TO HUMANS Extra 16F84 chips £3.84
DRAIN
of equipment. Power Supply £3.99
Kit No. 845 . . . . . . . .£64.95 KIT 812. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . £15.00
 PIC LCD DISPLAY DRIVER
16 Character x 2 Line display, pcb, pro-
grammed PIC16F84, software disk and
• Learn how to drive the display and write
your own code.
20W Amp. Module
all components to experiment with stand- • Ideal development base for meters, calcu- EPE May ‘05 -- Superb Magenta Stereo/Mono Module
ard intelligent alphanumeric displays. lators, counters, timers --- just waiting for
Includes full PIC source code which can your application! Wide bandwidth Low distor-
be changed to match your application. • Top quality display with industry stand- tion 11W /channel Stereo 20W
ard driver, data and instructions Mono True (rms) Real Power
KIT 860.....£19.99
Short Circuit & Overheat Pro-
PIC STEPPING MOTOR DRIVER tected. Needs 8 to 18V supply.
PCB with components and PIC16F84 Use this project to develop your own ap- Stable Reliable design
programmed with demonstration software plications. PCB allows ‘simple PIC pro-
to drive any 4 phase unipolar motor up to grammer’ ‘SEND’ software to be used to Latest Technology IC with lo-
24 Volts at 1 Amp. Kit includes 100 reprogram chip. cal feedback gives very high
Step Hybrid Stepping Motor Full soft-
performance.
ware source code supplied on disc. KIT 863.........£18.99
KIT 914 (all parts & heatsink for stereo or mono) £11.90
8 CHANNEL DATA LOGGER
From Aug/Sept.’99 EPE. Featuring 8 analogue inputs and serial data transfer to PC.
Magenta redesigned PCB - LCD plugs directly onto board. Use as Data Logger or as a
test bed for developing other PIC16F877 projects. Kit includes lcd, progd. chip, PCB,
Case, all parts and 8 x 256k EEPROMs
Magenta BrainiBorg
KIT 877.........£49.95 A super walking programmable robot with eyes that sense obstacles and daylight:
BrainiBorg comes with superb PC software CD (WIN95+ & XP) and can be pro-
grammed to walk and respond to light and obstacles on any smooth surface.
PIC16F84 MAINS POWER CONTROLLER
& 4 CHANNEL LIGHT CHASER / DIMMER CD contains illustrated constructional
details, operating principles, circuits
• Zero Volt Switching • With program source code disk. and a superb Educational Program-
• Opto-Isolated 5 Amp HARD FIRED • Chase Speed and dimming potentiom- ming Tutorial.
TRIACS eter controls.
• 12 Way keypad Control • Reprogram for other applications Test routines give real-time ‘scope
traces of sensor and motor signals.
KIT 855.........£39.95 Connects to PC via SERIAL port with
the lead supplied.
EPE MARCH APRIL MAY ‘98
PIC TUTOR 1 PIC16F84 STARTER SERIES
Kit includes all hardware, components, 3 motor/gearboxes.
Uses 4 AA batteries (not supplied). An Ideal Present!
The original PIC16F84 series by John Becker. Magenta’s Tutor board has individual
switches and leds on all portA and PortB lines, plus connectors for optional 4 digit seven KIT 912 Complete Kit with CD rom & serial lead £49.99
segment led display, and 16 x 2 intelligent lcd. Written for newcomers to PICs this series.
Disk has over 20 tutorial programs. Connect to a PC parallel port, send, run, and KIT 913 As 912 but built & tested circuit board £58.95
experiment by modifying test programs - Then Write and Program your Own

KIT 870... £27.95, Built...£42.95

16x2 LCD..£7.99. LED display..£6.99. 12VPSU..£3.99
EPE PIC Tutorial
EPE Apr/May/Jun ‘03 and PIC Resources CD
• Follow John Becker’s excellent PIC toolkit 3 series.
SUPER PIC PROGRAMMER • Magenta Designed Toolkit 3 board with printed component
Magenta’s original parallel port programmer. Runs with down- layout, green solder mask, places for 8,18, 28 (wide and slim),
loaded WINDOWS 95 - XP software. Use standard Microchip and 40 pin PICs. and Magenta extras.
.HEX files. Read/Prog/Verify wide range of 18,28,and 40 pin PICs. • 16 x 2 LCD, PIC chip all components and sockets included.
Including 16F84/876/877, 627/8, (Inc. ‘A’ versions) + 16xx OTPs.
KIT 880 (with 16F84) £34.99, built & tested £49.99
KIT 862... £29.99 Power Supply £3.99
KIT 880 (with 16F877) £39.99, built & tested £55.99
ICEBREAKER EPE TEACH-IN 2004
THE LATEST NOV 03 SERIES Additional Parts as listed in
All parts to follow this new Edu- ‘misc.’ Section (less RF mod-
cational Electronics Course. ules, Lock, and Motor/g.box)
Inc. Breadboard, and wire, as
listed on p752 Nov. Issue. Reprints: £1.00 per part.
KIT 920..........£29.99 KIT921.........£12.99

MAGENTA BRAINIBOT I & II

• Full kit with ALL hardware and
electronics.
• As featured in EPE Feb ‘03 (KIT
910)
•
PIC Real Time •
Seeks light, beeps, and avoids
obstacles
Spins and reverses when
In-Circuit Emulator •
‘cornered’’
Uses 8 pin PIC chip
• ICEbreaker uses PIC16F877 in-circuit Programs can be written, downloaded, • ALSO KIT 911 - As 910 PLUS
debugger. and then tested by single-stepping, run- programmable from PC serial port
• Links to standard PC Serial port (lead ning to breakpoints, or free run at up to leads and software CD included.
supplied). 20Mhz.
• Windows (95 to XP) Software included Full emulation means that all ports re- KIT 910....£16.99 KIT 911....£24.99
• Works with MPASM assembler spond immediately - reading and driv-
16 x 2 LCD display, Breadboard, Relay, ing external hardware.
I/O devices and patch leads. Features include: Run; set Breakpoint;
View & change registers, EEPROM, and
Featured in EPE Mar’00 Ideal for begin- program memory; load program; ‘watch
ners & experienced users. window’ registers.

KIT 900...£34.99 With serial lead & software disk, PCB, Breadboard,
PIC16F877, LCD, all components and patch leads.
POWER SUPPLY - £3.99 STEPPING MOTOR 100 Step £9.99 All prices include VAT. Add £3.00 p&p. Next day £6.99
Tel: 01283 565435 Fax: 01283 546932 email: sales@magenta2000.co.uk
 LF351N £0.44 2N3906 £0.05 BC638 £0.21 TIP42A £0.47

See Next / Last Months Ad. for

082005 A/D Converters Bridge Rectifiers
LF353N £0.40 Data Acquisi- 1A 50V £0.35 2N4401 £0.08 BC639 £0.11 TIP42C £0.43

COMPONENT ACCESSORIES
LF356 £0.52 tion 1A 100V £0.32 2N4403 £0.09 BC640 £0.13 TIP50 £0.31
LF411CN £0.98 AD420AN £25.38 1A 200V £0.39 2N5245 £0.80 BCY70 £0.22 TIP110 £0.28
LM301AN £0.40 AD557JN £6.75 1A 600V £0.40 2N5296 £0.57 BCY71 £0.29 TIP120 £0.32
LM311N8 £0.19 AD7528JN £11.42 1A 800V £0.43 2N5401 £0.12 BCY72 £0.20 TIP121 £0.34
LM319N14 £0.90 AD7545AK £14.04 1.5A 50V £0.19 2N5551 £0.07 BD124P £6.86 TIP122 £0.34
LM324 £0.20 AD7828KN £20.33 1.5A 100V £0.11 2N6491 £1.58 BD131 £0.48 TIP125 £0.31
LM335Z £1.12 DAC0800 £2.40 1.5A 200V £0.19 2N7000 £0.19 BD132 £0.46 TIP126 £0.31
LM339N £0.19 ICL7109CPL £7.75 1.5A 400V £0.20 2SB548 £0.30 BD135 £0.22 TIP127 £0.35
LM348N £0.36 uControllers 1.5A 600V £0.24 AC127 £0.50 BD136 £0.21 TIP132 £0.68
LM35DZ £1.46 1.5A 800V £0.26 AC128 £0.76 BD137 £0.23 TIP137 £0.64
AT89C2051 £6.38
Station Road, Cullercoats, LM358N
LM380N
£0.16
£0.90 PIC Series 1.5A 1kV £0.26 AC187
AC188
£0.68 BD138
£0.97 BD139
£0.19 TIP141
£0.23 TIP142
£0.93
£0.93
2A 100V £0.34
Tyne & Wear, NE30 4PQ LM386 £0.45 12C508A04P £0.78 2A 200V £0.34 ACY17 £4.84 BD140 £0.25 TIP147 £1.07
LM392N £0.79 12C509A04P £0.85 2A 400V £0.35 AD149 £1.29 BD150C £0.82 TIP2955 £0.67
Prices Exclude Vat @17½%. LM393N £0.21 16C54C04P £1.49 2A 800V £0.36 AD161 £0.73 BD201 £0.40 TIP3055 £0.63
LM748CN8 £0.37 16C54BJW £7.60 2A 1000V £0.45 AD162 £0.95 BD202 £0.70 ZVN2106A £0.40
UK Carriage £2.50 (less than 1kg) LM1881 £2.90 3A 200V £0.34 BC107 £0.15 BD232 £0.50 ZVN2110A £0.45
16C56A-04P £1.63
£5.50 greater than 1kg LM2901N £0.15 16F84-04P £3.14 3A 400V £0.40 BC107B £0.14 BD237 £0.32 ZVN3306A £0.28
Cheques / Postal orders payable to LM2917N8 £1.98 16F84-10P £3.76 3A 600V £0.33 BC108 £0.13 BD238 £0.44 ZVN4206A £0.52
ESR Electronic Components. LM3900N £0.72 16F627-04P £2.25 3A 1000V £0.33 BC108B £0.14 BD240C £0.37 ZVN4210A £0.56
LM3914 £1.97 4A 100V £0.78 BC108C £0.18 BD245C £1.10 ZVN4306A £0.74
PLEASE ADD CARRIAGE & VAT TO ALL ORDERS
LM3915 £2.24 16F627-20IP £2.25 4A 200V £0.76 BC109 £0.17 BD246C £1.18 ZVN4310A £0.88
4000 Series 74HC74 £0.19 74LS122 £0.31 LM13700 £1.04 17F628-20IP £2.58 4A 400V £0.86 BC109C £0.15 BD283 £0.61 ZVP2106A £0.42
4000B £0.27 74HC75 £0.31 74LS123 £0.31 LMC660CN £1.26 16F867-04SP £5.40 4A 600V £0.90 BC114 £0.19 BD284 £0.61 ZVP2110A £0.46
4001B £0.16 74HC76 £0.20 74LS125 £0.28 LMC6032IN £1.55 16F877-20P £5.79 6A 100V £0.49 BC115 £0.41 BD400 £0.79 ZVP3306A £0.32
4002B £0.19 74HC85 £0.23 74LS126 £0.25 LP311N £0.74 Voltage 6A 200V £0.64 BC118 £0.41 BD437 £0.38 ZTX300 £0.15
4008B £0.23 74HC86 £0.22 74LS132 £0.26 LP324N £0.75 Regulators 6A 400V £0.53 BC132 £0.36 BD438 £0.27 ZTX302 £0.17
4009UB £0.23 74HC107 £0.40 74LS133 £0.36 LP339N £0.75 7805 £0.27 6A 600V £0.67 BC134 £0.36 BD442 £0.37 ZTX450 £0.19
4010B £0.23 74HC123 £0.33 74LS136 £0.23 LT1013CN8 £4.64 7806 £0.29 8A 100V £0.98 BC135 £0.36 BD534 £0.47 ZTX451 £0.19
4011B £0.16 74HC125 £0.26 74LS138 £0.33 M34-1 £0.30 7808 £0.27 8A 200V £1.00 BC140 £0.75 BD535 £0.50 ZTX453 £0.26
4012B £0.16 74HC126 £0.46 74LS139 £0.26 M34-2 £0.30 7812 £0.27 8A 400V £1.20 BC142 £0.34 BD581 £0.62 ZTX500 £0.16
4013B £0.18 74HC132 £0.26 74LS145 £0.56 MAX202CPE £1.97 7815 £0.27 8A 600V £1.33 BC143 £0.38 BD597 £0.92 ZTX502 £0.17
4014B £0.30 74HC133 £0.34 74LS148 £0.64 MAX208CN £6.99 78L05 £0.22 8A 1000V £1.05 BC159 £0.17 BD646 £0.52 ZTX550 £0.22
4015B £0.27 74HC137 £0.30 74LS151 £0.29 MAX220CPE £5.06 78L06 £0.32 25A 100V £1.47 BC160 £0.28 BD648 £0.52 ZTX551 £0.22
4016B £0.20 74HC138 £0.26 74LS153 £0.38 MAX222CPE £5.06 78L08 £0.22 25A 200V £1.54 BC170B £0.16 BD650 £0.53 ZTX600 £0.33
4017B £0.20 74HC139 £0.31 74LS156 £0.36 MAX232CPE £1.30 78L12 £0.16 25A 400V £1.98 BC171B £0.16 BDX32 £1.78 ZTX600B £0.35
4018B £0.26 74HC151 £0.33 74LS157 £0.22 MAX483CP £3.13 78L15 £0.26 25A 600V £1.82 BC177 £0.15 BDX34C £0.45 ZTX605 £0.36
4019B £0.25 74HC153 £0.30 74LS158 £0.21 MAX485CP £2.08 78L24 £0.39 35A 50V £1.67 BC178 £0.18 BDX53C £0.53 ZTX651 £0.33
4020B £0.25 74HC154 £0.94 74LS160 £0.48 MAX631ACP £4.99 78S05 £0.53 35A 100V £1.57 BC179 £0.15 BDX54C £0.50 ZTX653 £0.37
4021B £0.31 74LS161 £0.32 MAX635ACP £4.99 78S12 £0.70 35A 200V £1.80 BC182B £0.09 BF180 £0.31 ZTX689B £0.36
74HC157 £0.40 MAX1232CP £2.80 35A 400V £1.44 BC182L £0.08 BF182 £0.31 ZTX690B £0.37
4022B £0.32 74HC158 £0.23 74LS162 £0.44 78S15 £0.32
4023B £0.23 74LS163 £0.32 MC1458N £0.27 7905 £0.23 35A 600V £1.90 BC183L £0.08 BF245B £0.40 ZTX705 £0.39
74HC160 £0.64 MC1488 £0.40 35A 1000V £2.32 BC184 £0.09 BF257 £0.33 ZTX750 £0.25
4024B £0.22 74HC161 £0.28 74LS164 £0.43 7912 £0.28
4025B £0.20 74LS165 £0.48 MC1489 £0.35 7915 £0.23 Thyristors BC184L £0.12 BF259 £0.33 ZTX751 £0.34
74HC162 £0.45 74LS173 £0.24 MC3302 £0.56 BC206B £0.72 BF337 £0.40 ZTX753 £0.40
4026B £0.67 74HC163 £0.26 7924 £0.38 2N5060 £0.19
4027B £0.22 74LS174 £0.24 MC4558P £0.33 79L05 £0.18 BC208 £0.72 BF422 £0.15 ZTX789A £0.41
74HC164 £0.23 MK484 £0.66 2N5061 £0.19 BC209A £0.72 BF423 £0.15 ZTX790A £0.41
4028B £0.21 74HC165 £0.35 74LS175 £0.30 79L12 £0.26 BT151-500R £0.65
4029B £0.38 74LS190 £0.60 NE521N £6.39 79L15 £0.28 BC212 £0.10 BF459 £0.33 ZTX851 £0.50
74HC173 £0.38 NE555N £0.17 C106D1 £0.36 BC212L £0.09 BF469 £0.36 ZTX853 £0.50
4030B £0.17 74LS191 £0.27 79L24 £0.30 PO102AA £0.30
74HC174 £0.27 74LS192 £0.60 NE556N £0.32 BC213L £0.12 BFX29 £0.29 ZTX951 £0.54
4035B £0.31 74HC175 £0.35 ADM666AN £3.44 TIC106D £0.49
4040B £0.23 74LS193 £0.43 NE565N £2.30 L200CV £1.67 BC214 £0.08 BFX84 £0.31 ZTX1048A £0.48
74HC193 £0.40 NE592 £0.62 TIC116D £0.66 BC214L £0.10 BFX85 £0.33 ZTX1051A £0.46
4041B £0.31 74LS195 £0.24 L296 £6.30 TIC126D £0.77
4042B £0.19 74HC195 £0.32 74LS221 £0.41 NE5532N £0.48 BC225 £0.15 BFX88 £0.27 ZTX1053A £0.45
74HC240 £0.32 L387A £2.72 Triacs
4043B £0.35 74LS240 £0.32 NE5534N £0.54 LM2940CT5 £0.75 BC237B £0.11 BFY50 £0.30
4044B £0.35 74HC241 £0.37 74LS241 £0.32 NE5539N £4.35 LM317LZ £0.29 BT136-500 £0.58 BC238B £0.11 BFY51 £0.22
4046B £0.35 74HC244 £0.40 74LS243 £0.30 OP07CN £0.80 LM317T £0.31 BT136-600 £0.50 BC250A £0.15 BFY52 £0.24
4047B £0.24 74HC245 £0.34 74LS244 £0.38 OP27CN £2.33 LM317K £2.28 BT137-600 £0.58 BC261B £0.30 BS107 £0.21
4048B £0.34 74HC251 £0.30 74LS245 £0.45 OP90GP £2.91 LM323K £2.40 BT139-500 £1.00 BC262B £0.24 BS170 £0.15 Quality
4049B £0.29 74HC253 £0.25 74LS247 £0.60 OP97FP £1.84 LM334Z £0.96 BT139-600 £1.20 BC267B £0.30 BU208A £1.53 Components
4049UB £0.24 74HC257 £0.25 74LS251 £0.24 OP113GP £3.44 LM337T £0.64 BTA08-600B £0.84 BC319C £0.13 BU326A £1.40 No surplus or re-
4050B £0.20 74HC259 £0.29 74LS257 £0.24 OP176GP £2.09 LM338K £5.47 BTA08-600BW£0.76 BC327 £0.07 BU500 £1.54 dundant stock. All
4051B £0.23 74HC273 £0.32 74LS258 £0.24 OP177GP £1.86 LM338T £1.10 BTA08-600C £0.96 BC327-25 £0.08 BU508A £1.40 from leading
4052B £0.32 74HC299 £0.61 74LS266 £0.14 OP200GP £5.60 LM723 £0.40 BTA08-600SW£0.99 BC328 £0.09 BU508D £0.98 manufactures.
4053B £0.22 74HC365 £0.28 74LS273 £0.32 OP213FP £5.20 LP2950CZ5.0 £0.82 BTA08-600TW£1.10 BC337-16 £0.10 BU806 £1.06
4054B £0.56 74HC367 £0.38 74LS279 £0.24 OP275GP £2.57 REF01CP £2.31 BTA12-600BW£0.92 BC337-25 £0.08 BUT11A £0.57 Quality
4055B £0.34 74HC368 £0.29 74LS283 £0.47 OP282GP £2.27 REF195GP £3.04 BTA16-600CW £1.45 BC338 £0.10 BUT11AF £1.14 Service
4060B £0.22 74HC373 £0.35 74LS365 £0.21 OP283GP £5.20 TL431CP £0.13 BTA16-600B £1.28 BC348B £0.14 BUX84 £0.78 Sameday des-
4063B £0.41 74HC374 £0.34 74LS367 £0.21 OP290GP £4.28 BTA26-600B £2.78 BC357 £0.25 BUZ11A £0.88
4066B £0.17 74HC390 £0.52 74LS368 £0.21 OP297GP £4.64 Diodes TIC206D £0.70 BC393 £0.73 BUZ900P £5.60 patch on all stock
4067B £2.20 74HC393 £0.36 74LS373 £0.39 OP400GP £11.81 1N914 £0.05 TIC206M £0.75 BC441 £0.40 BUZ905P £5.60 items. Friendly
OP495GP £8.69 1N916 £0.05 TIC226D £0.80 BC461 £0.41 IRF530 £0.45 helpful staff.
4068B £0.19 74HC541 £0.25 74LS374 £0.38
4069UB £0.17 74HC563 £0.56 74LS378 £0.62 RC4136 £1.00 1N4001 £0.05 TIC226M £1.00 BC463 £0.29 IRF540 £0.75
4070B £0.15 74HC573 £0.27 74LS390 £0.34 SG3524N £0.82 1N4002 £0.05 TIC246D £1.00 BC477 £0.52 IRF630 £0.42 Fast Delivery
4071B £0.20 74HC574 £0.30 74LS393 £0.33 SG3543 £6.88 1N4003 £0.03 TIC246M £1.00 BC479 £0.32 IRF640 £0.63 Nextday service
74LS395 £0.26 SSM2141P £3.21 1N4004 £0.04 TIC236D £1.12 BC516 £0.21 IRF740 £0.91 for all small
4072B £0.18 74HC595 £0.27
4073B £0.17 74HC597 £0.22 SSM2142P £6.16 1N4005 £0.04 ZO105DA £0.53 BC517 £0.12 IRF830 £0.68 (<1kg) orders at
74 Series SSM2143P £3.78 1N4006 £0.04 BC528 £0.20 IRF840 £0.78 no extra charge.
4075B £0.17 74HC688 £0.46 7407 £0.40 Diac
4076B £0.30 74HC4002 £0.31 TBA120S £1.04 1N4007 £0.03 DB3, 32V £0.14 BC537 £0.20 MJ2955 £0.90 3 day service for
4077B £0.28 Linear ICs TBA800 £0.75 1N4148 £0.03 BC546A £0.06 MJ2501 £1.60 orders >1kg
74HC4017 £0.36 1N4149 £0.07 Transistors
4078B £0.30 74HC4020 £0.36 AD524AD £23.04 TBA810S £0.64 BC546B £0.07 MJ3001 £1.84
4081B £0.16 AD548JN £2.48 TBA820M £0.53 1N5400 £0.08 2N2222A £0.16 BC546C £0.08 MJ11015 £2.45 No Minimum
74HC4040 £0.29 TDA1170S £4.80 1N5401 £0.08 2N2369A £0.51 BC547A £0.09 MJ11016 £2.78 Order
4082B £0.21 74HC4049 £0.31 AD590JH £5.28
4085B £0.28 AD592AN £4.48 TDA2004 £2.21 1N5402 £0.08 2N2646 £1.02 BC547B £0.09 MJE340 £0.33 Order what you
74HC4051 £0.50 TDA2030AV £1.24 1N5404 £0.09 2N2904A £0.35 BC547C £0.08 MJE350 £0.32 need, no pack
4086B £0.33 74HC4052 £0.34 AD595AQ £13.92
4093B £0.16 AD620AN £9.88 TDA2050V £2.51 1N5406 £0.10 2N2905A £0.30 BC548A £0.08 MPSA05 £0.14 quantities or min
74HC4053 £0.22 TDA2611A £1.88 1N5407 £0.10 2N2907A £0.28 BC548B £0.09 MPSA06 £0.11 order value.
4094B £0.29 74HC4060 £0.23 AD625JN £16.20
4098B £0.22 AD633JN £5.92 TDA2822A £0.79 1N5408 £0.10 2N3053 £0.31 BC548C £0.08 MPSA13 £0.09
74HC4075 £0.27 AD648JN £2.57 TDA2653A £2.99 6A05 £0.27 2N3054 £0.85 BC549B £0.09 MPSA42 £0.15 Quantity
4099B £0.35 74HC4078 £0.32 6A1 £0.30 2N3055 £0.58
4502B £0.32 AD654JN £7.18 TDA7052A £1.25 BC549C £0.09 MPSA55 £0.13 Discounts
74HC4511 £0.64 AD711JN £1.46 TED3718DP £5.03 6A2 £0.27 2N3439 £0.62 BC550C £0.11 MPSA56 £0.14 Available
4503B £0.40 74HC4514 £0.84 6A4 £0.28 2N3440 £0.50
4508B £1.40 AD712JN £2.51 TEA5115 £3.11 BC556A £0.08 STW80NE-10 £3.80 We offer dis-
74HC4538 £0.41 AD736JN £7.98 TL061CP £0.37 6A6 £0.32 2N3702 £0.09 BC556B £0.08 TIP29A £0.32 counts for all
4510B £0.45 74HC4543 £0.90 6A8 £0.30 2N3703 £0.10
4511B £0.30 AD797AN £6.58 TL062CP £0.60 BC557A £0.09 TIP29C £0.33 items subject to
4512B £0.27 74LS Series AD811N £5.50 TL064CN £0.29 6A10 £0.35 2N3704 £0.11 BC557B £0.09 TIP30A £0.47 quantity required,
4515B £0.99 74LS00 £0.22 AD812AN £6.32 TL071CN £0.30 BA157 £0.10 2N3705 £0.08 BC557C £0.11 TIP30C £0.37 phone, fax or
4516B £0.44 74LS01 £0.14 AD817AN £3.19 TL072CN £0.40 BA158 £0.08 2N3771 £1.44 BC558A £0.08 TIP31A £0.28 email for a quote.
4518B £0.26 74LS02 £0.22 AD820AN £3.41 TL074CN £0.37 BA159 £0.13 2N3772 £1.72 BC558B £0.09 TIP31C £0.35
4520B £0.34 74LS03 £0.29 AD822AN £5.20 TL081 £0.28 BAT41 £0.12 2N3773 £2.30 BC559A £0.08 TIP32A £0.29
4521B £0.62 74LS04 £0.22 AD829JN £6.41 TL082CN £0.32 BAT42 £0.10 2N3819 £0.29 BC560A £0.09 TIP32C £0.30
4526B £0.40 74LS05 £0.14 AD830AN £5.44 TL084CN £0.37 BAT46 £0.12 2N3903 £0.11 BC560B £0.08 TIP33C £0.74
4527B £0.40 74LS08 £0.19 AD847JN £5.95 TL7705ACP £0.82 BAT49 £0.27 2N3904 £0.05 BC636 £0.10 TIP41A £0.32
4528B £0.40 74LS09 £0.15 AD9696KN £7.73 TLC271 £0.63 BAT85 £0.08 2N3905 £0.10 BC637 £0.19 TIP41C £0.32
4529B £0.44 74LS10 £0.27 ADEL2020A £5.06 TS272CN £0.57 BAV21 £0.07
74LS11 £0.17 TS274CN £0.50 BAW62 £0.07 We carry a large range of capacitors in stock, including:
4532B £0.24 ADM222AH £3.55 Ceramic Mini Disc, Dipped Ceramic Multilayer, Dipped & Boxed Polyester,
4536B £1.00 74LS12 £0.25 ADM232AA £3.55 TS555CN £0.40 BAX16 £0.05
74LS14 £0.33 ADM485JN £2.97 TMP01FP £5.60 BY127 £0.18 Mylar Film, Polystyrene, Plastic Film, MKT Polyester, Tantalum Bead, Sub-min-
4538B £0.40 BY133 £0.10 iature Radial, 105°C Radial, Low Leakage Radial, Non Polarised Radial & Ax-
4541B £0.33 74LS15 £0.24 ADM666AN £2.72 UA741CN £0.19
74LS20 £0.27 ADM690AN £5.13 ULN2003A £0.38 OA47 £0.70 ial, PCB Can Electrolytics, Polypropylene & Ceramic Trimmers and Tuning
4543B £0.47 OA90 £0.33 capacitors. Full technical details available.
4555B £0.32 74LS21 £0.20 ADM691AN £6.48 ULN2004A £0.44 per 100 of one
4556B £0.40 74LS26 £0.17 ADM695AN £6.48 ULN2803A £0.42 OA91 £0.32 Resistors - Please State Value Required value only
4584B £0.27 74LS27 £0.25 ADM699AN £3.58 ULN2804A £0.44 OA200 £0.56 1/8W Carbon Film 5% E12 Series 10W-1M0 £0.02 Each, £0.80 per 100
4585B £0.47 74LS30 £0.20 CA3046 £0.65 EPROM’s UF4001 £0.08 ¼W Carbon Film 5% E12 Series 1W-10M £0.02 Each, £0.60 per 100
4724B £0.94 74LS32 £0.23 CA3130E £0.87 24LC08BP £0.73 UF4002 £0.08 ¼W Metal Film 1% E24 Series 10W-1M £0.04 Each, £1.72 per 100
40106B £0.19 74LS37 £0.31 CA3140E £0.63 24LC16BP £0.69 UF4003 £0.09 ½W Carbon Film 5% E12 Series 1W-10M £0.02 Each, £0.95 per 100
40109B £0.58 74LS38 £0.18 CA3240E £0.91 24LC32AP £1.14 UF4004 £0.08 2.5W Wirewound 5% E12 Series 0W1-220W £0.23 Each
40174B £0.46 74LS40 £0.14 DG211CJ £1.25 27128-200 £3.99 UF4005 £0.10 1W, 2W, 5W, 20W, 25W & 50W also in stock - selected values only, contact sales dept.
40175B £0.41 74LS42 £0.42 DG411DJ £2.00 27256-200 £3.99 UF4006 £0.10
Preset Resistors - Please State Value Required
74LS47 £0.50 ICL7106CPL £2.21 27C64A-15F £2.80 UF4007 £0.14
Enclosed, 10mm Square Horz / Vert. 100W - 1M0 0.15W £0.12 Each
74HC Series 74LS51 £0.24 ICL7107CPL £2.06 Zeners 2.7 to 33V
Skeleton, 10mm Dia. Horizontal. 100W - 1M0 0.1W £0.09 Each
74HC00 £0.16 27C256B-15F£2.60 500mW £0.06
Sub-min, 6mm Dia, Horizontal E3 200W-1M0 0.1W £0.12 Each
74LS73 £0.36 ICL7109CLP £5.76 27C512-15F1 £2.81
74HC02 £0.14 74LS74 £0.18 ICL7611DCP £1.00 1.3W £0.10
Multiturn, 10mm Square, Top Adjust. E3 100W-1M0 0.5W £0.81 Each
74HC03 £0.21 27C1001-15. £3.17 Multiturn, 19mm Long, End Adjust. E3 50W-1M0 0.5W £0.59 Each
74LS75 £0.30 ICL7621 £0.84 27C2001-15. £4.41
74HC04 £0.16 74LS83 £0.38 ICL7660SCP £0.80 27C4001-120£5.84
Potentiometers - Please State Value Required
74HC08 £0.16 74LS85 £0.48 ICM7555 £0.41 93C46N New Catalogue Single Gang ¼” Shaft, 25mm Dia.
£0.33 470W-2M2 Linear £0.56 Each
74HC10 £0.21 74LS86 £0.25 ICM7556 £0.88 Out Now Single Gang ¼” Shaft, 25mm Dia. 4k7,10k,47k,100k,1M,2M2 Log £0.56 Each
74HC11 £0.21 74LS90 £0.42 L165V £2.36 RAM Free with all orders Dual Gang¼” Shaft, 20mm Dia. 1k0-2M2 Linear £1.54 Each
74HC14 £0.18 74LS92 £0.45 L272M £1.21 GM76C88. £3.60 or via the internet. Dual Gang¼” Shaft, 20mm Dia.
Switched ¼” Shaft, 20mm Dia.
10k-470k Logarithmic
1k0-2M2 Linear
£1.54
£1.92
Each
Each
74HC20 £0.28 74LS93 £0.58 L293E £4.20
74HC27 £0.16 74LS107 £0.30 L297 £5.12 & Switched ¼” Shaft, 20mm Dia. 4k7-2M2 Logarithmic £1.92 Each
T e s t i o n PCB Mount, Splined Shaft, 16mm Dia. 470W-1M0 Linear £0.48 Each
Newment Sect
74HC30 £0.22 74LS109 £0.21 L298N £6.67
74HC32 £0.18 74LS112 £0.24 L4960 £2.81 PCB Mount, Splined Shaft, 16mm Dia. 470W,4k7,100k,1M0 Log £0.56 Each
74HC42 £0.36 74LS113 £0.23 s ur e Dual PCB, Splined Shaft, 16mm Dia. 10k,50k100k,500k Lin £1.05 Each
Mea
L6219 £4.48
74HC73 £0.40 74LS114 £0.36 LF347N £0.46 Dual PCB, Splined Shaft, 16mm Dia. 10k,50k,100k,500k Log £1.00 Each

Tel: 0191 2514363 Fax: 0191 2522296 Email: sales@esr.co.uk http: //www.esr.co.uk
 Editorial Offices:
EVERYDAY PRACTICAL ELECTRONICS EDITORIAL
Wimborne Publishing Ltd., 408 Wimborne Road East, Ferndown,
Dorset BH22 9ND
Phone: (01202) 873872. Fax: (01202) 874562.
Email: enquiries@epemag.wimborne.co.uk
Web Site: www.epemag.co.uk
EPE Online (downloadable version of EPE): www.epemag.com
EPE Online Shop: www.epemag.wimborne.co.uk/shopdoor.htm
See notes on Readers’Technical Enquiries below – we regret
lengthy technical enquiries cannot be answered over the tele-
phone.
Advertisement Offices:
EVERYDAY PRACTICAL ELECTRONICS ADVERTISEMENTS
VOL. 34 No. 8 AUGUST 2005 408 Wimborne Road East, Ferndown, Dorset BH22 9ND
Phone: 01202 873872 Fax: 01202 874562
Email: stewart.kearn@wimborne.co.uk

Editor: MIKE KENWARD

We’re At It Again Deputy Editor: DAVID BARRINGTON
Dosen’t seem like nearly two years ago does it? What am I referring to? Our next Teach-In Technical Editor: JOHN BECKER
course – Teach-In ’06 – starts in the November issue. As regular readers will know we run a Business Manager: DAVID J. LEAVER
different Teach-In series every other year; they generally run for nine or ten months and the last Subscriptions: MARILYN GOLDBERG
one ran from November ’03 through to August ’04. General Manager: FAY KEARN
Teach-In ’06 is being written by Mike Tooley BA who has been responsible for many books Editorial/Admin: (01202) 873872
and articles on electronics and who has over 30 years experience teaching electronics at all Advertising Manager:
levels from GCSE through to degree level. Mike has also been a regular contributor to EPE over STEWART KEARN (01202) 873872
the past 25 years. The new series is primarily aimed at GCSE (Level 2) standard but with some On-Line Editor: ALAN WINSTANLEY
subjects (e.g. microprocessors and PICs) developed to Level 3. So if you know of someone who EPE Online (Internet version) Editors:
will be starting GCSE soon, or someone who simply wants to learn about electronics, or brush up CLIVE (MAX) MAXFIELD and ALVIN BROWN
on their knowledge, please make sure they are aware of this new series. The November issue will
be published on October 13 – less than three months away now. READERS’ TECHNICAL ENQUIRIES
The course will culminate in a multiple choice on-line test which will test readers’ knowledge E-mail: techdept@epemag.wimborne.co.uk
and cover the whole series. A printed certificate will be awarded to those who gain a “pass” mark. We are unable to offer any advice on the use,
Very shortly we will be circulating advertisers with a list of parts used for the practical aspects purchase, repair or modification of commercial
equipment or the incorporation or modification
of the series and we expect a number of them to make kits available to ease the way for new- of designs published in the magazine. We
comers to get into electronics. We will also be leafletting all UK schools with information and regret that we cannot provide data or answer
special student/teacher offers so please watch out for that in September if you are in education or queries on articles or projects that are more
are teaching electronics. than five years old. Letters requiring a personal
Our aim is to encourage more people into our fascinating hobby both in the UK and around the reply must be accompanied by a stamped
world. self-addressed envelope or a self-
addressed envelope and international reply
Further Development coupons.
The Speed Camera Watch project we published back in the January ’05 issue led to some crit-
PROJECTS AND CIRCUITS
icism from readers about us encouraging people to speed – which was never our intention. The All reasonable precautions are taken to ensure
correspondence was published in Readout in the February to April issues. A number of readers that the advice and data given to readers is
also made suggestions about possible additions to the project and our contributor Mike Hibbet is reliable. We cannot, however, guarantee it and
now working on a Mark 2 version which will also provide warnings if you are exceeding the we cannot accept legal responsibility for it.
speed limit at any time, plus a number of other additions/improvements like heading in degrees, A number of projects and circuits published in
altitude, current position etc. EPE employ voltages than can be lethal. You
We expect to be able to publish the new version in the November issue. Don’t miss it, to make should not build, test, modify or renovate
sure of your copy every month please any item of mains powered equipment
unless you fully understand the safety
place a regular order with your aspects involved and you use an RCD
newsagent – see page 547 or take out a adaptor.
subscription and save on the cover price
– see page 572. COMPONENT SUPPLIES
We do not supply electronic components or
kits for building the projects featured, these
AVAILABILITY SUBSCRIPTIONS can be supplied by advertisers (see Shoptalk).
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Everyday Practical Electronics, August 2005 531

Constructional Project

Audio System –
Communications
Raymond Haigh

A preamplifier with automatic gain control (a.g.c.) and a power amplifier with
switched audio filtering for communications receivers and surveillance systems

W
ITH a preamplfier designed shown in Fig.1. Transistors TR1 and TR3 drain-source resistance rises and gain is
around discrete components this form a directly coupled audio amplifier. reduced. If the control voltage is high
project should overcome the Direct current negative feedback, via enough, for instance, under strong signal
problem of specialist i.c.s disappearing resistor R2, sets the working points of the conditions, the f.e.t.’s resistance increas-
from the hobbyist market that has dogged transistors. Signal frequency negative es to several thousand ohms, and gain
previous projects published over the years. feedback, via preset VR2, sets the gain. falls to single figures.
Using widely available transistors, the
design featured here is sensitive enough to Gain Control Control Voltage
permit the direct connection of dynamic Field effect transistor (f.e.t.) TR2 is con- Field effect transistor characteristics
microphones, effective in compressing the nected as a voltage controlled resistor (in vary widely, but most display greatest
dynamic range, and has low noise and dis- place of a conventional resistor) between resistance change over a control voltage
tortion levels. the emitter (e) of TR1 and the 0V rail. The swing of around –1.5V (low resistance) to
Also included is a single i.c. relationship between the f.e.t.’s drain- –2V (high resistance). Our two-transistor
(TBA820M) audio amplifier with switched source resistance and feedback preset VR2 preamplifier (Fig.1.) with its 9V supply
filtering. Teamed with the Preamplifier, the determines the gain of the circuit. cannot deliver an output of this magnitude
two circuits will considerably improve the Increasing the resistance presented by the without severe distortion, so transistor TR4
performance of simple communications f.e.t. reduces the gain. further amplifies the signal in order to pro-
receivers and, when used with electret In the absence of a control voltage, for vide an adequate control voltage.
microphones, will ensure good perform- example, under weak signal conditions, The gain of TR4 is set between around
ance for surveillance purposes. the f.e.t.’s drain-source channel has a 10 and 100 times by varying the applica-
resistance of around 400 ohms and the tion of negative feedback via its emitter.
Preamplifier Circuit gain of the circuit is about 250 times. Bypass capacitor C10 is connected to the
The full circuit diagram of the automat- When a negative-going control voltage slider (moving contact) of preset VR3,
ic gain controlled (a.g.c.) preamplifier is is applied to the gate (g) of TR2, its which acts as TR4’s emitter resistor.
As the slider is moved towards the 0V
rail, more of the emitter resistor becomes
un-bypassed, negative feedback increases,
the gain of the stage is reduced, and the
magnitude of the control voltage, for a
given signal input, falls. By this means, the
amount of signal compression can be set to
suit individual requirements.

On the Double
The voltage doubling rectifier system
formed by diodes D1 and D2 makes the
most of the signal delivered by transistor
TR4. With this arrangement, the charge
developed across capacitor C12, during
one half-cycle, is added to the rectified
voltage delivered during the next, and the
output at the anode (a) of D2 approaches
twice the peak value of the signal voltage.
The control voltage must be negative
going with respect to the 0V rail (to suit the
n-channel f.e.t.), and the diodes, signal
strength meter and capacitor C5 are con-
nected accordingly.

On the Attack
Reservoir capacitor C5, and the resist-
ance presented by the signal strength meter
circuit, have a time-constant that deter-
Line-up of circuit boards that combine to make this simple audio system. Small board, mines the speed with which the system
electret mic power supply; power amplifier (top) and (foreground) the preamplifier responds to changes in signal level. It

532 Everyday Practical Electronics, August 2005

should be as rapid as possible, but too short Accordingly, response
a time constant (resulting from a low value rolls off below about
At the hear
BASICS
of capacitance or resistance) will produce a 300Hz, and is about a voltage or t of all audio compresso
noticeable “breathing” or “pumping” 18dB down at 50Hz. The control current controlled sign r amplifiers is
sound as the system goes in and out of This reduces the output from voltage is obtained by al attenuator.
action during passages of speech. low frequency rum- increase, so the amplifier. As the rectifying the
do ou
A compromise has to be struck, and the ble that can be intro- uator, and th es the voltage fed ba tput tries to
ck
value quoted for C5 will be found suitable duced by micro- input is redu e rise in output for a gi to the atten-
ce
for most applications. Reducing it below phones in some nal is compr d, i.e., the dynamic ra ven change in
esse nge of the si
4·7µF will result in severe distortion, while environments. Junction field d. g-
values above 100µF or so will make the Alternative compo- as voltage effect transi
controlled re stors (f.e.t.s) can be us
attack too slow. nent values are list- of drain-so sistors. At ve ed
ur
ed (see Fig.1) to potential ch ce voltage, varying th ry low values
an
Noise Limiting assist readers who channel from ges the resistance of th e gate-source
require an extend- ohms. This ph a few hundred to se e drain-source
Care has to be taken when amplifying ve
ed low-frequency reduction sy enomenon is exploited ral thousand
low-level signals to minimize the introduc- stems and in Dolby no
response. More is alte ring the dynamic in m os t modern ci ise
tion of additional noise. The noise generat- rc
said about reduc- Th e f.e.t. can be ra ng e of audio signal uits for
ed by a bipolar transistor can be reduced by potential di connected as s.
ing audio band- vi on
operating it at a low collector current, typ- used to va der in the signal path e half of a
width in order to ry gain-red ,
ically between 10µA and 50µA. This tech- applied acro ucing nega or it can be
tiv
nique is adopted here, where feedback and improve clarity method adopss the controlled amplifi e feedback
ted in the ci er
biasing resistors R2 and R4 and the collec- later. rcuit describe . This is the
Preset poten- d here.
tor load resistor R1 fix the current through
TR1 at about 40µA. tiometer VR2 is
Many readers will be familiar with this the amplifier’s
arrangement which, until the widespread gain-setting sig-
introduction of integrated circuits, formed nal feedback
“resistor”. Its slider (moving contact) is The function of most of the components
the basis of most high-fidelity preampli- has now been covered. All that remain are
connected to bypass capacitor C6. Moving
fiers for use with low-output tape heads, TR3’s collector (c) load resistor R3, d.c.
the slider towards the emitter (e) of TR1
microphones and turntable pick-ups. increasingly bypasses the resistor at high blocking capacitors C7, C8 and C9, and
Indeed, the only novel element is the addi- frequencies, and the additional negative TR4’s base (b) bias resistor R6 and collec-
tion of the automatic gain control system. feedback further reduces gain in this region tor load resistor R8.
Input impedance, at the base (b) of TR1, of the audio spectrum. This measure great- Bypass capacitor C4 across TR3’s emit-
is around 50 kilohms, but the optimum sig- ly reduces the “hiss” introduced by the ter resistor, R4, has been given a low value
nal source impedance, for minimum noise, amplifier at high gain settings. in order to produce negative feedback at
is between 5 kilohms and 10 kilohms. This low frequencies and help with rolling off
has influenced the value of input poten- the response below 300Hz.
tiometer VR1. Supply Decoupling
The Preamplifier is decoupled from the
Frequency Response supply rail by resistor R5 and capacitor Signal Strength Meter
The frequency response of the basic circuit C3, the latter having a high value in order Some readers may wish to install a
is flat over the audio spectrum, but the values to ensure stability, particularly when the Signal Strength Meter (ME1), and preset
of d.c. blocking capacitors C1 and C2, at the unit shares a common battery supply with potentiometer VR4 acts as a series resist-
input, C8, at the output, and bypass capacitor a power amplifier. The control voltage ance so that a 50µA instrument can be
C4, have been kept small in order to attenu- amplifier, transistor TR4, is decoupled by used to measure the voltage across the
ate the lowest audio frequencies. resistor R7 and capacitor C11. a.g.c. line. Full-scale deflection is set by

Fig.1. Complete circuit diagram for the audio Preamplifier, with variable compression. The signal strength meter ME1 is
optional – see text

Everyday Practical Electronics, August 2005 533

 as shown in Fig.2 and Fig.9. If it is con-

COMPONENTS
Approx. Cost
Guidance Only £11 nected to a mains power supply, locate the
mains transformer and the mains wiring as
excl meter & far away as possible from the input cir-
batts cuitry.
PREAMPLIFIER C10 47µ radial elect. 16V
C11 470µ radial elect. 16V
Testing
Resistors On completion, check the board for poor
R1,R2 220k (2 off ) soldered joints or bridged copper tracks,
See Semiconductors and check the placement of components and
R3 6k8 SHOP D1,D2 1N4148 signal diode (2 off)
R4 560Ω the orientation of electrolytic capacitors and
TALK TR1,TR3, BC549C npn semiconductors.
R5,R7 100Ω (2 off ) page TR4 transistor (3 off)
R6 1M TR2 2N3819 n-channel field
R8 4k7 effect transistor
All 0·25W 5% carbon film
Miscellaneous
Potentiometers ME1 50µA moving coil panel
VR1 10k enclosed carbon meter (optional – see text)
preset
VR2,VR4 100k enclosed carbon Printed circuit board avail-
preset (2 off) able from the EPE PCB
VR3 470Ω enclosed carbon Service, code 516
preset (Preamp); screened
audio cable; mul-
Capacitors tistrand connect-
C1,C8 220n polyester (2 off) ing wire; nuts,
C2 47n polyester bolts and p.c.b.
C3 1000µ radial elect. 16V stand-offs; solder
C4,C5 10µ radial elect. 16V (2 off) pins; solder etc.
C6 10n polyester or ceramic
C7,C9, 4µ7 radial elect. 16V (3 off)
C12

adjusting VR4 when a very strong signal µ

is being processed.
A less sensitive 100µA meter can be fit-
ted at a pinch, but a higher current instru-
ment will load the output from the diode
voltage doubler excessively and reduce the
control voltage available at the gate (g) of
TR2. Most of the inexpensive units retailed
as signal strength meters have full-scale
deflections of 250µA or more, and are not
suitable for use in this circuit.
The time constant of the a.g.c. network is
affected by the setting of preset VR4, and it
may be necessary to increase the value of
capacitor C5 to 22µF if a 100µA meter is
fitted.
If a signal strength meter is not required,
set VR4 to maximum resistance and wire a
link across the meter output pins. Failure
to do this will remove the discharge path
from C5 and the a.g.c. circuit will not
function.

Construction
All the components for the
Preamplifier, except the optional signal
strength meter, are assembled on a single
printed circuit board (p.c.b.). The topside
component layout and full-size underside
copper foil master pattern are shown in
Fig.2. This board is available from the
EPE PCB Service, code 516.
Solder pins, inserted at the lead-out
points, will simplify the off-board wiring,
and they should be inserted first. Follow
these with the resistors and then the capac-
itors, beginning with the smallest. The
semiconductors should be mounted last,
516
and it is good practice to attach a miniature
crocodile clip to the leads of the f.e.t. (TR2)
to act as a heat shunt whilst soldering.
Do not rely on signal cable screening
Fig.2. Printed circuit board component layout, wiring details and full-size copper foil
braid to connect the 0V power rail to the
master pattern for the Preamplifier. A photograph of the completed circuit board is
Preamplifier. Make a separate connection,
shown above

534 Everyday Practical Electronics, August 2005

 If all is in order, set preset pots VR1,
VR2, VR3 and VR4 at minimum (fully
anti-clockwise) and bridge the output pins
to the signal strength meter if this facility
is not being used. Note that a digital test
meter cannot be connected in place of the
moving coil signal strength meter: its input
resistance is likely to be too high. A digital
meter can, however, be connected across
VR4 to check the control voltage.
Using screened cable, connect the
Preamplifier input to a suitable signal
source, and its output to an audio power
amplifier and speaker. Connect a well-
smoothed mains power unit or a fresh 9V
battery to the board. Current consumption
should be approximately 2mA.
With the input Sensitivity control, VR1,
set to deliver a signal large enough to acti-
vate the a.g.c. system, rotate Compression
control VR3 clockwise. The output from
the amplifier should reduce quite dramati-
cally if the input level has been set high.
Clockwise rotation of H.F. Response
preset VR2 will reduce the high frequency Fig.3. Waveform plot of the input/output voltages, at two settings of compression
response of the unit and have a noticeable control VR3, of the automatic gain control (a.g.c.) Preamplifier
effect on noise levels at high gain settings.
If a Signal Strength Meter is connected,
The input control, VR1, will have to be
clockwise rotation of preset VR4 will move
set almost at zero when the Preamplifier is
the needle pointer clockwise when the
connected to the detector in a superhet
a.g.c. system is operating, and full-scale
receiver, and an additional attenuator,
deflection can be set under strongest signal
between receiver and preamp, may prove
conditions.
helpful.
The settings of the various preset poten-
tiometers should, of course, be refined to
optimize performance when the unit is Microphones
brought into use. Very high quality studio microphones
can be insensitive, and they often require a
balanced input to minimize hum pick-up.
Performance They are not suitable for use with the pre-
A plot of the signal input and output at
amplifier described here.
two settings of the Compression control,
Screened cable must be used to connect
VR3, is given in Fig.3.
any microphone to the preamplifier, and
With the control set for maximum Fig.4. Circuit diagram for powering an
the various types are described, very
compression (curve B), signals up to electret microphone
briefly, below.
0·08mV peak-to-peak (0·03mV r.m.s.)
are amplified about 250 times. Above
this level, the gain of the preamplifier is Dynamic (Moving Coil)
progressively reduced and the dynamic Dynamic microphones can be connected
range of the signal compressed. directly to the input of the Preamplifier.
With inputs in excess of 0·5mV peak-to- Manufactured with impedances ranging
peak (0·17mV r.m.s.) the control voltage
moves into the region where f.e.t. TR2’s
from 50 ohms to 600 ohms, the units with
the highest impedance tend to give the COMPONENTS
resistance change is most pronounced and greatest output, and are best for use with
the output is held at between 30mV and this amplifying system.
35mV peak-to-peak (10mV r.m.s.) over the ELECTRET MIC. POWER BOARD
normal input range of the preamp. Electret
Turning back Compression preset VR3 Electret microphones are a modern Resistors See
(curve A) raises the compression threshold development of the capacitor microphone. R1 1k SHOP
and increases the output from the preamp. They contain a permanently charged plate, R2 10k TALK
the electret, which eliminates the need for All 0·25W 5% carbon film page
Sensitivity an external charging voltage. Basic output
Although the above figures define the is very low, but the units incorporate a field Capacitors
sensitivity of the unit, they are not neces- effect transistor (f.e.t.) to amplify the signal C1 100µ radial elect. 16V
sarily a clear guide to suitable signal to a useable level.
sources, and the following notes may prove A power supply is required for the f.e.t., Miscellaneous
useful. and some electret units have a battery com- MIC1 min. electret mic insert
Normal (low cost) dynamic microphones partment in the handle. Remote powering is
will usually deliver a more than adequate to be preferred, especially when the micro- Printed circuit board available from
signal, and electret microphones, with their phones are used for surveillance purposes, the EPE PCB Service, code 517
larger output, will ensure good perform- and a suitable circuit is given in Fig.4. (Elec.Mic); screened audio cable;
ance when the unit is used for surveillance Remote powering, via the signal cable, multistrand connecting wire; solder
purposes. is made possible by locating the micro- pins; nuts, bolts and p.c.b. stand-offs;
The output from the detector in a regen- phone amplifier’s load resistor, R1, at the solder etc.
erative receiver will fully load the preamplifier end of the line. The supply
Preamplifier, as should the output from an voltage is dropped by R2, and this resis-
active detector in a direct conversion
receiver. Passive product detectors in direct
tor, together with capacitor C1, decou-
ples the microphone from the power sup-
Approx. Cost
Guidance Only £7
ply. Approximately 4·5V is maintained excl meter &
conversion sets may require additional
across the microphone amplifier and its batts
amplification ahead of the preamp.

Everyday Practical Electronics, August 2005 535

 517
load, R1, and this is in accordance with
the recommendations of most electret
manufacturers.
If the circuit is used with other ampli-
fiers, the value of resistor R2 must be
adjusted to suit the supply voltage. A d.c.
blocking capacitor should also be provided Fig.5. Printed circuit board layout, copper foil master and wiring to the Electret
in the output lead; shown dashed in the cir- Mic. board
cuit diagram.

Circuit Board connection. Remember to insert a wire link The impedance of both types is high, typi-
A small printed circuit board (p.c.b.) for on the p.c.b. if the blocking capacitor is not cally between one million and five million
remote powering of electret microphone fitted in the output circuit. ohms, and the output can approach 50mV.
inserts from the Preamplifier board is Connecting these units directly to the
shown in Fig.5. This board is available Crystal and Ceramic Preamplifier will impair their low frequency
from the EPE PCB Service,code 517. Crystal and ceramic microphones rely response (which might not be a bad thing),
The connections to the electret micro- on the piezoelectric effect to convert the and performance may be improved by con-
phone board align with the connections on movement of a diaphragm into electrical necting them via a series resistor of 100 kilo-
the Preamplifier board, and the units should impulses. Rochelle salt is generally used hms (100kΩ), or even 220 kilohms (220kΩ).
be mounted as close together as possible. for crystal microphones, and lead zirco- The audio quality delivered by these
If, for some reason, the boards have to be nium titanate compounds for ceramic microphones is inferior to that of electret
parted, use screened cable for the signal units. and dynamic types.

Power Amplifier
T
HE clarity of speech signals can be response of the amplifier. Negative feedback Switch S1b connects capacitors of dif-
greatly improved by reducing the from the output at pin five is connected to ferent value, C5 and C6, into circuit in
response of the audio system to fre- pin one via a switched capacitor. The larger order to produce different levels of high
quencies below 300Hz and above 3000Hz. the value of the capacitor, the greater the frequency attenuation. Note that the low-
This practice is adopted by telephone com- negative feedback, and the greater the est value capacitor, C7, is permanently
panies world-wide. reduction in the high frequency response of connected in order to ensure stability.
Fairly complex active filters are com- the amplifier.
monly used to tailor the frequency response
in this way, but simpler measures can pro-
duce very acceptable results. An arrange-
ment of this kind has been adopted for the
Power Amplifier circuit, designed around a
TBA820M audio power amplifier i.c.,
depicted in Fig.6.

Feedback
The TBA820M i.c. (IC1) has two acces-
sible feedback networks. The first, brought
out at IC1 pin 2, uses resistor R1, connect-
ed to the 0V rail via a capacitor, to control
the gain. The lower the value of the resis-
tor, the greater the gain.
Reducing the value of the blocking
capacitor progressively increases feedback,
and reduces gain, as frequency is lowered.
Switch S1a connects capacitors of different
value, C1, C2 and C3, into circuit in order
to produce the different levels of low-fre-
quency attenuation.
The second feedback network, brought
out at IC1 pin 1, controls the high frequency

536 Everyday Practical Electronics, August 2005

Reactance
The above measures, by themselves,
COMPONENTS
Approx. Cost
Guidance Only £14
have a very noticeable effect on the fre- excl speaker, batts &
quency response of the amplifier. Roll-off extras
at the low and high frequency ends of the
spectrum is not, however, very steep, and
further measures need to be taken to POWER AMPLIFIER Miscellaneous
increase the rate of attenuation. Resistors L1 1·5mH inductor coil –
By placing a capacitor or inductor in R1 22Ω see text. Ferrite rod,
series with the loudspeaker or phones, its R2 56Ω See 9mm (3/8in) dia. ×
reactance (frequency dependant resistance) R3 1Ω SHOP 102mm (4in) long. 50g
can be used in a more direct way to modify R4 3k9 TALK (2oz) reel of 22s.w.g.
the response of the system. All 0·25W 5% carbon film page (21a.w.g.) enamelled
Output pin 5 is held at half the supply copper wire
voltage, and the speaker, LS1, has to be Potentiometers S1 4-pole 3-way rotary
connected via a d.c. blocking capacitor. VR1 10k rotary carbon, log. switch
Switch S1c selects capacitors of different S2 s.p.s.t. toggle switch
value, C10, C11 and C12. The smaller the Capacitors SK1 6·35mm (1/4in.) stereo
value of the capacitor, the greater its reac- C1,C8 100µ radial elect. jack socket, with
tance at low frequencies, and the more the 16V (2 off) switched contacts
low frequency output to the speaker is C2 22µ radial elect. 16V LS1 8 ohm loudspeaker
attenuated. C3,C10 10µ radial elect. (see text)
Conversely, the reactance of inductors 16V (2 off) B1 9V battery pack (6 × AA),
increases as frequency increases. Switch C4,C11 47µ radial elect. with holder
S1d connects different inductance values in 16V (2 off)
series with loudspeaker LS1 in order to C5 680p ceramic Printed circuit board available from
modify the high frequency response. C6 220p ceramic the EPE PCB Service, code 518;
The full winding of L1 has an inductance C7 68p ceramic 8-pin d.i.l. socket; l.e.d. holder; 3-core
of 1·5mH. An inductor of this value pres- C9 220n polyester screened audio cable; 4-core
ents a reactance of almost 48 ohms at C12 220µ radial elect. 16V screened audio cable; multistrand
5kHz. Placing it in series with an 8 ohm C13 100n ceramic connecting wire; nuts, bolts and p.c.b.
speaker will, therefore, produce an attenua- C14 470µ radial elect. 16V stand-offs; solder pins; solder etc.
tion of 8dB at 5kHz. Note: If the preamp and amplifier
Centre tapping L1 produces an induc- Semiconductors are assembled as a single stand-alone
tance of around 0·5mH. Connecting this D1 2mA low current red l.e.d. unit, a metal or plastic case, phono
into circuit gives a reduced level of high IC1 TBA820M audio power sockets, and speaker terminals, will be
frequency attenuation. amp i.c. required.

Fig.6. Full circuit diagram for the audio Power Amplifier with switched high and low frequency attenuation

Everyday Practical Electronics, August 2005 537

Response
Combining these measures produces the
frequency response curves displayed in
Fig.7. Because of the simplicity of the
arrangement, response is humped rather
than flat over the speech frequency range.
However, the 12dB per octave roll-off
beyond the band limits greatly improves
the clarity of signals overlaid by noise.
The first level of processing, curve B, is
usually all that is required. Background
rumble is eliminated from microphone sig-
nals, and the muffled, bass-heavy response
of a critically adjusted regenerative receiver
is corrected.
When high gain settings have to be used
to make very weak signals audible, heavy
processing, as depicted in curve C, may
prove helpful. Reproduction is very “thin”
in this mode, but voices are still clearly rec-
ognizable and readers involved in surveil-
lance, as well those interested in radio
reception, should find it useful.

Amplifier Fig.7. Frequency response plots of the audio Power Amplifier, with and without
Turning now to the actual Power Amplifier signal processing
circuit Fig.6, potentiometer VR1 acts as the
Volume control and resistor R1 pre-sets the way round as
gain of the circuit. The d.c. blocking capaci- shown. Use an 8-pin
tor for the input is located on the Preamplifier d.i.l. socket for IC1,
board. If the Power Amplifier is used with but do not insert the
other equipment, fit a 2·2µF electrolytic d.c. i.c. until the assem-
blocking capacitor in series with the input bly has been com-
(negative plate to the top-end of VR1). pleted and checked
Supply line ripple is rejected by capaci- for accuracy.
tor C4 and resistor R3 and capacitor C9 Using a holder
form a Zobel network that protects the for the i.c. will make
internal output transistors from damage by substitution and
high level transients. Stability at high and checking easier, and
low frequencies is ensured by bypass the socket should be
capacitors, C13 and C14. located on the board
Although quite rugged, the TBA820M first. Solder pins
chip does not contain overload protection should now be
circuitry. Care should, therefore, be taken inserted at the lead- Fig.8. Construction and winding details for inductor coil L1
to avoid shorting the speaker leads, and the out points, followed
maximum supply voltage (12V with an 8 by the resistors and
ohm speaker; 9V with a 4 ohm unit) should then the capacitors, smallest first. The induc- Provision is not made on the printed cir-
not be exceeded. tor coil L1 can be stuck in position with cuit board for the l.e.d. indicator D1 and its
cyanoacrylate adhesive (Superglue). dropping resistor R4. These components
Inductor Coil Remember to insert a wire link at the input form part of the off-board wiring (see
Details of the inductor (L1), which is if a d.c. blocking capacitor is not fitted. Fig.9).
wound on two short lengths of ferrite aerial
rod, are given in Fig.8. The wire gauge is not
critical, but it ought not to be smaller than
26s.w.g. (25a.w.g.). The author’s inductor was
wound with 22s.w.g. enamelled copper wire.
Use masking tape to bind the rods
together and to hold individual layers of the
winding in place. The rod can be cut by fil-
ing a deep groove around its circumference
before snapping it.
Only half of the coil is in circuit when
S1d is in mid-position. This should be the
two layers of the winding closest to the fer-
rite rods, and the correct conections are
shown in Fig.6 and Fig.9 (the inductances
of the two halves of the centre-tapped
winding are not equal).

Construction
The topside printed circuit board compo-
nent layout, interwiring details and full-
size underside copper foil master for the
Power Amplifier are shown in Fig.9. This
board is also available from the EPE PCB
Service,code 518 (Power Amp).
Assemble the board in the usual order of
ascending component size, ensuring that the Power Amplifier circuit board wired to the 4-pole 3-way attenuator/filter switch
electrolytic capacitors are inserted the correct using screened cables

538 Everyday Practical Electronics, August 2005

 Ω

518

Fig.9. Printed circuit board full-size underside copper foil master and off-board
Switch Wiring wiring details for the Power Amplifier. The screened leads between the p.c.b. and
In the prototype unit, four-core screened S1a to S1d must not be longer than 152mm (6in). Note the separate 0V lead to the
cable is used to connect switch-ways A, B Preamplifier board. The completed board is shown above right
and C to the board. Screening may not be
necessary (unscreened leads were not
tried), but it does make the wiring neater If all is in order, connect Volume con-
trol VR1, an 8 ohm speaker and a 9V
Speakers
and easier to follow. If very small size is not important, use a
Keep the switch wiring away from the battery or power supply to the p.c.b. 100mm (4in) or 150mm (6in) diameter
input pins, and twist the speaker leads to Current consumption, without the l.e.d. speaker. Larger units produce a bigger out-
minimize radiated fields. indicator, should be approximately put for a given electrical input, and repro-
5mA. duction is usually clearer. Speakers with a
Testing Connect a signal source and operate the high power rating can be insensitive and
As before, check the board for poor sol- filter switch. The progressive reduction in are best avoided for this purpose.
dered joints and bridged copper tracks, and bandwidth should be very evident. Enclosure venting should be equal to the
check the placement and orientation of Details of amplifier sensitivity are given effective cone area or the sound quality will
components. inset at the top of Fig.6. be muffled and “boxy”. អ

Everyday Practical Electronics, August 2005 539

 TECHNO-TALK MARK NELSON
SHORTENING THE WAIT
Will that bus ever come? Yes, maybe sooner rather than later as
new technology is brought into service, as Mark Nelson reveals

T
HERE are few acts of human faith the next three buses to arrive along with a extra buses or delay one vehicle if buses
greater than waiting for a bus. countdown of the number of minutes until become bunched together.
Fortunately new technology is reduc- expected arrival. London is implementing its own satellite
ing the uncertainty of this boring activity and Making this possible is a GPS satellite tracking system for buses, although currently
along with more accessible and comfortable tracking system, a central computer and a its automatic vehicle location (AVL) scheme
buses is assisting the renaissance of public data delivery mechanism. The tracking sys- relies on 5,000 beacons attached to lamp-
urban transport. The embodiment is new but tem monitors in real time the position of each posts across the metropolis. Bus locations are
the thinking behind it goes back more than vehicle, which the central computer then calculated at least once a minute using
half a century. analyses and uses to estimate the buses’ odometers on vehicle wheels and microwave
But first, a personal observation – it’s arrival times at each stop along the route. signals from the beacons. In turn the beacons
funny how people waiting for a train or bus Put like that it sounds quite straightfor- relay their signal to control systems in 80 bus
start talking sometimes. I shall never forget ward, but how do you get the data to each garages and thence to a central hub in
how a total stranger in London once told me indicator? First-generation systems used Chingford.
that he never consulted a timetable before he modems and telephone lines but these were
travelled, as the chances were he’d have to fearfully expensive. The latest thinking is BESI Before Beacons
run the last five minutes to make sure of mesh radio, which does away with the need London’s new GPS vehicle location sys-
catching his bus or train. By turning up when for high-powered conventional base stations. tem is amazingly the fourth embodiment of
it suited him, he avoided the aggravation of The system instead relies on a large num- the concept. Before the microwave beacon
knowing he had just missed one. ber of “nodes” connected by low-power system mentioned above came the Bus
If only all public transport users were so point-to-point radio links. Each bus stop Electronic Scanning Indicator (BESI for
easily satisfied. They expect frequent services receiver site is also a transmitter and repeats short). Developed in 1959, this is generally
that keep to time and adequate information the signal to other nodes in range. Messages regarded as the world’s first modern bus
when things go awry. And at the prices they are coded and are ignored by all nodes tracking system.
pay these days, perhaps this request is not an except the one identified by the code. The Revolutionary in its day, it involved fitting
unreasonable one. Be that as it may, the tech- fact that messages reach their destination via small reflective panels carrying binary codes
nology of keeping passengers informed is our a series of links is no great disadvantage in to the side of buses. A number of optical scan-
topic this time. this application. ners at traffic hot spots recorded the identities
Far more important is the fact that the of passing buses and transmitted this data to a
Terms of Reference mesh radio approach allows the use of low central point for analysis.
PIS and CIS IT and communications peo- power microwave devices at the nodes, This was not London’s first stab at regu-
ple are sometimes guilty of choosing rather reducing start-up costs and making it feasible lating bus services with electronics, howev-
uninspired acronyms for their creations. Their to provide information over a wider area. er. The first experiment took place as long
chosen term Passenger Information Systems The city of Portsmouth leads the way in ago as 1938. Known as the “electric bus
(PIS) has fortunately fallen into disuse these Britain with this technology and since last inspector”, it involved fitting buses with a
days but its replacement, CIS, is barely an November has equipped its entire fleet of 308 simple inductive transmitter connected to a
improvement. It stands for Customer buses and 37 bus shelters for this advanced 15-turn energiser coil on the roof of the
Information Systems, which always annoys information system. So far the network has vehicles, the signal being detected when the
traditionalists since these people are passen- cost £4.2 million but is already saving money, bus passed under antennas strung across the
gers, not customers. Wags, however, quote with an annual expenditure of £70,000 on roadway.
the old joke, what’s the difference between a phone line charges eliminated. The received impulses were amplified and
passenger and a customer? Answer: a cus- sent by telephone line to London Transport
tomer is a passenger who has paid his fair! Long Wait? headquarters, frequency-coded to indicate the
Producing timely information displays is Knowing that your bus won’t arrive for route of the bus. Here the signal was filtered
not difficult but deploying them at an eco- another ten minutes is not much of a consola- and further amplified so as to print a mark on
nomic cost often is. The airlines and rail- tion, but it does at least allow you to wander a slowly revolving paper chart and indicate
ways have managed this for years but they off to buy a paper or a cup of coffee, assured the exact time a bus passed the way point in
have a relatively small number of airports the bus won’t turn up while your back is question. Charts were changed daily and ana-
and stations to look after, with the added turned. It also eliminates another form of lyzed subsequently to study and trace the
advantage of existing fixed communications doubt, as I recall from when I was a bus con- cause of repeatedly recurring delays.
infrastructures. When it comes to delivering ductor in Canterbury. “You’re late,” Basic as the “electric bus inspector”
comparable information and displaying it at exclaimed a thunder-faced woman as we appears to our eyes, it was portrayed at the
several thousand bus stops in a network the arrived at her stop. But before I could reply time as a marvel of the age, with enthusias-
figures soon add up to telephone numbers, my driver put her right, shouting for all to tic descriptions in Wireless World and the
not helped by much lower average fares to hear: “No we’re not, we’re the next one run- Meccano Magazine. London Transport had
pay for this system. ning five effing minutes early!” great plans for the system and hoped to
Funny perhaps, but leaving ahead of the install pick-up antennas all over central
Meshed Net booked time is very bad business, whereas London, connected by landlines in tube
The solution, so far as we passengers are running late is excusable if the traffic is con- train tunnels. Alas World War Two was only
concerned, is an l.e.d. “next bus” display gested. For this reason large bus systems like just around the corner and these ambitious
installed under the roof of bus waiting shel- London’s have controllers who can turn buses plans had to be abandoned. With luck their
ters. Most of these are three-line affairs, back if their chances of reaching their desti- replacement will be in service seventy
showing the route number and destination of nation are hopeless. They can also draft in years later!

540 Everyday Practical Electronics, August 2005

News . . . A roundup of the latest Everyday
News from the world of
electronics

ANALOGUE TV SWITCH-OFF UPDATE

Barry Fox reports the latest news on the planned switch off
of the UK’s analogue TV transmissions

O FCOM has now decided on what it

sees as the best way to switch off
Britain’s analogue TV, starting in 2008 and
The 2K system was adopted to let the
UK start digital terrestrial TV before 8K
receiver chips were ready. Modern
Intellect, the trade association for the UK
hi-tech industry, says Ofcom's final report
is a “leap forward” to the provision of the
ending by 2012. receivers now have chips that automatical- best, most robust, and future-proof DTV
The three multiplexes used by the public ly work either with 2K or 8K signals. But network possible for the UK.
service broadcasters (BBC, ITV, Channels receivers sold for use with the failed On Says Laurence Harrison, Director of
4 and 5) will all use 64QAM modulation, Digital/ITV Digital service, early IDTVs Consumer Electronics at Intellect: “We
to deliver 24Mbps and six or seven TV and some early Freeview boxes will not welcome Ofcom's decision to adopt a
programme channels. Currently the BBC cope with 8K broadcasts and thus stop 64QAM/8K network (but) it is important
and Freeview use the more robust 16QAM working. The total number of affected sets that capacity is available for HD content on
system, which delivers 18Mbps and thus is around a hundred thousand. the DTT platform as manufacturers are
fewer programme channels. As the risk of The UK did have a single frequency free already producing HD-Ready products in
interference to analogue services disap- for the whole country (UHF channel 35), anticipation of this increased demand and
pears, digital transmitters are able to work but it was given to Channel 5 in 1996 for it is therefore vital that Public Service
at higher powers, so there is less need for a analogue use when C5 started broadcasting Broadcasters have the channel capacity
robust signal. Virtually all receivers auto- in 1997. New single frequencies can be available to broadcast in HD.”
matically switch between 16QAM and unlocked as analogue transmissions end. Intellect also worries about the reaction
64QAM, so no screens will go dark. from consumers who are left with dark
Ofcom also wants the broadcasters to Government Deliberating screens by the 8K switch. Intellect's fear is
switch from 2K Coded Orthogonal The Department of Culture Media and that manufacturers and dealers will be left
Frequency Division Multiplex modulation Sport, which is the government ministry pacifying angry customers and perhaps
to 8K COFDM, with around 8000 carriers responsible for broadcasting, says it has have to give them new sets.
used instead of around 2000. This will let yet to make a final decision on whether to But Intellect's message is so mildly worded
the UK use single frequency networks, follow the Ofcom recommendations. But that the message may not get through: "We
where several transmitters work on the the DCMS says the phased transition from are disappointed that Ofcom has failed to rec-
same frequency and the receiver picks up analogue to digital, starting in 2008 and ommend support to consumers with legacy
the strongest signal and rejects weaker sig- ending in 2012, was a Labour Party “man- products with 2K only receivers", is all that
nals which arrive with different delays. ifesto commitment”. Intellect says for public consumption.

Proteus VSM New Quasar Digital Labs For more information contact Quasar
Labcenter Electronics have added the Quasar Electronics have extended their Electronics Ltd, Dept EPE, PO Box 6935,
ARM7-based LPC2000 family to the range range of Electronic Projects Labs with four Bishops Stortford CM23 4WP. Tel: 0871
of microcontrollers supported by their new products: 717 7168. Fax: 07092 203496.
Proteus VSM co-simulation software. Their Electronic Digital Recording Email: sales@quasarelectronics.com.
Users can now simulate an LPC2000 Laboratory (EPLDR) at £24.95 Web: www.quasarelectronics.com.
device along with external peripherals makes a great introduction to the
such as displays and keypads, and also world of advanced electronic
general electronics such as signal process- digital recording technology. It
ing or power control circuitry. Firmware contains all the parts and instruc-
code running on the target device can be tions to build over 50 education-
single stepped and debugged as it interacts al and fun experiments.
with the rest of the system. With their Metal Detector
Chairman and Chief Software kits, one of them handheld,
Architect John Jameson said, “this is the you can learn by building
first time we have supported a 32-bit your own treasure
microprocessor within the VSM archi- hunter, for just £9.95 –
tecture and it makes for an impressive and who knows what
demonstration of the power of Proteus – you might find!
it’s quite something to see a The fourth intro-
hardware/software co-simulation of a duction is an
system powerful enough to run Linux!”. Electronic
For details about Labcenter’s full range R o o m
of products, including p.c.b. design and Alarm
microcontroller co-simulation, contact kit. At
Labcenter Electronics, Dept EPE, 53-55 only £4.95,
Main Street, Grassington, N.Yorks BD23 even on pock-
5AA. Tel: 01756 753440. Fax: 01756 et money you can keep your
752857. Web: www.labcenter.co.uk. room off-limits to unwanted invaders!

542 Everyday Practical Electronics, August 2005

 Ezireader
It’s good to hear of electronic devices PicoScope 2202 PC Scope
which are intended for use by the disabled.
Ezireader is a new device that falls into
that category. It is a light-weight handheld Pico Technology tell us that they have The USB 2.0 port makes the device
unit that allows partially-sighted people to released the latest addition to their easy to use with all standard desktop and
read their newspapers, or whatever, in range of PC oscilloscopes, the laptop PCs and removes the need to con-
large print on a TV or VCR screen. PicoScope 2202. Connected to your PC figure printer ports.
Ezireader is simply plugged into the and powered by its USB 2.0 port, this The PicoScope 2202 is priced at £199
SCART socket, its power supply connects dual-channel scope has 8-bit resolution, plus VAT. For more information contact
to a normal mains power socket. Point the 20MHz sampling rate and a 32KB Pico Technology Ltd., Dept EPE, The
device at the text to be read, press AV on memory. In combination with the Mill House, St Neots, Cambs PE19 1QB.
the TV’s or VCR’s remote control, and the PicoScope and PicoLog software Tel: 01480 396395. Fax: 01480 396296.
image can be seen enlarged by about 10 to included, the unit acts as an oscillo- Email: sales@picotech.com.
15 times on the screen. scope, spectrum analyser, multimeter Web: www.picotech.com.
Ezireader’s inventor Harry Mitchell is and data logger.
partially sighted and registered blind. This new unit has
Although TV readers were already avail- been designed with
able commercially, he felt they were too the hobbyist and
expensive for most people. So he put his educational markets
mind to work, basing his creative ability on in mind. With its
his previous history in the field of elec- high sampling rate,
tronics. The result is Ezireader, currently the oscilloscope is
costing £135 for a black and white unit, or useful in a variety of
£165 for colour. electronic applica-
Harry is also looking for people who tions, including
would be prepared to assemble these units, audio amplifiers,
and he has an advert in respect of this in switched-mode
our Classifieds section. power supplies and
For more details contact Harry Mitchell, microcontrollers,
17 Woodpath House, Woodpath, Southsea, and for displaying
Hants PO5 3DX. Tel: 02392 830158. waveforms obtained
from laboratory
experiments.

WCN’s Latest Arrivals

WCN Supplies have sent us a shorty-
catalogue detailing their “latest arrivals”.
Amongst the items are a 12V 24Ah
Wave Goodbye to the Mouse?
sealed lead-acid rechargeable gel-type Anyone who uses a mouse or joystick user can either use the mouse or wave
battery, for £19.95, that you might con- knows the problem – fatigue and aches and commands.
sider if you are building the Motor pains caused by precise repetitive finger Motorola has a different answer to the
Amplifier elsewhere in this issue. For clicking. British research company Qinetic same problem (WO 2004/061751). Some
less-demanding applications, their 12V lets the user share control of the PC PCs already have an optical sensor that
2.3Ah rechargeable battery for £4.95 between ordinary mouse finger action and reads the user’s fingerprint instead of
could well be of interest to you. sweeping hand gestures (WO asking for a password. Motorola will
WCN have a good selection of electron- 2004/102301). make the sensor larger so that the user
ics components, some at prices which A mat like a mouse mat has crossed can slide a finger tip over the surface.
you’d be hard pressed to match elsewhere. lines of l.e.d.s embedded in the surface, The sensor detects the direction and
If you are not already on their mailing list to emit timed pulses of infra-red. Sensors speed at which the finger print ridges and
– you should be. in the mat detect reflections from a hand furrows are moving.
For more information contact WCN moving above. In learning mode the PC Barry Fox
Supplies, Dept EPE, The Old Grain Store, is taught to associate the user’s chosen
Rear of 62 Rumbridge Street, Totton, gestures with basic commands, like open
Southampton SO40 9DS. and close programmes, scroll through a
Tel/Fax: 023 8066 0700. page or read email. From then on the Hitchhiker’s Pocket
Email info@wcnsupplies.fsnet.co.uk.
Guide
Hitchhiker fans will be delighted to
The events will be hosted by one of the know that a real version of the Hitchhiker’s
Abracadabra! UK’s leading physiologists and former
magician, Professor Richard Wiseman, and
Guide to Galaxy (H2G2) can be purchased
and, in a manner of speaking, kept in your
Perhaps slightly off-topic for an electron-
ics mag (but we have occasionally pub- will involve jaw-dropping performances pocket. The BBC’s website recently high-
lished designs of an illusory/magical by critically acclaimed Las Vegas magician lighted this intriguing fact, stating that “the
nature), the Science Museum in London is Jeff McBride. mobile edition has been made by the BBC
putting on two shows, in which “the secrets “This is the first time that science and rather than the ‘great publishing houses of
of magic and illusion are debunked”. magic have been brought together in this Ursa Minor’ who, in Douglas Adam’s
Their press release says that “the enig- way”, says Professor Wiseman. book, created the original”. It was released
matic world of magic and illusion is to be “Conjuring is undergoing a renaissance in to coincide with the UK release of the
unlocked after centuries of secrecy at the the UK. It is great to have this opportunity H2G2 film.
UK’s only venue dedicated to debates on to explore the topic.” Owners of smartphones and handheld
contemporary science, the Science The tickets are free but must be pre- computers will be able to access the guide
Museum’s Dana Centre.” There are to be booked on 020 7942 4040 or via while they are out and about. The portable
two “unique” evenings of spectacle, dis- tickets@danacentre.org.uk. The Dana edition contains 7000 articles from the
cussion and illusion on 27 and 29 July at Centre is at 165 Queens Gate, London H2G2 site, covering life, the Universe and
the Centre, which is fast developing a rep- SW7 5HE. Note that the Centre is for over everything. To access it send “H2G2” in a
utation for creating innovative science 18s only. The events will be webcast live text message to 81010, or simply visit
events for adults. on www.danacentre.org.uk. www.bbc.co.uk/mobile/h2g2.

Everyday Practical Electronics,August 2005 543

 PIC N’ MIX
Our periodic column for your PIC programming enlightenment
JOHN BECKER

How to get the DS1307 RTC chip working with PICs

T
HIS time we examine an example of
how to use a Real Time Clock (RTC)
chip, the Maxim DS1307. The first
time the author tried to use this chip, he had
difficulty getting it to work due to inade-
quacy of its datasheet. It took a consider-
able amount of time to resolve.
The DS1307 is the RTC used in the Pain
Monitor described elsewhere in this issue
(Aug ’05). It is an 8-pin device that once
programmed with the correct time and
date, will continue to update that data
every second for as long as the chip’s back-
up battery is connected to it, even though
the +5V supply to the rest of the circuit is
Fig.2. Timing diagram for the DS1307
switched off.
It counts seconds, minutes, hours, days
of the week, days of the month, month and
Because the RTC SCL and SDA pins can
be left floating when the PIC’s controlling
Example Control Code
The initial stage of the routine for writ-
year, and is leap year compatible. It pins are put into high-impedance read- ing data to the RTC is shown in Listing 1.
requires its own external 32768Hz clock mode, these lines are each biased high by a In it the equated names for the SDA and
crystal, which should have a specified resistor, typically of 10kΩ, although the SCL lines are SDATA and TCLK. At label
capacitance of 12·5pF to ensure good accu- value is not critical. RTCLOCK, the port pins used are first set
racy. A practical circuit diagram for its use Any time the RTC is to be read from or to output mode (these commands could be
is shown in Fig.1. written to, its address command is sent set elsewhere in the program). Both port
serially to the chip via the SDA line, each pins are then set high, and then SETSTOP
data bit being clocked into the chip using (Listing 2) is called to ensure that the RTC
the SCL line. Only if that address is valid is in Stop mode.
to the RTC will it accept further com- After this, SETSTART is called, telling
mands, either telling it to receive new data the RTC to expect an ID address to be
being written to it, or to output its current sent to it. The only ID address it will
clock and calendar data. The control wave- respond to at this time is B’11010000’
forms are shown in Fig.2. (the serial EEPROM chip in Pain

LISTING 1: Send address code to RTC

Fig.1. Basic connection diagram for the
DS1307 RTCLOCK: BANK1
bcf TRISC,SDATA ; ensure port pins are in output mode
The backup battery used in the Pain bcf TRISC,TCLK
Monitor is a Saft LP142503PF, 1/2AA, BANK0
950mAh, 3·6V non-rechargeable Lithium bsf PORTC,SDATA ; set data and clock line pins high
battery with p.c.b. tags. This will keep the bsf PORTC,TCLK
RTC running for about 10 years. Its RS call SETSTOP ; send Stop command to RTC
stock number is 203-3894. Other batteries call SETSTART ; send Start command to RTC
from 2V to about 3·6V can also be used. movlw B’11010000’ ; ID address for write mode
call RTCCLKOUT ; send ID to RTC
Control Logic movlw B’00000000’
call RTCCLKOUT
; set RTC for data address 0
The RTC has two control lines, SCL and
SDA (clock and data) which in the Pain
Monitor are connected to the PIC’s Port C
pins RC3 and RC4, which also have the LISTING 2: Stop and Start mode commands
same functional names of SCL and SDA.
In reality, however, the chip can be con- SETSTOP: bcf PORTC,SDATA ; take data low while clk is low
nected to any two PIC port pins, with suit- bsf PORTC,TCLK ; take clk high while data is low
able adjustment to the software. bsf PORTC,SDATA ; take data high while clk is high
The chip operates in I2C mode, a technique return
that allows 2-line data transfer between a host
device and a slave. In this case the host is the SETSTART: ; TCLK & SDATA assumed to be high
PIC and the slave is the RTC. Since I2C bcf PORTC,SDATA ; take data low while clk is high
devices only respond to commands that are bcf PORTC,TCLK ; take clk low while data is low
addressed specifically to them, several I2C return
devices can share the same two lines.

Everyday Practical Electronics, August 2005 545

 Note that after each write operation, the
LISTING 3: Send data byte to RTC RTC address counter is automatically incre-
mented, ready for the next data byte to be sent.
RTCCLKOUT: movwf BYTEOUT ; store W value in BYTEOUT The formatting for the data is shown in
movlw 8 ; set loop counter to 8 (bits to do) Table 1. Note in particular the CH bit (bit
movwf LOOP 7) in address line 00H. This bit controls the
RTC’s oscillator. When the bit is set to 1
CLK1: rlf BYTEOUT,F ; rotate BYTEOUT left to get MS bit first the oscillator is disabled. The oscillator is
bcf PORTC,SDATA ; set SDATA low only enabled when the bit is set to 0.
btfsc STATUS,C ; is CARRY set ? The default value is 1 when the RTC is
bsf PORTC,SDATA ; yes, set SDATA high powered up for the first time (and after the
bsf PORTC,TCLK ; clk up backup battery has been renewed). This
bcf PORTC,TCLK ; clk down means that the RTC can only increment its
decfsz LOOP,F ; decrement loop, is it now zero? time keeping after bit 7 is cleared to 0. Any
goto CLK1 ; no, so repeat loop program sending the seconds data to the
call WAITACKRTC ; yes, wait for RTC to acknowledge RTC must also clear this bit (in the exam-
; code now follows on directly to Listing 5 ple program, the bit is automatically
cleared to 0 in the CLKSEC register).
LISTING 4: Wait acknowledgement from RTC Having set the current time and calendar
data into the RTC, from now on it can be
WAITACKRTC: BANK1 read as real time data whenever you want,
bsf TRISC,SDATA ; set SDATA as input by calling the READRTC routine partially
BANK0 illustrated in Listing 6.
bsf PORTC,TCLK ; take clk high At label GETRTCVALUE, the five com-
mands for reading the CLKSEC data are
WAIT1: btfsc PORTC,SDATA ; wait for SDATA to go low shown. The same commands are repeated
goto WAIT1 for all values required, but with the ANDed
bcf PORTC,TCLK ; take clk low value being changed to suit the specific
BANK1 value being read, and with a different des-
bcf TRISC,SDATA ; set SDATA as output while clk is low tination register of course (see Table 1).
BANK0
return Subtle Points
There is a subtlety here that must not be
LISTING 5: Send clock and calendar data to RTC overlooked in the full program. When
reading the last data value from the RTC, it
movf CLKSEC,W is not SENDACKREAD which is called
call RTCCLKOUT ; send secs to RTC & wait ACK after calling RTCCLKREAD, but SEND-
movf CLKMIN,W NOTACKREAD, in which the acknowl-
call RTCCLKOUT ; send mins to RTC & wait ACK edgement bit is now inverted.
;repeat for CLKHRS, WKDAY, CLKDAY, MONTH, YEAR Neither SENDACKREAD nor SEND-
call SETSTOP ; set RTC into Stop mode NOTACKREAD are listed here, but may be
return examined in the Pain Monitor ASM code.
As with writing to the RTC, when read-
ing data the first few commands must send
the RTC ID and the first address that will
Monitor only responds to an ID code of It is assumed in Listing 4 that acknowl- be accessed.
B’10100000’). edgement will be received and the routine It should be noted though, that when set-
In the RTC ID code bit 0 determines waits indefinitely until it is. Whilst a ting for Read mode, the RTC must first be
whether the code sets the RTC into Write timeout could be inserted here, there set into Write mode, by the ID byte bit 0
mode (0) or Read mode (1). It must be set seems little point as any failure would be being cleared to 0. Then the start address is
for Write mode (0) in this routine. The ID due to a catastrophic event (such as chip sent and the RTC is put into Stop mode.
code is sent via routine RTCCLKOUT, in failure), from which recovery could not Now the Start command is sent, followed
Listing 3. be made. by the ID code again, but this time with bit
The comments in Listing 3 explain Next the address at which the first data 0 set to 1, to put it into Read mode. This is
what happens, but it’s worth comment- byte to be stored is sent, zero in this case another subtlety that was not at first appre-
ing that the bits are sent serially in order (B’00000000’). Now the actual time and ciated when the RTC chip was investigated
of most significant (MS) bit first, least calendar data can be sent to the RTC. by the author for the first time.
significant (LS) bit last. After all eight Listing 5 shows part of the routine. Here It was here that the RTC datasheet was
bits have been sent, WAITACKRTC is the register values have all been previously found to be most unclear. It was not obvi-
called (Listing 4), in which acknowl- preset (see later) and they are output to the ous at first that the RTC must initially be
edgement from the RTC is awaited to RTC in the order stated. The register names put in Write mode through its ID value as
confirm data receipt. should be self-explanatory. in Listing 1, and then put into Read mode.

Table 1: Timekeeper Registers

ADDRESS Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 FUNCTION RANGE
00H CH 10 Seconds Seconds Seconds 00-59
01H 0 10 Minutes Minutes Minutes 00-59
12 10 Hour 1-12
02H 0 10 Hour Hours Hours +AM/PM
24 PM/AM 00-23
03H 0 0 0 0 0 DAY Day 01-07
04H 0 0 10 Date Date Date 01-31
05H 0 0 0 10 Month Month Month 01-12
06H 10 Year Year Year 00-99
07H OUT 0 0 SQWE 0 0 RS1 RS0 Control –

546 Everyday Practical Electronics, August 2005

It had appeared that Write mode could be
set directly, without Listing 1 being repeat- LISTING 6: Read time and date from RTC
ed first – not so! This fact was eventually
revealed by Googling the web. READRTC:
When sending the address from which
to read (or write), you could in principle ; repeat Listing 1 here (excl BANK/TRIS), to put RTC into Write mode first
read any time or date value by amending
the Start address accordingly. call SETSTOP ; set RTC into Stop mode
At each Read step RTCCLKREAD is call SETSTART ; set RTC into Start mode
called (not shown here) in which the eight movlw B’11010001’ ; set ID for read mode (bit 0 = 1)
data bits of the required value are read call RTCCLKOUT ; send ID
back serially, again in order of MS to LS, BANK1
and built up into a byte within STORE. bsf TRISC,SDATA ; set SDATA as input
BANK0
Getting Data for RTC GETRTCVALUE: call RTCCLKREAD ; read 1 byte
Having shown how clock and calendar call SENDACKREAD ; send acknowledgement of read
data can be written to and read from the movf STORE,W ; get read byte value from STORE
RTC, we come to the question of how that andlw 127 ; AND value with 127 (B’01111111’)
data can be set into the PIC in the first place. movwf CLKSEC ; put it into destination register
There are several options, the best of which
is that used in the Pain Monitor. Its PC pro-
gram has been written to take the data from
the PC’s own time and date registers, split it be prepared in advance of the time display the time and date data on an l.c.d.
into its component parts and then sent via a required, and then sent to the PIC when the controlled by the PIC. The Pain Monitor
serial link from the PC to the PIC. The required time arrives. Data sending and its uses such a routine for the time values. It
process is too complex to illustrate here, and extraction by the PIC only takes a few sec- should not be difficult to extend that rou-
interested readers should extract the relevant onds, and so moderately accurate time tine to also show calendar data as well on a
sections of the Pain Monitor PC and PIC could be set this way. cyclic basis (time/date/time etc).
codes and copy them into their own program. The other option is to use switches to set It will be seen from Table 1 that each
A second option is to allocate PIC EEP- the data into the PIC. As has been shown in value must usually be sent to the l.c.d. as
ROM data space for the values, and then pro- several EPE PIC projects, only three push- two nibbles, MS first, LS second. Each
gram the values into the PIC from a data file. button switches are needed for this. One to nibble value should be ORed with 48 to
When the PIC is reset following this data step through the registers to be pro- convert it to the ASCII code for that value.
send, it should be programmed to read the grammed, and two for incrementing or
EEPROM locations and store those values decrementing the value of each register. Resources
into the RTC. Toolkit TK3 allows this to be Such a technique was used in the author’s All software referred in this article can
done via its Send EEPROM Message facility. PICronos Wall Clock of June ’03. be downloaded from the EPE Downloads
The drawback is that it will be slightly site, access via www.epemag.co.uk.
difficult to set the time exactly. The sug- Data Display Maxim’s datasheet for the DS1307 can be
gestion, though, is that the data file should You will, of course, probably wish to downloaded from www.maxim-ic.com.

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Everyday Practical Electronics, August 2005 547

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548 Everyday Practical Electronics, August 2005

Constructional Project

Motor Amplifier
Ken Ginn

The power with which this unit can drive a heavy-duty motor is astonishing!

S Design Concept
OME years back the author was bit- current rating of each motor would have
ten by the bug to build a radio con- Consequently the author set out to build to be within the current capability of the
trolled combat robot. Plans were a unit that would integrate with a conven- controller, since in combat the motors are
laid and the mechanics were built with a lot tional model speed controller, and also take expected to stall.
of work from a team of three engineers the stall current of the motors. This was ɀ Bomb proof (if at all possible)!
including himself. calculated to be about 40A for each motor
The classic wedge shape robot was born with a supply voltage of 24V drawn from a Radio Control
with a pair of 24V d.c. permanent magnet pair of onboard 12V gel-cell batteries Most RC systems use PPM (Pulse
electric motors, previously used on an arranged in series. Position Modulation) or PWM (Pulse
electric wheelchair. These were needed to The following design conditions had to Width Modulation) to convey the infor-
supply drive for the robot. Mild steel be met: mation from the handheld Transmitter to
square section tubing and a few square
metres of 3mm aluminium sheeting was ɀ Run from an on-board 24V d.c. supply the model’s RC Receiver. Essentially the
RC system in the transmitter translates
also used in the construction. ɀ Run permanent magnet 150W d.c. the position of a joystick or switch into
The weapon was an angle grinder motors a pulse width of approx 1·0ms to 2·0ms
attached to the front of the monster, this ɀ Interface with readily available radio every 20ms or so. The actual timing may
weapon was driven by a 24V Canadian control (RC) model speed controllers vary slightly from manufacturer to
electric shower pump motor. The manufacturer.
assembly weighed in just within the ɀ Easy to install and maintain
This pulse width signal is fed to a
maximum weight limit at the time – ɀ Be able to trim each motor speed inde- servo which responds by either moving
which was 70kg. pendent of the transmitter joystick (rotating) to a new position, or, if fed
Looking around at the time of building,
ɀ Emulate the function of the conven- with an unchanging signal, will remain in
all of the conventional radio control model a steady-state condition, i.e. not moving.
tional RC model speed controller – having
speed controllers were found to be unsuit- The servo can be replaced by a speed
full proportional speed control forward and
able for use with the robot. Despite the controller.
reverse
stated current ratings of some (120A peak), When the transmitter joystick is moved
they could not take the load and stall cur- ɀ Run the drive motors to stall condi-
tion and automatically recover. The stall from the central position, i.e. stop then
rents of the robot’s motors. forward, the speed controller will then
cause the motor to rotate in one direction.
Moving the joystick back through the
dead zone (stop or neutral) to the other
extreme will cause the motor to reverse
direction.

On Time
For a number of years the means to con-
trol d.c. electric motors has been to use the
PWM technique. Essentially what happens
is that the full supply voltage is switched
on and off very fast to the motor. The On to
Off period (mark-space ratio) is varied to
set or alter the motor’s speed. In essence,
with a short On and long Off ratio, the
motor will rotate slowly.
As the On time increases, the greater the
rotation speed. By varying the On/Off
ratio, the speed can be almost infinitely
variable between stop and full speed. Full
torque is essentially available from the
motor throughout the whole range of
speed.
The Futaba MC 210CB speed controller
used with the prototype drives motors at
approximately 50Hz, and the motor
amplifier keeps in step with the Futaba.

Everyday Practical Electronics, August 2005 549

 This was actually noticed load resistor R1, which partly simulates the
in the first of many controllers motor to the primary speed controller.
built, where the robot did a In parallel with R1 are two opto-isolators.
neat right hand turn, when it The first, IC1, isolates and permits the puls-
should have been running es of either polarity (a.c.) from the primary
straight. A few tweaks of the speed controller to pass onto the following
preset on the right hand motor circuit for conditioning. The second, IC2,
drive (the weakest motor) and permits the primary speed controller’s d.c.
the robot ran in a straight line. signals to pass only when the polarity of the
signal permits the optoisolator diode to be
Circuit Diagram forward biased. When reverse biased, diode
The main circuit diagram D1 conducts instead.
for the Motor Amplifier is The a.c. signal through IC1 is passed to
shown in Fig.1. It basically monostable IC3a. Its falling edge triggers
has two parts. One part takes the input at pin 5, causing the output at pin
the drive signal and increases 6 to go high for a period set by capacitor
its current carrying capability C1 and the combined resistance of R5 and
– the amplifier. The second preset VR1. The latter sets the pulse width
Futaba MC210CB Speed Controller part is a means to detect the at a value from 70µs to 2·5ms. From pin 6,
polarity of the initial drive the output controls transistor TR1 via
signal. Since the model’s diode D3.
speed controller has a forward Diode D2 also sends the main drive sig-
Design Detail and reverse function, this has to be detect- nal to the base (b) of TR1, bypassing IC3a,
This circuit is designed to interface with ed by the primary speed controller. The and effectively forming an OR gate with
a simple primary speed controller. The lat- motor current reversing relay also has to be D3, so that the pulse produced by the
ter does all the signal processing and sorts switched when the primary speed con- monostable tags onto the end of the drive
out the relationship between the joystick troller’s polarity reversal is detected. pulse.
position and the speed and direction. The The control signal is derived from the Transistor TR1 forms an emitter-follower
secondary speed controller (amplifier – primary speed controller. Its supply volt- and its emitter (e) drives l.e.d. D7, via buffer
this unit) increases the current and voltage age has to be greater than 4·5V, preferably resistor R10, to indicate that pulses are being
capacity and delivers power to the d.c. 5·0V. This ensures the correct drive current fed to the drive f.e.t.s, TR3 to TR6. Diodes
motor allowing, for example, a 150W 24V for the input to the amplifier. The drive sig- D5 and D6 are additional protection for the
wheelchair motor to be controlled with nal is input at connector PL1 and is fed to drive circuitry to limit negative transitions
considerable ease.
Higher rating motors have not been test-
ed with this unit, but there seems no reason
why a motor rating of 500W or more could
not be successfully driven. This design
went through considerable testing, and at COMPONENTS D5, D6

D7
40EPS08 power
diode, 40A (2 off)
green l.e.d., 3mm
the end of two fights, in which there was
considerable abuse of the motors and the D8 amber l.e.d., 3mm
controller, the controller remained cool. D9 red l.e.d., 3mm
AMPLIFIER TR1 BC182L npn transistor
Each power f.e.t. driving the motor has a
maximum continuous current rating of TR2 TIP122 npn Darlington
Resistors transistor
60A. A safe limit to the current would, with R1 680Ω
four f.e.t.s, be in the order of 150A,
See TR3 to TR6 STW60NE10 or
R2 330Ω SHOP FQA70N10
although this has not been tried. At 200A, R3, R4 10k (2 off) TALK
the f.e.t.s would have to dissipate about n-channel power
R5, R9, 2k2 (4 off) page MOSFET (4 off)
160W maximum as heat. With a supply R10, R15
voltage of 24V the power delivered to each IC1 TLP620 optoisolator (a.c.)
R6 1M IC2 SFH618A-2
motor would be 4·8kW! R7 6k8 optoisolator (d.c.)
R8 1k
Speed Control R11 to R14 100Ω (4 off)
IC3 4528 dual monostable
The primary speed controller relates the IC4 7812 12V 1A voltage
R16 4k7 regulator
controlling pulse width to a form which R17 PTC thermistor,
provides forward, stop and reverse speeds,
450mA, 30V Miscellaneous
typically varying from 1·0ms to 2·0ms. For
R18, R19 SIOV-S14K25 31V RLA d.p.d.t. relay, 24V,
example, pulse width varying from 1.4ms
d.c. varistor (2 off) contacts rated for
to 1ms would set the motor’s forward
All 0·6W 5% metal film unless stated motor current
speed going progressively faster up to full
speed. The dead zone between 1.4ms and B1, B2 12V 15Ah gel-cell
1.6ms will provide no drive to the motor. Potentiometer battery (2 off)
With a pulse width of 1·6ms to 2·0ms, the VR1 100k preset, min.
primary speed controller will drive the round Printed circuit board, available from the
motor in reverse, EPE PCB Service, code 520; 16-pin d.i.l.
The longer the pulse from the receiver Capacitors socket, tinned copper wire, 24s.w.g.; 2-
servo’s output the faster the reverse speed C1 to C3, 100n polyester, 63V, way pin header; 3-way pin header; 4-way
will be. This pulse width information is C5, C7 5mm pitch (5 off) pin header; transistor thermal insulating
updated every 20ms, producing a PWM C4 220µ radial elect, 25V washers, plus bolts and nuts; heatsink,
drive at about 50Hz. C6 470µ radial elect, 35V 16s.w.g. aluminium sheet, approx
There is also a variable pulse width C8 10,000µ, can elect. 120mm x 40mm; heavy-duty connecting
monostable included in an attempt to 50V, chassis mount- wire, to suit relay current; heavy-duty
equalize the drive to the two main motors. ing, plus clip p.c.b. terminal bolts with nuts and cable
Where two robot drive motors are sourced, connectors (3 off); solder.
maybe from two separate places, or a Semiconductors
replacement motor does not match the one D1 to D3 1N4148 signal diode
replaced, the monostable tags another
pulse on the end of the main drive pulse to D4
(3 off)
1N4002 rectifier diode
Approx. Cost
Guidance Only £37
excl robot hardware
attempt to equalize the drive to the weaker
motor.

550 Everyday Practical Electronics, August 2005

 Author’s combat robot in early stages
of development

and protect the circuitry from inductive puls-

es generated by the motors. Component R19
is a 31V varistor incorporated to limit any
positive voltage transients occurring that
might destroy the drive transistors.
Monostable IC3b will receive a trigger
pulse only when the forward drive signal
polarity causes IC2 to conduct and pass the
signal through the opto-isolator. A reverse
drive signal will not be accepted.
This monostable’s timing is set to be
greater than the frame rate of the RC system
used. In this case the pulse repetition rate is
20ms. However, once triggered, the time for
which the monostable remains On is set for
28ms (by C2 and R6), so the monostable will
be retriggered before it has a chance to time
out, so keeping its output pin 10 constantly
high (On). This provides current to drive the
relay driver, TR2, a Darlington transistor
which provides current for the drive motor
reversing relay via connector PL2.
In this circuit, protection is arranged for
brief input supply voltage transients to be
limited to 31V by a second varistor, R18.
Thermistor R17 limits any excesses caused
by longer transients.

F.E.T. Selection
One important consideration for this cir-
cuit was the selection of the f.e.t.s to drive
the motors, those having the lowest RDS (On
resistance), being preferable, subject to price.
The RDS of the chosen STW60NE10 f.e.t. is
only of the order of 16mΩ (milliohms), the
alternative FGA70N10 is 23mΩ.
It is worth noting though, that the effect
of the RDS within each individual f.e.t. is
negligible compared to the cabling of the
entire robot and the internal resistance of
the robot’s motive batteries and relays etc.
Consequently, the additional expense of
“better spec” components was not felt to be
worthwhile.
During two heavy fights the controller
remained cool, despite several times being
thrown around and the motors stalling.

Choice of Relay
In the case of a combat robot using a
relay to achieve reverse drive to the motor
a suitable relay has to be sourced, bearing
in mind the energising current for this
design is supplied from a 24V source. The
majority of relays readily available appear
to stop at about a contact current of 25A
a.c., with a contact life expectancy of
around 100,000 operations.
Such relays may seem capable of operat-
ing at greater currents than those specified,
Fig.1. Circuit diagram for the Motor Amplifier but their life will be substantially reduced.

Everyday Practical Electronics, August 2005 551

 Motor Amplifier – Circuit Board Construction

Fig.2. Printed circuit board component layout and full-size copper foil master for the Motor Amplifier. Note the heavy-duty
lead-off wires from the terminal bolts A, B and C

552 Everyday Practical Electronics, August 2005

Construction
Details of the printed circuit board com-
ponent and track layouts are shown in
Fig.2. This board is available from the EPE
PCB Service code 520. One board is
required for each motor.
First solder the on-board link wires since
three may be obscured by varistor R19. Note
that the wire link to the left of TR2 is best
sheathed with a length of sleeving, to prevent
the possibility of it shorting to TR2’s tab.
Assemble the rest of the components in
ascending order of size, with static sensitive
components last, taking the usual precautions
with latter. The f.e.t.s (TR3 to TR6) and power
diodes (D5, D6) are attached to the board
together with a heatsink plate and insulating
washers. A socket is used for monostable IC3,
but not for optoisolators IC1 and IC2.
Once construction is complete a number
of tests have to be performed, since the cir-
cuit is going to take a high amount of
power in use. Spending five minutes on
each circuit checking for faults could save
a great deal of heartache, and perhaps pre- Completed amplifier board wired to the heavy-duty motor relay
vent the circuit from suffering a catastro-
phe. The amount of power available from a Before any power is applied to the circuit Once the initial surge has subsided, the
pair of 12V gel-cells is phenomenal! check the following with a Multimeter: current drawn should drop down to a qui-
Check the board for any wrongly placed ɀ resistance between PL3 pins 1 and 4, escent level of less than 15mA. Check that
components, and for the correct polarity of this should be greater than 5kΩ the voltage at the input to regulator IC4 is
capacitors and diodes. Check too for any ɀ resistance between points “A” and the same as the supply voltage.
solder bridges between pads and tracks. “B”, “A” and “C”, with the meter’s positive The output from regulator IC4 should be
lead remaining on “A”. This should read 12V, within 100mV or so and l.e.d. D9
high. Connecting the multimeter around should illuminate, indicating that power is
the wrong way will put the diodes into con- applied to the circuit. The other l.e.d.s, D7
duction and cause a misreading. and D8, should remain off.
ɀ most importantly, the resistance Connect a radio control receiver and pri-
between the heatsink and “B” and “C” mary speed controller to the input of the
should be very high (open circuit) amplifier, see Fig.3a. In place of the motor,
Should any faults be detected, sort out connect the test circuit shown in Fig.4.
the problem before applying full current. These components should be temporarily

Setting Up
Once satisfied with the tests, the 24V
power source can be applied at connector
SK3/PL3 pins 1 and 4, observing the cor-
rect polarity. If a current limited power sup-
ply is not to hand, insert a 100Ω 1W resis-
tor in the positive line. This will serve to
Fig.3b. Relay contact wiring details limit any fault current which may occur.

Fig.4. Low current “motor” test circuit

COMPONENTS
TEST CIRCUIT

Resistors
R1 470Ω 2W
R2, R3 2k2 0·6W 5% (2 off)

Semiconductors
D1 red l.e.d.
D2 green l.e.d.
D3, D4 1N4001 rect. diode (2 off)

Fig.3a. Circuit for the battery supply, relay contacts, motor and coil. Also shown are
the R/C receiver and speed controller connected to the p.c.b. signal input SK1/PL1
Approx. Cost
Guidance Only £0.70
Everyday Practical Electronics, August 2005 553
hard-wired to the poles of the relay,
although they could be mounted on a piece
of stripboard if preferred.
The test circuit is a safety measure to check Fig.6. Basic schematic configuration,
out the motor driver and relay connections using two speed controllers to control a
before a high power motor is connected and large model mobile robot. Motor reversing
large amounts of current are drawn, thus relays omitted for clarity
avoiding any problems should there be a
component or wiring fault.
Switch on the radio control equipment and
set the transmitter joystick to the central posi-
tion. L.E.D.s D7 and D8 on the p.c.b. should
remain off. Follow the setting up instructions
for the primary speed controller as per the
manufacturer’s instructions. Set the speed con-
troller as though it were being used without the
amplifier, as with a small motor for example.
Note that when the joystick is moved out
of the neutral position, one or other of the
test circuit l.e.d.s of Fig.4 will begin to
pulse and illuminate in sympathy with l.e.d.
D7 on the amplifier board. As the joystick
is moved progressively away from the neu-
tral position, the active l.e.d. in the test cir-
cuit will progressively get brighter.
Reverse the joystick, and this test l.e.d.
will extinguish as the joystick passes
through neutral. The other test l.e.d. will
now illuminate as the motor changeover
relay operates and changes polarity. Again,
as the joystick is moved progressively
away from the neutral position, this l.e.d.
will illuminate, and l.e.d. D8 on the ampli-
fier board should also now be illuminated, Noise Suppression independent control of each motor, giving
the robot a good degree of manoeuvrabili-
indicating that the relay has energised. There is a need to reduce the electrical
noise generated at the drive motor’s termi- ty. Tests prove that it is more than able to
If all is well, it is now safe to disconnect the cope with running and stalling currents up
test circuit of Fig.4, and the 100Ω 1W current nals. This can be significantly reduced with
a handful of components preferably close to 80A.
limiting resistor if used, and connect the drive The amplifier may also be used as a sin-
motor to the circuit. Bear in mind that the cir- to the motor commutator where the electri-
cal noise is generated, see Fig.5. gle unit to boost the drive current of a sin-
cuit will now draw large amounts of current gle speed controller, in a model boat for
and the source has to cope with the increased Capacitors placed from each terminal to
ground, and across the two supply termi- example. The design here is not limited to
power. Be aware the motor should be clamped use with just combat robots.
down if the unit is tested without it being in the nals will reduce the noise significantly. The
addition of a varistor serves to reduce any When running the unit in the model or
robot. Mount smoothing capacitor C8 (Fig.3a) robot, if the relay appears to chatter or oscil-
close to the relay. transients which may be generated at this
point to within safe limits. late when changing over to being energised,
this is not a fault of the circuit. Rather, it is
Next Stage more a function of the internal resistance of
With the unit(s) assembled in the robot, the power source being too high in relation
further testing is best accomplished with to the starting current of the motors.
the drive wheels off the ground, so impos- The combination of the internal resist-
ing a minimal load on the circuit. Check for ance of the power source and the internal
correct rotation of both motors when they resistance at start up of the motors could
are going forward and in reverse. reduce the voltage supply from a healthy
Next, in a safe area only, put the robot on 24V down to 15V. Use batteries that are
the ground and check operation of the well able to supply the starting current. អ
Fig.5. Circuit diagram for the motor speed controller. Check for correct for-
suppression components ward and reverse motion, and for
straight running. Should the robot turn
to one side, adjust preset VR1 of the
amplifier on the weakest side. That
COMPONENTS will be the side to which the robot
will turn in a straight run. Adjust
VR1 until the robot achieves a
straight run. Clockwise rotation of
MOTOR (EACH) VR1 shortens the timing of mono-
stable IC3b, anti-clockwise length-
Resistor See ens the pulse.
R1 varistor 31V d.c. S H O P
TALK
page Conclusion
Capacitors This motor amplifier was
C1 to C3 100n ceramic disc, 5mm designed for use with a combat
pitch (3 off) robot, and arranged with one joystick
Motor 24V d.c. power to suit controlling the left-hand motor and a
application second controller driving the right-
hand motor (see Fig.6). This allowed
Approx. Cost
Guidance Only £1 Internal structure of the author’s
excl motor prototype combat robot

554 Everyday Practical Electronics, August 2005

 READOUT WIN AN ATLAS LCR ANALYSER
WORTH £69
Email: john.becker@wimborne.co.uk An Atlas LCR Passive Component
Analyser, kindly donated by Peak Electronic
John Becker addresses some Design Ltd., will be awarded to the author
of the general points readers of the Letter Of The Month each month.
have raised. Have you anything The Atlas LCR automatically measures
interesting to say? inductance from 1µH to 10H, capacitance
from 1pF to 10,000µF and resistance from
Drop us a line! 1Ω to 2MΩ with a basic accuracy of 1%.
All letters quoted here have previously been replied to directly.

GPS Validity
ᗂ LETTER OF THE MONTH ᗂ Dear EPE,
With reference to Mike Hibbett’s let-
ter (May ‘05). The GPS validity flag in a
Water Monitoring for Boats Back at the power distribution panel $GPGGA data string can have one of
Dear EPE, the pump has its own circuit breaker, three values:
A friend of mine came up with this but because the switching relay is
idea and I send it in on his behalf. The remote, it is not easy to monitor the 0 = Invalid GPS position
thing I like about it is that it is very voltage at the pump. Instead, I used a 1 = Valid GPS position
inexpensive and does not resort to reed relay with 10 turns of copper wire 2 = Valid differentially corrected GPS
unnecessary complexity. We spent wrapped round it. The current to the position
many hours discussing possible pump is fed through this coil. The con- Colin Gill,
schemes, including flow monitoring tacts of the reed are used to turn on a via email
and measuring head of water – all of small mechanical battery travel clock
which presented quite difficult (not l.c.d.). Thanks Colin, but there are also the
mechanical as well as electronic prob- When the tank is full, the clock is codes V and A which I referred to in my
lems. In the end we decided that no zeroed. Thereafter, the time indicated original PIC to GPS Interfacing article
matter what solution was chosen there on the clock is an indication of how of Jan ’04, and which my Garmin GPS
were going to be significant errors and much water has been used. Once a year handset outputs.
a crude indicator like a petrol gauge the boat gets drained down providing However, if you take the ASCII values
would probably be sufficient. an opportunity to find out how long it of A and V they are 65 and 86 respec-
We have a narrow boat with a large takes to empty. There are many reasons tively, thus their binary values have bit 0
water tank located at the front and bat- why this is not an accurate measure but set to 1 for A, and bit 0 set to 0 for V.
teries/control panel at the rear. We it is a simple and low hassle solution. Perversely in one sense, A is used for
wanted a way of determining very Richard Edwards, Valid, and V for invalid, but if you relate
approximately how much water was in via email, the bit 0 value to your 0 and 1 values,
the tank without having to use a dip- somewhere on the UK canal system they have the same meaning.
stick. The water tank is actually part of Going one step further, the ASCII for 0
the boat’s hull so the geometry is not a Thanks Richard, that’s an interesting is 48 (bit 0 = 0), and that for 1 is 49 (bit
simple rectangular structure. Also, the solution, and long may the current take 0 = 1), and so the argument holds true,
motor that pumps the water to the point you where you wish! I might even add, indicating that it is perhaps better to
of use is located at the front of the boat “may the force (of the weir) not be with check the value of bit 0 of the validity
along with the relay that operates it. you” – but perhaps not ... code rather than its actual character
value. Perhaps I’ll use that technique in
any future GPS design I do. Character 2
does not seem to have a Garmin letter
Stripboard Musical Frequencies equivalent.
Can anyone see a problem with my
Dear EPE, Dear EPE, logic on this?
In response to Godfrey Manning’s sol- Just a “quicky” that might help read-
dering problems with stripboard (May ers. Referring to Smart Karts May ‘05
’05), one solution and the method I’ve page 366, the frequencies of musical Text Editor
been using for years without any prob- notes is required (Calculating Values box Dear EPE,
lems is to polish the board in your usual on that page). I have my own Referring to Readout June ‘05, anoth-
way (I use wire wool) then wipe the HTML/JavaScript program that offers er editor to use with your excellent TK3
tracks/pads down with white spirit. The this and covers the two most convention- is Microchip’s IDE editor with its colour
solder will then flow and leaving smooth al scales. You are welcome to ask readers sensitive text and line number options.
shiny joints, who would like a copy to send me a pre- Ignoring any MPlab options, I run both
Plumbers use a similar method when formatted floppy disk with pre-paid/pre- programs together and use the task bar to
soldering sheet zinc on flat roofs. The addressed return mailing facilities. change from one to the other, which is
joints are first cleaned with spirit of The conditions are that the program is useful when working with large files.
salt prior to soldering. Hope this info for free distribution, remains my copy- Brian Milner,
helps. right and the copyright declaration (that via email
Craig Patterson, appears on the program’s screen) is not
via email to be erased. It is offered without war- We all have our favourite editors Brian.
ranty, although I’ll do my best to fix any For normal article text writing I actually
Thanks Craig, I would add that whilst bugs that are drawn to my attention. use an ancient steam-driven thing called
this solves your stripboard cleanliness Godfrey Manning G4GLM, Volkswriter 3 which I’ve used for maybe
problems, you have to be very cautious 63 The Drive, Edgware, 18 years and is DOS-based. I just prefer
about the use of any abrasive on p.c.b. Middx. HA8 8PS its no-nonsense simplicity over such bells
tracks for fear of cutting through them, and whistles packages as Word etc.
especially the thin ones. With p.c.b.s I Thanks Godfrey, that looks useful. I I must repeat the caution, though, that
use a special abrasive pad designed for use various methods through QB and VB any text editor for use with PIC program
the purpose that does the job nicely. for similar but not as nicely as you’ve writing must not insert hidden format-
Good p.c.b. supplies stockists sell them. done it. ting commands into its files.

Everyday Practical Electronics, August 2005 555

L.C.D. Problems Ultrasonic Radar quick charge (= C/4) their charging volt-
Dear EPE, Dear EPE, age increases to significantly above nom-
Just to let you know I’ve solved the I was fascinated with your design for inal cell voltage and reaches a maximum
problem of l.c.d. contrast that I report- your PIC Ultrasonic Radar (June ‘05). I near full charge, after which it declines
ed to you. It turned out that the con- think it is perhaps a little difficult for on further quick charging. After the max-
trast pin had to be connected to the readers like myself to integrate within imum is reached the charger switches to
wiper of a 20kΩ pot with the other their own robot designs. As an alterna- trickle charging (< C/16). The chargers
ends connected to +5V and 0V (rather tive I would suggest an “off the shelf” also impose a maximum charging time in
than just taking the contrast pin to 0V module ready-assembled sensor featur- case of defective cells.
via the pot). ing an analogue output signal which can The cheap chargers that come with
Ed Haslam, interface to a PIC directly. Using your sets of batteries are often not properly
via email motor drive circuit the area could be designed and should only be used with
scanned for obstacles. the included batteries. In order to avoid
Thanks Ed, this is worth highlighting. I enjoy EPE immensely although I damage, they are often designed only
Whilst most alphanumeric l.c.d.s. on the tend to cheat and use a PICAXE as it is for trickle charging. Even then, if used
market are what I would call “industry easy to program in BASIC so you can get with cells of much lower capacity they
standard”, in as much that several man- the project up and running very quickly. can damage them, and if used with
ufacturers use the same basic control cells of higher capacity they may not
protocol, there are still those available Chris Lewis, do a satisfactory job.
which are not. via email In my chargers I use the Dallas-
When purchasing an l.c.d. for a pub- Maxim MAX712 charger controller
lished design, always check that it has Thanks for that Chris i.c. Except for a d.c. “wall wart”, few
the same pinouts and that its contrast pin other components are required for a
can be controlled in the same manner as Laser Radar? very effective charger. But, it must be
we show. Note also that some l.c.d.s Dear EPE, designed for a specified number of
require a negative voltage on one side of Referring to your PIC Ultrasonic cells in series and a specified cell
the controlling pot, although this seems Radar (June ’05), I could not help think- capacity. I use a six position rotary
to be rare. ing that an IR l.e.d. receiver and a cheap switch to select the number of cells; all
laser pen instead of the ultrasonic bits are 500mAh. For a fixed number of
RC Switching would give a much sharper image and a cells the sensing resistor can be
Dear EPE, lot bigger range. switched to allow for different cell
Regarding the Radio Controlled If the laser unit was mounted on an capacities. It just depends on what is
Model Switcher (June ‘05). This shows electric motor shaft with an indexing wanted.
three wires coming from the receiver to a disk an almost instantaneous 2D picture Ed Grens, via email
three pin connection, with pin 2 connect- could be obtained. No doubt if the motor
ed to the input of the PIC, which detects unit could be induced to tilt up and down Thanks Ed.
the PPM signal. However the standard as well in synchronisation a 3D image
for RC equipment is to use pin 2 (the could be produced. Valves Offer
middle one) as the +5V line from the George Chatley, Dear EPE,
receiver with the ground and signal wires via email I have been given a box of old TV set
either side. This removes the possibility valves like the PL500, plus sundry other
of shorting out the receiver or blowing I’ve thought about such techniques bits like carbon speakers, phone inserts
up any device connected to it should the many times George, but it’s timing the etc. They are of unknown condition. I
connector be plugged in the wrong way return echo that is beyond me. Light am loth to throw them away as by now
round. travels at 186,000 miles a second. What they must be like gold dust, but if any-
sort of frequency would be needed to body wants them and will pay the
Malcolm Crabbe, time an echo across say three metres? postage, let me know via email.
via email Beyond my calculator at this moment! George Chatley,
And certainly beyond the scope of timing via email,
The RC unit’s designer Ken Ginn electronics on the hobbyist scene. But in HX1YAMAHA@aol.com
replied to Malcolm: terms of safety, Mike says he’d have no
problem if a laser pen or keyring were to Thanks for that kind offer George.
As far as I am aware there is no stan- be used in a published project. Looking via Google a photo of the
dard configuration for the servo output Well readers, any thoughts you can PL500 is shown on the National Valve
socket of radio control equipment. This offer me about resolving my perception Museum site, www.t-type.org/static/
may be as the reader implies for Futaba of the timing problem? museum.htm, and is defined as a pur-
manufactured RC equipment, which is pose designed television line output
probably the most popular in the UK. NiMH Charger valve, the American name for which is
But there are certainly many manufactur- Dear EPE, a sweep tube. Its peak anode voltage is
ers, such as Graupner, Fleet, Robbe and This is in response to the letter con- quoted as 7000V.
many more who have adopted their own cerning NiMH battery chargers in March
configuration. ‘05. Electronics Woodenly Disguised
My thinking on the configuration I I have designed several chargers for In Techno Talk some time ago it was
have chosen was that is was far safer to NiMH batteries and make them for vari- reported that mobile phone masts are
have an intermediate pin, the signal ous voltages from 500mAh NiMH prism being manufactured to look like the
path, separating the power lines. The cells. These I buy surplus for $0.25 US natural surroundings in which they are
reason is that if there was ever a solder each. installed, pine trees for pine forests,
bridge at this point, from pad to adja- No proper NiMH charger should palm trees for the desert, and so on.
cent pad, it would not short out the ever overcharge any NiMH battery so Recently I spotted one, to my left a
NiCad battery pack. In the RC receiver, long as the correct number of cells in mile before the Orpington turn-off from
doing so would certainly burn out the series are involved. However, if used at the M25 anti-clockwise carriageway. It
wiring and even damage the printed cir- excessive rates with batteries of small- took a later second pass to confirm
cuit in the receiver! These rechargeable er capacity than those for which it was what it was. And did it blend in with its
batteries will supply a hefty current if designed, this can lead to overheating surroundings? What do you think – a
shorted out. and damage. cross between a conifer and monkey-
Ken Ginn, Such chargers utilize the property of puzzle tree on the edge of deciduous
via email NiMH (and NiCad) cells that under woodland? I find it hilarious!

556 Everyday Practical Electronics, August 2005

INTERFACE
Robert Penfold
USING A D/A CONVERTER TO GIVE AN A/D CONVERSION

D igital-to-analogue conversion has

recently formed the subject of several
Interface articles. This type of conversion
the D/A converter until it is (more or less)
equal to the input voltage. When the input
shifts to a higher or lower voltage, the con-
this method is that it is not particularly
fast. Using an 8-bit D/A converter it can
take up to 255 increments of the output
is used in numerous practical applications, verter reaches this equilibrium point at a voltage before the conversion is complete.
but a conversion in the opposite direction correspondingly higher or lower output Even using parallel interface to the D/A
is probably used to an even greater extent. potential. This is reflected in a higher or converter, the maximum number of con-
With the aid of analogue-to-digital conver- lower value fed to the converter. versions per second is unlikely to be very
sion it is possible for a computer to be used The system works equally well if the high. Using software written in a relative-
for anything from simple monitoring tasks input signals to the voltage comparator are ly slow language such as Visual BASIC
to making highly accurate measurements. swapped, with the input voltage being fed would slow things down still further, giv-
At one time it was quite common for a to the inverting (–) input. The output of ing perhaps a hundred conversions per
digital-to-analogue converter chip to be the comparator will be high initially, and second under worst case conditions. The
used as the basis of a simple analogue-to- will go low when the output of the con- time taken for each conversion actually
digital converter. Although this might verter exceeds the input potential. Correct varies enormously, and is roughly propor-
seem pointless, the D/A chips of the time operation will be obtained provided the tional to the input voltage. A high reading
were much cheaper than the A/D variety. software is written to accommodate this takes about 100 times longer than a very
Where something less than the ultimate in method of working. low reading.
speed and accuracy would suffice,
an A/D converter based on a D/A Some Gain
chip was often a good choice. Despite its limitations, this
Converter economics have method of conversion can be
changed somewhat over the years, used to advantage in some appli-
and currently there is probably no cations. As a simple example,
point in using this technique on here we will consider its use in
price grounds. The basic technique measuring the current gain of a
can still be useful though. transistor. The conventional
The general scheme of things approach is to feed a small cur-
used in this type of A/D conver- rent to the base of the test com-
sion is shown in Fig.1. The input ponent and then measure the
voltage is applied to the inverting resultant collector current. The
(–) input of a voltage comparator, current gain is equal to the col-
and the comparator’s non-invert- lector current divided by the base
ing (+) input is fed from the output current. Since the base current is
of the D/A converter. In practice the same for every device tested,
the voltage comparator is usually Fig.1. It is easy to use a D/A converter in an A/D con- the gain is proportional to the
an operational amplifier (op. amp) verter but the software has to make up for the lack of collector current.
used “open loop”. hardware This makes it very easy to con-
vert the collector current into a gain
Filling in the Blanks Shortcomings reading, but this method has its drawbacks.
This type of A/D converter needs some Provided the D/A converter and voltage The main one is that the gain is not being
software to compensate for the shortcom- comparator are of a suitably high stan- measured at a certain current. Low gain test
ings in the simple hardware. The convert- dard, it is possible for this type of A/D devices produce a small collector current,
er is essentially a basic counter type, but conversion to achieve quite accurate while high gain transistors produce a much
with software filling-in for some missing results. However, it is probably not the higher collector current. The practical
hardware. best choice where the ultimate in accuracy importance of this is that, in general, the cur-
In order to take a reading it is necessary is required. A more serious drawback of rent gain is greater at higher test currents.
for the software to steadily increase the
value fed to the D/A converter, starting
from zero. The state of the comparator’s
output is checked prior to each increment
in the value supplied to the D/A converter.
Initially, the output voltage of the D/A
converter will be zero, and the input volt-
age will usually be at the higher potential.
The output of the comparator is therefore
low initially.
As the output potential of the D/A con-
verter is increased, it approaches and even-
tually exceeds the input potential. When
this occurs, the output of the comparator
goes high. This is detected by the software’s
monitoring routine, and the value supplied
to the D/A converter is not incremented any
further. The value currently output to the
D/A converter provides the result of the
A/D conversion.
All this system is actually doing is to Fig.2. This setup tests the transistor at a fixed collector current, giving more reliable
steadily increment the output potential of results than the more common method of using a fixed base current

558 Everyday Practical Electronics, August 2005

This method of measurement therefore has
the effect of exaggerating the difference
between low and high gain devices.
This can give the impression that a low
gain but serviceable device is a dud. Testing
the device at a higher collector current
would give a more realistic assessment of its
gain.
A few additions to the A/D setup of
Fig.1 provide a method of transistor gain
measurement that avoids this problem.
The new scheme of things is shown in
Fig.2. The base (b) of the test transistor is
driven from the output of the D/A convert-
er via a current converter, which provides
an output current that is proportional to
the output voltage of the D/A converter.
This gives a range of 255 different base
currents.
The voltage comparator has one input
fed with a reference voltage and the other
input monitors the collector voltage of the
test transistor. The value of the collector
load resistor, the supply voltage, and the Fig.3. Circuit diagram for the A/D converter. It has a full scale potential of 2·55
reference potential are chosen to produce a volts and a resolution of 10 millivolts
balance at the inputs of the voltage com-
parator when the required test current is
achieved. A measurement is made by Listing 1
steadily incrementing the base current Private Sub Command1_Click()
while monitoring the output of the voltage
comparator. For loopcount = 0 To 255
Initially the comparator’s non-inverting Out &H378, loopcount
(+) input will be at the higher potential, Label1.Caption = loopcount
and its output will therefore be high. As If (Inp(&H379) And 16) = 16
the base current is increased, the collector Then loopcount = 255
current of the test device also increases. Next loopcount
This produces a higher voltage drop
through the load resistor and a reducing End Sub
voltage at the collector of the test transis-
tor. Eventually, the collector voltage Private Sub Form_Load()
drops below the reference potential and Fig.4. Connections to the printer port are made
the output of the comparator goes low. via a 25-way male D connector. The cable
End Sub
This is detected by the software’s moni- should be no more than about two metres long
toring routine, and the base current is not
incremented any further.
With this method of measurement the which is read at bit 4 of the handshake An If instruction tests the state of the
gain is measured at a fixed collector cur- input register. Some of the handshake lines Select In line at address &H379, and uses
rent, and it is the base current that is varied. have built-in inverters, but the Select In a bitwise And instruction to mask the other
The value from the converter is proportion- line is not inverted. Therefore, bit 4 of the seven bits of this register. The loop contin-
al to the base current, but there is no easy handshake input register going high indi- ues normally until the Select In line goes
correlation between the base current and cates that the converter has reached the high, and a value of 16 is returned.
the gain of the test transistor. However, the appropriate input value. Variable “loopcount” is then set at a value
base and collector currents are both known The CA3130E does not have an internal of 255, bringing the looping action to a
quantities, and a simple software routine is compensation capacitor. Discrete capacitor halt. This line is preceded by one that
all that is needed in order to calculate and C2 is therefore included in order to ensure writes the “loopcount” value to the label
display the appropriate figure for current that IC2 provides stable operation. component, so the final value of this vari-
gain. An advantage of using a PC based Both the AD557JN and the CA3130E able is displayed when the routine stops.
system for awkward measuring applica- are MOS devices, and the standard anti- In theory, the value on the label is incre-
tions is that any complications can usually static handling precautions should there- mented each time the routine goes through
be handled by the software, keeping the fore be observed when dealing with these a loop. Of course, in practice the looping is
hardware reasonably simple. components. Few op. amps have the char- so rapid that only the final value is actual-
acteristics required for use in this circuit, ly displayed. Fig.5 shows the program
so the use of alternative types for IC2 is after a reading has been taken. The full
Converter Circuit not recommended. Most op. amps will not scale voltage and resolution of the circuit
The circuit diagram for a very simple
work at all in this circuit. The connections are the same as those of the D/A converter
A/D converter, based on the method out-
to the printer port are made via a 25-way chip, or 2·55V and 10mV in other words.
lined in Fig.1, is shown in Fig.3. IC1 is an
male D connector (Fig.4).
AD557JN 8-bit D/A converter chip. This
chip has been covered in recent Interface
articles so it will not be considered in Software
detail here. It uses parallel interfacing, so A routine to take and print readings can
its data inputs (pins 1 to 8) can be driven be very simple indeed. The sample pro-
direct from the data outputs of a PC’s gram in Listing 1, which utilises
printer port. The output voltage range is 0 Inpout32.dll, requires a form equipped
to 2·55V, giving a resolution of 10mV with a button (Command1) and a label
The voltage comparator is a CA3130E (Label1). The label should have a suitably
op. amp (IC2). This can operate from a sin- large text size set via the Font property.
gle 5V supply, which avoids the need for Operating the button starts a For…..Next
dual supplies and (or) a higher supply loop that increments the variable “loop-
potential for the comparator. It also means count” from 0 to 255. On each loop, the
that its output operates at levels that will current value stored in this variable is out-
directly drive a handshake input of the put to the base address of the printer port
printer port without any problems. The (&H378). This provides rising output
input used in this case is the Select In line, potential from the D/A converter. Fig.5. Test program displaying a reading

Everyday Practical Electronics, August 2005 559

Constructional Project

Pain Monitor
John Becker
A patient welfare logger that also has applications for other occasional event
logging requirements, as in sailing, golfing or wildlife watching, for example.

R
ECENTLY, Dr. Mark Piper, Talking with Mike, the author felt that it
Consultant Anaesthetist at was an idea that he would like to explore SPECIFICATIONS
Wansbeck General Hospital, further. Pain is a subjective experience and
Ashington, Northumberland, emailed its perception will vary from patient to ɀ Line of 10 pushbutton switches
Editor Mike: patient. Consequently, Mark was asked if representing and recording pain
there are any electrical waves the body gen- threshold values
There is a need for a “pain meter” in erates when experiencing pain and which ɀ Two pushbutton switches to
modern hospital practice. This meter needs could be electronically monitored? To record presence or absence of
to prompt the patient to record an assess- which Mark replied: other patient conditions, such as
ment of their pain and store this informa- nausea or itch
tion for downloading. This would help in You have hit on the problem that ɀ 13 l.e.d.s to visually indicate
research into pain relief after surgery. underpins all research into pain. It is conditions selected
There are many “pain scales” used. A subjective. Pain in humans is difficult to ɀ Additional general purpose l.e.d.
common one is the visual analogue score. measure. However, it is still important to ɀ PIC microcontroller controlled
This is a 100mm line, one end represents no measure. The type of pain scores are ɀ Real-time clock chip, non-volatile
pain, the other end represents the “worst visual analogue scoring (previously ɀ Serial EEPROM (non-volatile
pain imaginable”. The patient is expected described), using verbal descriptor rat- memory), with 32K byte storage
to mark along this line where their pain ings (No, Mild, Moderate, Severe Pain). ɀ Serial interface to PC (any current
severity is, for example: All scoring systems are ways of asking Windows platform) via RS232
the question “How bad is the pain?” and device
finding some way to statistically analyse ɀ PC file generated to suit viewing
the data. and analysis via Windows Excel
There are conventional pain measures ɀ PIC monitors switch presses,
in clinical research. To make data between records which switch and the time
The NHS does not have the adequate patients comparable, the data set needs to pressed
nursing resources, and research and audit be similar. A device that prompts the ɀ Provision for monitoring up to 99
into pain is not a clinical priority. If a tool patient, records the score and patients on the same unit
was available that allowed the patients stores the data would ɀ L.C.D. displays latest recorded
to record their pain scores this patient data
be useful.
would be helpful. ɀ Unit can be switched off without
Could this be a focus for memory loss
an EPE design challenge ɀ Battery powered
for your readers? ɀ Optional audio output via buzzer

Design Criteria
Further discussions with Mark led to the
formulation of the design criteria shown in
the Specifications table.
Sketching out a block diagram, it was
found that there was a need for PIC moni-
toring and control of the following:
ɀ switches, 13 pins
ɀ l.e.d.s, 14 pins
ɀ serial EEPROM, 2 pins
ɀ RS232 interface, 2 pins
ɀ real-time clock (RTC), 2 pins
ɀ l.c.d., 6 pins
A total of 39 pins, but as the RTC and
EEPROM can be multiplexed readily,
using their in-built selection via dedicated

Everyday Practical Electronics, August 2005 561

 • Controlling eight l.e.d.s (D3 to D10)
Port C (RC0 to RC2, RC5):
• Monitoring four switches (S1, S2,
COMPONENTS
S12, S13), biased normally-high by R1 to
R4 Resistors
• Controlling four l.e.d.s (D1, D2, D12, R1 to R4 10k (7 off)
D13) R8 to R10 See
R5, R7 470Ω (2 off) S H O P
Port C (RC3, RC4): R6 1k TALK
• Data exchange with EEPROM (IC4) page
and RTC (IC5) (multiplexed by software Potentiometer
address) VR1 10k min cermet
round preset
Port C (RC6, RC7):
Capacitors
• Data exchange with RS232 serial I/0 C1, C2 100n ceramic disc,
controller IC3 5mm pitch (2 off)
C3, C4 10p ceramic disc,
Port A (RA0 to RA2): 5mm pitch (2 off)
Multiplex selection of l.c.d., switches C5 to C9 1µ radial elec. 16V
and l.e.d.s (excluding S11, D11, D14) is (5 off)
controlled by Port A:
• RA0 controls the E pin (enable write) Semiconductors
of the l.c.d. when data is written to it D1 to D14 red l.e.d., high
• RA1 controls the bank selection of brightness (14 off)
l.e.d.s D1 to D13 through their commoned D15 1N4148 signal diode
cathodes, buffered by resistor R5 IC1 78L05 +5V 100mA
• RA2 controls the bank selection of regulator
switches S1 to S13 IC2 PIC16F876 micro-
Fig.1. Pain Monitor block diagram controller, prepro-
Port A (RA3 to RA5): grammed (see text)
• RA3 activates optional buzzer WD1 IC3 MAX232 RS232
transmission addresses, that brought the interface
count down to 37 PIC I/O (input/output)
• RA4 controls general purpose l.e.d. IC4 24LC256 serial
D14, buffered by R7 EEPROM
pins needed.
It was obvious that a PIC16F877
• RA5 monitors S11, biased normally- IC5 DS1307 serial I2C
high by R10, and controls l.e.d. D11 real-time clock
device, having 33 usable I/O pins, could
do the job if a minor bit of multiplexing Switches S1 to S10, S12, S13 all have
was used. However, on further considera- Miscellaneous
dual roles, selected via S11. They normally B1 9V PP3 type battery
tion, it became apparent that the smaller monitor the patient’s perceived welfare, but
PIC16F876, having 22 I/O pins, could be B2 3V Lithium battery,
when their second role is activated via S11, p.c.b. mounting
coaxed into service if more sophisticated they are used to select the ID number allo- S1 to S13 push-to-make switch,
multiplexing techniques were used, and cated to the patient, from 1 to 99. high profile, round
having several devices accessed by the In Fig.2 the l.e.d.s and switches are rep- top, p.c.b. mounting
same pins. See block diagram Fig.1. resented in a block outline, the internal (13 off) (see text)
logic of which is illustrated in Fig.3. S14 min. s.p.s.t. toggle
Circuit Diagram switch
The resulting complete circuit diagram
for the Pain Monitor is shown in Fig.2.
Port A Control Logic SK1 9-pin serial connector,
Pin RA0 is always used in output mode. female, panel
The PIC16F876 microcontroller is It is normally held low to prevent the l.c.d. mounting
notated as IC2, and is run at 4MHz as set from accepting Port B data generated in WD1 piezo sounder (optional)
by crystal X1 in conjunction with capaci- response to switch and l.e.d. requirements. X1 4MHz crystal, low
tors C3 and C4. Its I/O pins are used as It is toggled as usual when required to send profile
follows: X2 alphanumeric l.c.d.
data to the l.c.d. module, 2-line x 16-
Pin RA1 is held low in output mode character (per line)
Port B pins (RB0 to RB7): when data is to be sent to l.e.d.s. D1 to D13.
• Outputting data to the l.c.d. (X2) X3 32.768kHz crystal,
It is set to input mode (high impedance) capacitance 12.5p
• Monitoring eight switches (S3 to when data is being sent to the l.c.d. and Printed circuit board, available from
S10), biased normally-high by Port B when the switches are being read. the EPE PCB Service, code 519; 8-pin
internal pull-ups Pin RA2 is held low in output mode when d.i.l. socket (2 off); 16-pin d.i.l. socket;
28-pin d.i.l. socket; PP3 battery clip;
plastic case 204mm × 150mm ×
40mm; connecting wire; solder, etc.

Approx. Cost
Guidance Only £45
excl meter &
batts

data is being read from the switches. It is set

to input mode (high impedance) when data is
being sent to l.e.d.s. D1 to D13.
Pin RA3 is always set to output mode,
normally low, going high when the optional
buzzer WD1 is to be sounded.
Pin RA4 is always set to output mode,
normally high, going low when l.e.d. D14 is
to be turned on.

562 Everyday Practical Electronics, July 2005

 Fig.2. Circuit diagram for the Pain
Monitor, also see Fig.3

Everyday Practical Electronics, August 2005 563

 519

Fig.4. Printed circuit board component

and track layouts

Other decoupling. Switch S14 turns on the 9V

supply. Current consumption is about
Components 17.5mA with no l.e.d.s on, rising to about
The remaining 30mA with two l.e.d.s on.
components in Diode D15 and R6 protect the +5V line
Fig.2 have the fol- if the PIC is programmed in situ from a
lowing functions: dedicated PIC programmer via connector
Resistors R8 and TB2. Preset VR1 sets the l.c.d. screen
R9 bias high the contrast.
Fig.3. Switch multiplexing logic clock and data pins IC4 is the serial EEPROM which
of the EEPROM records the monitored data. It is a 256K-bit
and RTC devices. (32K byte) device as featured in many
Capacitors C5 to C9 EPE data logging designs. It is accessed
Pin RA5 is normally held in input mode are associated with the ±10V biasing of the under 2-line I2C protocol.
(high impedance), but set low in output PC interface connections of the RS232 chip, The RTC device, IC5, is also accessed
mode when the switches are read. IC3. This communicates with a PC via sock- under I2C protocol. It is controlled by its
The outputs at pins RA4 and RA5 are et SK1 and a standard serial interface cable own oscillator, activated by crystal X3,
always changed at the same time as each connected to the PC’s COM1 or COM2 port. which is specified as a 32.768kHz, 12.5pF
other (except during data exchange with IC1 regulates the 9V d.c. primary power device. The RTC is powered by its own
PC). Thus the buzzer is normally always supply (e.g. PP3 battery, B1) down to +5V. dedicated 3V Lithium battery, which can
activated when l.e.d. D14 is turned on. Capacitors C1 and C2 provide +5V line typically power it for around 10 years,

564 Everyday Practical Electronics, August 2005

roughly the same as the shelf life of such
batteries. This means that the RTC is not
turned off when the main 9V supply is
switched off.
Consequently, the RTC continually gen-
erates real-time clock and calendar data
throughout its battery life. This data is
immediately accessible to the PIC once the
main supply has been switched on.
The initial clock and calendar data is set
into the RTC from the PC’s own real-time
clock when such a link is established via
SK1. The RTC does not become active until
this data has been sent for the first time fol-
lowing the unit’s assembly.

Construction
The component and track layout details
for the Pain Monitor’s printed circuit board
are shown in Fig.4. This board is available
from the EPE PCB Service, code 519. Enclosure Line 1 shows the ID NO (patient number),
and Event A (pain) value. Line 2 shows the
Assemble the board in ascending order of The case used to house the prototype is
plastic and measures 204mm × 150mm × values for Events B and C (allocated to what-
component size, starting with the link wires ever condition you wish – e.g. itch or nausea
and d.i.l. sockets for IC2 to IC5. 40mm. Its hole drilling positions can be
marked on it using a photocopy of Fig.4 as as Mark suggests). The clock display at the
Two initial points to note – the board must right of line 2 will remain at 00:00:00 until
maintain a low profile to allow the l.e.d.s and a template. The holes should allow the
switches to be pressed without friction. the RTC has been initialised via the PC. It
switches to protrude through the case when may be necessary to adjust preset VR1 to
the board is mounted behind it. This means The l.c.d. slot can be cut by first drilling
a perimeter of small holes, then cutting with improve the l.c.d. screen display contrast.
that the electrolytic capacitors and crystal X3 Press one of the 10 in-line switches; l.e.d.
need to be positioned with their bodies hori- a craft knife and smoothing with a file.
Socket SK1 and switch S14 should be D14 should turn on as an acknowledgement
zontal to the board. Additionally, crystal X1 of the press. When the switch is released its
must be a low-profile type. Ensure the top of mounted in one side of the case.
associated l.e.d. will come on, the Event A
regulator IC1 is set low, or even position this
device horizontally too. Testing value on the l.c.d. will change to match the
Before inserting the d.i.l. i.c.s and connect- switch number pressed and D14 will be
Conversely, the switches should be chosen turned off. Try the test with the other switch-
so that their push-tops are high-profile and are ing the l.c.d., or connecting power from bat-
tery B1, thoroughly check the board for sol- es, excluding S11 at this time. Each time a
well above the tops of the d.i.l. i.c.s. Get the switch is pressed and held pressed, any turned
type which have rounded tops to make hole dering and component positioning errors.
Connect and switch on battery B1, then check on l.e.d.s, apart from D14, will be turned off.
drilling simpler. Those used in the prototype, Switch S11 is the one that controls the ID
which should be avoided if possible, have that +5V (within a few millivolts) is present at
the output of regulator IC1. Always switch number selection mode. Press and release it.
square tops requiring either a square cut-out, Having released it l.c.d. line 2 will display a
or a round hole of at least 11mm diameter. off B1 before making any changes to the
board (beware that B2 is always connected to message similar to:
The l.e.d.s should be positioned so that
their tops will be about 5mm above the case. the RTC’s B2 power pins 3 and 4).
Initially, mount them somewhat higher, and When satisfied, plug in the prepro-
then desolder and lower them once the board grammed PIC (see later) and connect the
is mounted in the case, allowing them to be l.c.d. Check the 5V supply line again.
more accurately aligned before resoldering. On power-up, the l.c.d. should initialise
All the wired connections to the off- into its 2-line 4-bit control mode, and dis-
play information similar to: Note the small arrow indicating the value
board components should be made on the which can be changed.
trackside of the board. Pin connections for Now pressing any of the 10 in-line
standard l.c.d.s are shown in Fig.5. switches causes the ID number to change
and match the switch number. If you now
press S13 (B/+) the value of 10 will be
added to the displayed value. Pressing S13
again adds a further 10. The maximum is
99. Similarly, pressing S12 (C/–) deducts 10
from the displayed value, to a minimum
limit of one.
The number-changing switches may be
pressed as often as required. But note that
pressing S1 to S10 will always set the ID
number to that switch number.
Having changed the ID number to that
required, press S11 again. On releasing it
the new ID number is now active, and
patient welfare recording resumes, for this
new patient.
When the ID is changed, the recorded
Events data for the new ID replaces the pre-
vious Events data (as held in the last 512
Fig.5. Pin connections for standard bytes of the EEPROM).
l.c.d. module
Recording Data
The switch information relating to patient
Battery B2 for the RTC has p.c.b. mount- welfare is recorded to the EEPROM on
ing tabs and should be soldered to the rear each successful release of the relevant
of the board. Do not short the battery’s ter- switch. This data can later be downloaded
minals together when doing so! to a PC for viewing.

Everyday Practical Electronics, August 2005 565

 Time button to send the currently required
setting, as well as the time and date. The
default for the unit following its assembly is
delay off.
With the delay turned off the PIC
responds almost immediately to any switch
press, as you will have found already. With
the delay on, when any switch is pressed
there is a delay of about three seconds
before the PIC accepts the press as valid. At
the moment of the switch press, the l.c.d.
displays a message on line 2, WAIT FOR
LIGHT, indicating that the switch must
remain pressed until the delay has ended.
The end of the delay is indicated by the
The main screen for the Pain Monitor’s PC program l.e.d. D14 being turned on and screen line 2
showing OK. The switch can now be
released, on which D14 will go out again
Downloading will be discussed presently, An example of a typical VB6 display of and the l.c.d. will show new data on line 2.
but first install the remaining chips, RTC, the program’s main screen is shown above. If the three seconds delay is active and a
EEPROM and RS232, then check the +5V The program can be run in one of two switch is not pressed for long enough, all
power line again. ways, either through its source code if you l.e.d.s will remain off until one of them is
The EEPROM will record data in have VB6 installed, or via a standalone correctly activated.
response to each successful keypress. Data is facility if you do not. The source code will
recorded in order of ID number, year, month,
day (date), hours, minutes, seconds, Events
not be discussed, but running the standalone
version is as follows.
EEPROM Clearance
Next, the unit’s EEPROM should be
A, B and C values. Eight bytes in all, as the Having copied the files to your PC (see cleared, all values being reset to zero. Click
Event values are combined into one byte. later), click on the PainMonitor.exe file icon on the PC screen’s Reset PIC button to start
With B and C it is only the act of pressing the (a lightening flash) to launch the program. this process. It is a fairly slow process to
switch that is recorded, not the number of Connect the serial cable between the Pain clear all 32768 EEPROM bytes, taking
times it has been pressed (the l.c.d. shows a Monitor and one of your PC’s serial ports, about two and half minutes to complete.
cumulative count for the B and C values). e.g. COM1 or COM2. The unit cannot be This is due to the various delays required
Event A can be a value of between 1 and used with a USB port. The cable should be within the PIC software for the procedure to
10 (bits 0 to 3), B and C are allocated 0 if one of the “standard” (straight through) perform correctly.
unpressed, or 16 or 32 (bits 4 and 5) respec- types, such as used with external modems. During the clearance time, a bargraph on
tively if pressed, so fitting all three values On the screen at the right are two “radio” the PC screen tracks the progress. The l.c.d.
into six bits of a byte. buttons, marked COM1 and COM2. Click also displays a tracking message, for example:
on the one that matches the port into which
you have plugged the cable. This informa-
tion is recorded to disk and recalled each
time the program is run. It may be changed
by the same buttons whenever you wish.

After each 8-byte batch is recorded the Setting Calendar and Time On completion, the l.c.d. screen reverts to
memory address counter is advanced by The first thing to do now is set the current the normal monitoring display, and the PC
eight places. A message stating RECORD calendar and time data into the PIC. Click screen reverts to standby mode.
COUNT is shown on l.c.d. line 2, followed on the Send Time button. This causes the The EEPROM clearance can also be
by a number. The number is the EEPROM PC’s current calendar and time values to be done from the unit itself. With the unit
memory address divided by eight, thus rep- sent to the PIC, which then installs them switched off, press switch S11 and hold it
resenting a batch (eight bytes) count of the into the RTC chip. They should never need pressed. Switch on the power, wait a
events recorded. The count is displayed for to be sent again, for the life time of the RTC moment for the unit to initialise and display
about two seconds before the screen reverts battery, B2. The RTC device even keeps the message that the EEPROM is being
to its normal monitoring mode. track of leap year facts. cleared. Switch S11 can now be released.
The maximum count should not be allowed However, it is believed that the RTC does
to exceed 4032 otherwise the counter rolls not update itself for winter/summer daylight Downloading to PC
over to zero, and starts again, overwriting pre- saving changes. These, though, are known to Having cleared the EEPROM, press any
vious data. (Essential program “housekeep- the PC for the country selected (this will nor- switches you wish on the Pain Monitor to
ing” data is held in the last 512 bytes of the mally be your own country unless the PC set- record example data. Then switch off the unit
EEPROM and these 64 blocks are not avail- tings have been changed). Consequently, fol- until you are ready to download the data.
able for other data storage.) It is recommend- lowing a daylight saving change (e.g. GMT
When ready to download, switch on the
ed that the data should be downloaded to the or BST for the UK), the revised time can be
PC before the maximum is reached, and the unit, click on the PC screen Download button
sent to the PIC via the Send Time button.
EEPROM then erased (see later). to start the data download from all 32K bytes
Handshakes of the EEPROM. Again a bargraph tracks the
PC Interface The PC software expects handshakes progress. The l.c.d. screen simply shows the
one-line message:
Having recorded a few events, the EEP- when exchanging data with the PIC. If these
ROM contents can be downloaded to the are not received in approximately five sec-
PC. First, though, the PC must run its spe- onds, a time-out occurs and a screen mes-
cially written program. Details for obtain- sage informs you of the fact, advising you
ing and copying this software to your PC to check your serial cable and power supply
are given in the Resources section later. connections (the PIC unit must have its
The program has been written in Visual main battery switched on).
Basic 6 (VB6) and its purpose is to down- The downloading does not change the
load data from the unit’s EEPROM, clear Switch Response Delay contents of the EEPROM, and once it is
the EEPROM when required, set the RTC The Send Time button also allows a complete, further data recording starts from
clock and calendar real-time values, and to switch response delay to be turned on or off. the last available address before download-
produce data files suited to examination via The function is set via the Delay On tick box ing started.
Excel or a text editor such as Notepad or at the bottom of the screen. Click on it to On completion of the download, the l.c.d.
Wordpad etc. The program does not offer toggle between the settings. A tick means screen again reverts to the normal display.
any graphics display or other data analysis. that the delay will be active. Click the Send The PC, though, now takes the downloaded

566 Everyday Practical Electronics, August 2005

 the Editorial office (a small handling charge
applies – see the EPE PCB Service page) or
it can be downloaded free from the EPE
Downloads site, accessible via the home
page at www.epemag.co.uk. It is held in the
PICs folder, under Pain Monitor. Download
all the files within that folder.
This month’s Shoptalk provides informa-
tion about obtaining pre-programmed PICs.
The PIC program source code (ASM)
was written using EPE Toolkit TK3 soft-
ware (also available via the Downloads site)
and a variant of the TASM dialect. It may be
translated to MPASM via TK3 if preferred.
The run-time assembly is supplied as an
Simulated example of monitored data after download and shown through MPASM HEX file, which has configura-
Windows Notepad tions embedded in it (crystal XS, WDT off,
POR on, all other values off). If you wish to
data, formats it suitably for viewing via
Excel etc., and sorts it into order.
Other applications program the PIC yourself, simply load this
HEX file into the PIC using your own PIC
As stated in this article’s sub-title, the
The sorting process groups data in prior- Pain Monitor can be used for other applica- programming software and hardware.
ity order of ID number, date in relation to tions. Three such come to mind and no The PC interface software was written
YY:MM:DD, and time in relation to doubt you will think of others. under Visual Basic 6 (VB6), but you do not
HH:MM:SS, followed by the values for One possible use is for recording moder- need VB6 to be installed on your PC in
Events A, B and C. Blank lines are placed ately-slow sports events which allow time order to run it.
between each ID number group for ease of for the ID number to be set, such as sailing Whether or not VB6 is installed, copy
viewing. (but probably not motor racing!). all of the Pain Monitor files (except the
Having completed the sort, the data is With sailing, for example, the ID number PIC files if you prefer) into a new folder
output to a file having a name prefix of could be that of a particular craft. Switch S13 called C:\Pain Monitor, or any name of
PainMonitor plus the date and time of the (Event B) being pressed to record the time of your choosing, on Drive C (the usual hard
download, followed by the extension .XLS. the start of a race. S12 (Event C) could drive letter).
For example: record its completion time. Switches S1 to If you do not have VB6, you also may
S10 (Event A) could be pressed at various need three other files, comdlg32.ocx,
PainMonitor 26JAN05 23-32-29.XLS stages during a race to record the progress, Mscommctl.ocx and Msvbm60.dll, held
e.g. the time at which a particular buoy is on our 3·5inch disk named Interface Disk 1,
When the file has been saved, it is imme- passed. Mike says that craft handicaps could and in the Interface folder on our
diately opened for viewing as a text file, be calculated from such recorded data. Downloads page (they are also included
through Windows Notepad or Wordpad, Golfers might also find the unit useful to with the TK3 software, in Disk 2). These
depending on its size. record their scores at various holes. files must be copied into the same folder as
Click the text screen’s normal X button to Another is for the unit to be used as a the other Pain Monitor files.
close it. The file can be recalled by clicking wildlife monitor. You could, for instance, These three files are not supplied with the
on the View Data button. regard the ID number as representing a par- Pain Monitor software as they are common
The Directory button allows you to select ticular bird or animal, e.g. 1 for heron, 2 for to several EPE VB6 projects and amount to
any previously recorded Pain Monitor file for cormorant, etc. Having seen the creature, about 1MB of data.
viewing. The facility has a variety of func- select its allocated ID number, then press the Additionally, the VB6 source code makes
tions which allow the folder path in which the appropriate switch S1 to S10 to record the use of Joe Farr’s excellent Serial Interface
files are stored to be selected. The one you quantity seen and the time of the sighting. for PICs (Oct ’03) software. In order to
need to select is that for the folder in which access (and perhaps modify for your own
you placed the Pain Monitor VB6 software. Conclusion purposes) the Pain Monitor VB6 source
There is a Notes button on the screen The Pain Monitor is currently being field code files, you need to have Joe’s software
which causes detailed notes about the tested by Mark Piper and a commercial role installed on your PC as well (see his pub-
Directory screen options to be displayed. for it is under consideration. lished text). This is also available via our
It has been a Downloads site.
challenge to the Without Joe’s software installed, if you
author to achieve try to access the Pain Monitor VB6 source
realisation of this code, it will crash.
design, but also a Note that you should not attempt to
satisfaction in the “install” the Pain Monitor VB6 files via
knowledge that he Explorer or other similar PC facility. Use
has been able to Windows’ own normal Copy facility. អ
design something
that has potentially
wider social bene-
fits. Should you
have ideas for other
such beneficial
designs, let the
author know via
EPE,
john.becker@
wimborne.co.uk

Resources
Software, includ-
ing source code
files, for the PIC
unit and PC inter- Example of a section of Windows
face is available on Excel showing some of a downloaded
Simulated example of the directory screen 3·5inch disk from data file

Everyday Practical Electronics, August 2005 567

Surfing The Internet

Net Work
Alan Winstanley

Let There Be Delight though and ensure that anti-virus software is updated and that
spyware is constantly dealt with. I will be looking into these
This month has been a very special one in the history of this
Internet column (which itself started life in October, 1996). After issues in forthcoming columns. I am also happy to report that
well over a decade of chomping at the bit, watching enviously as Tiscali does not have a problem with sending own domain mail
the rest of country surfed the Internet at ever-increasing speeds, either, unlike BT. (This is a real headache for some users and I
and being brushed off by an intransigent British Telecom and their will be suggesting some workarounds in future articles.)
cruel “trigger levels”, against all the former odds ADSL finally
arrived with a bang at the author’s worklab.
Net More Benefits
Not all ISP’s tariffs permit more than one PC to share a single
Joyful was the day on 25 May 2005 when I could finally hit the
ADSL port, but for the writer the next question is how to connect
Upgrade button on the Tiscali web site and – at long last – order
other computers and a laptop to the same network. A Linksys
broadband services for my fax number.
802.11b wireless access point was hooked up to the gateway, and
The entire process went extremely smoothly (once I remem-
USB WiFi dongles were used on the laptop and on another PC in
bered my web site log-in password!). Tiscali is to be congratulated
the building, to connect them to the Internet. The Linksys equip-
on providing a very efficient and informative upgrade process, in
ment is neat and stackable, and I am sticking with a pile of sepa-
which regular updates were emailed out, the documentation rate Linksys devices, even though newer combined units are now
arrived within 48 hours and a conversion date was duly set for two available.
weeks hence. In fact, as a pleasant surprise, ADSL was enabled Forget any idea of instantly “going wireless” and the entire
within the week: I know this because Tiscali sent another email out building coming alive with powerful WiFi internet access. It must
of the blue advising that the broadband service had now been be said that WiFi may not be the most reliable method of hooking
switched on, and when I looked under the desk at the newly- to a network, so expect some debugging and trial and error. In the
installed router, the ADSL l.e.d. had suddenly illuminated! writer’s case, having four brick walls and a large copper water
Tiscali’s free ADSL modem and two free microfilters arrived in heating tank in the way did nothing to help with signal strength.
plenty of time as well, in a packet that fitted conveniently through Wireless network reliability depends enormously on bricks, peo-
the letterbox. Tiscali’s entire upgrade process could not be faulted, ple, concrete, pipework, radiators, water tanks and the odd steel-
which I suppose is one of the benefits of being a late adopter – the cased PC or filing cabinet not getting in the way. Near line of sight
rest of the country having been the guinea pigs for the UK’s ADSL transmission is preferable.
rollout programme. To start with, Tiscali 512k has been chosen, The aerial location and r.f. transmission pattern can also play a
which has a 30GB per month limit that is more than enough for the part; perhaps consider using an internal antenna on the wireless
time being. Higher speeds have tighter restrictions, and an attrac- access point if necessary. Helped along by an unofficially-long
tive piece of software that helps you monitor usage totals is the DU USB extension lead, a USB dongle was Blu-tacked to the wall, in
Meter from www.dumeter.com. A 30 day trial can be downloaded. near line-of-sight of the WAP, and effective links were finally
Since the writer has a small network, a somewhat overpowered established with another PC. Another machine uses a PCI 802.11g
but futureproof ADSL2+ gateway has been used to connect the card successfully. Meanwhile, the laptop works fine on WiFi with
network to the phone socket. Of course, a microfilter (supplied) is its USB dongle, even at the bottom of the garden.
needed to separate out the lower frequency signals for the fax Again, rather than spend a lot of time struggling to re-invent the
machine, and any other telephones or fax machines connected to wheel, consider leaving this to a reputable networking professional
extensions on the same ADSL-enabled line each need their own who will also (absolutely critically) configure the security for your
microfilters. wireless system that will prevent any wireless-enabled neighbours
from thieving your bandwidth or snooping on your machines.
On Guard
Compared with the frustrations of dialup, having ADSL always- Homeplug: Networks For Live Wires
on Internet access has been a surreal experience. Mail is checked If wireless networking isn’t for you, then more recently
and filtered immediately. Web sites that were beyond reach due to networking through the mains electricity supply has started to
bandwidth constraints now spring into life. Machines can be left to take off, applying the new Homeplug standard (see www.home-
look after themselves without worrying about time-outs. For some- plug.org). In effect, Ethernet can be fed into the ring mains and
one working in today’s knowledge-based economy, broadband special mains adaptors act as Ethernet ports for network clients
Internet access is life transforming. such as PCs, Homeplug-capable DVD and HDTV. One Homeplug
Always-on access brings its own risks, of course, including adaptor product claims a range of 500 metres at 14Mbps.
viruses, snooping, hijacking, keylogging Trojans and other spy- An excellent source of network components, WiFi, antenna,
ware. There comes a point where it is more cost effective to leave Homeplug adaptors and interesting information is available from
some aspects to experts, especially concerning networking and Solwise of Hull (www.solwise.co.uk), well worth browsing and
security. Working on the principle that I know my limits and life is bookmarking. The same web site explains remarkably well why
too short to fight with IT equipment, for the sake of one hour’s faster is not always better or more reliable, especially comparing
labour a network professional has configured properly the router, wireless 802.11g with its slower stablemate 802.11b, as used on
the network and the security settings. It is money well spent, and the author’s wireless access point.
having a robust network sheltering behind a router brings with it Needless to say, readers, there are many exciting and interesting
peace of mind and some added security benefits. times ahead, and I’ll be sharing useful hints, tips and pointers in
For single PC users having an ADSL modem, ensure that future editions of Net Work – The Internet column.
Windows Firewall (XP) is on. One must be even more vigilant You can email me at alan@epemag.demon.co.uk

568 Everyday Practical Electronics, August 2005

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Everyday Practical Electronics, August 2005 569

Readers’ Circuits

Ingenuity Unlimited
BASED
WIN A PICO PC Our regular round-up of
WORTH £586 readers’ own circuits.
OSCILLOSCOPE 5GS/s Dual Channel Storage We pay between £10 and


Oscilloscope £50 for all material pub-
z Sp e c tr u m lished, depending on length

5 0 M H
Analyser and technical merit. We’re

Multimeter looking for novel applications and circuit designs, not simply mechani-
ter

Frequency Me cal, electrical or software ideas. Ideas must be the reader’s own work
n te r fa c e .

U SB I and must not have been published or submitted for publication else -
ou h a v e a n o v el where. The circuits shown have NOT been proven by us. Ingenuity
If y
ch
circuit idea whi Unlimited is open to ALL abilities, but items for consideration in this
to
would be of use column should be typed or word-processed, with a brief circuit
er s t h e n a description (between 100 and 500 words maximum) and include a full
other read
ours. circuit diagram showing all component values. Please draw all circuit
cope could be y
Techno log y P C-based oscillos l b e a w a r d ing a schematics as clearly as possible. Send your circuit ideas to:
Pico
, Pi c o Te chnology wil
Every 12 mo n th s the best IU Ingenuity Unlimited, Wimborne Publishing Ltd., 408 Wimborne Road
ta l s to ra g e oscilloscope for e
PicoScope 3205
d ig i ta Logger/Scop East, Ferndown, Dorset BH22 9ND. (We do not accept submissions
sio n. In a d d it ion a DrDAQ Da u n ne r u p. for IU via email). Your ideas could earn you some cash and a prize!
submis the r
be presented to
worth £59 will

Helix Thermostat Spiralling Into Control

T HE Seebeck effect will be familiar to

most EPE readers – when heat or cold
is applied to one of the junctions of a cir-
Multiturn preset VR1 is used to take
advantage of IC1’s offset adjustment fea-
ture, and is used to adjust the thermostat.
heated, and it is “quiescent” when the
temperature equalises across its length.
These characteristics might find special
cuit composed of two different metals, a Resistor R3 and transistor TR1 represent a applications. An obvious advantage is that
small amount of electricity is generated. simple current amplifier to switch relay a sensor made of copper may withstand
Less familiar, however, is that a thermo- RLA. temperatures up to 1083ºC. In fact if plat-
electric effect may occur in a circuit com- When the circuit is first powered up, inum wire were used, this would increase
posed of a single metal. For this, one only VR1 needs to be adjusted so that l.e.d. D1 to 1755ºC. A further advantage is that,
needs to twist a wire into a helix, and to just extinguishes. When heat is applied to since the thermistor measures relative tem-
heat it to one side of the helix. the thermistor’s “pad”, a potential differ- perature, it would be ideal, if suitably
For the circuit described here, the author ence is generated across the inverting and arranged, for sensing rising heat in a room.
created such a sensor, or “thermistor”, non-inverting inputs of IC1, and the output Thus it would serve as a very cheap and
using seven turns of 24s.w.g. (0·56mm of IC1 switches high, thus triggering the effective fire alarm system. With the ther-
diameter) copper wire wound on a 10mm relay via TR1. mistor reversed, the circuit would of
diameter former. At one side of the helix, It needs to be borne in mind that the course detect falling temperature.
he twisted the wire into a small, flat zig- “thermistor”, unlike a standard thermistor, Thomas Scarborough,
zag “pad” measuring about 10mm by measures relative changes in temperature. South Africa
10mm, to maximise the area affected by It therefore effec-
the heat of a candle flame. This “pad” was tively compares
situated at the base of the helix. the temperature
Using a single candle flame, this gener- between the “pad”
ated nearly 1mV and 0·5µA, which in and the helix.
terms of modern electronics is a very use-
ful amount. In fact a candle flame is not Hot Property
required, since the circuit shown in Fig.1 One may won-
may be triggered with a mere ten degrees der what the use-
change in temperature. fulness of such a
circuit might be.
Circuit Details Three possibili-
Referring to Fig.1, IC1 represents a sim- ties immediately
ple comparator. The thermistor “pad” is present them-
wired to IC1’s inverting input pin 2, and selves in its char-
the thermistor helix is wired to non-invert- acteristics. The
ing input pin 3. Resistors R1 and R2 are “thermistor”
not strictly necessary in the circuit, but add effectively has
stability, particularly where mains wiring zero resistance, it
is present in the vicinity, otherwise the generates a small Fig.1. Circuit diagram for the Helix Thermostat. The helix
wire helix may act as a pick-up coil. voltage when thermistor is wound using 7 turns of 24s.w.g. copper wire

570 Everyday Practical Electronics, August 2005

 Meter Identifier Measuring Up To It

T HE circuit diagram shown in Fig.2 is for a device I was asked

to build for a friend who, when walking around radio rallies etc,
trying to find a 100µA meter, had trouble locating one. Firstly
because some meters are not marked with the f.s.d. (full scale
deflection), secondly because some meters have special scales like
ºC or volts.
Switch S2, when in position G (green) puts 33 kilohms (33kΩ)
into circuit, limiting the maximum current that can be drawn to
about 40µA. This will give over three-quarters f.s.d. on a 50µA
meter. It is important that the meter needle should not go “hard
over” to f.s.d. in case this damages it and prevents the true f.s.d.
from being seen.
On range G the meter will give just below half f.s.d. for 100µA
meters. On range Y (yellow) the meter will give just below 400µA
for a 500µA meter or just below half f.s.d. for 1mA. On range R
(red) it will give 8mA for 10mA or 100mA movements. The range
names refer to the colour codes used for the prototype’s S2 switch
positions. Fig.2. Circuit diagram for a simple Meter Identifier
Pushbutton switch S3 operates on red and will give current lim-
ited by the lamp (LP1) for 1A upwards for continuity checks. The
red range and S3 also serve as a battery test point.
Extra or different ranges can be added as felt necessary. When
INGENUITY UNLIMITED
using the unit, start at range G the lowest current. BE INTER ACTIVE
You must ask the stall holders permission before testing any
meters! IU is your forum where you can offer other readers the
benefit of your Ingenuity. Share those ideas,
Jim Littler G4HPH,
earn some cash and possibly a prize.
Wigan, Lancs

The Terminator Arnie’s Aid? both l.e.d.s to flash alternately. The combi-
nation of R8, R9 and C3 provide a fairly
symmetrical flash rate but their values are
not critical.
Tony Lee,
Old Reynella, S. Australia

Fig.3. The Terminator speech timer circuit diagram

A FRIEND who organises guest speakers

for his Probus Club sought my help.
Apparently many of the speakers tend to
hard-to-ignore manner. This indicates the
termination of the speaker’s segment.
The prototype comprised two LM/NE555
ramble on and exceed the time scheduled for timers, IC1 and IC2, although a dual NE556
their talk. Could I design an instrument that timer could be used instead. IC1 is configured
he could operate from his seat at the back of as a conventional timer and IC2 as a slow-run-
the room which would discreetly signal the ning oscillator. When power is applied via
speaker to draw their talk to a close? The ter- switch S1, trigger pin 2 of the timer is momen-
minator circuit shown in Fig.3 is the result! tarily taken to ground via C1 and R3, which
When power is applied, two events are triggers the timer. Capacitor C2, resistor R4
set in motion. A five minute delay period is and preset VR1 determine the delay period.
initiated and an ultrabright l.e.d., D1, Transistor TR1 is now switched on by IC1’s
begins to glow. The appearance of the light output, pin 3, which temporarily disables the
warns the speaker that he/she is nearing the oscillator, IC2, by taking its reset pin 4 to 0V.
end of the allotted time. During the delay, D1 glows continuously,
After a lapse of approximately five min- while D2 remains off. At the end of the tim-
utes, the l.e.d. starts to flash alternately ing sequence, IC1 pin 3 goes low, turning off
with a second ultrabright l.e.d., D2, in a TR1, thus enabling the oscillator, allowing

Everyday Practical Electronics, August 2005 571

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572 Everyday Practical Electronics, August 2005

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Everyday Practical Electronics, August 2005 573
PICmicro TUTORIALS AND PROGRAMMING
HARDWARE

VERSION 3 PICmicro MCU

DEVELOPMENT BOARD
Suitable for use with the three software packages
listed below.
This flexible development board allows students to learn
both how to program PICmicro microcontrollers as well as
program a range of 8, 18, 28 and 40-pin devices from the
12, 16 and 18 series PICmicro ranges. For experienced
programmers all programming software is included in the
PPP utility that comes with the development board. For
those who want to learn, choose one or all of the packages
below to use with the Development Board.

Makes it easier to develop PICmicro projects

Supports low cost Flash-programmable PICmicro devices

Fully featured integrated displays – 16 individual l.e.d.s,
quad 7-segment display and alphanumeric l.c.d. display

Supports PICmicro microcontrollers with A/D converters £158 including VAT and postage

Fully protected expansion bus for project work

USB programmable supplied with USB cable and

Can be powered by USB (no power supply required) programming software
SOFTWARE
NEW V3 Suitable for use with the Development Board shown above.

ASSEMBLY FOR PICmicro V3 ‘C’ FOR PICmicro FLOWCODE FOR PICmicro V2

(Formerly PICtutor) VERSION 2 Flowcode is a very high level language
Assembly for PICmicro microcontrollers V3.0 The C for PICmicro microcontrollers CD- programming system for PICmicro
(previously known as PICtutor) by John ROM is designed for students and microcontrollers based on flowcharts.
Becker contains a complete course in professionals who need to learn how to Flowcode allows you to design and simulate
programming the PIC16F84 PICmicro program embedded microcontrollers in C. complex robotics and control systems in a
microcontroller from Arizona Microchip. It The CD contains a course as well as all the matter of minutes.
starts with fundamental concepts and software tools needed to create Hex code Flowcode is a powerful language that uses
extends up to complex programs including for a wide range of PICmicro devices – macros to facilitate the control of complex
watchdog timers, interrupts and sleep modes. including a full C compiler for a wide range devices like 7-segment displays, motor
The CD makes use of the latest simulation of PICmicro devices. controllers and l.c.d. displays. The use of
techniques which provide a superb tool for Although the course focuses on the use of macros allows you to control these
learning: the Virtual PICmicro micro- the PICmicro microcontrollers, this CD- electronic devices without getting bogged
controller. This is a simulation tool that ROM will provide a good grounding in C down in understanding the programming
allows users to write and execute MPASM programming for any microcontroller. involved.
assembler code for the PIC16F84
Complete course in C as well as C Flowcode produces MPASM code which is
microcontroller on-screen. Using this you programming for PICmicro microcontrollers compatible with virtually all PICmicro
can actually see what happens inside the
Highly interactive course
Virtual C programmers. When used in conjunction
PICmicro MCU as each instruction is PICmicro improves understanding
with the Version 2 development board this
executed which enhances understanding. Includes a C compiler for a wide range of provides a seamless solution that allows

Comprehensive instruction through 45 PICmicro devices
Includes full Integrated you to program chips in minutes.
tutorial sections
Includes Vlab, a Virtual Development Environment
Includes
Requires no programming experience
MPLAB software
Compatible with most

Allows complex PICmicro applications to
PICmicro microcontroller: a fully functioning be designed quickly
Uses international
simulator
Tests, exercises and projects PICmicro programmers
Includes a standard flow chart symbols (ISO5807)

covering a wide range of PICmicro MCU compiler for all the PICmicro devices. Full on-screen simulation allows debugging
applications
Includes MPLAB assembler and speeds up the development process

Visual representation of a PICmicro
Facilitates learning via a full suite of
showing architecture and functions
demonstration tutorials
Produces ASM
Expert system for code entry helps first time code for a range of 18, 28 and 40-pin
users
Shows data flow and fetch execute devices
Professional versions include
cycle and has challenges (washing virtual systems (burglar alarm, buggy and
machine, lift, crossroads etc.)
Imports maze, plus RS232, IrDa etc.).
MPASM files.

Minimum system requirements for these

items: Pentium PC running Windows 98,
NT, 2000, ME, XP; CD-ROM drive;
64MB RAM; 10MB hard disk space.
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Everyday Practical Electronics, August 2005 575

Constructional Project

Back to Basics – CMOS

Logic Devices
Bart Trepak

Part 5 – Kitchen Timer and Room Thermometer

This short series of articles illustrates how useful circuits can be designed simply
using CMOS logic devices as the active components

T
HERE are many simple operations
in a kitchen which require short
timing intervals without constant Fig.5.1. Block diagram for the
attention, and simply needing a signal to Kitchen Timer
alert the user that the operation has been
completed. Such devices are available in
the shops, including electronic timers fea-
turing crystal controlled timing with l.c.d.
displays. But if such sophistication is not
really needed, it can still be almost as
cheap to build your own, and much more
fun!
The timer described here can be set for
periods of up to nine minutes in one minute
increments, but a simple component
change can result in, say, a 4·5 minute peri-
od in 30 second increments, or 18 minutes
Circuit Diagram pulses occur at approximately equal time
intervals.
The complete circuit diagram for the
in two minute increments. Longer periods Kitchen Timer is shown in Fig.5.2. The When Start/Set switch S1 is pressed and
are impractical unless the timing is repeat- decade counter is shown as IC2. At switch released, the counter is advanced from output
ed or the clock oscillator redesigned. The Q0 to Q1, turning on l.e.d. D1. With Q0 now
on, assuming IC2 is reset, its Q0 output
elapsed time is displayed to the nearest low, capacitor C1 starts to charge, causing the
will go high and the alarm may sound
minute and an alarm indicates the end of voltage at IC1a input pin 2 to fall. When the
briefly. All of the l.e.d.s. will be off and
the period. lower logic threshold of this input is reached,
timing capacitor C1 will be uncharged.
the monostable formed by IC1a and IC1b is
Basic Operation In principle, a clock oscillator based on a
Schmitt NAND gate (as built around IC1c
triggered and IC1b output pin 4 goes low for
This design is based on a 4017 decade a short period, defined by capacitor C2 and
counter. To make a simple timer using it, and used to sound the alarm in this project)
resistor R3. This switches on transistor
all that is required is an oscillator to pulse could be used with suitable values of resis- TR1, discharging C1 ready for
the clock input once every 30 seconds or tor and capacitor to provide the 30 another timing period.
every minute, causing the outputs to be second or one minute clock pulses.
triggered high in sequence at this rate. In practice, however, all such
Connecting l.e.d.s to each output will thus oscillators produce a longer delay
show the state of the counter, indicating before the first pulse than for sub-
the number of periods elapsed and the sequent pulses and this would lead
number still left to run. A block diagram of to fairly large timing errors.
the circuit is shown in Fig.5.1. This is because the timing capacitor
The counter can be set for the delay begins charging from 0V during
required by advancing the count manually the first cycle, instead of from the
by a pushbutton switch connected to the lower switching threshold of the
Inhibit pin 13 (assuming that the logic lev- gate as occurs in subsequent
els at the CLK pin is in its correct state). cycles. The clock
This also starts the timer which will con- oscillator
tinue to run from the set position. When in this
the counter rolls over to its zero position, project
the clock oscillator is disabled and an h a s
oscillator driving a piezo sounder is therefore
switched on via a monostable to briefly b e e n
indicate the end of the timing period. designed to
Since the l.e.d.s remain off following discharge the
the end of the timing period, the circuit timing capacitor
draws virtually no current in the stand-by at the end of each
condition and therefore no on/off switch clock period, thus
is provided. making sure that all

576 Everyday Practical Electronics, August 2005

 Fig.5.2. Full circuit diagram for the Kitchen Timer

In principle, a diode from the output of

IC1a, which goes high for the C2/R3 peri-
of IC2 remains low until the counter has
cycled through all outputs Q1 to Q9 and back
COMPONENTS
od, could be used to discharge C1, but to Q0, the clock circuit will continue to pro-
there would still be a residual charge on C1 duce pulses and the l.e.d.s light up in turn.
because of the 0·6V forward voltage drop When the count again reaches Q0 and KITCHEN TIMER
of the diode. Since the voltage across a sat- this output goes high, the oscillator will
urated transistor is only about 0·1V this stop as C1 will no longer charge via Resistors See
will discharge C1 more fully, resulting in a R1/VR1 and will discharge fully to be R1 680k SHOP
much smaller timing error. ready for another timing cycle. Output Q0 R2 1k TALK
When the output of IC1b returns to its high going high creates a pulse across capacitor R3, R6 1M (2 off) page
state, the counter is advanced by one count C4, causing IC1c input pin 13 to go high R4, R7 10k (2 off)
and transistor TR1 is switched off, allowing for about five seconds, determined by the R5 470Ω
C1 to begin charging again. As the Q0 output C4/R6 values. All 0·25W 5% carbon film

Potentiometer
VR1 1M skeleton preset

Capacitors
C1 100µ radial elect. 16V
C2, C3, 100n ceramic disc,
C5 5mm pitch (3 off)
C4 4µ7 radial elect. 16V

Semiconductors
D1 to D9 red l.e.d. (9 off)
TR1 BC558 pnp transistor
IC1 4093 hex Schmitt
trigger inverter
IC2 4017 decade counter

Miscellaneous
S1 min. push-to-make
switch
WD1 passive piezo sounder
element

Printed circuit board, available

from the EPE PCB Service, code
521;14-pin d.i.l. socket; 16-pin d.i.l.
socket; 9V battery and connector;
case to suit; connecting wire; solder,
etc.

Approx. Cost
Guidance Only £12
excl case &
Fig.5.3. Kitchen Timer printed circuit board component layout, wiring details and batts
full-size underside copper foil track master

Everyday Practical Electronics, August 2005 577

 The positive-going pulse enables the the circuit either way
oscillator formed around IC1c to briefly around. There are
sound the alarm, WD1, via IC1d, signify- also six wire links
ing the end of the timed period. Capacitor required on the board
C5 and resistor R7 set the alarm tone fre- to complete the cir-
quency. IC1d is used as an inverter to drive cuit and these may be
the piezo sounder in anti-phase, thus pro- made from discarded
ducing a louder sound. component leads.
When the pulse from C4 ends and IC1c The choice of case
pin 13 is again held low via resisitor R6, for this unit is left to
the oscillator stops and the current drain of the user.
the circuit falls to just a few microamps.
Set-Up and
Construction Use
Printed circuit board component and Setting up consists Completed prototype timer circuit board
track layout details for the Kitchen Timer of adjusting the value
are shown in Fig.5.3. This board is avail- of the timing resist-
able from the EPE PCB Service, code 521. ance, using preset light in turn at the set intervals. Assuming a
Care should be taken to ensure that all VR1, to give a period of one minute one minute time base, a maximum time of
l.e.d.s and electrolytic capacitors are insert- between pulses. Other timing ranges, e.g. nine minutes can elapse before the alarm
ed the correct way around and normal pre- 30 seconds could be accommodated by will sound.
cautions are taken when handling CMOS altering the value of C1 or by switching in To set up a time of five minutes, say, the
devices, as discussed in Part 1. The board is other values of resistor. switch should be pressed repeatedly until
designed to accommodate all of the com- Because of the difficulty in calibrating l.e.d. D5 is lit and the timer is then allowed
ponents with the exception of the piezo very long periods, partly due to the prob- to continue from there. After one minute,
sounder and the battery. These components lems associated with very large values of D4 will light indicating that four minutes of
should be connected to the circuit using capacitance and/or resistance, this circuit is the cycle remain, followed by D3 after
flying leads. not suited for oscillator cycle periods another minute and so on. Finally when D1
Note that WD1 is simply a piezo element longer than two or three minutes. goes out and output Q0 goes high, the alarm
which does not contain any internal driving To operate the timer, press the Start/Set will sound indicating that five minutes have
circuitry and as such it may be connected to switch, on which the l.e.d.s will start to elapsed since S1 was first pressed.

Room Thermometer
E
LECTRONIC thermometers have l.e.d.s. These are normally turned off to need for further amplification of the signal
all but replaced the old mercury or save power, but may be turned on by means before it can be used. Although over a wide
alcohol-in-glass types in most appli- of a pushswitch when a reading is required. range the resistance change is not linear, it is
cations. The electronic types can usually good enough for monitoring temperature over
respond much faster to temperature Basic Operation a relatively narrow range, such as in this appli-
changes, and also allow the display to be All electronic thermometers contain a sen- cation where a range of say 14°C to 23°C is
remote from the sensor, allowing greater sor which converts a change in temperature to adequate.
flexibility in use. They can also be more a change in some electrical property such as This simple thermometer is different from
accurate and, depending on the sensor, can resistance, output current etc. In most cases, most because the changes in resistance of the
be used over greater temperature ranges. this is converted to a voltage which is then fur- thermistor are not converted to a voltage but
It has to be said, though, that the ther- ther processed (amplified, etc.) before being are used directly to alter the period of a mono-
mometer design described here is not the fed to some sort of analogue-to-digital con- stable. The resultant output pulse, whose
last word either in range or accuracy (per- verter (ADC) and output to a digital display. length is proportional to temperature, is used
haps a temperature indicator would be a Of the many different sensors available, a to switch on an oscillator forming a simple
more apt description), as it is intended to thermistor is used here for simplicity. ADC where the number of pulses produced in
display the temperature of a room where Thermistors exhibit a relatively large change a given time depends on the temperature of
neither of these attributes is particularly in resistance with temperature, removing the the thermistor.
important.
Here the range is limited to 10°C and
this is displayed in one degree steps on ten

Fig.5.4 Block schematic for the Room Thermometer

578 Everyday Practical Electronics, August 2005

 Fig.5.5. Complete circuit diagram for the Room Thermometer

The pulses are then simply counted and waveform (a). Diode D11 in combination
the result displayed on a row of ten l.e.d.s. with resistor R1 and preset VR1 ensures
The block diagram in Fig.5.4 shows the main
components of the thermometer, a sensor,
that the high (reset) period is very much
shorter than the low period. VR1 is includ-
COMPONENTS
monostable, oscillator and counter/display. ed to enable the reset period to be adjusted.
The circuit operates in two stages. The first The rising edge of this waveform is dif-
measures the temperature by counting pulses ferentiated by capacitor C2 and resistor R2 ROOM THERMOMETER
from the temperature sensitive oscillator and to create a short positive-going pulse at
then displaying the count. A second oscillator IC1b pins 5 and 6, waveform (b). IC1b is Resistors See
SHOP
controls the rate at which this occurs. The used as an inverter and its output at pin 4 R1 10M TALK
measurement cycle is made very short so that goes low in response to the pulse, wave- R2 10k page
its effect on the display is not noticeable. form (c), quickly charging C3 via diode R3, R4 390Ω (2 off)
D12, waveform (d). R5 n.t.c. thermistor,
Circuit Description This causes the input of inverter IC1c to 20k at 25°C
The full circuit diagram for the Room go high, waveform (e), thus enabling IC1d All 0·25W 5% carbon film or better,
Thermometer is shown in Fig.5.5. It is to oscillate at a frequency determined by except R5
based around a 4017 decade counter, IC2, C4 and R4/VR2, waveform (f).
which controls the l.e.d. display. The Capacitor C3 now discharges via the Potentiometers
operation of this circuit is probably best thermistor R5 until the upper threshold of VR1 10k skeleton preset
understood by referring to the waveforms gate IC1c is reached, indicated by the dot- VR2 4k7 skeleton preset
diagram in Fig.5.6 – but note that it is not ted line in waveform (d). At this point, the
to scale as the display period is very much output of IC1c goes low, switching off Capacitors
longer compared to the measurement IC1d. The length of time for which IC1c C1 100n ceramic disc,
period shown. output remains high depends on the resist- 5mm pitch
Schmitt trigger NAND IC1a is config- ance of the thermistor, which in turn C2 to C4 10n ceramic disc,
ured as an oscillator which resets the count- determines how many clock pulses are 5mm pitch (3 off)
er when its output goes high, as shown in produced by IC1d. C5 100µ radial elect. 16V

Semiconductors
D1 to D10 red l.e.d. (10 off)
D11, D12 1N4148 signal diode
(2 off)
IC1 4093 quad Schmitt
inverter
IC2 4017 decade counter

Miscellaneous
S1 min. push-to-make
switch

Printed circuit board, available from

the EPE PCB Service, code 522; 14-
pin d.i.l. socket; 16-pin d.i.l. socket; 9V
battery and connector; case to suit;
connecting wire; solder, etc.

Approx. Cost
Guidance Only £10
excl case and
batts
Fig.5.6. Room themometer circuit waveforms

Everyday Practical Electronics, August 2005 579

 The thermistor specified has a negative Fig.5.7. Printed
temperature coefficient which means that circuit board
as its temperature rises, its resistance falls. component lay-
This causes IC1c to remain high for a out and full-size
shorter time as the temperature increases, underside copper
leading to fewer clock pulses and thus a foil master pat-
lower count. This is slightly unusual but tern for the
with the form of display chosen, it is not a R o o m
problem as it simply means that l.e.d. D1 Thermometer.
indicates the highest temperature and l.e.d.
D10 the lowest. (below) Prototype
It should also be noted that, although Thermometer cir-
IC1d starts producing clock pulses as cuit board. The
soon as IC1c output goes high rectangular
(at the beginning of l.e.d.s have been
replaced with
standard types

the reset pulse), many of these are not will be produced and the counter would Assemble with the same care and
counted as the counter remains reset “wrap around” to display a high tempera- attention as advised for previous designs
until the output of IC1a goes low. The ture again. Output Q9 is therefore connect- in this series. Normal precautions for
counter then advances on each positive ed to IC2’s Inhibit pin 13 to prevent further handling CMOS and other components
clock transition so that, in the example counting in this case. The two extreme should be followed. The thermistor can
shown in Fig.5.6, although a total nine l.e.d.s in the display should therefore be be soldered to the board either way
low to high clock transitions are pro- regarded as 14°C or lower and 23°C or around.
duced, only five of these are counted, higher. To calibrate the unit, turn preset VR1
causing output Q6 to go high. The circuit may be powered by a 9V fully clockwise and check that l.e.d. D10
Outputs Q0 to Q5 will also go high battery. To save battery power, the and some of the adjacent l.e.d.s can be
briefly, but this is for such a short time that l.e.d.s are only allowed to light when turned on by varying VR2. If this is not
the eye does not normally respond to their switch S1 is pressed. If a continuous possible, back off VR1 slightly.
l.e.d.s turning on. However, in low ambi- display is required, the switch can be Place the thermistor in a place that is
ent light, this may be noticed as a slight replaced by a wire link. In this case a about one degree higher than the lowest
flicker of the display, but to the casual 9V d.c. supply from a mains adaptor temperature to be monitored and adjust
observer only one l.e.d. will appear to be would be preferable. VR2 so that l.e.d. D9 lights. An ordinary
on at any time. thermometer will be of help here. With
The thermistor has a quoted resistance Limitations the thermistor at a temperature one
of 20 kilohms (20kΩ) at 25°C, but as with A simple circuit of this sort obviously degree below the maximum, adjust VR1
all electronic components this is subject to lacks the accuracy, resolution or stability until l.e.d. D2 is lit. Repeat the last two
a certain tolerance. The device used in the of many alternative designs but it should steps readjusting VR1 and VR2 if neces-
prototype had a resistance of 19·6kΩ ris- be adequate for this uncritical application. sary until D2 and D9 light when
ing to about 30kΩ at 16°C (i.e. roughly One source of error is the basic non-lin- required.
1kΩ per °C). earity of the thermistor resistance with In practice it may be easier to measure
To enable the circuit to be calibrated changes in temperature although, as men- the thermistor resistance at the two
easily and for variations in thermistor tioned earlier, over small temperature extreme temperatures and substitute resis-
resistance to be accommodated, both the ranges/changes the non-linearity is not too tors of this value for the thermistor when
clock oscillator frequency and the start of pronounced. calibrating the unit. The thermistor used in
the count period are made adjustable, by Another problem is the exponential the prototype had a resistance range of
presets VR2 and VR1 respectively. nature of the voltage ramp across capaci- 19·6kΩ and 28·6kΩ at the temperature
Preset VR1 is adjusted so that at the tor C3 due to it being discharged by a extremes chosen.
highest temperature (say 23°C) the reset resistor. With the test model, a 22kΩ preset
period is just greater than monostable There are ways round these problems in potentiometer set for 19·6kΩ, together
IC1c’s output period, so that no clock a more sophisticated design, but such with nine 1kΩ resistors connected in
pulses are counted and only Q0 goes techniques are beyond the scope of this series was therefore used to simulate the
high. At the lowest temperature (14°C), article. resistance of the thermistor at various tem-
when IC1c’s output stays high for the peratures in the range. For calibration pur-
longest period, the clock frequency is Construction poses, it will also be found useful to short
adjusted by means of VR2 to provide The printed circuit board component out pushswitch S1 so that the display is
nine positive going clock transitions and copper track layout details for the permanently on.
during this counting period. Room Thermometer are shown in Fig.5.7.
If the resistance of the thermistor should This board is available from the EPE PCB Next Month
fall below this minimum, more clock pulses Service, code 522. Daily Reminder and a Whistle Switch.

580 Everyday Practical Electronics, August 2005

Regular Clinic

Circuit
Surgery
Alan Winstanley and Ian Bell
We continue with our primer on CompactFlash (CF) cards, with more pointers and
snippets of code intended for experienced microcontroller enthusiasts

Table 1. Card identify information from a 32MByte CompactFlash card

Back in a CompactFlash
In last month’s Circuit Surgery we out- Word no Hex Bytes Meaning
lined some of the software aspects of using
a CompactFlash (CF) memory card with a 0 84 8A 848A Signature
PIC or similar microcontroller. Some of 1 01 EC 1EC hex = 492 cylinders
the various commands and registers which 2 00 00 Reserved
are used to control the card were 3 00 04 0004 heads
explained. This month we will cover some 4 00 00 Obsolete
of the techniques of actually reading and 5 02 00 0200 hex = 512 bytes per sector (obsolete)
writing data, sketching some PIC code that 6 00 20 0020 hex = 32 sectors per track
could be used to read and write a 7-8 00 00 F600 hex = 62976 sectors per card
CompactFlash card. F6 00
A CompactFlash card is a semiconductor 9 00 00 Obsolete
memory device, but from the user’s per- 10-19 30 30 Serial number 00000000002011600087
spective it is designed to behave like a disk 30 30
drive. This means that data is read and 30 30
written one sector at a time rather than as 30 30
individual bytes. This is relatively easy to 30 30
cope with in software. It also means that 32 30
the card may be formatted by a PC using a 31 31
file system. If you want to use, or even 36 30
simply avoid damaging, a PC file system 30 30
then you may be faced with a demanding 38 37
programming task. We will return to this 20 00 00 Obsolete
point later. 21 00 02 Obsolete
Last month we introduced the Identify 22 00 04 0004 ECC bytes passed on Read/Write
Device command (EC hex) and gave an Long commands
example of some typical PIC assembly 23-26 52 65 “Rev 1.15” Firmware revision in ASCII
code to use this command. Reading data 76 20
after issuing the Identify Device command 31 2E
will provide you with a byte sequence sim- 35 31
ilar to that shown in Table 1. This was 27-46 53 41 “SAMSUNG CF/ATA” Model number in ASCII
obtained from a 32MByte Fuji branded 4D 53
CompactFlash card. Your software can 55 4E
work out the size of the card from the four 47 20
bytes in Words 7 and 8 which give the 43 46
number of sectors. 2F 41
In this case there are 0000F600 hex sec- 54 41
tors, which is 62976 in decimal. 20 20 (remaining bytes are space character)
Multiplying this value by the number of
bytes per sector, which is 512, gives card, we have to set up the address of the Logical Block Addressing in which the
32243712 bytes (roughly 32MBytes), first sector we want to write to. To do this card sectors are addressed by a 28-bit
which obviously matches the specification we write to the appropriate card registers. value. This potentially gives access to a
of our card in this example. Note that Word We need to set the Select Card/Head maximum of 137GBytes with sectors of
5 contains the number of bytes per sector, (address 6), Cylinder High (address 5), size 512 bytes, but most currently available
but the CompactFlash specification docu- Cylinder Low (address 4), Sector Number cards are smaller than this, so the upper
ment indicates this value is obsolete. The (address 3) and Sector Count (address 2) address bits will always be zero.
specification also explicitly states that the registers. Setting bit 6 of the Select Card/Head
host reads 512 bytes from the buffer after The Select Card/Head Register controls Register to 1 selects LBA mode. Bits 5 and
issuing the Read Sector command. the mode in which the card is addressed. 7 should be set to 1 for backward compati-
Assuming a sector size of 512 should be This can be either Cylinder/Head/Sector bility reasons. Bit 4 is the drive number and
OK for most cards. (CSH) Mode or Logical Block Addressing would usually be 0. So the top four bits of
Before reading to or writing from the (LBA) Mode. It is probably easier to use the Card/Head Register should be set to

Everyday Practical Electronics, August 2005 581

 (0x20) is issued, the value on the data bus
is read and not written, and the card’s
Output Enable (OE) line is pulsed low
rather than WE. To do the reading the data
bus port direction must be changed to input
(it was an output during the sector address
and command writing operations). This is
accomplished using the PIC’s data direc-
tion register (TRISx), as in Listing 1E.
Do not forget to return the data bus port
direction to output before issuing further
commands, performing a write, or chang-
ing the sector address.

Experimenting
As mentioned earlier, CompactFlash
cards can be formatted when used with a
PC. Experimenting with using a card with
a PIC may destroy this formatting and pre-
vent you from accessing files on the card.
Fig.1. Screen shot from WinHex looking at the raw byte data on a CompactFlash You are therefore advised to experiment
with a blank card until you are confident
1110 (E in hexadecimal) for LBA opera- time. The write operation must be per- about the way the card works and have
tion. The lower four bits are bits 27 to 24 of formed 512 times the value written to the developed reliable code.
the 28 bit LBA sector address, and unless Sector Control Register, so your code will If you simply want to use the card as a
the card is very large these will be zero. In need a loop set up to do this. If the Sector large memory for a PIC and will never try
Listing 1A the code sets up LBA mode and Control value is 0x00 256 sectors should to access the card with a PC, you don’t
sets the upper four address bits to 0. be written. have to worry about formatting. If you
The value of CF_ADDR (the Card/Head Reading follows the same pattern except, want to be able to still use the card with a
Register address) is defined to be 0x06 as of course, the Read Sector command PC or other device, then things get trickier.
discussed last month. Assuming the
CF_WRITE subroutine simply pulses the
card’s write line (WE) low with appropri- Listing 1A
ate timing. The example of code given last movlw 0xE0 ; Value to select LBA and set upper address bits to 0
month included this operation in an in-line movwf CF_DATA ; Put the value on the data bus
rather than a subroutine form. movf HEAD_REG,0 ; Card/Head Register Address
Next we need to set the remaining 24 bits movwf CF_ADDR ; Put address onto the bus
of the sector address. This requires three call CF_WRITE ; Do the write.
bytes. A useful way to do this is to store the
address in three registers (here we have Listing 1B
named them CFADDR23TO16, CFAD- movf CFADDR23TO16,0 ; Sector address bits 23 to 16
DR15TO8, and CFADDR7TO0). The val- movwf CF_DATA ; Put on data bus
ues in these registers are then written to the movf CYL_HI_REG,0 ; Cylinder High Register address (0x05)
Cylinder High, Cylinder Low, and Sector movwf CF_ADDR ; Put on address bus
Number registers respectively. Again we call CF_WRITE ; Write the value to the CF card
have predefined values for the register
addresses (0x05, 0x04 and 0x03 respective- movf CFADDR15TO8,0 ; Address bits 15 to 8 to Cylinder Low Register
ly), as discussed last month. The code in movwf CF_DATA
listing 1B thus sets up the sector address. movf CYL_LO_REG,0
We can read or write up to 255 consecu- movwf CF_ADDR
tive sectors at a time. The number of sectors call CF_WRITE
to be accessed by it is written to the Sector
Control Register. Assuming we have previ- movf CFADDR7TO0,0 ; Address bits 7 to 0 to Sector No. Register
ously stored this value in a register named movwf CF_DATA
NUMOFSECS and defined the address movf SEC_NUM_REG,0
(0x02) of the register as SEC_CNT_REG movwf CF_ADDR
we can continue as in Listing 1C, using the call CF_WRITE
same pattern of code as above.
Listing 1C
Get Ready to Write movf NUMOFSECS,0 ; Write no. of sectors to Sector Control Register
We are nearly ready to read data from or movwf CF_DATA
write data to the card, but first we need to movf SEC_CNT_REG,0
issue a Write Sector or Read Sector com- movwf CF_ADDR
mand as appropriate. This follows the call CF_WRITE
same pattern as issuing the Identify Device
command, for which we gave some sample Listing 1D
code last month. Once the command is movf WRITE_SEC,0 ; Sector write command on data bus
written we need to set the card’s address movwf CF_DATA
bus to the address of the data register movf COMMAND_REG,0 ; Command Register address on address bus
(0x00) ready for the actual read or write movwf CF_ADDR
operations. For example, to issue the write call CF_WRITE
command (0x30), assuming this is defined movf DATA_REG,0 ; Data Register address on address bus ready for write
as WRITE_SEC and that the command movwf CF_ADDR
register address (0x07) is defined as COM-
MAND_REG we would use the code
shown in Listing 1D. Listing 1E
To write the data each byte is placed on movlw 0xFF ; Set data PIC lines to input
the data bus and the card’s Write Enable movwf TRISx ; x is port letter of data bus port
(WE) line is pulsed low for sufficient

582 Everyday Practical Electronics, August 2005

Your PC will probably format the card One cheat that may provide a workaround trying to decode and understand the file
with a FAT16 file system; this is fully pub- without the need to fully decode the file sys- system formatting information.
licly documented and is beyond the scope tem is to create a file (or files) on a blank There are a number of software applica-
of this article, so if necessary you can card of the size you need for the data for tions which enable you to do this, one
research exactly how all the files are your PIC program. Hopefully this file will example being WinHex (www.x-ways
arranged on the card. It must be added that be contiguous if the card is empty. .net/winhex/index-m.html).
it is not simple because files are not neces- The file can be created with dummy data A typical screen shot from WinHex is
sarily stored in contiguous portions of the in it (e.g. a text file containing a large num- shown in Fig.1, in this case looking at the
memory, so you have to use the File allo- ber of space characters). If you know the Microsoft FAT16 formatting information
cation Table (FAT) to find which clusters starting address, size and format of the file in the first bytes on the card (the card is
(groups of sectors) the file occupies. you can overwrite it with the PIC program being read via a standard USB multiformat
A formatted but otherwise empty card without corrupting the file system. As long card reader). WinHex can search for
will contain formatting data in the first sec- as the file is not relocated by the operating strings or byes sequences on the card,
tors of the card. Writing to this area with system (e.g. by a defragging operation) which is useful for locating the address of
your PIC code will destroy the formatting. you should be able to access it using files or data in the card’s memory space.
If you avoid the first few hundred sectors Windows programs and create and use As will be seen, using CF cards is not
(say start at sector 5000 or 10000 to be other files on the card, but this approach very straightforward or trivial but there are
safe) you can write to the card, hopefully will never be 100% guaranteed. various modes in which they can be
without corrupting the formatting. utilised without incurring too many techni-
However the PC will not see the data you Debugging cal setbacks.
write as a file and will happily overwrite it It is useful to be able to look at the raw We hope you find this introduction to
if it chooses to create a file in that part of data on a CompactFlash card with your PC CompactFlash cards useful. If you wish to
the card’s memory. If the card is not empty, if you are trying to debug PIC software that experiment further, in the June ’05 issue
then writing to a random location beyond should have written particular values to we reproduced a p.c.b. design which is
the initial sectors with your PIC code may known locations in the card’s memory. It is available from the EPE PCB Service. Let
corrupt files on the card. also useful to see the raw data if you are us know how you get on! I.M.B.

Back to Basics – Kitchen Timer/Room Thermometer

No component buying problems should arise when shopping for
parts for the Kitchen Timer and Room themometer, this month’s two
Back to Basics projects. When ordering the piezoelectric sounder for
the Kitchen Timer, make sure it is a “passive” element only type – one
without any internal driver/oscillator circuit.
It is likely that suppliers will offer a choice of negative temperature
Pain Monitor coefficient thermistors varying slightly from the specified 20kΩ at 25°C in
As previously, we have found only two listings for the 24LC256 256 the article. As we are only measuring room temperature changes, and a
kilobit serial EEPROM memory chip, used in the Pain Monitor project. certain amount of tolerance is acceptable, they should be OK for this
This was from Jaycar Electronics (see their ad on back cover), code circuit. The disc thermistor used in the prototype came from Rapid
ZZ8485 and Farnell (
0870 1200 100 or www.farnellinone.co.uk), Electronics (
01206 751166 or www.rapidelectronics.co.uk), code
code 300-1696. 61-0415.
The Dallas/Maxim DS1307 serial I2C realtime clock (RTC) chip is The two printed circuit boards are obtained from the EPE PCB
currently listed by Rapid Electronics (
01206 751166 or Service, codes 521 (Kitchen) and 522 (Room Therm) – see page 589.
www.rapidelectronices.co.uk), code 82-0566. For datasheet
details you could log-on to www.maxim-ic.com. Motor Amplifier
Paperwork for the Monitor shows that the RTC battery is a Saft The SIOV-S14K25 31V d.c. varistor for the Motor Amplifier project was
LS14250, 1/2AA, 3·5V 950mAh and measures just 25mm long by about purchased form Farnell (
0870 1200 100 or www.farnellinone.co.uk),
12mm wide (1in × 0.5in). It was purchased (credit card only) from RS code 580-168. The 450mA 30V positive temperature coefficient
Components (
01536 44079 or rswww.com), code 203-3894. Other thermistor also came from the same source, code 606-911.
batteries from 2V to 3·6V could also be used. They also supplied the We have a problem with the 24V d.c. power relay used by the author
specified 32·768kHz low-profile crystal, code 226-1443. in his unit. This heavy-duty relay is marked as an RS Component part
The MAX232 RS232 series interface i.c. is one of the more popular and carries the stock code 348-425, which unfortunately is now obso-
interface devices and most components advertisers should have lete. The technical details show it as having: 24V d.c. 277 ohm coil,
stocks. The same applies to the “click-effect” or “tactile” pushbutton with double-pole changeover contacts rated at 20A. Readers will
switches. It is the extended plunger type that is required. Note that need to select a relay, possibly an automotive type, with contacts
although they have four connecting pins, each switch contact is joined rated to suit their own particular application. We see from the Display
to two pins so they must be inserted correctly on the p.c.b. Electronics ad on page 522 the they “hold” over 100,000 relays/con-
For those readers unable to program their own PICs, fully tactors, so they may be able to help here.
programmed PIC16F876 microcontrollers can be purchased from Other items sourced from Farnell – see above – include the
Magenta Electronics (
02083 565435 or www.magenta2000.co.uk) 40EPS08 40A power diode, code 646-179; the n-channel power
for the inclusive price of £10 each (overseas add £1 for p&p). The MOSFET STW60NE10 60A, code 364-1351 and the FQA70N10 70A,
software, including source code files, is available on a 3·5in. PC-com- code 394-4414. Note the STW60NE10 is no longer produced but they
patible disk (Disk 8) from the EPE Editorial Office for a sum of £3 each have stocks. The FQA device is the recommended alternative.
(UK), to cover admin costs (for overseas charges see page 589). The The two opto-isolators types SFH618A d.c. and TLP620 a.c. are both
software is also available for free download via the Downloads link on listed by Rapid Electronics (
01206 751166 or www.rapidelectronics
our UK website at www.epemag.co.uk. .co.uk), codes 58-0514 (d.c.) and 58-0524 (a.c.) respectively. The printed
The printed circuit board is available from the EPE PCB Service, circuit board is available from the EPE PCB Service, code 520.
code 519 (see page 589). The 2-line 16-character (per line) You need two 12V gel-cell batteries connected in series to give a
alphanumeric display is a standard l.c.d. module and most of our good low impedance source for the main 24V supply. These are fair-
components advertisers should be able to offer a suitable device. ly expensive items and you need 15Ah cells or better. Readers may
be interested in a “flyer” from WCN Supplies (
023 8066 0700 or
Audio System – Communications www.wcnsupplies.net) offering 12V 24Ah gel type for £19.95 each.
Practically all the components required for the three circuits that
make up the Audio System – Communications project should be
readily available from our component advertisers. PLEASE TAKE NOTE
Most suppliers should be able to suggest a suitable meter for the Crossword Solver (May 05)
optional signal strength meter facility. However, do heed the remarks Page 317 Fig.1 and page 318 Fig.2. The author advises that a 4.7kΩ
regarding selecting a meter. resistor be connected between IC1 pin6 (RA4) of the PIC to the +5V line.
Another item that should be easy to locate is the miniature omni-
directional electret microphone insert. Certainly try Sherwood Cybervox (July ’05)
Electronics (see ad on page 592) and Cricklewood Electronics Page 464 Fig.6. The capacitor at the top-centre of the p.c.b. marked
(
020 8452 0161 or www.cricklewoodelectronics.com). C19 should be annotated C13
Small quantities of enamelled copper wire, in 50g (2oz) reels, for the Toolkit TK3 V3.05
Power Amplifier inductor coil, is obtainable from JAB Electronic The latest version of the TK3 software is now available on our
Components (
0121 682 7045 or www.jabdog.com) mail order only. Downloads site (via www.epemag.co.uk) and on CD from the
You will, of course, need to specify the wire gauge size. Editorial Office (see EPE PCB Service page). The principal differences
The three printed circuit boards are available from the EPE PCB from the version V3.00 is that the PIC18F programming routine has
Service, codes 516 (Preamp), 517 (Electret Mic) and 518 (Power been considerably speeded.
Amp) – see page 589.

Everyday Practical Electronics, August 2005 583

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584 Everyday Practical Electronics, August 2005

 Theory and Reference
BEBOP TO THE BOOLEAN BOOGIE addition to a wealth of technical information, myriad Since Foundations of Wireless was first published
Second Edition nuggets of trivia, and hundreds of carefully drawn illustra- over 60 years ago, it has helped many thousands of
Clive (call me Max) Maxfield tions, the CD-ROM contains a set of lab experiments for readers to become familiar with the principles of radio
This book gives the “big picture’’ of digital electronics. the virtual microcomputer that let you recreate the expe- and electronics. The original author Sowerby was suc-
This indepth, highly readable, up-to-the-minute guide riences of early computer pioneers. If you’re the slightest ceeded by Scroggie in the 1940s, whose name became
shows you how electronic devices work and how they’re bit interested in the inner workings of computers, then synonymous with this classic primer for practitioners
made. You’ll discover how transistors operate, how print- don’t dare to miss this! and students alike. Stan Amos, one of the fathers of
ed circuit boards are fabricated, and what the innards of Over 800 pages in Adobe Acrobat format modern electronics and the author of many well-known
memory ICs look like. You’ll also gain a working knowl- books in the area, took over the revision of this book in
CD-ROM Order code BEB2 CD-ROM £21.95 the 1980s and it is he, with his son, who have produced
edge of Boolean Algebra and Karnaugh Maps, and
understand what Reed-Muller logic is and how it’s used. this latest version.
And there’s much, MUCH more. The author’s tongue-in- RADIO! RADIO! (Third Edition) NEW
400 pages Temporarily out of print
cheek humour makes it a delight to read, but this is a Jonathan Hill
REAL technical book, extremely detailed and accurate. A celebration in words and pictures of the development
Contents: Fundamental concepts; Analog versus digi- of the British wireless set from it’s experimental begin- GETTING THE MOST FROM YOUR MULTIMETER
tal; Conductors and insulators; Voltage, current, resis- nings in Victorian England, to the foundation of a domes- R. A. Penfold
tance, capacitance and inductance; Semiconductors; tic wireless manufacturing industry and the inception of This book is primarily aimed at beginners and those of
Primitive logic functions; Binary arithmetic; Boolean alge- broadcasting in the early 1920’s. The story continues on limited experience of electronics. Chapter 1 covers the
bra; Karnaugh maps; State diagrams, tables and throught the design-conscious 1930’s (where the radio basics of analogue and digital multimeters, discussing the
machines; Analog-to-digital and digital-to-analog; really came into it’s own as a piece of furniture), to the relative merits and the limitations of the two types. In
Integrated circuits (ICs); Memory ICs; Programmable ICs; war-torn and austere days of the 1940’s. Chapter 2 various methods of component checking are
Application-specific integrated circuits (ASICs); Circuit The first transistor radios began to appear in the second described, including tests for transistors, thyristors, resis-
boards (PWBs and DWBs); Hybrids; Multichip modules half of the 1950s and in this new edition, this rather neglect- tors, capacitors and diodes. Circuit testing is covered in
(MCMs); Alternative and future technologies. ed area has been fully covered by a section all of it’s own Chapter 3, with subjects such as voltage, current and
which includes a directory listing of nearly 3,000 different continuity checks being discussed.
470 pages – large format Order code BEB1 £26.95 transistor models. The book finishes after the 1960s, by In the main little or no previous knowledge or experi-
which time our long established and once great radio ence is assumed. Using these simple component and cir-
BEBOP BYTES BACK (and the industry had all but been destroyed by foreign imports. cuit testing techniques the reader should be able to con-
CD-R Now with 320 pages and over 1,000 illustrations, infor- fidently tackle servicing of most electronic projects.
Beboputer Computer Simulator) OM
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Radio! is the first and still the only truly comprehensive 96 pages Order code BP239 £5.49
Clive (Max) Maxfield and Alvin
Brown book of its kind ever to be published.
DIGITAL GATES AND FLIP-FLOPS
This follow-on to Bebop to the 320 pages (A4 Hardback) Order code RR1 £40.95
Ian R. SInclair
Boolean Boogie is a multimedia This book, intended for enthusiasts, students and techni-
extravaganza of information SCROGGIE’S FOUNDATIONS OF WIRELESS cians, seeks to establish a firm foundation in digital elec-
about how computers work. It AND ELECTRONICS – ELEVENTH EDITION tronics by treating the topics of gates and flip-flops thor-
picks up where “Bebop I’’ left off, S. W. Amos and Roger Amos oughly and from the beginning.
guiding you through the fascinating Scroggie’s Foundations is a classic text for anyone work- No background other than a basic knowledge of elec-
world of computer design . . . and ing with electronics, who needs to know the art and craft tronics is assumed, and the more theoretical topics are
you’ll have a few chuckles, if not belly of the subject. It covers both the theory and practical explained from the beginning, as also are many working
laughs, along the way. In addition to over 200 megabytes aspects of a huge range of topics from valve and tube practices. The book concludes with an explanation of
of mega-cool multimedia, the CD-ROM contains a virtual technology, and the application of cathode ray tubes to microprocessor techniques as applied to digital logic.
microcomputer, simulating the motherboard and standard radar, to digital tape systems and optical recording
computer peripherals in an extremely realistic manner. In techniques. 200 pages Order code PC106 £9.95

Music, Audio and Video

QUICK GUIDE TO ANALOGUE SYNTHESIS ELECTRONIC MUSIC AND MIDI PROJECTS VIDEO PROJECTS FOR THE ELECTRONICS
Ian Waugh R. A. Penfold CONSTRUCTOR
Even though music production has moved into the digi- Whether you wish to save money, boldly go where no musi- R. A. Penfold
tal domain, modern synthesisers invariably use ana- cian has gone before, rekindle the pioneering spirit, or sim- Written by highly respected author R. A. Penfold, this book
logue synthesis techniques. The reason is simple – ply have fun building some electronic music gadgets, the contains a collection of electronic projects specially designed
analogue synthesis is flexible and versatile, and it’s rel- designs featured in this book should suit your needs. The for video enthusiasts. All the projects can be simply con-
atively easy for us to understand. The basics are the projects are all easy to build, and some are so simple that structed, and most are suitable for the newcomer to project
same for all analogue synths, and you’ll quickly be able even complete beginners at electronic project construction construction, as they are assembled on stripboard.
to adapt the principles to any instrument, to edit exist- can tackle them with ease. Stripboard layouts are provided There are faders, wipers and effects units which will
ing sounds and create exciting new ones. This book for every project, together with a wiring diagram. The add sparkle and originality to your video recordings, an
describes: How analogue synthesis works; The essen- mechanical side of construction has largely been left to audio mixer and noise reducer to enhance your sound-
tial modules every synthesiser has; The three steps to individual constructors to sort out, simply because the vast tracks and a basic computer control interface. Also,
synthesis; How to create phat bass sounds; How to majority of project builders prefer to do their own thing in there’s a useful selection on basic video production
generate filter sweeps; Advanced synth modules; How this respect. techniques to get you started.
to create simple and complex synth patches; Where to None of the designs requires the use of any test equip- Complete with explanations of how the circuit works, shop-
find soft synths on the Web. ment in order to get them set up properly. Where any set- ping lists of components, advice on construction, and guid-
If you want to take your synthesiser – of the hardware ting up is required, the procedures are very straightforward, ance on setting up and using the projects, this invaluable
or software variety – past the presets, and program and they are described in detail. book will save you a small fortune.
your own sounds and effects, this practical and well- Projects covered: Simple MIIDI tester, Message grabber, Circuits include: video enhancer, improved video
illustrated book tells you what you need to know. Byte grabber, THRU box, MIDI auto switcher, Auto/manual enhancer, video fader, horizontal wiper, improved video
switcher, Manual switcher, MIDI patchbay, MIDI controlled wiper, negative video unit, fade to grey unit, black and white
60 pages Order code PC118 £7.45 keyer, vertical wiper, audio mixer, stereo headphone
switcher, MIDI lead tester, Program change pedal,
Improved program change pedal, Basic mixer, Stereo amplifier, dynamic noise reducer, automatic fader, pushbut-
QUICK GUIDE TO MP3 AND DIGITAL MUSIC
mixer, Electronic swell pedal, Metronome, Analogue echo ton fader, computer control interface, 12 volt mains power
Ian Waugh
unit. £10.95 supply. £10.95
MP3 files, the latest digital music format, have taken the
music industry by storm. What are they? Where do you 124 pages Order code PC116 £5.45 124 pages Order code PC115 £5.45
get them? How do you use them? Why have they thrown
record companies into a panic? Will they make music
easier to buy? And cheaper? Is this the future of music? THE INVENTOR OF STEREO – THE LIFE AND WORKS PC MUSIC – THE EASY GUIDE
All these questions and more are answered in this OF ALAN DOWER BLUMLEIN Robin Vincent
concise and practical book which explains everything Robert Charles Alexander How do I make music on my PC? Can I record music onto
you need to know about MP3s in a simple and easy-to- This book is the definitive study of the life and works of my PC? What’s a sequencer? How can I get my PC to print
understand manner. It explains: one of Britain’s most important inventors who, due to a a music score? What sort of a soundcard do I need? What
How to play MP3s on your computer; How to use cruel set of circumstances, has all but been overlooked by hardware and software do I need? How do I connect a key-
MP3s with handheld MP3 players; Where to find MP3s history. board to my PC?:
on the Web; How MP3s work; How to tune into Internet Alan Dower Blumlein led an extraordinary life in which his Just a few of the questions you’ve probably asked. Well,
radio stations; How to create your own MP3s; How to inventive output rate easily surpassed that of Edison, but you’ll find the answers to all these questions, and many
record your own CDs from MP3 files; Other digital audio whose early death during the darkest days of World War more, in this book. It will show you what can be done, what
music formats. Two led to a shroud of secrecy which has covered his life it all means, and what you will need to start creating your
and achievements ever since. own music on your PC. It’s an easy read, it’s fully illustrated
60 pages Order code PC119 £7.45 His 1931 Patent for a Binaural Recording System was and it will help you understand how a computer can be used
so revolutionary that most of his contemporaries regard- as a creative music tool.
ed it as more than 20 years ahead of its time. Even years It covers soundcards, sequencers, hard disk digital audio
ELECTRONIC PROJECTS FOR VIDEO ENTHUSIASTS after his death, the full magnitude of its detail had not
R. A. Penfold recording and editing, plug-ins, printing scores with notation
been fully utilized. Among his 128 patents are the princi- software, using your PC as a synthesiser, getting music onto
This book provides a number of practical designs for pal electronic circuits critical to the development of the
video accessories that will help you get the best results and off the Internet, using Windows, sample PC music set-
world’s first elecronic television system. During his short ups, FAQs, a glossary, advice on hardware and software,
from your camcorder and VCR. All the projects use working life, Blumlein produced patent after patent
inexpensive components that are readily available, and and a list of industry contacts.
breaking entirely new ground in electronic and audio
they are easy to construct. Full construction details are engineering. 116 pages Order code PC117 £11.95
provided, including stripboard layouts and wiring dia- During the Second World War, Alan Blumlein was deeply
grams. Where appropriate, simple setting up proce- engaged in the very secret work of radar development and
dures are described in detail; no test equipment is contributed enormously to the system eventually to become HIGH POWER AUDIO AMPLIFIER CONSTRUCTION
needed. ‘H25’ – blind-bombing radar. Tragically, during an experi- R. A. Penfold
mental H2S flight in June 1942, the Halifax bomber in which Practical construction details of how to build a number of
The projects covered in this book include: Four channel
Blumlein and several colleagues were flying, crashed and audio power amplifiers ranging from about 50 to 300/400
audio mixer, Four channel stereo mixer, Dynamic noise watts r.m.s. includes MOSFET and bipolar transistor
limiter (DNL), Automatic audio fader, Video faders, Video all aboard were killed. He was just days short of his thirty-
ninth birthday. designs.
wipers, Video crispener, Mains power supply unit.
109 pages Order code BP356 £5.45 420 pages Order code NE32 £17.99 96 pages Temporarily out of print

Everyday Practical Electronics, August 2005 585

 FAULT FINDING, circuits and design
DISCOVERING PICS BOOK + CDROM Micro-controllers and PLCs, Digital broadcasting, OPERATIONAL AMPLIFIER USER’S HANDBOOK
W.D.Phillips + HARDWARE Electronic security. R. A. Penfold
A good introduction to PIC pro- The first part of this book covers standard operational
440 pages Order code NE21 £19.99
gramming, covering everything you need to know to get amplifer based “building blocks’’ (integrator, precision
you started. No previous knowledge of microcontrollers is rectifier, function generator, amplifiers, etc), and consid-
required, but some previous experience with electronic cir- PIC IN PRACTICE ers the ways in which modern devices can be used to give
cuits is assumed. Covers the basic concept of a microcon- David W. Smith superior performance in each one. The second part
A graded course based around the practical use of the PIC describes a number of practical circuits that exploit mod-
troller, fundamentals of a PIC-based circuit and using the
microcontroller through project work. Principles are intro- ern operational amplifiers, such as high slew-rate, ultra
MPLAB program. Further chapters introduce binary, PIC duced gradually, through hands-on experience, enabling
architecture, the instruction set, the PIC memory map and low noise, and low input offset devices. The projects
hobbyists and students to develop their understanding at include: Low noise tape preamplifier, low noise RIAA pre-
special registers plus real world programming. Four simple their own pace. The book can be used at a variety of levels.
projects are also fully described; a Wavy Wand, an amplifier, audio power amplifiers, d.c. power controllers,
Contents: Introduction to the PIC microcontroller; opto-isolator audio link, audio millivolt meter, temperature
Electronic Dice, a Games Timer and a Pulse Monitor. Programming the 16F84 microcontroller; Using inputs; monitor, low distortion audio signal generator, simple
The associated CDROM contains the book in PDF format, Keypad scanning; Program examples; The 16C54 microcon- video fader, and many more.
MPLAB (plus instruction manuals in PDF format) and all the troller; Alphanumeric displays; Analogue to digital conversion;
programs covered in the book as assembler (ASM) files. Radio transmitters and receivers; EEPROM data memory; 120 pages Order code BP335 £5.45
In addition a p.c.b. based hardware kit is also available that Interrupts; The 12C5XX 8-pin microcontroller; The 16F87X
makes up into the Wavy Wand which will spell out a short microcontroller; The 16F62X microcontroller; Projects;
message via a line of l.e.d.s when waved through the air. Instruction set, files and registers; Appendices; Index.
A BEGINNERS GUIDE TO CMOS DIGITAL ICs
190 pages, A4 spiral bound 272 pages Order code NE39 £17.49 R. A. Penfold
Getting started with logic circuits can be difficult, since many
Book + CDROM Order code DOC1 £22.00 of the fundamental concepts of digital design tend to seem
COIL DESIGN AND CONSTRUCTIONAL MANUAL rather abstract, and remote from obviously useful applica-
Book + CDROM + Hardware Order code DOC2 £28.50 B. B. Babani tions. This book covers the basic theory of digital electronics
A complete book for the home constructor on “how to and the use of CMOS integrated circuits, but does not lose
PRACTICAL OSCILLATOR CIRCUITS make’’ RF, IF, audio and power coils, chokes and sight of the fact that digital electronics has numerous “real
A. Flind transformers. Practically every possible type is dis- world’’ applications.
Extensive coverage is given to circuits using capacitors cussed and calculations necessary are given and The topics covered in this book include: the basic
explained in detail. Although this book is now twenty concepts of logic circuits; the functions of gates, invert-
and resistors to control frequency. Designs using
years old, with the exception of toroids and pulse ers and other logic “building blocks’’; CMOS logic i.c.
CMOS, timer i.c.s and op.amps are all described in transformers little has changed in coil design since it
detail, with a special chapter on “waveform generator’’ characteristics, and their advantages in practical circuit
was written. design; oscillators and monostables (timers); flip/flops,
i.c.s. Reliable “white’’ and “pink’’ noise generator circuits
are also included. Various circuits using inductors and 96 pages Order code BP160 £4.49 binary dividers and binary counters; decade counters
and display drivers.
capacitors are covered, with emphasis on stable low fre-
quency generation. Some of these are amazingly simple, PRACTICAL ELECTRONIC FAULT FINDING AND 119 pages Order code BP333 £5.45
but are still very useful signal sources. TROUBLESHOOTING
Crystal oscillators have their own chapter. Many of the Robin Pain
circuits shown are readily available special i.c.s for To be a real fault finder, you must be able to get a feel for what
simplicity and reliability, and offer several output frequen- is going on in the circuit you are examining. In this book Robin
cies. Finally, complete constructional details are given for
an audio sinewave generator.
Pain explains the basic techniques needed to be a fault finder.
Simple circuit examples are used to illustrate principles and
concepts fundamental to the process of fault finding. This is
audio AMPS
133 pages Order code BP393 £5.49
not a book of theory, it is a book of practical tips, hints and VALVE & TRANSISTOR AUDIO AMPLIFIERS
rules of thumb, all of which will equip the reader to tackle any John Linsley Hood
PRACTICAL ELECTRONICS HANDBOOK – job. You may be an engineer or technician in search of infor- This is John Linsley Hood’s greatest work yet, describ-
mation and guidance, a college student, a hobbyist building a ing the milestones that have marked the development of
Fifth Edition. Ian Sinclair
project from a magazine, or simply a keen self-taught ama- audio amplifiers since the earliest days to the latest
Provides a practical and comprehensive collection of teur who is interested in electronic fault finding but finds books
circuits, rules of thumb and design data for professional systems. Including classic amps with valves at their
on the subject too mathematical or specialised. heart and exciting new designs using the latest compo-
engineers, students and enthusaists, and therefore The fundamental principles of analogue and digital fault
enough background to allow the understanding and nents, this book is the complete world guide to audio
finding are described (although, of course, there is no such amp design.
development of a range of basic circuits. thing as a “digital fault” – all faults are by nature analogue). Contents: Active components; Valves or vacuum
Contents: Passive components, Active discrete This book is written entirely for a fault finder using only the tubes; Solid-state devices; Passive components;
components, Circuits, Linear I.C.s, Energy conversion basic fault-finding equipment: a digital multimeter and an Inductors and transformers; Capacitors, Resistors,
components, Digital I.C.s, Microprocessors and oscilloscope. The treatment is non-mathematical (apart from Switches and electrical contacts; Voltage amplifier
microprocessor systems, Transferring digital data, Ohm’s law) and all jargon is strictly avoided. stages using valves; Valve audio amplifier layouts;
Digital-analogue conversions, Computer aids in elec- Negative feedback; Valve operated power amplifiers;
tronics, Hardware components and practical work, 274 pages Order code NE22 £25.99 Solid state voltage amplifiers; Early solid-state audio
amplifiers; Contemporary power amplifier designs;
Preamplifiers; Power supplies (PSUs); Index.
250 pages Order code NE24 £25.99
BOOK ORDERING DETAILS
All prices include UK postage. For postage to Europe (air) and the rest of the world (surface) AUDIO AMPLIFIER PROJECTS
please add £2 per book. For the rest of the world airmail add £3 per book. CD-ROM prices R. A. Penfold
include VAT and/or postage to anywhere in the world. Send a PO, cheque, international money A wide range of useful audio amplifier projects, each
order (£ sterling only) made payable to Direct Book Service or card details, Visa, Mastercard, project features a circuit diagram, an explanation of the
Amex, Diners Club or Switch/Maestro to: DIRECT BOOK SERVICE, WIMBORNE PUBLISHING circuit operation and a stripboard layout diagram. All
LIMITED, 408 WIMBORNE ROAD EAST, FERNDOWN, DORSET BH22 9ND. constructional details are provided along with a shop-
ping list of components, and none of the designs
Books are normally sent within seven days of receipt of order, but please allow 28 days for requires the use of any test equipment in order to set
delivery – more for overseas orders. Please check price and availability (see latest issue of up properly. All the projects are designed for straight-
Everyday Practical Electronics) before ordering from old lists. forward assembly on simple circuit boards.
For a further selection of books see the next two issues of EPE. Circuits include: High impedance mic preamp, Low
impedance mic preamp, Crystal mic preamp, Guitar and
Tel 01202 873872 Fax 01202 874562. E-mail: dbs@wimborne.co.uk GP preamplifier, Scratch and rumble filter, RIAA pre-
Order from our online shop at: www.epemag.co.uk amplifier, Tape preamplifier, Audio limiter, Bass and treble
tone controls, Loudness filter, Loudness control, Simple
graphic equaliser, Basic audio mixer, Small (300mW) audio
power amp, 6 watt audio power amp, 20/32 watt power
amp and power supply, Dynamic noise limiter.
BOOK ORDER FORM A must for audio enthusiasts with more sense than
money!
Full name: ............................................................................................................................................... 116 pages Order code PC113 £10.95 £5.45

Address: ..................................................................................................................................................
VALVE AMPLIFIERS
................................................................................................................................................................. Second Edition. Morgan Jones
This book allows those with a limited knowledge of the
................................................................................................................................................................. field to understand both the theory and practice of valve
audio amplifier design, such that they can analyse and
.............................................. Post code: ........................... Telephone No: ............................................. modify circuits, and build or restore an amplifier. Design
principles and construction techniques are provided so
Signature: ................................................................................................................................................ readers can devise and build from scratch, designs that
actually work.
፬ I enclose cheque/PO payable to DIRECT BOOK SERVICE for £ ................................................... The second edition of this popular book builds on its
main strength – exploring and illustrating theory with
፬ Please charge my card £ ....................................... Card expiry date............................................... practical applications. Numerous new sections include:
output transformer problems; heater regulators; phase
Card Number ............................................................................. Switch/Maestro Issue No..................... splitter analysis; and component technology. In addition to
Card Security Code ................ (the last three digits on or just below the signature strip) the numerous amplifier and preamplifier circuits, three
major new designs are included: a low-noise single-
Please send book order codes: .............................................................................................................. ended LP stage, and a pair of high voltage amplifiers for
driving electrostatic transducers directly – one for head-
................................................................................................................................................................. phones, one for loudspeakers.
Please continue on separate sheet of paper if necessary
288 pages Order code NE33 £32.99

586 Everyday Practical Electronics, August 2005

 WIRELESS for the
WARRIOR
Volume 4
CLANDESTINE RADIO
A technical history of Radio
Communication Equipment in
clandestine and special forces operations

Volume 4 ‘Clandestine Radio’ – not only ‘spy’ equip- Volume 3 ‘Reception Sets’ – the receivers described
ment but sets used by Special Forces, Partisans, span the era 1932 to the 1960s, and coverage includes
Resistance, ‘Stay Behind’ organisations, Diplomatic not only reception sets specifically designed or adapted
Service, Australian Coast Watchers, RDF and intercept for the British Army, but also sets adopted from other
receivers, bugs and radar beacons. The information has arms (RN and RAF), special receivers, direction find-
been compiled through the collaboration of a vast num- ing receivers, army broadcast reception sets, Canadian
ber of collectors and enthusiasts around the world. and Australian army sets, commercial receivers adopt-
Volume 4 includes information on more than 230 sets ed by the army, and army welfare reception sets.
and ancillaries. It contains 692 pages in hardback
format, and features over 850 photographs, 360 line PRICES INCLUDING POSTAGE
drawings and 440 data tables. Europe airmail,
Rest of World Rest Of World
Volume 1 ‘Wireless Sets No.1 to 88’ – covers the early UK surface mail airmail
radios, prior to the outbreak of World War II, and
Vol 1 £33.00 £34 £44
wartime sets which were never released in large quanti-
Vol 2 £43.50 £47* £55.95*
ties or were abandoned after trials. Vol 3 £42.50 £47 £55.95
Vol 4 £45 £49* £57.95*
Volume 2 ‘Standard Sets for World War II’ – pro-
vides information in detail of mass-produced Wireless *For delivery to Canada Vol.2 and Vol 4 can only be sent by
surface post.
Sets such as No.18, 19, 22 and 38. Additionally includ-
ed are a number of post-war sets on which development Cheques made payable to Direct Book Service.
Direct Book Service, Wimborne Publishing Ltd,
had been started during World War II. 408 Wimborne Road East, Ferndown, Dorset BH22 9ND
Tel: 0202 873872 Fax: 0202 874562
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Please send me: Wireless For The Warrior

..........(quantity) Vol 1; ..........(quantity) Vol 2; ..........(quantity) Vol 3; ..........(quantity) Vol 4

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Post Code ................................................ 6 I enclose cheque/postal order/bank draft to the value of £.....................

6 Please charge my Visa/Mastercard/Amex/Diners Club/Maestro

£........................... Card No: ....................................................................................... WIRELESS

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WARRIOR
Everyday Practical Electronics, August 2005 587
 NO VE
W RS
AV IO
AI N 2
EPE PIC LA
BL
E
RESOURCES
CD-ROM V2
Version 2 includes the EPE PIC
Tutorial V2 series of Supplements
ONLY
(EPE April, May, June 2003)
The CD-ROM contains the following
£14.45
INCLUDING
Tutorial-related software and texts: VAT and P&P
ɀ EPE PIC Tutorial V2 complete series of articles plus Order on-line from
demonstration software, John Becker, April, May, June ’03 www.epemag.wimborne.co.uk/shopdoor.htm
or www.epemag.com (USA $ prices)
ɀ PIC Toolkit Mk3 (TK3 hardware construction details), or by Phone, Fax, Email or Post.
John Becker, Oct ’01
ɀ PIC Toolkit TK3 for Windows (software details), John
Becker, Nov ’01 EPE PIC RESOURCES V2
Plus these useful texts to help you get the most out of your CD-ROM ORDER FORM
PIC programming:
Please send me ........ (quantity) EPE PIC RESOURCES V2 CD-ROM
ɀ How to Use Intelligent L.C.D.s, Julyan Ilett, Feb/Mar ’97 Price £14.45 each – includes postage to anywhere in the world.
ɀ PIC16F87x Microcontrollers (Review), John Becker,
April ’99 Name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ɀ PIC16F87x Mini Tutorial, John Becker, Oct ’99
ɀ Using PICs and Keypads, John Becker, Jan ’01 Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ɀ How to Use Graphics L.C.D.s with PICs, John Becker,
Feb ’01 ................................................
ɀ PIC16F87x Extended Memory (how to use it), ................................................
John Becker, June ’01
ɀ PIC to Printer Interfacing (dot-matrix), John Becker, . . . . . . . . . . . . . . . . . . . . . . . . . . Post Code . . . . . . . . . . . . .
July ’01
ɀ PIC Magick Musick (use of 40kHz transducers), អ I enclose cheque/P.O./bank draft to the value of £ . . . . . . . . .
John Becker, Jan ’02
អ Please charge my Visa/Mastercard/Amex/Diners Club/
ɀ Programming PIC Interrupts, Malcolm Wiles, Mar/Apr ’02 Switch/Maestro
ɀ Using the PIC’s PCLATH Command, John Waller,
July ’02 £ ...............................................
ɀ EPE StyloPIC (precision tuning musical notes),
John Becker, July ’02 Card No. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ɀ Using Square Roots with PICs, Peter Hemsley, Aug ’02 Card Security Code . . . . . . . . . . (The last 3 digits on or just under
ɀ Using TK3 with Windows XP and 2000, Mark Jones, the signature strip)
Oct ’02
ɀ PIC Macros and Computed GOTOs, Malcolm Wiles, Valid From . . . . . . . . . . . . . . . .Expiry Date . . . . . . . . . . . . . .
Jan ’03
ɀ Asynchronous Serial Communications (RS-232), Switch Issue No. . . . . . . . . . . . . . . .
John Waller, unpublished
SEND TO: Everyday Practical Electronics,
ɀ Using I2C Facilities in the PIC16F877, John Waller,
Wimborne Publishing Ltd.,
unpublished
408 Wimborne Road East, Ferndown, Dorset BH22 9ND.
ɀ Using Serial EEPROMs, Gary Moulton, unpublished Tel: 01202 873872. Fax: 01202 874562.
ɀ Additional text for EPE PIC Tutorial V2, Email: orders@epemag.wimborne.co.uk
John Becker, unpublished Payments must be by card or in £ Sterling – cheque or bank draft
drawn on a UK bank.
NOTE: The PDF files on this CD-ROM are suitable to
use on any PC with a CD-ROM drive. They require Normally supplied within seven days of receipt of order.
Adobe Acrobat Reader – included on the CD-ROM Send a copy of this form, or order by letter if you do not wish to cut your issue.

BECOME A PIC WIZARD WITH THE HELP OF EPE!

588 Everyday Practical Electronics, August 2005
 PCB SERVICE
Printed circuit boards for most recent EPE constructional projects are available from
the PCB Service, see list. These are fabricated in glass fibre, and are fully drilled and
PROJECT TITLE
Spontaflex Radio– Tuner
– Coil Pack
– Audio Amplifier
– Tuning Capacitor Board
刂Safety Interface
APR ‘05
Order Code
494
495
496
406
497
Cost
£5.55
£5.71
£5.55
£4.28
£6.18
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roller tinned. All prices include VAT and postage and packing. Add £1 per board for
airmail outside of Europe. Remittances should be sent to The PCB Service, 刂Crossword Solver MAY ’05 499 £6.66
Everyday Practical Electronics, Wimborne Publishing Ltd., 408 Wimborne Road 20W Amplifier Module 500 £5.14
East, Ferndown, Dorset BH22 9ND. Tel: 01202 873872; Fax 01202 874562; Back-To-Basics 2
Email: orders@epemag.wimborne.co.uk. On-line Shop: www.epemag. – Water Level Alarm 501 £5.39
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Everyday Practical Electronics (Payment in £ sterling only).
NOTE: While 95% of our boards are held in stock and are dispatched within 刂PIC Ultrasonic Scanner JUN ’05 503 £6.66
seven days of receipt of order, please allow a maximum of 28 days for delivery 刂Radio Control Model Switcher 504 £5.87
– overseas readers allow extra if ordered by surface mail. Back-To-Basics 3
Back numbers or photostats of articles are available if required – see the Back
Issues page for details. We do not supply kits or components for our projects. – Scarecrow 505 £5.55
– Digital Lock 506 £6.66
Please check price and availability in the latest issue. CompactFlash Interface Board 507 £6.66
A large number of older boards are listed on our website. LF/VLF Converter JUL ’05
Boards can only be supplied on a payment with order basis. – Fixed Capacitor Board 508 £5.71
– Mixer/Oscillator Board 509 £5.86
– Buffer Amplifier 510 £5.23
PROJECT TITLE Order Code Cost – Q-Multiplier 511 £5.23
Bat-Band Convertor MAR ’04 436 £4.76 – Tuning Capacitor Board 406 £4.28
Back-To-Basics 4 – Doorchime 512 £6.34
刂MIDI Health Check – Transmitter/Receiver 437 pair £7.61
– Electronic Dice 513 £6.02
Emergency Stand-by Light 438 £5.55
刂Cybervox 514 £6.82
刂PIC Mixer for RC Planes – Software only – –
Multi-Clap Switch 515 £6.66
刂Teach-In ’04 Part 5 – Software only – –
Audio System AUG ‘05
Infra-Guard APR ’04 439 £5.07 – Preamplifier 516 £6.02
刂Moon Clock 442 £5.71 – Mic. Supply Board 517 £5.23
刂Teach-In ’04 Part 6 – Software only – – – Power Amp 518 £6.02
刂EPE Seismograph Logger APR ’04 刂Pain Monitor 519 £7.14
Control Board 440
Sensor Amp. Board 441 }
pair £6.50 MotorAmp
Back-To-Basics 5
520 £7.45

In-Car Lap-Top PSU MAY ’04 443 £4.60 – Kitchen Timer 521 £5.87
Beat Balance Metal Detector 444 £4.60 – Room Thermometer 522 £6.02
Teach-In ’04 Part 7 – Transmitter 445 £4.91
Receiver 446 £4.75
Moisture 447 £4.44
刂PIC Quickstep
Body Detector MkII
JUNE ’04 448
449
£5.71
£4.91
EPE SOFTWARE
刂Teach-In ’04 Part 8 – Software only – – Software programs for EPE projects marked with a single asterisk 刂 are
刂MIDI Synchronome – Software only – – available on 3·5 inch PC-compatible disks or free from our Internet site. The
Hard Drive Warbler JULY ’04 450 £4.60 following disks are available: PIC Tutorial V2 (Apr-June ’03); EPE Disk 3
刂Bongo Box 451 £6.02 (2000); EPE Disk 4 (2001 – excl. PIC Toolkit TK3); EPE Disk 5 (2002); EPE
Portable Mini Alarm – Sensor 452 £5.23 Disk 6 (2003 – excl. Earth Resistivity and Met Office); EPE Disk 7 (2004);
– Counter 453 £5.07 EPE Disk 8 (Jan 2005 to current cover date); EPE Earth Resistivity
刂Teach-In ’04 Part 9 Logger (Apr-May ’03); EPE PIC Met Office (Aug-Sept ’03); EPE
PIC Combination Lock Alarm Monitor 454 £5.07 Seismograph (Apr-May ’04); EPE Magnetometry Logger (July-Aug ’04);
刂EPE Magnetometry Logger 455 £5.71 EPE Teach-In 2000; EPE Spectrum; EPE Interface Disk 1 (October ’00
Keyring L.E.D. Torch AUG ’04 456 £4.12 issue to current cover date). EPE Toolkit TK3 software is available on the
刂Teach-In ’04 Part 10 – PIC Curtain or Blind Winder 457 £5.39 EPE PIC Resources CD-ROM, £14.45. Its p.c.b. is order code 319, £8.24.
Simple F.M. Radio – F.M. Tuner 458 £5.07 刂刂The software for these projects is on its own CD-ROM. The 3·5 inch
– Tone Control 459 £4.75 disks are £3.00 each (UK), the CD-ROMs are £6.95 (UK). Add 50p each for
– Audio Power Amp (TDA2003) 347 £4.60 overseas surface mail, and £1 each for airmail. All are available from the
– Power Supply 460 £5.39 EPE PCB Service. All files can be downloaded free from our Internet FTP
刂EPE Scorer – Control Board 461 £6.66 site, accessible via our home page at: www.epemag.co.uk.
– Display Board 462 £7.93
– Slave Board 463 £5.55
刂PIC to Mouse/Keyboard – Software only – –
EPE Wart Zapper SEPT ’04 464 £4.60 EPE PRINTED CIRCUIT BOARD SERVICE
刂Radio Control Failsafe 465 £4.76
刂AlphaMouse Game 466 £4.60 Order Code Project Quantity Price
刂Rainbow Lighting Controller – Software only – –
刂Moon and Tide Clock Calendar OCT ’04 467 £5.55 .....................................................................................
Volts Checker 468 £4.20
刂Smart Karts – Software only – Name ...........................................................................
Logic Probe NOV ‘04 469 £4.76
Thunderstorm Monitor 470 £5.39
Address .......................................................................
MW Amplitude Modulator ..............................................................................
– V.F.O./Buffer 471 £4.76
– Modulator/PA 472 £5.07
– Power Supply 473 £4.76 Tel. No. .........................................................................
Super Vibration Switch DEC ‘04 474 £4.75
Wind Direction Indicator 475 £6.18 I enclose payment of £................ (cheque/PO in £ sterling only) to:
刂PIC Flasher Mk2
– Control Board
– Transmitter
476
477
£4.75
£4.44
Everyday
– Multipurpose Board
– Simple Cycler
478
479
£4.75
£4.44
Practical Electronics
– Luxeon V Controller 480 £4.44 MasterCard, Amex, Diners
– Power Supply 473 £4.76
Light Detector JAN ‘05 481 £4.44 Club, Visa or Switch/Maestro
刂Camera Watch 482 £6.03
Gate Alarm – Oscillator 483 £4.92 Card No. ................................................................................
– Delay/Timer 484 £4.92
Valid From ....................... Expiry Date ...............................
刂Sneaky – Transmitter FEB ‘05 485 £4.60
– Receiver 486 £4.91 Card Security Code ............. Switch/Maestro Issue No .........
刂PIC Electric Mk2 – Control 487 £5.87 (The last 3 digits on or just under the signature strip)
– Sensor 488 £5.71
Sound Card Mixer 489 £7.29 Signature ..............................................................................
Headphone Monitor MAR ’05 490 £5.71
EPE Cat Flap 491 £6.02 NOTE: You can also order p.c.b.s by phone, Fax, Email or via our
刂Bingo Box – Main 492 £9.04 Internet site on a secure server:
– Big Digit Display 493 £10.31 http://www.epemag.wimborne.co.uk/shopdoor.htm

Everyday Practical Electronics, August 2005 589

ELECTRONICS MANUALS ON CD-ROM £29.95 EACH
ELECTRONICS SERVICE MANUAL THE MODERN ELECTRONICS MANUAL

SPECIAL
OFFER
Order both Manuals
together and

Everything you need to know to get

SAVE £10 The essential reference work for
started in repairing electronic equipment everyone studying electronics

Around 900 pages
Fundamental principles
Troubleshooting
Over 800 pages
In-depth theory
Projects to build

techniques
Servicing techniques
Choosing and using test Detailed assembly instructions
Full components
equipment
Reference data
Manufacturers’ web links checklists
Extensive data tables
Manufacturers’ web

Easy-to-use Adobe Acrobat format
Clear and simple layout links
Easy-to-use Adobe Acrobat format
Clear and

Vital safety precautions
Professionally written
Supplements simple layout
Comprehensive subject range

SAFETY: Safety Regulations, Electrical Safety and First Aid. Professionally written
Supplements
UNDERPINNING KNOWLEDGE: Electrical and Electronic Principles, BASIC PRINCIPLES: Electronic Components and their
Active and Passive Components, Circuit Diagrams, Circuit Characteristics; Circuits Using Passive Components;
Measurements, Radio, Computers, Valves and Manufacturers’ Data, Power Supplies; The Amateur Electronics Workshop; The
etc. PRACTICAL SKILLS: Learn how to identify Electronic Uses of Semiconductors; Digital Electronics; Operational
Components, Avoid Static Hazards, Carry Out Soldering and Wiring, Amplifiers; Introduction to Physics, including practical
Remove and Replace Components. TEST EQUIPMENT: How to experiments; Semiconductors and Digital Instruments.
Choose and Use Test Equipment, Assemble a Toolkit, Set Up a CIRCUITS TO BUILD: The Base Manual describes 12
Workshop, and Get the Most from Your Multimeter and Oscilloscope, projects including a Theremin and a Simple TENS
etc. SERVICING TECHNIQUES: The Manual includes vital guidelines Unit.
on how to Service Audio Amplifiers. The Supplements include similar ESSENTIAL DATA: Extensive tables on diodes,
guidelines for Radio Receivers, TV Receivers, Cassette Recorders, transistors, thyristors and triacs, digital and linear i.c.s.
Video Recorders, Personal Computers, etc. TECHNICAL NOTES: EXTENSIVE GLOSSARY: Should you come across a
Commencing with the IBM PC, this section and the Supplements deal technical word, phrase or abbreviation you’re not familiar
with a very wide range of specific types of equipment – radios, TVs, with, simply look up the glossary and you’ll find a
cassette recorders, amplifiers, video recorders etc. REFERENCE comprehensive definition in plain English.
DATA: Diodes, Small-Signal Transistors, Power Transistors, Thyristors, The Manual also covers Safety and provides web links
Triacs and Field Effect Transistors. Supplements include Operational to component and equipment Manufacturers and
Amplifiers, Logic Circuits, Optoelectronic Devices, etc. Suppliers.
Full contents list available online at: www.epemag.wimborne.co.uk
SUPPLEMENTS: Additional CD-ROMs each containing approximately 500 pages of additional information on specific areas of
electronics are available for £19.95 each. Information on the availability and content of each Supplement CD-ROM will be sent to you.

Presentation: CD-ROM suitable for any modern PC. Requires Adobe Acrobat Reader which is included on the CD-ROM.
Wimborne Publishing Ltd., Dept Y08, 408 Wimborne Road East, Ferndown, Dorset BH22 9ND. Tel: 01202 873872. Fax: 01202 874562.

PLEASE send me
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590 Everyday Practical Electronics, August 2005

 CLASSIFIED
Everyday Practical Electronics reaches twice as
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electronics magazine, our sales figures prove it.
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If you want your advertisements to be seen by the largest readership at the most economical price our classified and semi-display pages
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TOTALROBOTS Microcontroller
Microcontroller kits, 8052 core, no
ROBOTICS, CONTROL & development tools needed, runs
ELECTRONICS TECHNOLOGY BASIC in firmware, I2C, LCD and
Infrared drivers built in. Program in
High quality robot kits and components BASIC and then run stand alone.
UK distributor of the OOPic microcontroller Prices from £14.95 + P & P
www.byvac.com
Secure on-line ordering
Rapid delivery
Highly competitive prices
Visit www.totalrobots.com BOWOOD ELECTRONICS LTD
Tel: 01737 371688 Suppliers of Electronic Components
Place a secure order on our website or call our sales line
All major credit cards accepted
Web: www.bowood-electronics.co.uk
Unit 1, McGregor’s Way, Turnoaks Business Park,
X-10 ® Home Automation Chesterfield, S40 2WB. Sales: 01246 200222
We put you in control TM Send 60p stamp for catalogue

Why tolerate when you can automate?

An extensive range of 230V X-10 products
and starter kits available. Uses proven Power
Line Carrier technology, no wires required. Miscellaneous
Products Catalogue available Online. MAKE YOUR HOBBY PAY. Assemble units
Worldwide delivery. for the partially sighted. Local customers, sole
area, instruction manual, material suppliers and,
Laser Business Systems Ltd. completed unit supplied. Details 02392 830158
E-Mail: info@laser.com
HI-FI BARGAIN £14.99. Stereo amplifier
http://www.laser.com modules, power-supplies and hundreds of new
Tel: (020) 8441 9788 components; KIA 1 Regent Road Ilkley LS29
Fax: (020) 8449 0430
VALVES AND ALLIED COMPONENTS IN
STOCK. Phone for free list. Valves, books and
magazines wanted. Geoff Davies (Radio), tel.
01788 574774.

FREE! PROTOTYPE PRINTED CIRCUIT

BOARDS! Free prototype p.c.b. with quantity
orders. Call Patrick on 028 9073 8897 for details.
N.R. BARDWELL LTD Agar Circuits, Unit 5, East Belfast Enterprise
ELECTRONIC COMPONENT SUPPLIES Park, 308 Albertbridge Road, Belfast BT5 4GX.
Stock of l.e.d.s, Semiconductors, Resistors,
Capacitors and many more items. PRINTED CIRCUIT BOARDS – QUICK
Send 44p for lists or visit our secure online SERVICE. Prototype and production artwork
ordering at www.bardwells.co.uk
288, Abbeydale Road, Sheffield. S7 1FL raised from magazines or draft designs at low
Email - sales@bardwells.co.uk cost. PCBs designed from schematics.
Production assembly, wiring and software pro-
gramming. For details contact Patrick at Agar
BTEC ELECTRONICS Circuits, Unit 5, East Belfast Enterprise Park,
308 Albertbridge Road, Belfast BT5 4GX.
READY TO PAY FOR TECHNICIAN TRAINING Phone 028 9073 8897, Fax 028 9073 1802,
Email agar@argonet.co.uk
DESIGNING... NATIONAL ELECTRONICS
/technical know how, prototype of continuous VCE ADVANCED ICT WANTED URGENTLY. Old half inch ferrite
monitoring / portable gas detector system with HNC AND HND ELECTRONICS rods. Must be half inch in diameter and be six
digital display (ppm reading) alarm system
using Figaro (Japan) gas sensor (semiconduc- FOUNDATION DEGREES inches long or more. Will pay very good money
NVQ ENGINEERING AND IT for the rods.Contact Peter Tankard on Tel: 0114
tor type) or Citicel-UK (electrochemical type). 2316321 between 9am and 10pm.
Basic circuitry may be supplied by us. You DESIGN AND TECHNOLOGY
will have to issue an attorney licence. Expert
electronic engineers may contact on:
LONDON ELECTRONICS COLLEGE ½ PRICE VALVES AND RADIO &
20 PENYWERN ROAD ELECTRONIC COMPONENTS. Catalogues
Telephone No - 91-22-26361469 EARLS COURT, LONDON SW5 9SU available for £1, refundable on 1st order. Over
TEL: (020) 7373 8721 1480 valves and over 500 radio/electronic com-
EMAIL abhitron@bom5.vsnl.net.in ponents. Sound Systems, 676 Foxhall Road,
www.lec.org.uk
Ipswich, Suffolk, IP3 8NQ.Tel: 01473 272218

Everyday Practical Electronics, August 2005 591

 Rechargeable Batteries With Solder Tags
NIMH NICAD
ADVERTISERS
AA 2000mAh ......................£2.82
C 4Ah ...................................£4.70
D 9Ah ...................................£7.60
AA 650mAh ...................... £1.41
C 2.5Ah ...............................£3.60
D 4Ah ...................................£4.95
INDEX
PP3 150mAh ..................... £4.95
AUDON ELECTRONICS . . . . . . . . . . . . . . . . . . . . . . .544
AVIT RESEARCH . . . . . . . . . . . . . . . . . . . . . . . . . . . .544
Instrument case with edge connector and screw terminals BITZ TECHNOLOGY . . . . . . . . . . . . . . . . . . . . . . . . .569
Size 112mm x 52mm x 105mm tall BREADBOARDING . . . . . . . . . . . . . . . . . . . . . . . . . .557
BULL GROUP . . . . . . . . . . . . . . . . . . . . . . . . . .Cover (ii)
This box consists of a cream base with a PCB slot, a cover plate to pro- DISPLAY ELECTRONICS . . . . . . . . . . . . . . . . . . . . . 522
tect your circuit, a black lid with a 12 way edge connector and 12 screw
terminals built in (8mm pitch) and 2 screws to hold the lid on. The cream EASYSYNC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .569
bases have minor marks from dust and handling price £2.00 + ESR ELECTRONIC COMPONENTS . . . . . . . . . . . . . .530
VAT(=£2.35) for a sample or £44.00+VAT (=£51.70) for a box of 44.
FAST COMPONENTS . . . . . . . . . . . . . . . . . . . . . . . .522
JAYCAR ELECTRONICS . . . . . . . . . . . . . . . . . .Cover (iv)
JPG ELECTRONICS . . . . . . . . . . . . . . . . . . . . . . . . .592
LABCENTER . . . . . . . . . . . . . . . . . . . . . . . . . . .Cover (iii)
MAGENTA ELECTRONICS . . . . . . . . . . . . . . . . .528/529
NURVE NETWORKS LLC . . . . . . . . . . . . . . . . . . . . . .571
PEAK ELECTRONIC DESIGN . . . . . . . . . . . . . . . . . .560
PICO TECHNOLOGY . . . . . . . . . . . . . . . . . . . . . . . . .544
866 battery pack originally intended to be
QUASAR ELECTRONICS . . . . . . . . . . . . . . . . . .524/525
used with an orbitel mobile telephone it RD RESEARCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . .541
contains 10 1·6Ah sub C batteries (42 x SHERWOOD ELECTRONICS . . . . . . . . . . . . . . . . . . .592
22 dia. the size usually used in cordless
screwdrivers etc.) the pack is new and STEWART OF READING . . . . . . . . . . . . . . . . . . . . . .522
unused and can be broken open quite
easily £7.46 + VAT = £8.77
ADVERTISEMENT OFFICES:
Please add £1.66 + VAT = £1.95 postage & packing per order
408 WIMBORNE ROAD EAST, FERNDOWN, DORSET BH22 9ND
JPG Electronics PHONE: 01202 873872
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SHERWOOD ELECTRONICS EPE SUBSCRIPTIONS

SAVE 71p AN ISSUE OVER UK NEWSTAND PRICES
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SP5 25 x 5mm 1 part LED clips SP138 20 x 2·2/63V radial elect. caps. 6 months £19.50 standard air service or £28.50 express airmail,
SP6 15 x 3mm Red LEDs SP140 3 x W04 1·5A bridge rectifiers 12 months £37 standard air service or £55 express airmail,
SP7 12 x 3mm Green LEDs SP142 2 x CMOS 4017
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SP26
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SP33 4 x CMOS 4081 SP160 10 x 2N3904 transistors
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SP36
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12 x 100/35V radial elect. caps.
SP164
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SP41 20 x Mixed transistors SP171 8 Metres 18SWG solder www.epemag.com.
SP42 200 x Mixed 0·25W C.F. resistors SP172 4 x Standard slide switches
SP47 5 x Min. PB switches SP173 10 x 220/25V radial elect. caps
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SP174
SP175
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SP112 4 x CMOS 4093 SP187 15 x BC239 transistors Mag, PO Box 2769, Plattsburgh, NY 12901-0239 or Express
SP115 3 x 10mm Red LEDs SP189 4 x 5 metres solid core wire
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SP118 2 x CMOS 4047 SP195 3 x 10mm Yellow LEDs Email address: expsmag@expressmag.com.
SP124 20 x Assorted ceramic disc caps SP197 6 x 20 pin DIL sockets Web site: www.expressmag.com.
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SP133 20 x 1N4004 diodes Everyday Practical Electronics, periodicals pending, ISSN 0262 3617 is
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