ICD 08559

V JANUARY 1988 $2.50

CANADA $3.50

T M

THE MAGAZINE FOR ELECTRONICS & COMPUTER ENTHUSIASTS

Add a Delayed-Trigger
to Your Oscilloscope
Build a Battery-Powered
Wireless Microphone
More Full-Construction Plans:
A $30 Phototachometer
For Troubleshooting
Audible Continuity Tester A Phototachometer for
Frequency Counters (p. 32)
Trips Down to 50 Milliohms
Interfacing Commodore Computers
Miniature LED Beacon

Delayed Trigger for Oscilloscopes (p. 18;

New Monthly Columns: Solid -State Devices Computer Capers

Also: How to Build a 1-Hz to 300 -kHz Function Generator Evaluating Daetron's New
o
MC300 Capacitance Meter & Quick Charts by Stella Forrest Mims on Touch Tone
11 Remote Control Latest Technical Books & Literature Electronic & Computer
74820 08559 News ... and more
 OPTOelectronics inc

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#AC -1200
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#1200H 1.2 GHZ
Small enough to fit into a shirt pocket, our new 1.2 GHz and 1.3 GHz, 8 digit frequency counters are not toys!
They can actually out perform units many times their size and pricel Included are rechargeable Ni -Cad batteries
installed inside the unit for hours of portable, cordless operation. The batteries are easily recharged using the AC
adapter/charger supplied with the unit.
The excellent sensitivity of the 1200H makes it ideal for use with the telescoping RF pick -up antenna;
accurately and easily measure transmit frequencies from handheld, fixed, or mobile radios such as: Police,
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"bug " transmitters. Use with grid dip oscillator when designing and tuning antennas. May be used with a probe
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#1200HKC Model 1200H in kit form, -1200 MHz counter complete including
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#1200HC Model 1200H factory assembled -1200 MHz counter, tested and
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#P -100 Probe, direct connection 50 ohm, BNC connector $18.00
#CC-70 Carrying case, black vinyl with zipper opening. Will hold a counter and
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 EDITORIAL STAFF
N Art Salsberg
Editor -in -Chief
ELE
THE MAGAZINE FOR ELECTRONICS 8 COMPUTER ENTHUSIASTS
ICS Alexander W. Burawa
Managing Editor
Dorothy Kehrwieder
Production Manager
JANUARY 1988 VOLUME 5, NUMBER 1 Elizabeth Ryan
Art Director
FEATURES Barbara Scully
Artist
18 A Delayed- Trigger Accessory
for Oscilloscopes Pat Le Blanc
Florence V. Martin
Low -cost way to add a laboratory -grade facility to
Phototypographers
general -purpose scopes.
By Jan Axelson & Jim Hughes Hal Keith
Illustrator
25 An FM Wireless Microphone Bruce Morgan
Battery -powered microphone eliminates trailing Photographer
cable, transmits on FM Broadcast band.
By Anthony J. Caristi Joseph Desposito, Leonard Feldman,
Forrest Mims III
18 32 The Photo(Tach) -Pulser Contributing Editors

- -
A phototachometer adapter for frequency counters. BUSINESS STAFF
By Crady VonPawlak
Richard A. Ross
ND
SECONDARY
38 A Miniature LED Beacon Publisher
Adds more realism to model airplanes, trains, etc., Art Salsberg
I

7J
I

7J
and is an attention -getting device in jewelry and Associate Publisher
science -fair projects. By Dan Becker
Dorothy Kehrwieder
40 A High -Performance General Manager
Audible Continuity Tester Frank V. Fuzia
Stand -alone instrument tests circuits and com- Controller
ponents for continuity down to 50 milliohms. Arlene Caggiano
By Adolph A. Mangieri Accounting
46 Interfacing Commodore's User Port Catherine Ross
Circulation Director
Using a C -128, C -64 or VIC -20 to monitor real -world
analog events. By John Iovine SALES OFFICES
54 A Low-Cost Function Generator Modern Electronics
76 North Broadway
Delivers individually adjustable sine, triangle and
square waves from less than 1 Hz to almost 300 kHz. Hicksville, NY 11801
By Anthony J. Caristi (516) 681 -2922
Eastern Advertising Representative
COLUMNS Peter Conn
60 Electronics Notebook Sales Assistant
Touch Tone Remote Control. By Forrest M. Mims III Cheryl Chomicki
76 North Broadway
78 68 Solid -State Devices Hicksville, NY 11801
New monthly column on semiconductor technology
(REAR J._ (516) 681-2922
and developments. By Harry Helms
VIEW) Midwest & West Advertising Representative
72 PC Capers Market /Media Associates
12 New computer- oriented column. By Ted Needleman 1150 Wilmette Ave.
11 76 Software Focus Wilmette, IL 60091
(312) 251-2541
PB7 Quick Charts By Stella. By Art Salsberg
10 J
Ted Rickard
9 vas 78 Product Evaluation Greg Morin
SP-2 Daetron MC300: More Than Just A Capacitance Kevin Sullivan
-I 8 F. N PB5 Meter By J. Daniel Gifford Offices: 76 North Broadway, Hicksville, NY 11801. Tele-
CC phone: (516) 681 -2922. Modern Electronics (ISSN 0748-
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3 C PBO F- 8 Modern Electronics News Entire contents copyright 1988 by Modern Electronics,
Inc. Modern Electronics or Modern Electronics, Inc. as-
2 B 14 New Products sumes no responsibility for unsolicited manuscripts. Al-
low six weeks for delivery of first issue and for change of
A GND ( I- 80 Books & Literature address. Printed in the United States of America.
Postmaster: Please send change of address notice to
Modern Electronics, Inc., 76 North Broadway, Hicks-
90 Advertisers Index ville, NY 11801.
46

4 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 ftaduo Ihaek Parts PIae___%
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CIR('I F:9 ON FREE INFORMATION ('ARD

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 5
 NEW FROM EEB UI/Ill/EDITORIAL ill/It
NOW buy that test equipment
you've wanted and save! Reader Feedback
DIPMETER 1.5 To 250 MHz
AM Modulation 6 Plug -In Coils
Xtal -osc 1 -15 MHz Editors always relish receiving letters Requests for parts sources inun-
9V battery date our mail room, as you might im-
from readers, you should know;
DM4061
good, bad and challenging, it doesn't agine. If a stamped, self- addressed
matter. This keeps us in touch with envelope is provided, we'll normally
$109.95 Value respond if it relates to parts from a
our readership, which has many mu-
ONLY $7995 tual benefits. project we published. Too many
+$4 UPS For example, keen-eyed readers such queries concern parts that are
pick up on those tiny glitches in arti- not obtainable locally, though. We
Measure resonance of antennas and
tank circuits. cles -"Cl in the schematic reads 0.1 simply don't know which parts sup-
Check for Harmonic radiation. microfarad, while the Parts List has ply stores in one's neighborhood car-
Use as OSC for Rec. alignment. it as 1.0. Which is correct ?" -that ries what parts. The country's too
More uses detailed in the RSGB Hand-
book, pages 18.15 to 18.21.
somehow escape our proofreaders' big for us to help here. The way to go
(and editors' and authors') eyes from is mail- order, of course. That's why
RF SIGNAL GENERATOR time to time. These reports are al- you should scour the parts listings of
SG4160 100 KHz - 150 MHz to
450 MHz on harmonics.
ways posted in our next available advertisers in Modern Electronics,
- RF Output 100 mVs. "Letters" department. We thank and why you should gather as many
Modulation: Int. - 1 KHz you thoughtful people for sharing current mail-order company cata-
Ext. - 50 Hz to 20 KHz. logs as possible, getting updated
these discoveries with all of us.
'I ' - - Crystal OSC 1 - 15 MHz.
Readers' letters also let us know ones from time to time. It was a
$219.95 Value ONLY $14995+ $4 UPS
what subjects they'd like us to cover waste of time for all concerned, for
RF POWER METER /LOAD in the future, which articles they example, to get a batch of reader let-
PM330 1.8 to 500 MHz. liked best, etc. Similarly, advertised ters seeking a parts source for two
'w, 50 OHM -N -J Connector.
5W, 20W, 120 Watts.
and editorialized products circled on devices in a recent Modern Electron-
Accurate to +/- 10%. the postpaid Free Information Ser- ics project when one of our advertis-
$109.95 Value ONLY$7995 + $4 UPS vice card bound into every issue ers in the same issue, DigiKey, had
FREQUENCY COUNTER point out what product areas are them listed in its ad.
FC5250 10 Hz to 150 MHz. most popular. We get biweekly item- Finally, we also get lots of letters
7 Digit readout. ized reports on this, which serves as from readers seeking obscure or
Gate 1s & 6 sec. especially fine guidance from re- hard -to- obtain parts, schematics, a
e . e ., ,
Accurate to +/- 1 count.
spondents. At the same time, adver- piece of used equipment they'd like
25 - 100 mV to 30 MHz;
SENSITIVITY: 100 - 300 mV to 150 MHz tisers get mailing labels from us with to buy, sell or trade, etc. In most
the names and addresses of readers cases, we haven't been able to help.
$169.95 Value ONLY $12995 +$4 UPS
requesting more information about Nevertheless, there's obviously an
AC Adapter is included with unit.
their products. This eases their mail- important need here that has not
RF ATTENUATOR DC-500 MHz ing chores and speeds data to our been satisfied. Therefore, starting in
RFA8000 0 - 81 dB in
dB steps.1
readers. the near future, we will publish
Accurate to +/- .3 dB Naturally, we also get letters re- FREE OF CHARGE non- commer-
Steps 1, 2, 3, 5, 10 and 20 dB questing customized electronic de- cial classified ads, maximum of three
50 OHm -'/2 Watt Insertion Loss .5 dB. signs for some purpose: "I'd like to lines, for subscribers so that our vast
$299.00 Value ONLY $14995+ $4 UPS build a circuit that would .... Could number of readers can help out each
you send me a schematic ?" We can- other. A recent Modern Electronics
SWR /RF ANTENNA METER mailing label must accompany the
SWR3P Read SWR, RF power and
not generally provide such consulta-
field strength. tion work unless we've published a copy. Such free personal ads will be
Z21/ 1.7 to 150 MHz.
10 or 100 watt range.
SWR +/- 5 %;
project that coincidentally meets the
need. Nor do authors have the time
published on a space -available, first-
come /first- served basis.
POWER +/- 10% accuracy. to do this. We will, however, pass on Let's hear from you soon.
any inquiries to an author if a
$29.95 Value ONLY $1995 +$4 UPS
stamped, self- addressed envelope is
Prices and Specs Subject to Change
provided. It's up to them whether or
Electronic Equipment Bank not to respond, though. If something
EEB 516 Mill Street, N.E. relates directly to their project, they
Vienna, Virginia 22180
Virginia orders, technical questions often do. But, please, no consult-
703-938-3350 ing- design requests.
VISA. MASTERCARD. CHOICE. and DISCOVER

800 -368 -3270

CIRCLE 41 ON FREE INFORMATION CARD
6 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics
11111111/LETTERS//Il/Ill

Hard At Work switch -mode final amplifier make this Author Updates
I enjoyed your review of the "Chess - design cleaner and more efficient than Those read,,. s who would like to obtain
master 2000" game program in the De- earlier designs. With lower static and bet- a printed- circuit board with improved
cember 1987 issue. Your review was right ter propagation coming up in the winter layout and ground plane for the "Fre-
on target from what I have seen of this months, communications enthusiasts quency-to- Voltage Converter" featured
marvelous game. But you overlooked the should really enjoy working with it. in the November 1987 issue of Modern
most significant feature -at least, from John H. Davis (Continued on page 71)
the perspective of the employees in our Warm Springs, GA
office. We have found that < Alt P > is
by far the most useful command of this
program.
Peter R. O'Dell
St. James, NY
You're right! The hot key instantly sub-
stitutes a business -like spreadsheet on the
screen. -Ed.

Communications Feedback
Chuck Steer's "Communications"
column in the September 1987 issue was
particularly interesting to me, having op-
erated similar transmitters over the past Let IF/CM
five years. However, there were several
shortcomings in the discussion of FCC ELEC O dC
as E ¡\
Regulations, and the collector and emit-
ter of Q2 are shown reversed in the sche- UG H T ¡\ " fl

matic diagram.
Section 15.111 of FCC Rules permits you with their huge
license -free operation over a wide range
of the vlf spectrum, but limits field selection of electronic
strength to a distance of 300 meters. This
limit is less than the 50 microvolts per me-
ter stated for the 1,700 -meter band. It
parts and components.
poses problems for DX and is hard to Many MCM customers have told us that they used to be forced to
measure for purposes of rule compli- buy from several parts and components suppliers to get all the items they
ance. Section 15.112 specifies frequen- needed. But after they ordered a copy of our FREE 160 -page Catalog and
discovered that it contained virtually every product they could ever want...
cies from 160 to 190 kHz -not 170 to 190 at prices that allowed them to improve their service profits substantially...
kHz as stated. The input power to the fi- they switched to MCM ELECTRONICS. Our huge inventory of nearly
nal stage is limited to watt, not the out-
1 10,000 items, flexible payment terms
put power. Signals outside the 160 -to- and rapid order turnaround can "light
190 -kHz range must be at least 20 dB be- up your life," too. So, get your copy of
low the carrier level, which includes spur- the MCM ELECTRONICS Catalog IVIIVI
today and see what you've been missing!
ious signals, harmonics and sidebands! Clltiitr'OÌ11CS
The choice of operating frequency must
take into account the type of modula- For your FREE copy,
tion used. So 161 to 189 kHz would
probably be safe for code, and low -pass-
call TOLL -FREE!
filtered (to 3 kHz) voice could be used 1- 800 -543-4330
with frequencies of 163 to 187 kHz. In Ohio, call 1 -800- 762 -4315
However, unfiltered voice and music In Alaska or Hawaii, call
would require a carrier frequency close to 1- 800 -858 -1849
the center of the band to prevent out -of-
band emissions.
Overall, this was a fascinating project. MCM ELECTRONICS
The CMOS oscillator and driver and the 858E. CONGRESS PARK DR.
CENTERVILLE, OH 45459
A PREMIER Company
SOURCE NO. ME-31
CIRCLE 42 ON FREE INFORMATION CARD
Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 7
Ill/il! MODERN ELECTRONICS NEWS/il/Ill
FAX GOES PUBLIC. The use of facsimile machines to transmit and receive
documents, which is expanding rapidly, will be getting an extra boost
if US FAX Inc. has its way. The company announced plans to place more
than 2,000 public fax machines in hotels, airports, quick -print shops
and other retail locations in 1988. Its nationwide fax transmission
system will be used, employing digital packet- switched communications
technology that is said to make it cheaper to communicate via fax than
over telephone lines. Subscribers to US FAXSYS ($10 /month; $2 /month
charter subscribers) can transmit a three -page document from Boston to
Los Angeles, for instance, at a reported cost of only 24 cents vs. 91
cents charge over voice phone lines that carry fax traffic today. Sub-
scribers can, of course, receive and send messages to non -subscribers.
Each subscriber is also assigned one or more electronic mailboxes that
can be accessed from any fax machine in any location.

EEPROMS IN A FLASH. Commonplace ultraviolet- erased EEPROMs can be ex-

pecting a challenger soon in the form of the FLASH EEPROM. Through an
agreement between SEEQ Technology and National Semiconductor Corp., a
line of pin -compatible FLASH EEPROMs will be marketed, starting with
SEEQ's 128 -Kb NMOS device up to SEEQ's 1 -Mb CMOS device. Each company
will serve as a second source to the other. The FLASH devices can be
electrically erased and reprogrammed in less than one minute compared
to the 20 minutes required for a UV EPROM. Additionally, the erase/
program process of the FLASH can be achieved in a single step using one
piece of equipment, while the UV type requires a two -step cycle with
several pieces of equipment.

ARTISTIC VCR'S. Sony Corp. introduced three SuperBetamax VCRs that in-
corporate digital video -processing circuits that can turn a user into
a video artist. The digital machines can fill a TV screen with 9 or
16 separate images that can be updated in six discrete time periods.
A zoom feature enlarges selected picture areas up to four times normal
size. Special effects can be generated, too, such as solarizing a
picture's color. Also, a picture within a picture can be inserted in a
TV screen's corner.

COMPUTER AIDS. Learning Odyssey is shipping its first computer -aided

instruction program for teaching computer -aided design (CAD), a booming
computer application area. Called "Basic CAD Operations Course," it
works together with the "Junior Drafter" PC CAD software, providing 60
hours of on -line instruction in CAD and mechanical drafting. It's the
first of ten educational CAD programs being readied. (For more info,
call 619- 488- 0533.)...Plies Development Corp.'s Quikinfo software ($49)
for engineers, techs and scientists converts any number in the equiva-
lent unit of another measurement system, such as horsepower to kilowatts.
Containing hundreds of conversion equivalents, grouped by category,
the memory- resident, low -cost pop -up software can be called from within
any application program such as Lotus 1 -2 -3. It runs on IBM -compatible
machines and occupies 80K of memory. (713- 493 -3679 for information.)

SW AID FOR AIDS. The BBC World Service had an AIDS disease phone -in
over its shortwave transmissions that gave listeners a chance to ques-
tion a leading medical expert on the health problem. Calls to a London
phone number and Q & A's were broadcast worldwide. The one -hour phone -
in was preceded by a 30- minute documentary on the disease.

8 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 CABLE EOUIPMEN1

PRICES
SLASHE D
WHILE YOU WHIP.
Aunt Matilda at Pacetic Celle Co.. Inc.. and
Call
get a pleasant surprise: Instant price cuts even
on our own cut -to- the -bone prices!
Here's how: Just supply her (or one of our other
operators) with anybody else's published prices
(even wholesale, if you're a dealer) for
the unit you want; and if their price
beats our published price, we'll match
it -or
even beat it! Simple as that.
Of course, you'll have to look far and
wide to beat our prices (see below) and
we're betting that Aunt Matilda will seldom
need her "little hatchet" and can partake of her
cherished afternoon nap. Which is fine with
us -she makes us nervous with that thing!
(Not to mention our competition!)

Check our prices on Scientific Atlanta Units!

1 10 OR 1 10 OR
ITEM ITEM
UNIT MORE UNIT MORE
RCA 36 Channel Converter (Ch.3 output only) 29.00 18.00 *Minicode (N -12) 89.00 58.00
Panasonic Wireless Converter (our best buy) 88.00 69.00 * Minicode (N -12) with Vari Sync 99.00 62.00
400 or 450 Converter (manual fine tune) 88.00 69.00 * Minicode VariSync with Auto On -Oft 145.00 105.00
*Jerrold 400 Combo 169.00 11900 Econocode (minicode substitute) 69.00 42.00
Jerrold 400 Hand Remote Control 29.00 18.00 Econocode with VariSync 79.00 46.00
*Jerrold 450 Combo 199.00 139.00 *MLD- 1200 -3 (Ch.3 output) 99.00 58.00
*Jerrold 450 Hand Remote Control 29.00 18.00 *MLD- 1200 -2 (Ch.2 output) 99.00 58.00
Jerrold SB- Add -On 89.00 58.00 *Zenith SSAVI Cable Ready 17600 125.00
*Jerrold SB- Add -On with Trimode 99.00 70.00 Interference Filters (Ch.3 only) 24.00 14.00
*M -35 B Combo unit (Ch.3 output only) 99.00 70.00 *Eagle PD -3 Descrambler (Ch.3 output only) 119.00 65.00
*M -35 B Combo unit with VariSync 109.00 75.00 *Scientific Atlanta Add -on Replacement Descrambler 119.00 75.00

CHECK US OUT -WE'LL Quantity Item

Output
Channel
Price
Each
TOTAL
PRICE

MEET OR BEAT THE OTHER'S

ADVERTISED WHOLESALE
OR RETAIL PRICES!
MusterrCc,d)1 VISA SUBTOTAL
California Penal Code #593 -D forbids us from Shipping Add
shipping any cable descrambling unit to anyone $3.00 per unit
residing in the state of California.
COD & Credit
Prices subject to change without notice Cards -Add 5% C>
z
Pacific Cable Co., Inc. PLEASE PRINT

Name
TOTAL
Ó
V
73251/2 Reseda Blvd., Dept. 1 -20 W
Address City
Reseda, CA 91335 ID

State Zip Phone Number V

(818) 716 -5914 (818) 716 -5140 ( )

O
Cashier's Check Money Order C.O.D. Visa Mastercard II
NO COLLECT CALLS!
Acct. If Exp Date
4
IMPORTANT When ordering, please have Signature t.
the make and model number of the equipment p
used in your area -Thank you! DECLARATION OF AUTHORIZED USE -
YOU MUST SIGN AND RETURNFOR OUR RECORDS
I, the undersigned,
that all products purchased, now and in the future, will only
do hereby declare under penalty of perjury
be used on cable TV systems with proper
rt
*Call for availability authorization from local officials or cable company officials in accordance with all applicable federal and o
r.
state laws. FEDERAL AND VARIOUS STATE LAWS PROVIDE FOR SUBSTANTIAL CRIMINAL AND CIVIL aa
Prices subject to change without notice PENALTIES FOR UNAUTHORIZED USE.
f
Jerrold is a registered trademark of General Instruments Corp. Dated: __ _. _. Signed'
_ e

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 9

Train for the Fastest Growing Job Skill in America

Only NRI teaches you to

service all computers as you
build your own fully IBM
compatible microcomputer
With computers firmly estab- systems. Only NRI includes a real -world experience that in-
lished in offices -and more and powerful computer system as cludes training in programming,
more new applications being part of your training, centered circuit design and peripheral
developed for every facet of around the new, fully IBM PC maintenance.
business -the demand for
trained computer service tech-
compatible Sanyo 880 Series
computer. No experience necessary
NRI builds it in
-
nicians surges forward. The As part of your training,
Department of Labor estimates you'll build this highly- rated, Even if you've never had any
that computer service jobs will 16 -bit IBM compatible com- previous training in electronics,
actually double in the next ten puter system. You'll assemble you can succeed with NRI
years -afaster growth rate than Sanyo's "intelligent" keyboard, training. You'll start with the
for any other occupation. install the power supply and basics, then rapidly build on
disk drive, and interface the them to master such concepts as
Total systems training high- resolution monitor. digital logic, microprocessor
No computer stands alone.. . The 880 Computer has two design, and computer memory.
it's part of a total system. And operating speeds: standard You'll build and test advanced
if you want to learn to service IBM speed of 4.77 MHz and a electronic circuits using the
and repair computers, you have remarkable turbo speed of 8 exclusive NRI Discovery Lab®,
to understand computer MHz. It's confidence - building, professional digital multimeter,

Learn Computer Servicing Skills with NRI's "Hands-On" Training .. .

Using NRI's unique Action Audio Cassette, you are talked You'll set up and perform electronics experiments and After you build this digital logic probe, you'll explore the
through the operation and practical application of your demonstrations using your NRI Discovery Lab. You'll even operation of the Sanyo detached "intelligent" keyboard
hand-held digital multimeter -the basic, indispensable interface the lab with your computer to "see" keyboard. and its dedicated microprocessor.
tool for the computer specialist. generated data.
 Your NRI total systems training
includes all of this: NRI Discovery
Lab' to design and modify circuits
Four-function digital multimeter with
walk -you -through instruction on audio tape
Digital logic probe for visual examination
of computer circuits Sanyo 880 Series
Computer with "intelligent" keyboard
and 360K double- density, double -sided
disk drive High resolution monochrome
monitor 8K ROM, 256K RAM Bundled software
including GW BASIC, MS DOS, WordStar, Calc Star Reference manuals. schematics.
and bite -sized lessons.

and logic probe. Like your full-color catalog, with all the If the card has been
computer, they're all yours to facts about at-home computer used, write to NRI Schools,
keep as part of your training. training. Read detailed descrip- 3939 Wisconsin Ave., N.W.,
You even get some of the most tions of each lesson, each exper- Washington, D.C. 20016.
popular software, including iment you perform. See each
WordStar, CalcStar, GW Basic piece of hands -on equipment
and MS DOS. you'll work with and keep. MAISCHOOLS
And check out NRI training in McGraw-Hill Continuing Education Center
Send for 100page free other high -tech fields such as 3939 Wisconsin Avenue, NW
catalog Washington, DC 20016 ''''i.1
Robotics, Data Communi- i?ñi.
Send the post-paid reply card cations, TV /Audio /Video We'll Give You Tomorrow.
today for NRI's 100 -page, Servicing, and more. IBM is a Registered Trademark of International Business
Machine Corporation.

as You Build Your Own Sanyo 880 Computer System.

The power supply is assembled in the main unit of the corn

- Next, you install the disk drive. You learn disk aivr operation Using the monitor, you focus on machine language program-
puter. You check out keyboard connections and circuits with and adjustment, make a copy of MS-DOS operating disk and ming, an incispensa Ire troubleshooting tool for the techni-
the digital multimeter included for training and field use. begin your exploration of the 8088 CPU. cian. You continue by reaming BASIC larguage programming.
 JIiI/NEW PRODUCTS /11/ILINEMIIIMIll
For more information on products Software, MyCalc from Software
described, please circle the appropri- Tool Works, the ATI Interactive
ate number on the Free Information Trainer and a custom version of
Card bound into this issue or write to HOT, a Desktop Manager from Ex-
the manufacturer. ecutive Systems. $995.
CIRCLE 10 ON FREE INFORMATION CARD
-MINRCJNF.R twtií

Beginner's Personal
Computer Hidden Antenna System
HeadStart from Vendex Pacific Inc. The "Hidden Antenna System"
(Great Neck, NY) combines IBM from Grove Enterprises (Brasstown,
PC- and XT-compatible hardware NC) combines a flexible antenna
with a 30-dB -gain preamplifier for
and a HeadStart operating environ-
continuous 100 -kHz to 1,000 -MHz compact antenna system. A separate
ment designed for the novice user.
receiving applications, making it preselector is also available to elimi-
The latter walks the user through the
ideal for indoor shortwave, long - nate shortwave intermodulation and
computer's operations and includes
wave and vhf /uhf scanner listening, image interference in particularly
a most -used software package.
even TV and FM reception. Two out- troublesome installations. $48 to
put connectors permit simultaneous $100, depending on options.
use of two receivers on the same CIRCLE II ON FREE INFORMATION CARD

Turbo -888 -XT is built around a protected. The Function Generator

Breadboard Test Equipment Blox provides sine, sawtooth and
4.77/8 -MHz 8088 -2 microprocessor.
It comes with 512K of RAM, bat- Everything needed to support bread- square waves from 0.1 Hz to 1 MILz,
tery- backed clock /calendar, two boarding designs is one way to de- with amplitude or frequency modu-
360K 5.25 -inch floppy -disk drives, scribe Elenco Electronics' (Wheel- lation capability. The Logic Probe
seven IBM -compatible slots, one ing, IL) Function Blox line of Bread- Blox has four logic level indicators
each serial, parallel and game ports, board Test Equipment. The Bloxs and a standard logic probe. The Di-
a floppy controller that handles up to are designed to interlock with the ori- gital Clock Blox provides a square -
four drives, high-resolution graphics ginal breadblox for a unique and in- wave frequency of 1 Hz to 50 MHz
card that is compatible with mono- expensive way of obtaining test and includes crystal-locking capabil-
chrome, Hercules and color graphics equipment. Six different Function ity. The Resistor Blox provides 20
and a high-resolution TTL mono- Bloxs are available: a dc regulated different resistor values plus a
chrome video monitor (color option- power supply, Function Generator, 100,000 -ohm potentiometer. The
al). The compact system unit can ac- Logic Probe, Digital Clock, Resistor Capacitor Decade Blox provides 20
commodate an optional hard -disk Decade box and Capacitor Decade different capacitances from 47 pico-
system and a 3.5 -inch microfloppy- box. farads to 10 microfarads.
disk drive. Also included are MS- Outputs from the dc Power Sup- All function Bloxs have eight sol-
DOS and the HeadStart operating ply Blox are + 5 volts at 1 ampere, derless- connector slots that each
environment. -5 volts at 0.4 ampere and + 12 consist of five contact points. Each
Software bundled with the system volts at 0.3 ampere. All supply lines accepts 20- to 26 -gauge wires and
include: The Executive Writer and are fully regulated and short -circuit component leads. $14.95 to $24.95.
The Executive Filer from Paperback CIRCLE 15 ON FREE INFORMATION CARD

14 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 scope comes with X -Y plotter con- channel PLL synthesized random-
Digital Storage Oscilloscope nections and pen -lift control. GPIB access tuner; and automatic power-
Featuring a 60 -MHz storage band- and RS-232C interfacing options are on, rewind, play and repeat func-
width, Tektronix's new Model 2221 available for direct waveform output tions. $549.95.
digital storage oscilloscope adds to a printer or plotter or for instru- CIRCLE 17 ON FREE INFORMATION CARD
measurement cursors and readout to ment control and waveform trans-
a 4096-point record, averaging, and fers to a computer. $3995. Analog/Digital I/O Board
100-ns peak- detect capabilities. This CIRCLE 16 ON FREE INFORMATION CARD for Apple Computers
combination full- featured analog/ Naylor Industries' (Indianapolis,
digital- storage oscilloscope also of- Digital VHS VCR IN) Data I/O 8 is an analog and digi-
fers accumulated peak- detect (en- Nine -picture channel search, pic- tal interface card for Apple II, II +
veloping). ture-in- picture (P -I -P), freeze frame and Ile computers. It provides eight
and digital strobe special effects channels of analog inputs (eight bits,
highlight Sharp's new Model VC- 2.5- microseconds and 0 to + 5.10
D800U digital videocassette record- volts) and eight channels of analog
er. This VCR nine -channel picture outputs (eight bits and 0 to + 5.10
search displays still pictures of pro- volts) as well as 24 TTL -level digital
grams on nine stations. P -I -P per- input bits and 24 TTL-level latched
mits simultaneous viewing of a TV digital output bits. The card allows
program and video tape by insetting the computer to make electrical mea-
either image in any corner of the TV surements, send and receive control
Along with measurement cursors screen so you can watch a prerecord- signals and generate waveforms for
and more signal processing, the ed tape and still keep tabs on what is industrial, scientific and educational
Model 2221's 4096 -point record going on on a selected channel. applications.

I
length features 100-ns peak detec-
tion. The 4096 -point record equals
four end -to -end scope displays, which
quadruples time resolution over typi-
cal 1024 -point DSOs and provides
higher definition for biomedical,
mechanical vibration and single -shot
or low-duty- factor waveforms. Peak
detection ensures at least one sample
on noise or switching spikes as nar- The Data I/O 8 is easily pro-
row as 100 ns for digital design and A simple record timer features a grammed in BASIC and, for maxi-
troubleshooting where narrow spikes return function that enables you to mum speed, assembly language. It
or fault conditions are often missed simply set the VCR to record an on- comes with a 40-page manual that
with conventional scopes. going program. When a recording is contains eight software examples of
Waveform sampling is done as a completed, the tape automatically BASIC programs, 11 specification
20- megasample/second rate. A sepa- rewinds to the beginning of the re- tables and a glossary. Also included
rate reference memory can be used corded segment for easy playback. are four cables that bring the signals
to store 4096 -point single -channel On- screen display simplifies pro- from the card to the back of the com-
captures or for dual -channel 2048 - gramming by prompting you through uter. The card is designed to be in-
point records. Voltage and time cur- the process of setting channel, week/ stalled in any slot 1 through 7. $295.
sors can be included on any stored day, start time and length, and re- CIRCLE 18 ON FREE INFORMATION CARD
waveform. cording mode for four programs.
All waveform captures are sup- Other features include: a Blue Screen Trigger -Grip
ported by pre- and post- trigger capa- Noise Elimination system mutes the Solvent Applicator
bility. Other modes include signal audio and turns the screen blue at the Micro Care Chemical Corp. (Farm-
averaging, accumulated peak detect end of a tape; HQ and double comb ington, CT) has announced the Trig-
(envelope mode), X -Y mode, and filter for superior picture quality; 14- ger Grip Applicator, a reusable re-
scan and roll modes on sweeps slow- day, 4 -event programmable timer mote sprayer for spot defluxing of
er than 0.1 second /division. with daily/weekly repeat; 35 -func- printed- circuit cards and cleaning
For stored waveform output, the tion wireless remote controller; 110- electronic assemblies with the com-

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 15

NEW PRODUCTS
pany's solvents. Made of aircraft - carrier signal and directs the call to flashing red to indicate power re-
quality aluminum and rugged nylon, the receiving FAX machine. sumption after a blackout. (All fault
Trigger Grip is equipped with an This patented branching device is detection trigger points are factory
OmniglassTM heat shield to protect claimed to eliminate the need for in- set in accordance with ANSI stan-
the feeder tube from hot soldering stalling a dedicated telephone line dard C84.1.) A Clear button resets
iron tips. It attaches directly to the the unit and automatically provides
valve orifice of solvent aerosol cans. full- function testing of all electrical
The grip is designed for operator circuits and LEDs.
comfort and to increase control
while in use.

just for FAX or for other telephone-

activated peripheral equipment. If a
dedicated line is already in use, the
TF 4 can further expand usage of the
line by providing a private voice
mailbox (answering machine), access Monitron 2000 responds to a volt-
to a FAX machine and one other ad- age disturbance or power interrup-
ditional telephone device. Equip- tion in 0.5 microsecond, identifies
ment that can be used with the the source and locks on the appropri-
Fresh solvent constantly flows switcher include such items as a com- ate LED until the Clear button is
through a brush to eliminate con- puter modem, order -taking system, pressed. It monitors all 117-volt ac
tamination that occurs with tradi- information announcement system, power -supply lines at a range of fre-
tional swab-dipping and brush pro- and any other telephone -related de- quencies in accordance with IEEE
cedures. Strong, dense white nylon vice. The TF 4 offers many connec- 587 Category A standards.
or natural bristle Spray Thru brushes tion arrangements and provides With its own desktop stand, Moni-
insert into the Trigger Grip assem- greater usage of a standard tele- tron 2000 can be placed anywhere
bly. The brushes are replaceable phone line, with or without a key sys- within a work station where it pro-
when worn out and can be trimmed tem. It comes with modular connec- vides continuous visual access for
for cleaning hard -to -reach places. tors for easy installation. checking its functioning status and
An optional bench mounting kit that CIRCLE 20 ON FREE INFORMATION CARD power supply condition. Velcro
keeps the Micro Care Solvent System mounts can be used to secure it to a
and Trigger Grip applicator off the Voltage Disturbance computer terminal, power filter or
workbench but close to the operator Early Warning Device auxiliary power supply.
is also available. A low -cost power -line monitor that The product is mounted in an ABS
CIRCLE 19 ON FREE INFORMATION CARD detects and classifies power-supply plastic case that measures 5 "D x
3 "H x 1 "W. $299.
irregularities that can adversely af-
Telephone Switcher fect computer software, hardware CIRCLE 21 ON FREE INFORMATION CARD

AutoSwitch TF 4 from Command and data integrity has been an-

Clock /Calendar Module
Communications, Inc. (Denver, CO) nounced by Mendon Electronics
is a telephone switcher that permits Corp. (Pittsford, NY). The Moni- Integrity Technology's (Milpitas,
remote access to and control over tron 2000 features individual single - CA) PC -Clock Calendar module is
three different telephone devices that function LEDs that are clearly la- designed to be used in IBM PC, XT,
are all connected to a single tele- beled for spike, high voltage, low Personal System /2 Model 25 and
phone line. Especially designed for voltage, dropout and power failure. compatible computers without oc-
facsimile machines, the TF 4 incor- A dual mode off/on LED indicates cupying an expansion slot. The mod-
porates a special circuit that automa- the unit's operational status: green
tically recognizes an incoming FAX for normal continuous operation or (Continued on page 84)

16 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 NEW! NEW! Scanner Frequency Listings
The new Fox scanner frequency directories will help
you find all the action your scanner can listen to. These
new listings include police, fire, ambulances & rescue
squads, local government, private police agencies,
Bearcat® 800XLT -RA
List price $499.95/CE price $289.95 /SPECIAL
12-Band, 40 Channel
Priority control
No- crystal scanner
Search/Scan AC /DC

CB Radios & hospitals, emergency medical channels, news media,

forestry radio service, railroads, weather stations, radio
common carriers, AT&T mobile telephone, utility com-
Bands: 29-54, 118.174, 406 -512, 806-912 MHz,.
The Uniden 800XLT receives40 channels in two banks.
Scans 15 channels per second. Size 914" x 41/2" x 121/2."

Scanners
panies, general mobile radio service, marine radio OTHER RADIOS AND ACCESSORIES
service, taxi cab companies, tow truck companies,
Panasonic RF-2600 -RA Shortwave receiver $179.95
trucking companies, business repeaters, business radio
(simplex) federal government, funeral directors, vet- RD55 -RA Uniden Visor mount Radar Detector $98.95
erinarians, buses, aircraft, space satellites, amateur RD9 -RA Uniden"Passport" size Radar Detector ... $169.95
radio, broadcasters and more. Fox frequency listings NEW! BC 70XLT -RA Bearcat 20 channel scanner ... $168.95
Communications Electronics; feature call letter cross reference as well as alphabetical BC 140 -RA Bearcat 10 channel scanner $92.95
the world's largest distributor of radio- listing by licensee name, police codes and signals. All BC 145XL -RA Bearcat 16 channel scanner $98.95
Fox directories are $14.95 each plus $3.00 shipping. BC 175XL -RA Bearcat 16 channel scanner $156.95
scanners, introduces new models of State of Alaska- RL019 -1; Baltimore, MD /Washington, BC 210XLT-RA Bearcat 40 channel scanner $196.95
CB & marine radios and scanners. DC-RL024 -1; Chicago, IL- RL014-1; Cleveland, 01-1- BC -WA-RA Bearcat Weather Alert" $35.95
RL017-1; Columbus, 01-1- RL003.2; Dallas /Ft. Worth, R1080 -RA Regency 30 channel scanner $118.95
NEW! Regency/ TS2 -RA TX-Awl 3-1; Denver /Colorado Springs, CO- RL027 -1; R1090 -RA Regency45 channel scanner $148.95
Detroit, MI/ Windsor, ON- RL008.2; Fort Wayne, IN
Allow 30 -90 days for delivery after receipt of order UC102-RA RegencyVHF2 ch. Watt transceiver $117.95
/Lima, OH- RL001.1; Houston, TX- RL023.1; Indian- 1

due to the high demand for this product. apolis, IN- RL022.1; Kansas City, MO/ KS- RL011 -2; P1412-RA Regency 12 amp reg. power supply $189.95
List price $499.95/CE price $339.95 Los Angeles, CA- RL016.1; Louisville /Lexington, KY- MA549-RA Drop -in charger for HX1200& HX1500 ... $84.95
12 -Band, 75 Channel Crystalless AC/DC RL007-1; Milwaukee, WI /Waukegan, IL- RL021 -1; MA518 -RA Wall charger for HX1500 scanner $14.95
Frequency range: 29- 54,118 -175, 406 -512, 806 -950 MHz Minneapolis/St. Paul, MN- RL01O.2; Nevada/E. Central MA553 -RA Carrying case for HX1500 scanner $19.95
The Regency TS2 scanner lets you monitor CA- RL028 -1; Oklahoma City/Lawton, OK- RL005.2; MA257 -RA Cigarette lightercord for HX12 /1500 $19.95
Military, Space Satellites, Government, Railroad, Pittsburgh, PA/Wheeling, W -RL029 -1; Rochester/ MA917 -RA Ni-Cad battery pack for HX1000/1200 $34.95
Syracuse, NY- RL020.1; Tampa/St. Petersburg, FL- SM MX7000 -RA Svc. man. for MX7000 8 MX5000 $19.95
Justice Department, State Department, Fish & RL004.2; Toledo, OH- RLOO2.3. A regional directory
Game, Immigration, Marine, Police and Fire Depart- B -4 -RA 1.2 V AAA Ni-Cad batteries (set of four) $9.95
which covers police, fire ambulance & rescue squads, B -8-RA 1.2 V AA Ni-Cad batteries (set of eight) .... $17.95
ments, Aeronautical AM band, Paramedics, Am- local government, forestry, marine radio, mobile phone,
ateur Radio, plus thousands of other radio fre- FB -E -RA Frequency Directory for Eastern U.SA .... $14.95
aircraft and NOAA weather is available for $19.95 each.
quencies most scanners can't pick up. The Regency RD001 -1 covers AL, AR, FL, GA, LA, MS, NC, PR, SC, TN FB -W-RA Frequency Directory for Western U.S.A. ...$14.95
TS2 features new 40 channel per second Turbo & VI. For an area not shown above call Fox at 800 -543- ASD-RA Air Scan Directory $14.95
Scan" so you wont miss any of the action. Model 7892 or in Ohio 800 -621 -2513. SRF -RA Survival Radio Frequency Directory $14.95
TS1 -RA is a 35 channel version of this radio without TSG-RA "Top Secret" Registry of U.S. Govt. Freq $14.95
the 800 MHz. band and costs only $239.95. Regency® Informant" Scanners TIC-RA Techniques for Intercepting Comm. $14.95
Frequency coverage: 35 -54, 136- 1 74 406 -5 12 MHz. RRF -RA Railroad frequency directory $14.95
Regency® Z60 -RA The new Regency Informant scanners cover virtu-
ally all the standard police, fire, emergency and
EEC -RA Embassy& Espionage Communications $14.95
List price $299.95/CE price $148.95 /SPECIAL CIE -RA Covert lntelligenct , Elect. Eavesdropping $14.95
8 -Band, 60 Channel No-crystal scanner weather frequencies. These special scanners are MFF-RA Midwest Federal Frequency directory . $14.95
Bands: 30-50, 88 -108, 118 -136, 144-174, 440 -512 MHz. preprogrammed by state in the units memory. Just A60 -RA Magnet mount mobile scanner antenna $35.95
The Regency Z60 covers all the public service pick a state and a category. The Informant does the A70 -RA Base station scanner antenna $35.95
bands plus aircraft and FM music for a total of rest. All Informant radios have a feature called MA548 -RA Mirror mount Informant antenna $39.95
Turbo Scan" to scan up to 40 channels per second. USAMM -RA Mag mount VHF ant. w/ 12' cable $39.95
eight bands. The Z60 also features an alarm The INN -RA is ideal for truckers and is only USAK -RA 3/4" hole mount VHF ant. w/ 17' cable $35.95
clock and priority control as well as AC /DC $249.95. The new INF2 -RA is a deluxe model and Add $3.00 shipping for all accessories ordered at the same time.
operation. Order today. has ham radio, a weather alert and other exciting Add $12.00 shipping per shortwave receiver.
features built in for only $324.95. For base station
Regency® Z45 -RA use, the INF5 -RA is only $199.95 and for those
Add $7.00 shipping per radio and $3.00 per antenna.

List price $259.95/CE price $139.95 /SPECIAL who can afford the best, the N F3 -RA at $249.95, is
I
BUY WITH CONFIDENCE
7 -Band, 45 Channel No-crystal scanner a state -of-the -art, receiver that spells out what To get the fastest delivery from CE of any scanner,
Bands: 30-50, 118 -136, 144 -174, 440-512 MHz. service you're listining to such as Military, Airphone, send or phone your order directly to our Scanner
The Regency Z45 is very similar to the Z60 model Paging, State Police, Coast Guard or Press. Distribution Center" Michigan residents please add 4%
listed above however it does not have the commer- sales tax or supply your tax I.D. number. Written pur-
cial FM broadcast band. The Z45, now at a Regency® HX1500 -RA chase orders are accepted from approved government
agencies and most well rated firms at a 10% surcharge
special price from Communications Electronics. List price $369.95/CE price $218.95 for net 10 billing. All sales are subject to availability,
11 -Band, 55 Channel Handheld/Portable
Regency® RH256B -RA Search Lockout Priority Bank Select acceptance and verification. All sales on accessories
are final. Prices, terms and specifications are subject to
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Project

A Delayed-Trigger Accessory
for Oscilloscopes
A low -cost way of adding a laboratory -grade facility
to inexpensive general-purpose oscilloscopes

what if you want to examine the os-

cillations more closely? Trying to
trigger at a lower voltage will cause
multiple traces, as in Figure 1(B).
Figure 1(C) shows how, with de-
layed trigger, you can have the oscil-
loscope's sweep begin at any point
you select. The trigger is delayed so
that the oscilloscope sweep begins at
the point of interest in the waveform.
Then the timebase can be expanded,
as in Fig. 1(D), for more detailed
observation.
You can also use delayed trigger-
ing to focus on a puticular pulse in a
stream of data. In this case the delay
would be timed from a trigger sig-
By Jan Axelson & Jim Hughes fully adjustable from 10 microsec- nal- perhaps a "write" pulse -that
onds to 300 milliseconds. occurs at a specific time before the
Laboratory-grade oscilloscopes pulse stream.
often include a delayed trig-
The Programmable Timer
gering capability that allows About the circuit
you to "hold off" the sweep until a This project uses a 7250 programma-
specified time (which you select) af- ble timer integrated circuit whose Shown in Fig. 2 is the schematic dia-
ter a trigger signal occurs. With this outputs are optimized for decimal gram, minus power supply, of the
feature, instead of being limited to counting. By wiring selected outputs delayed trigger circuit. The circuit
the trigger points available in a cir- in an AND configuration, you can consists of three basic parts: compa-
cuit, you can trigger at any time you choose any pulse width from 1 to 99 rator ICI, which senses the trigger
choose. If your oscilloscope doesn't times the width of the main timebase voltage; flip-flop IC2, which triggers
have built-in delayed triggering, you oscillator pulses. Our delayed trigger a timer; and programmable timer
can add to it the circuit to be de- accessory takes advantage of this IC3, which outputs the delay pulse.
scribed to upgrade it at very low cost. feature to provide several user -se- Action begins when a signal is con-
To use our delayed- trigger acces- lectable delay ranges. nected to one input of LM311 com-
sory, you need an oscilloscope that Figure 1 illustrates how the de- parator ICI, whose trip level is set by
has an external trigger input or two layed trigger accessory can be used to potentiometer Rl. This trip level is
channels, a signal to examine, and a extend the capabilities of an oscillo- adjustable from 15 to + 15 volts.
signal on which to trigger. Delayed scope. Figure 1(A) shows an oscillo- When the input at pin 2 of ICl goes
triggering is generated by an ICM7250 scope display of a square -wave pulse higher than the input at pin 3, the
programmable timer integrated cir- followed by a decaying, oscillating output at pin 7 goes high. Switch SI
cuit. Width of the timer's output waveform. The sweep is triggered transposes the two comparator in-
pulses, and thus the delay time, is near the top of the main pulse. But puts, permitting triggering on either

18 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 WIll1JwsJanuary 1988
base -oscillator frequency by a speci-
fied amount, permitting programming
of different pulse widths. Wiring to-
gether two or more outputs has the
effect of ANDing the individual out-
puts so that an output goes high only
when all connected outputs are high,
and the output pulse width is the sum
of all of the connected outputs.
Different pulse widths are selected
by S2, S3 and R7. The Table details
the outputs that are available for
each position setting for S2.
Switch S2 is a double -pole six-po-
sition switch (only four positions are
used) that is used to select different
IC3 outputs. With SI set to position
1, TRIGGER OUT connects to pin 1,
the divide-by -1 output, and the out-
put pulse goes low for 10 microsec-
onds. In position 2 of S2, the divide -
Fig. 1. Waveform (A) is triggered near the top of the main pulse. Lowering the by-1 and divide -by -4 outputs are
trigger voltage results in the multiple traces shown in (B). Because the trigger wired together to give a pulse width
signal is delayed in (C), the oscilloscope sweep begins at point of interest on wave- of 50 microseconds (10 plus 40 mi-
form. For closer examination, timebase can now be expanded as shown in (D). croseconds). Position 3 (divide -
by-10) gives a pulse width of 100
microseconds, and position. 4 gives
the rising or falling edge of the input 3. The IC's output, a single low -go- 500 microseconds (divide -by 40 and
signal. ing pulse, connects to TRIGGER OUT. divide- by -10).
Resistor R4 provides hysteresis to TRIGGER OUT also connects to the By adjusting potentiometer R7, you
give the comparator "snap- action" trigger input (external or channel 2) can increase the width of the outputs
response, which is important for on the oscilloscope with which this by up to six times. The delay avail-
quick response to slowly varying in- project is used. When TRIGGER OUT able at each position overlaps the
puts. Diodes Dl and D2 protect IC1 goes high, the oscilloscope sweep is range provided by the previous posi-
against damage from inputs that are triggered; so the width of the output tion, so any delay from 10 microsec-
greater in magnitude than the supply pulse equals the delay time for the os- onds to 3 milliseconds is available.
voltages. cilloscope sweep. In addition, the For longer delays, S3 is used to de-
When pin 7 of ICI goes high, it timer resets and waits for another select C4 and select C5. This causes
clocks D -type flip-flop IC2, causing trigger pulse. the pulse width of the timebase oscil-
the Q output of IC2 at pin 13 to go Width of the divide-by -1 output lator, and thus the delay times, to in-
high. Capacitor C3 then charges pulse at pin 1 of IC3 equals the RC crease by a factor of 100. The result
through resistor R6, resetting the time constant of the components at is full pulse width, or delay time, ad-
flip-flop. The result is a 5- microsec- pin 13. In this circuit, the RC timing justability from 10 microseconds to
ond duration pulse that triggers IC3 components are R7, R8 and C4 or 300 milliseconds.
and prevents this timer from retrig- C5. When IC3 is triggered with C4 The bipolar power supply for the
gering until the next time IC2 is selected and potentiometer R 7 set for delayed- trigger accessory is shown
clocked. (Only half of IC2 is used in minimum resistance, the width of the schematically in Figure 5. This sup-
this project. Inputs to the unused pulse at pin 1 is 10 microseconds (10 ply uses a 25 -volt center -tapped
flip -flop on the chip are tied to microseconds is the product of R8 transformer to generate the + 15
ground to assure stable operation.) times C4, which is 10,000 ohms times volts and -15 volts required by the
Timer IC3 is configured to operate 0.001 microfarad.) circuitry in the accessory.
in a monostable, or one -shot, mode. Four of the eight programmable Transformer T1 steps down the
The pinout for the IC3 7250 pro- outputs of IC3 are used in this appli- 117 -volt ac line potential to 25.2
grammable timer is shown in Figure cation. Each output divides the time- volts and bridge rectifier RECT1

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 19

 +15V
R7
R8 C5
50K 0.11.1F
10K
+15V
o
D1
+15V +15V
0
+15V
o
+15V
o
S3
1N914 C4
R5 0.0014F
20K
9 13
R2 o S1A RC
10K
R1 3
100K O TRIGGER
IC1
CLOCK R6 C6
b LM31 1

R3
'

20K IC3 0.01 µF

-15V o I

IC2
10K I
4 ICM7250 M
12
4013B D31
S1B
Trigger R4 10 10
R RESET
470K
>
in

D2 v/v- s
C3 +1 .4 *10 40
1N014 3,4.,,6 7 1 3 eI T

é2 1 = O
NC
O
001µF R9
N
\
O lOK
-15V S2A
+15V
S2g
1
Trigger out dP

PARTS LIST
Semiconductors C5- 0.1 -µF timing S2 -2-pole, 6-position rotary switch
D1,D2,D3 -1N914 or similar silicon C7,C8- 100 -µF electrolytic S3 -Spdt toggle or slide switch
diode C9,C10,C11,C12- 0.1 -µF ceramic S4 -Dpst toggle or slide switch
IC1 -LM311 comparator Cl 3 , C 14 -10 -µF electrolytic T1-25.2-volt, 450 -mA center -tapped
IC2 -4013B CMOS D -type flip -flop Resistors (1/4-watt, 10% tolerance) power transformer
IC3- ICM7250 programmable timer R2,R3,R8,R9- 10,000 ohms Printed -circuit board or perforated
(ICM7240 can be substituted; see text) R4- 470,000 ohms board with holes on 0.1 -inch centers
IC4 -78L15 + 15 -volt regulator R5,R6- 20,000 ohms and suitable soldering or Wire Wrap
-
IC5 -79L15 15-volt regulator R1- 100,000 -ohm, linear-taper, panel - hardware; sockets for ICI, IC2 and
RECT1 -50 -volt, 1- ampere bridge mount potentiometer IC3; suitable enclosure; pointer -type
rectifier R7- 50,000 -ohm, linear -tape, panel - control knobs (3); fuse holder; ac line
Capacitors (25 WV minimum) mount potentiometer cord with plug; rubber grommet; la-
C1,C2,C6- 0.01 -µF ceramic Miscellaneous beling kit and clear acrylic spray (see
C3- 330 -pF ceramic F1 -0.5-ampere slow -blow fuse text); 'A-inch spacers; machine hard-
C4- 0.001 -µF timing SI -Dpdt toggle or slide switch ware; hookup wire; solder; etc.

Fig. 2. Complete basic schematic diagram of delayed- trigger accessory minus its + 15- and - 15-volt ac power supply.

changes the stepped -down ac voltage Construction If you cannot obtain a 7250 pro-
to pulsating dc. Because transformer grammable timer, you can substitute
ratings are given as rms voltage (0.7 Component values for this project the ICM7240, which is nearly identi-
x peak voltage), peak output from are not critical. However, because cal to the 7250 but has binary -coded
T1 is actually about 36 volts, which is the combination of R7, R8 and C4 or outputs. For this project, the only
sufficient to enable using Tl to gen- C5 sets the delay time, components difference between the two is in the
erate potentials that can be con- that are stable in value are recom- delay ranges. With the 7250 the out-
verted to both + 15 and -15 volts. mended here. If available, use 1 -per- puts selected at positions 3 and 4 of
Using Tl's center tap as a reference, cent precision resistors and tempera- S2 are divide -by -10 and divide -
IC4 regulates the + 15 -volt, IC5 the ture- stable capacitors, such as the by-50. With the 7240 these will be di-
- 15 -volt supply rails. Y5P series. vide-by -16 and divide- by-80. These

20 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 Install and solder into place regula- When the acrylic spray has com-
1 16 v+ tors 105 and 106 in their respective pletely dried, mount the various
2 z 15 Carry out locations, referring back to Fig. 4 for controls and jacks on the front pan-
1's
4 7 14 TBI /O (timebase pinout details. el. Make sure the potentiometers
8 4 13 RC in/out) When you've finished wiring the and rotary switch are properly ori-
10 5 12 MOD circuit -board assembly, remove Y. ented so that their knob pointers are
20 6 11 Trigger inch of insulation from 18 8 -inch positioned properly for the panel
10s
40 7 10 Reset lengths of hookup wire. Plug one markings.
80 8 9 GND end of these wires into all unoccu- Mount the fuse holder and power
pied holes on the circuit -board as- transformer in their respective loca-
Fig. 3. Pinout for 1CM7250 pro- sembly, except those labeled T1 and tions inside the enclosure. Twist to-
grammable timer integrated circuit. T1 C.T., and solder into place. gether the fine wires in both conduc-
Next prepare the enclosure by tors at the end of the cord and spar-
drilling appropriate-size holes in the ingly tin with solder. Route the cord
will give slightly different, but still front panel to accommodate the four through the rubber grommet and in-
usable, delay ranges on the accessory. switches, two potentiometers and to the enclosure and tie a knot in it in-
You can fabricate a printed- circuit four jacks (see lead photo for de- side the case about 4 inches from the
board on which to mount and wire the tails). Drill a hole through the enclo- end. The knot serves as a strain relief.
components, using the actual -size sure's back panel to provide entry Solder one line cord conductor to
etching- and -drilling guide shown in for the power cord and install the one of the fuse holder lugs and the
Figure 6. Alternatively, if you prefer fuse block. Then drill the holes for other to one toggle lug on S4. Then
not to make a pc board, you can use mounting the circuit board and connect and solder a short wire be-
perforated board with holes on 0.1- transformer in the case. Use a dry - tween the free lug of the fuse holder
inch centers and suitable soldering or transfer lettering kit or tape labeler and the other toggle lug of S4. Deter-
Wire Wrap hardware. Whichever to identify the front panel controls mine which of the power transform-
method of wiring you choose, use and jack. If y iu dry-transfer letter- er's leads are to the primary (117 -
sockets for the DIP integrated circuits. ing to the panel spray on two or three volt) winding and connect and solder
Referring to Fig. 7, insert and light coats of clear acrylic to protect these to the stationary-contact lugs
solder the IC sockets -not the ICs the lettering. Wait until each succes- of S4A and S4B.
themselves -into place. Set aside the sive coat dries before spraying on Plug TI's secondary and center -
ICs themselves for installation after the next. tap leads into the holes labeled T1
initial checks have been made on
the fully wired circuit. Follow up Delay Outputs Available
wiring the board with the capacitors,
diodes and resistors, making sure to Switch IC3 Delay (C4 Selected) Delay (CS Selected)
observe proper polarity for the elec- S2 Output(s) in Microseconds (µs) in Milliseconds (ms)
Position Selected Minimum Maximum Minimum Maximum
trolytic capacitors and the diodes.
Then solder into place a bare wire at 1 1 10 60 1 6
JUMPER, which can be either a cut- 2 1 and 3 50 300 5 30
3 5 100 600 10 60
off resistor or capacitor lead or a 3,000
4 5 and 7 500 50 300
length of stripped solid hookup wire.

O
T1

I INr 1C4 OUT

+15V IC4
78L15T
F1 S4A 125.2V
C.T.
RECT1
C7
I100µF
1T0.1µF
C9
COM
C11
I01µF
C13
T10µF NI I TOUT
COM
78L15T
1 IN 105 OUT
o 15V
S4B IC8 79L15T
C12 1 c14 O
T 100µF COMI 100F
105

117Vac /77
COMI I ICUT
IN

Fig. 4. Schematic diagram of delayed- trigger accessory's bipolar power supply. 79L151

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 21

 free ends of the wires on the circuit -
board assembly to the various con-
trols, switches and input and output
jacks into the circuit. Remove Y. inch
of insulation from both ends of an
appropriate length of hookup wire
and connect and solder this from the
TRIGGER INPUT to the TRIGGER OUT-
PUT ground jacks.
Slide pointer -type control knobs
onto the shafts of RI, R7and S2. Ro-
tate the knobs and note the maxi-
mum counterclockwise and clock-
wise positions of the pointer on the
potentiometer knobs. Rotate the
knob on the rotary switch and note
where the pointer rests for each posi-
tion (remember that only four posi-
tions are of interest if you are using a
six -position switch). If necessary, re-
orient the pot or switch to obtain per-
Fig. 5. Actual -size etching-and -drilling guide to use for fabricating printed - fect indexing with the panel markings.
circuit board.
Checkout & Use
and TI C.T. in Fig. 6 and solder into electrical tape or heat -shrinkable Before plugging the,ICs into their re-
place. Then mount the circuit -board tubing to cover all exposed 117 -volt spective sockets, power up the circuit
assembly inside the enclosure with ac line -potential wiring on S4 and the and use a voltmeter set to read at
%-inch spacers and % -inch machine fuse holder. least 20 volts dc to check for proper
screws, lockwashers and nuts. Use Referring to Figs. 6 and 7, wire the power routing. Connect the meter's
common lead to circuit ground (eith-
er ground jack on the front panel,
for example). Then touch the "hot"
meter lead to pin 18 of the ICI sock-
et, pins 8 and 14 of the 1C2 socket
Si -R5- JUMPER
and pin 16 of the 1C3 socket. In all
(K -R4- S2- -W PE four cases, you should obtain a read-
;v-
R

ing of approximately + 15 volts.

o S2- 2 -) S3 Touching the hot lead to pin 4 of the
IC2 S2 E-
K IC1 socket should yield a reading of
N
o S2 E-- -jS1A -5 volts.
CO
o - Once your readings are correct,
-C2-
I

Trigger out
power down the project and wait a
-04-- -4 S3 couple of minutes for the charges to
Ti
SECONDARY
REGT -05- -*S3
bleed off the electrolytic capacitors
COM
R1 in the power supply. Then install the
OUT 1C4 IN
ICs in their respective sockets, taking
I T1
C.T.
care to properly orient each and
M Ú Ú
I * c7,) TI I
making sure that no pins overhang
the sockets or fold under between
Trigger in ground ICs and sockets as you push the ICs
into place. Handle IC2 and IC3 as
you would any other MOS device.
Fig. 6. Wiring guide forpc board. Use this as component placement guide ifyou To check operation of the delayed -
wire circuit on perforated board. trigger accessory, you need a test os-

22 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 R2 cillator. Circuit operation is easiest
+15V +15V to observe when the period of the test
signal is slightly longer than the delay
time. Thus, it is best to have avail-
able signals of several frequencies;
10 kHz, 1 kHz, 100 Hz, 10 Hz, and 1
R1 R7
TRIGGER LEVEL DELAY ADJUST Hz are recommended. You can use a
square wave output from a bench
No connection signal generator for these.
If a bench generator isn't avail-
IC3 able, you can use a spare 7250 IC to
R2
Pin 3 build the simple oscillator shown in
IC1 IC1 No Figure 8. By using two timing resis-
Pin 3 Pin 2 connection tors and connecting a jumper wire to
Junction of
D1,D2,R3 I03 different outputs as shown, all the
Pin 7 required frequencies can be obtained.
To begin checkout, set S3 to "µs"
No connection (C4 selected), set S2 to position 1 (pin
S1 S2 1 of IC3 selected), and set R7 to mini-
TRIGGER SLOPE DELAY SELECT
mum resistance. The position of SI
isn't important at this point.
Ca
F1 117Vac
Power up the project, connect a
IC3 10 -kHz signal and ground reference
Pin 13
T1
to the TRIGGER IN jacks, and moni-
T1
C5 tor pin 7 of ICI with your oscillo-
S3 sa scope. Adjust R1 until a rectangular
DELAY RANGE POWER waveform appears at pin 7. Then
check pin 13 of IC2 for a 5- microsec-
Fig. 7. Wiring guide for switches and potentiometers.
ond positive -going pulse occurring
each time pin 7 of ICl goes high.
Next, connect your scope to TRIG-
GER OUT on the project and check for
a 10 -kHz rectangular wave. Varying
the setting of R7 will cause the
"low" portions of the waveform to
vary from 10 microseconds to 60 mi-
croseconds in width, though the total
period of the waveform will remain
constant. The length of time the
waveform is low in each cycle is the
delay time generated by the circuit.
To see the delay in action, set up
your scope to display the 10 -kHz
output of the test oscillator on chan-
nel 1. Leave the oscillator also con-
nected to TRIGGER IN on the project.
Then set the scope to trigger on chan-
nel 2 or external trigger. Connect
TRIGGER OUT of the delayed-trigger
accessory to the trigger source you've
chosen on the scope. Shown in Fig. 9
is a drawing of the test setup.
Circuit -board assembly and power transformer mount on floor of enclosure, Adjust the trigger level on the
switches, controls and jacks on front panel. scope for a stable display. The sweep

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 23

 lay is increased and decreased.
R3
t0K
R1 Use this same 1 -kHz input to

o-
1K
J1
.o 1
16
0
J2 check position 3 of S2. Then use a
ICI 100 -Hz signal to observe position 4.
R2
0 5 i0 ICM7250 0.047µF 100K Refer to the table for the delay times
Oscillator
available at each position. Then
Till out
O 8 80
13

, -
change S2 back to position 1, select
C5 with S3, and observe delays rang-
<
T ing from 1 to 6 milliseconds -100
times as long as the original 10 -mi-
Fig. 8. A 7250 wired as shown here serves as a suitable test oscillator for check- crosecond delay.
ing out operation of project. Input a 10 -Hz signal and check the
delays at positions 2 and 3 of S2. Fi-
will begin 10 microseconds after the side -down" as you change the trigger nally, a 1 -Hz signal will allow you to
output of IC1 goes high. Varying R7 slope from the rising to falling edge observe the longest delays, at position
will increase the delay and cause the or vice versa. 4 of S2. The final delay should be ad-
waveform to "shift left" on the dis- When you set S2 to position 2, the justable to about 300 milliseconds.
play even farther. The trigger delay is delay increases by a factor of 5; in- To use the accessory, do the
easy to see when displaying a rec- stead of 10 to 60 microseconds, the following:
tangular wave because the sweep can delay will vary from 50 to 300 micro- (1.) Select a trigger signal of equal
now be set to begin anywhere along seconds. Change the input signal to 1 or lower frequency than that of the
the flat parts of the pulses, not just kHz and expand your timebase on signal to be observed.
on their rising and falling edges. the scope for better observation of (2.) Connect the signal to be ob-
Flipping switch S1 to its alternate this delay. Again, varying R7 will served to channel 1 of the oscillo-
position will turn the display "up- cause the waveform to shift as the de- scope.
(3.) Set the oscilloscope's trigger
slope to + and trigger source to ex-
ternal or channel 2.
(4.) Connect the trigger signal to
TRIGGER IN on the delayed- trigger
clis/div
accessory.
1

TIMEBASE
(5.) Connect TRIGGER OUT on the
accessory to the trigger source input
Ö
TRIGGER
(external or channel 2) selected on
the scope.
LEVEL EXT.

CHANNEL 1 SLOPE SOURCE (6.) Adjust trigger slope and level

INPUT
EXTERNAL
I on the delayed- trigger accessory for
OSCILLOSCOPE I cf
TRIGGER IN
a stable display on the oscilloscope
screen.
(7.) Adjust the delay range and de-
lay time on the accessory to "tune
TEST OSCILLATOR DELAYED -TRIGGER ACCESSORY in" the desired portion of the
waveform.
o TRIGGER
LEVEL
rlIS
1011v
(8.) Expand the timebase on the
scope if desired to examine the signal
DELAY
RANGE
DELAY
SELECT
DELAY
ADJUST
more closely.
As you use the delayed trigger ac-
SLOPE cessory, you'll almost certainly come
to rely on it as much as laboratory us-
l TRIGGER
O INPUT
TRIGGER
OUTPUT
v ers do with their very expensive
scopes. In fact, you may even decide
that you don't have to trade your old
scope in for a newer -technology
Fig. 9. Initial setup for testing delayed-trigger accessory. model if you had that in mind. AE

24 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

Project

An FM Wireless
Microphone
A battery powered microphone
eliminates the trailing cable while
it transmits on a frequency in the
FM broadcast band

By Anthony J. Caristi this inherent sensitivity is too "hot" of audio amplifier stage Q1 as a
for your application, such as in PA small ac voltage.
Microphones for recording announcing where the user usually Gain of the QI stage is held at
and public- address appli- speaks directly into the microphone about 4.7 by the ratio of the collector
cations are cumbersome element, an option allows you to re- and emitter resistance values. The
to handle due to the long umbilical duce the sensitivity so that back- output of the audio amplifier stage,
cord that connects them to an ampli- ground noises will be largely excluded. at the collector of Ql, is then coupled
fier. Many professionals eliminate Some of the applications for this to the base of r -f oscillator Q2.
the cable problem by using miniature project include using it as a minia- Transistor Q2 and its components
wireless microphones that have their ture PA system or as an electronic make up a classic Colpitts oscillator.
own built -in amplifier /transmitter, babysitter while you monitor sounds To produce oscillation, the transis-
doing away with cables. As a result, from another room. You can even tor's base and collector are connect-
they have more freedom to move build two wireless microphones to ed to opposite ends of an LC "tank"
around without worrying about use as a simple wireless system in circuit, with the emitter connected
snarling cable and a trip hazard. The your home. For the kids, this can be somewhere between these two points.
FM wireless microphone to be de- a fascinating toy that lets them sing When the gain of this arrangement
scribed here can give you the same and talk through an FM radio. exceeds unity (1), the circuit oscil-
advantages. It is low in cost, yet high lates at a frequency determined by
in audio quality.
About the Circuit the parallel resonant frequency of
Our wireless microphone is de- Shown in Fig. 1 is the complete sche- the tank circuit.
signed to work with an FM receiver, matic diagram of the FM wireless mi- In the oscillator stage, the LC tank
tuner or radio. Since its r -f output is crophone. Microphone element MIC is composed of coil LI and the series
very low in power, and has a usable is an electret type that is powered combination of C4 and CS. The base
transmitting range of 50 feet or less, from battery BI through resistor RI. of Q2 is held at r -f ground potential
it should not interfere with your When sound reaches the microphone by C3, and the "cold" side of LI is
neighbors' FM reception. Its ex- element, the current through Rl is held at ground potential by C7. This
tremely high sensitivity allows it to varied in accordance with the intensi- effectively places the base of Q2 at
pick up voices and sounds several ty of the sound intercepted. This pro- the same r -f point as the cold end of
feet away; so there is nothing critical duces an ac voltage through RI that the tank circuit.
about locating it in a pick -up area. If is coupled through Cl into the base The voltage-divider action of C4

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 25

 17 Antenna
R1; R6 1.1 R8 R9
`2'
2.2K 47K (see text) 47K 1K

C6
10pF
02 - Q3
2N5179
1\
2N5179
B1
9V C4
22pF
M:>/
MIC
C R7 C5
1K 47pF

PARTS LIST

Semiconductors C6 -10pF ceramic (NPO temperature Shack Cat. No. 270-090 or similar)
Q1- 2N3904 or similar silicon npn stable) Printed -circuit board; shield (see
transistor Resistors (1/4-watt, 10% tolerance) text); snap connector for B1; wire for
Q2,Q3- 2N5179 or similar silicon r -f R1 -2,200 ohms antenna; solder; etc.
npn transistor R2,R6,R8-47,000 ohms
Capacitors (50 WV) R3- 10,000 ohms Note: The following items are available
Cl,C2,C7-0.01 -µF ceramic R4 -4,700 ohms from A. Caristi, 69 White Pond Rd.,
C3-0.001 -µF ceramic R5,R7,R9 -1,000 ohms Waldwick, NJ 07463: Pc board, $5.00;
2N5179 transistor, $3.75 each; set of 22 -,
C4 -22-pF ceramic (NPO temperature Miscellaneous
B1-9 -volt transistor battery 47- and 10 -pF NPO temperature -stable
stable)
capacitors, $1.75. Ass $1.00 P &H. New
C5 -47-pF ceramic (NPO temperature L1-Inductor (see text) Jersey residents, please add state sales tax.
stable) MIC -Electret microphone (Radio

Fig. 1. Complete schematic diagram of wireless FM microphone.

and C5 provides a simple means of To enhance the frequency stability limits current flow. The antenna for
placing the emitter of Q2 at the opti- of the oscillator, an additional stage the microphone connects directly to
mum r -f point. This is one-third (33 has been included in the circuit to the collector of Q3.
percent) above ground potential and buffer the oscillator from the anten-
ensures that the circuit oscillates. na. With this stage, Q3, small Construction
Resistor R6 forward biases Q2 so changes in capacitance due to physi- Due to the r -f nature of the wireless
that the transistor draws collector cal positioning of the antenna will microphone's circuit, printed- circuit
current and is forced into oscillation. have an attenuated effect on the os- construction is mandatory. For this
Since the bias voltage at the base of cillator circuit. The result is much board, you need a pc blank that is
Q2 is modulated by the ac signal volt- less frequency drift. clad on both sides with copper. One
age variations from Ql, the frequen- Taken at its collector, the output side will be etched in the usual man-
cy of oscillation in the Q2 circuit va- of Q2 is capacitively coupled into the ner to produce the wiring pattern to
ries in accordance with the frequency base of r -f amplifier /buffer Q3. Re- which component leads are soldered.
of the sound reaching the micro- sistor R8 forward biases transistor The other side will serve as a ground
phone element. Thus, the oscillating Q3. The resulting current flow in this plane to which only selected leads
signal from Q2 is frequency modu- stage causes Q3's collector to output (those that are grounded, of course)
lated to conform with the needs of an r -f signal composed of the fre- are soldered as well. It serves a sec-
the FM receiver, tuner or radio with quency- modulated output from Q2. ond function as a shield for the cir-
which the project is used. Resistor R9 in Q3's collector circuit cuit. You can make your own pc

26 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 board or purchase a ready -to -wire tion first on the bottom of the board,
board from the source given in the clip off excess lead lengths and then
Note at the end of the Parts List. solder the ground -plane side connec-
You can home fabricate your own tion with only enough solder to make
pc board with the aid of the actu- a secure electrical connection. Then
al -size etching-and -drilling guide use the ohmmeter to make sure that
shown in Fig. 2. Note in Fig. 2 that the other leads do not short against
the ground -plane side of the board is the ground plane. Install and solder
not shown in the usual etch -and -drill
, O into place the remaining capacitors
format. Because this side of the
board is not to be etched at all, only
000
00 0000
CP f0ÓO 0 and resistors.
At this point, you might wish to
the hole-drilling /clearing informa-
tion is graphically presented. In this
e OÓ0OOpN8 consider the circuit option that lets
you reduce the sensitivity of the mi-
illustration, all holes to be drilled are crophone pickup. If your wireless
identified by either circles or solid o -Clear these holes of copper .
microphone is to be used to pick up
black dots. -Do not clear these holes. sounds at some distance from the mi-
When fabricating the board, make crophone element, you need do
sure to mask off the top side with Fig. 2. Actual-size etching-and- drill- nothing. On the other hand, if you
etch resist to prevent the copper from ing guide (upper) and drilling /hole- wish to use the project as a hand-held
being removed by the etchant. After clearing details (lower) for double- microphone for direct close -up pick-
the board has been etched, trim it to sided printed- circuit board. up, this option should be incorporat-
size. Then carefully drill all holes ed to prevent overmodulating the r -f
through the board as indicated, us- carrier and, thus, audio distortion.
ing the pattern of pads on the wiring For reduced microphone sensitivi-
side to accurately locate where each grounded leads of Q2 (case only) and ty, you can eliminate the QI amplifi-
hole is to be drilled. Q3 (emitter and case) to the copper er stage in its entirety. That is, omit
After using a No. 60 bit to drill the trace on the bottom and the ground C2, QI and R2 through R5. Then
component lead holes, turn over the plane on the top of the board. When simply connect Cl from the junction
board and orient it as shown in the the transistors are soldered into of the microphone's + terminal and
ground -plane illustration in Fig. 2. place, there should be no more than Rl to the R6/C3 /Q2 base junction.
Carefully mark all holes indicated by '/, inch of space between the bottoms No changes need be made to the pc
open circles. Then very carefully iso- of their cases and the board. board if you exercise this option. In
late these holes from the copper -clad Use an ohmmeter to check that fact, if you wish, you can build in a
ground plane by drilling with a 3/, 6- any lead that is not supposed to be switching arrangement between the
inch diameter bit only enough to grounded does not short to the cop- output side of Cl and the base inputs
clear copper from around the holes. per cladding on the top of the board. of QI and Q2 in alternate positions
Do not drill all the way through the Refer back to Fig. 1 to make sure. If of a miniature two -position slide
board! When you are finished, there you find any lead that does short to switch. Doing this gives you a choice
should be eight holes from whose the ground plane but should not, between full- sensitivity and reduced-
edges you have not removed the cop- gently bend it until it no longer does. sensitivity modes of operation.
per cladding, all indicated by the sol- Once the transistors have been You can mount the microphone el-
id black dots in the illustration. mounted, install and solder into ement directly at the edge of the
Now wire the board exactly as place C3, C5, R3, R5 and R7, all of board, using short lengths of cut -off
shown in Fig. 3. Start with the tran- which have one lead that goes to cir- component lead between the ele-
sistors, making sure that they are cuit ground. Solder this lead to the ment's terminals and the appropriate
properly based as you plug their copper cladding on both sides of the holes in the board. Be sure to proper-
leads into the holes. Note that Q2 board as you did for the transistors. ly polarize the microphone element.
and Q3 have four leads, one each for When installing these components, Solder the negative ( -) lead of the
the emitter, base and collector and a leave about 'AG inch of lead length on microphone element to the copper
final one that is internally connected the top of the board to make it easy cladding on both sides of the board.
to the case. Make sure all leads are to solder the appropriate leads to the Instead of mounting the micro-
soldered to the pc board after install- ground plane. phone element directly on the board,
ing each transistor. Solder the It is easiest to solder the connec- you can locate it elsewhere and make

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 27

interconnections with an appropri-
ate length of shielded cable. Use the
center conductor for the "hot" (+ )
and the shield for the ground ( -)

;
sides of the element.
-C7- R8
I I I I -CS- R9
Now hand -wind inductor LI, us-

III
R5 R3 R2 R7
R1 R4 R6
ing either 20 -gauge enameled copper
wire (preferred) or 20 -gauge bare sol- I L1 B

id hookup wire. First cut the wire to C4 C6

E Q1 c
exactly 41/2 inches long so that it C2-
MIC
"tunes" to the center of the FM 'Cl . B

broadcast band. Carefully scrape

away 1/4 inch of the enamel insulation. ANTENNA
Wrap this wire around an ordinary "CASE
pencil, making 3'/ turns and wind- Fig. 3. wiring diagram for pc board.
ing as tight as possible. Slide the coil
off the pencil and note that it should
have two equal- length "tail" ends
that are parallel with each other. tom of the board. Flip over the board sheet metal, such as copper or brass.
(They may not be exactly parallel and clip the excess length of the red - Copper flashing, available from
with each other, due to the springi- insulated wire as close as possible to lumberyards and roofing supply
ness of the wire, but will become so the board's surface. Then solder the houses, works well, as does thin
once the tails are plugged into the black-insulated wire to the ground brass sheet obtainable from most
holes in the circuit board.) plane and clip off its excess lead hobby shops.
Press the coil end -to -end between length. Check with your ohmmeter Trim the copper or brass sheet to
your thumb and forefinger until the to make sure that the red wire is not 2'/,6 by 2 inches. Then use a soft lead
spacing between the turns is about shorted to the ground plane. pencil or a scribing tool to strike the
one wire diameter. This spacing is The antenna for your wireless mi- fold lines and mark the center of the
not critical, but if done correctly will crophone should be as short as possi- '/ -inch diameter hole to be drilled.
make it easier to plug the tails into ble but not so short that it provides Place the marked sheet metal in the
the holes in the circuit board. less than satisfactory operation. jaws of a vise, lining up one of the
If you used ordinary bare solid Start with a 6 -inch length of insulat- fold lines with the vise's jaws and
hookup wire to wind the coil, place a ed solid hookup wire. Strip '/a inch bend first the inner -channel edges
strip of electrical tape on the ground of insulation from one end and plug and then the outer tab edges. You
plane in the LI area to provide insu- this end into the hole labeled ANTEN- will not be able to make complete 90-
lation in case the coil sags or is NA and solder into place. degree bends using the vise. The idea
pushed against the copper cladding. With the circuit board fully wired, is to get clean, sharp bend lines. You
Plug the coil into the holes in the refer back to Fig. 1 and use your can square up the bends by hand with
board so that the tails protrude ohmmeter to make certain that no the aid of slip -joint pliers.
about '/,6 to % inch on the bottom of component leads not shown connect- Once the U- channel shield has
the board and there is air space be- ed to circuit ground touch the been bent to shape, punch the loca-
tween the bottom of the coil and the ground plane on the top of the tion of the '/a -inch hole to be drilled.
circuit board's ground plane. Solder board. Readjust the position of any Then drill the hole, backing up the
into place. component that registers a short cir- metal with a scrap wood block to get
Tightly twist together the fine cuit to the ground plane to eliminate as clean a hole as possible. Use a'/,6-
wires in both battery snap connector the short circuit. inch bit to drill the hole. Then care-
leads and sparingly tin with solder. To preserve the frequency stability fully enlarge the hole to its final '/c-
Place the circuit -board assembly sol- of the circuit, you must place an r -f inch diameter with a tapered reamer.
der side up and plug the red snap shield on the top of the board after
connector wire into the hole labeled the circuit has undergone prelimi- Checkout
B1 + and the black wire into the. hole nary check. Fabrication of the shield Before plugging the battery into its
labeled Bi - (see Fig. 3). Solder both is very simple, as shown in Fig. 4. snap connector, perform a visual
connections to the pads on the bot- You can use any thin solderable check of the board to ascertain that

28 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

there are no short circuits or cold-
soldered joints on either side of the 2'/,6"
board. Reflow the solder on any 1'/92"
joint that appears to be question-
able. Double check all transistor bas -
ings. If you wish to be absolutely cer-
tain of your wiring, perform a final
ohmmeter check, with the aid of Fig.
1, to ascertain that all component
leads that are not supposed to be
grounded are not shorted to the
ground plane. When you are satis-
fied that all is well, plug a 9 -volt bat- 2
tery into the project's battery snap
connector. dia
Use an ordinary FM radio to check
that the circuit is working. Start at
the low end of the FM band and very
slowly tune the radio upward in the
band. At some point near the middle
of the band, you should hear either
silence as the radio responds to the
microphone's r -f carrier or "howl-
ing" as acoustic feedback between
the radio and microphone causes os-
cillations.
If you turn the volume control on
the radio low enough, you will be
able to eliminate the feedback so that
when you talk into the microphone
you hear your voice. Keep in mind
that the sensitivity of the micro-
phone is very high (unless you opted
Fig. 4. Fabrication details for project's r-f shield.
for reduced sensitivity); hence, you
need only whisper into the micro-
phone for this test. the coil's leads do not short to the short a component lead that should
After you have pinpointed the ground plane (and that no turns of not be connected to the ground
wireless microphone's signal on the the coil touch the ground plane if you plane. Place the shield over the cir-
FM dial, mark the frequency at used bare solid hookup wire to make cuit -board assembly with the '/a -inch
which it appears. You will note that the coil). hole centered over L1 and use more
when the shield is mounted to the cir- When you are satisfied that your solder at the four corners to make
cuit -board assembly the received sig- wireless microphone is operating as mechanically secure electrical and
nal will be shifted some 3 MHz high- it should and is tuned to approxi- mechanical connections. You do not
er in frequency on the dial. mately where you want it to be on the need continuous beads of solder; in
If you wish to tune your micro- FM dial, attach the shield by solder- fact, you do not want them should
phone for a specific approximate fre- ing it to the perimeter of the copper you ever have to service the circuit.
quency on the FM dial, perhaps to ground plane. After the shield is in place, power
avoid interfering with a station on a To simplify soldering, first flow a up your microphone again and tune
given frequency, you can increase thin film of solder onto the ground the FM radio to a dead spot on the
the spacing between the turns of LI plane at all four corners of the board dial, where no stations are broad-
to raise its operating frequency or de- and on the four corners of the under- casting until you hear the micro-
crease the spacing to decrease the fre- side of the shield's tabs. Make sure
quency. Be sure as you do this that that no solder flows far enough to (Continued on page 90)

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 31

Project

The Photo(Tach)- Pulser

A photo tachometer adapter for frequency counters

By Crady VonPawlak ered project, which this one is. The

tradeoff, though, is the LM324's
When you need a photo - narrow bandwidth, which is unity
tachmometer to trouble- gain at 1 MHz.
shoot an infrared re- To prevent Ul from reacting to
mote control transmitter for a TV small changes in ambient light, the
receiver or VCR, to determine the chip's input is coupled to the emitter
rpm of a spinning shaft, etc., nothing of QI through capacitor Cl. If the
else will do. Commercial phototach- value of Cl is small enough, simple
ometers, of course, are expensive in- changes in room or outdoor lighting
struments. Fortunately, you can will not be passed on and amplified.
build the Photo -Pulser accessory de- The penalty for this small value of
scribed here at a cost that should not capacitance is that it passes little cur-
exceed about $30 for all new parts, rent. To compensate for this, the val-
including enclosure. Its low cost is ue of R4, which provides the op
made possible by connecting it to a amp's noninverting ( + ) input with a
frequency counter. dc path to ground, must be fairly
Our Photo -Pulser is a fairly simple large to prevent attenuating the in-
accessory device to build and use. It coming signal. There is a penalty
is designed to serve as the "front here, too. That is, if R4's value is
end" for a frequency counter from made too large, current through Cl
whose display you can read revolu- can cause the output of UI to latch.
tions per minute directly. Its TTL- If R2 is set to a high enough resis-
level output will directly drive almost tance, the amplifier can break into
any digital frequency counter now in lector -emitter junction. This current oscillation.
use, including the Frequency Count- is then converted to a voltage by po- To obviate the possibility of oscil-
er Accessory for Digital Multimeters tentiometer R2. The magnitude of lation and increase overall band-
described in the November 1987 is- the voltage developed is determined width of the circuit, the amplifier is
sue of Modern Electronics. by the amount of light that strikes QI made up of two op -amp stages as
This accessory has only two con- and its proportional current and the shown. The first stage, following Cl ,
trols: a combined power switch and resistance of R2. By varying R2's re- is a noninverting amplifier with a
rotary SENSITIVITY control and a sistance, the threshold or "sensitivi- gain of 101. Here, gain is determined
pushbutton switch to turn on a built - ty" of the circuit can be set to an in- by the relationship of R6 and R5,
in infrared -emitting energy source where Vout = (R6/R5) x Vi + 1.
coming signal.
for those occasions when ambient or An LM324 quad operational am- The same is true for the second stage,
reflected light level is too low to pro- plifier is used in this circuit for U/. which has a gain of 11. Therefore,
vide a reliable reading. This particular chip was selected be- overall gain with both op -amp stages
cause it is conveniently designed spe- in cascade is 101 x 11, or approxi-
About the Circuit cifically for use with a single supply mately 1,111.
The complete schematic diagram of voltage, eliminating the need for a If a gain on the order of 1,000 is se-
the Photo -Pulser is shown in Fig. 1. more complex and costly split power lected, bandwidth is moved closer to
As light strikes the sensitive surface supply normally required by many 1 kHz. To achieve an overall gain of

of phototransistor Ql, a proportion- op amps. Consequently, the LM324 1,000 and still retain reasonable
al current is passed through the col- is an ideal choice for a battery -pow- bandwidth, the pin 7 output of the

32 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 Fig. d. Complete schemati. n diagram of the Photo- Pulser.

n v. Y

F. P

m
Cr=

T
P-

N Y
°+"
§'
Ç
aE SE Res

e ,4

Say You Saw It In Mod =ern Electronics January 1988 / MODERN ELECTRONICS / 33
 PARTS LIST Pulser that is a clean 0 -to -5 -volt,
Semiconductors TTL -level square wave whose fre-
CR I,CR2-High- output infrared quency is the same as that of the in-
light- emitting diode in T -1 package put signal.
CR2,CR3- Diffused -lens red light- The square -wave output appears
emitting diode in T -1'%, case at two points: female BNC jack JI
Q1- Broadband phototransistor in for connection to a frequency coun-
T -1'/ case ter or oscilloscope, and at light -emit-
U1 -LM324 quad operational amplifier ting diodes CR3 and CR4. The LEDs
U2- 74HCT14 high -speed CMOS hex serve two functions: When no signal
Schmitt trigger
is present, only CR3 will be on and
U3 -78L05 fixed + 5 -volt regulator in
TO-92 package
doubles as a power-on indicator;
Fig. 2. Built -in hysteresis allows when a signal of proper amplitude
Capacitors
C1 -680 to 1,000 pF
Schmitt trigger to operate on sine appears at U2, CR3 and CR4 alter-
C2-0.33 -µF tantalum waves (upper trace) to produce nately flash at the rate of the input
C3-0.1 -µF tantalum square-wave output (lower trace). frequency.
Resistors ('/, -watt, 5% tolerance) In addition to simply indicating
R3 -1,000 ohms proper triggering, CR3 and CR4 will
R4,R8- 100,000 ohms amplified to a usable level, it is fed appear to glow (they are actually
R5,R7- 10,000 ohms through dropping resistor R9 to flashing) with equal intensity. On the
R6 -I
megohm 74HCT13 high -speed CMOS hex other hand, if the signal is spiky, one
R9,R10,R11 -470 ohms Schmitt trigger U2, which has LED will appear brighter than the
R12 -100 ohms
LS /TTL -compatible outputs. The other. This "spike" indication is im-
R1 -220 ohms, % -watt
R2- 1-megohm, linear- taper, panel - output of U3 is impedance and portant because even if the light
mount potentiometer risetime matched with LS (low - source has a 50- percent duty cycle, as
Miscellaneous power Schottky) devices. A 74HCT- with a fluorescent light, the actual re-
-9
BI -volt battery 14 was chosen for U3 instead of a ceived signal may be greater or less
J1 -Male BNC connector (see text) garden-variety 74LS14 for its low than 50 percent due to reflections
S1 -Spst normally -open, momentary - power consumption and increased from nearby objects adding to (in-
action pushbutton switch fan -out characteristics. phase) or subtracting from (out -of-
S2-Spst switch (part of R2; see text) A Schmitt trigger operates like a phase) the waveform. Careful aim-
Printed -circuit board; sockets of U 1 simple inverter, except that it has a ing of Ql (moving the light source or
and U2; suitable enclosure (Pac Tec small amount of hysteresis. For the the Photo -Pulser) will minimize the
No. HP -9VB or similar; see text);
pointer -type control knob for R2;
output of the Schmitt trigger to effects of reflections
heat -shrinkable tubing; clear self - change state from low to high or Power for the project is supplied
stick plastic sheet (see text); hookup from high to low, the input wave- by a single 9 -volt transistor battery
wire; solder; etc. form must pass through upper and (BI). This battery's output is regu-
lower thresholds. So long as this is lated down to a stable 5 volts by posi-
true, the shape of the actual wave- tive low -power regulator U3. (Al-
form is irrelevant. An example of though the 78L05 operates identical-
first stage, which has a moderate this is illustrated in Fig. 2. ly to the 7805, its pinout is reversed.
gain of 100, is fed into the second The upper trace in Fig. 2, taken at Input is at pin 3, output is at pin 1
stage-at the pin 10 noninverting the emitter of Q], shows a 120 -Hz and common or ground is at pin 2.)
( +) input -which has a lower gain sine wave (generated by a fluorescent Tantalum bypass capacitors C2 and
of 10. With this type of arrangement, light 10 feet away) that has an ampli- C3 stabilize the output and prevent
any noise produced by the first stage tude of +200 millivolts. This sine U3 from breaking into oscillation.
is amplified by the second stage, wave is then amplified to meet the For CRI and CR2, infrared -emit-
which makes this setup a poor choice lower and upper threshold require- ting diodes were chosen for greater
where minimal distortion and low ments of the Schmitt trigger. Hence, efficiency and an output wavelength
noise are key factors. However, in even though the signal at QI is a sine that is closest to that of a given pho-
the case of the Photo -Pulser, the ef- wave, after amplification to at least totransistor's peak sensitivity. These
fects of this type of noise are VT + (2.7 to 3.3 volts dc) and going IR- emitting diodes provide an on -de-
insignificant. -
below VT (1.3 to 2.1 volts dc), it mand reflected point- source of light
Once the incoming signal has been produces an output from the Photo- via pushbutton switch S2. If you

34 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 TOP < s2 +
a CR3 CR
RID
ÑMî +8

J
1111111
gi= 1111111j

f i

1 î J. Re

L J
Fig. 3. Actual-size etching- and-drilling guide for fabricating
at
R6

Fig. 4. Wiring guide for pc board.

ce

printed-circuit board.

were to measure the rpm of a spin-

DASHED LINE INDICATES CLEAR
ning shaft that has alternating black PROTECTIVE WINDOW BEHIND
and white surfaces in poor or indirect APERTURE. CLEAR ACETATE, ETC.
reflected light, for example, CR1
and CR2 would provide a light 1.300
source for making measurements.
0.225
1.000
Before you select a phototransis-
tor for QI , make certain that it is sen-
sitive to a broad spectrum of visible
light. Motorola's MRD series is sen-
sitive to light ranging from 450 to 0.250 - FRONT VIEW ENCLOSURE -
( LOWER HALF )
1,000 nanometers (nm) in wave-
length, with peak sensitivity in the
Fig. S. Cutout details for machining end panel of enclosure lid to permit (R-
800 -nm range. Using good judgment
emitting diodes and phototransistor to face outward.
here will extend both the sensitivity
and versatility of the Photo -Pulser.
If you want to learn more about of Ul makes printed- circuit board fore soldering their leads to the cop-
pyroelectric devices, I highly recom- construction of the Photo -Pulser al- per pads on the bottom of the board.
mend the Optoelectronics Device most mandatory to assure quiet op- Also, make sure you properly base
Data Book from Motorola. This eration. You can fabricate the single - the transistor.
book is chock full of circuit examples sided pc board from the actual -size A Pac -Tec No. HP -9VB enclosure
ranging from simple optical switches etching- and -drilling guide shown in is ideal for the project because it has
to ultra- high -speed fiber -optic data Fig. 3. Wire the board exactly as a separate battery compartment with
links. It also contains a detailed sec- shown in Fig. 4, using sockets for U] its own separate slide- off /on cover
tion on photo- semiconductor theory. and U2 (do not install the ICs in the for convenient battery replacement.
sockets until after initial checks have If you use this particular enclosure
been made). Make sure the LEDs, (or another with roughly the same di-
Construction IR- emitting diodes and tantalum ca- mensions), use Fig. 5 to guide you in
The small output at QI and high gain pacitors are properly polarized be- cutting the slot through which QI,

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 35

 move the protective layer on the tape
until you are ready to apply the label
to the panel. Turn over the label and
carefully trim it to the outside edge
PHOTO X PULSER of the border.
Peel the protective layer from the
POWER tape and carefully apply the label to
the panel, making sure the cross -
points of the cutouts are centered in
DUTY CYCLE the holes in the panel. Burnish away
any bubbles. Then use an X -acto
knife fitted with a No. 11 blade to
trim away the label material that cov-
ers the panel holes.
I used a potentiometer switch
`%%Itsi from Radio Shack for S2, attaching
POINT SOURCE it to R2. To wire R2 as a rheostat as
shown in Fig. 1, first turn the shaft of
® - ® - the pot fully clockwise. Then use an
ohmmeter to determine which of the
pot's outer lugs register maximum
resistance with respect to the center
ON /OFF MIN. MAX. wiper lug. Solder 3 -inch lengths of
GAIN hookup wire to the wiper and maxi-
mum- resistance lugs of the pot. If
you wish, you can solder a wire from
the remaining lug to the center lug;
otherwise, leave the minimum-resis-
tance lug unconnected.
Mount the pot in its hole on the en-
ED closure panel and rotate it's shaft
fully counterclockwise. Place a point-
TTL OUT er -type knob on the shaft, aligning
the pointer on the knob with the MIN
index on the panel. If necessary, re-
move the knob and reposition the
Fig. 6. Front panel machining and legend details. Make photocopy of this art-
pot to obtain perfect indexing.
work and use directly as panel label, as detailed in text.
Female BNC connector J1 is too
long to fit over the battery compart-
CR1 and CR2 point outward. Then ton switch, potentiometer and BNC ment. Therefore, modify it as fol-
use Fig. 6 to locate the holes for the connector. lows: Use an X -acto or similar minia-
LEDs, pushbutton switch, rotary Use the second photocopy of Fig. ture saw to trim the connector's
control and BNC connector. 6 as a panel label. Before trimming it threaded length to about '/,6 inch
Make two same -size photocopies to the outer border, carefully apply a long. Then bend the center conduc-
of Fig. 6. Trim one copy along the sheet of clear self-stick "document tor at a 90- degree angle to the con-
outside edge of the border line. Place protector" plastic to the artwork ductor's normal axis; make sure the
this copy on the lid of the enclosure, side. Work slowly and carefully. This center conductor does not short
carefully centering it all around, and self-stick plastic sheeting can be ob- against the threaded portion of the
mark the locations of the five holes tained from most stationery stores. connector.
on the box lid. Drill pilot holes with a Once the plastic is down on the art- Plug the BNC connector into the
'/, 6 -inch bit and follow up with a work, turn it over and apply enough TTL OUT hole in the enclosure's pan-
-inch bit. Then enlarge each hole as wide double-sided permanent -type el. Solder a 3 -inch length of hookup
needed with a tapered reamer to just adhesive tape to cover the entire ex- wire to the washer that came with the
accommodate the LEDs, pushbut- posed area of the label. Do not re- connector. Slide the washer onto the

36 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

threaded end of the connector and With power turned off, measure the terclockwise, just before the click of
follow with the supplied hex nut. voltage delivered to the circuit at the the switch), CR3 should light. If not,
If you prefer not to modify the + BATTERY ( "hot" meter lead) and check the wiring of CR3 and CR4 for
BNC connector as detailed above, - BATTERY points to confirm that proper polarity.
you can use the J1 hole as an exit for the battery is delivering approxi- If everything looks good so far,
a 50 -ohm coaxial cable (not longer mately + 9 volts dc. aim the Photo-Pulser at a turned -on
than 1 meter) terminated in a male Turn on the power by rotating the fluorescent light up to 15 feet away
BNC connector at the outside end. control knob just until you hear and or a CRT screen between 1 and 2 feet
The other end then directly connects feel the click. Connect the meter's away and adjust the gain until both
to the appropriate points on the cir- common lead to pin 11 and its hot LEDs light. To test the point- source
cuit -board assembly. Make sure to lead to pin 4 of Ul's socket. The me- LEDs, adjust R2 for about mid-gain
connect the cable's shield to circuit ter should indicate + 9 volts. Next, and wave your hand in front of the
ground and the center conductor to connect the meter's common lead to window at the end of the enclosure
the signal- output hole. Also, find a pin 7 and its hot lead to pin 14 of while pressing S2. Now CR3 and CR4
way to provide mechanical strain re- U2's socket. This time, your reading should flash as your hand or fingers
lief for the cable. A convenient should be + 5 volts. pass by.
means is to use a nylon cable tie that Once you are satisfied that your Once you know that your Photo -
binds the cable to the circuit board wiring is okay, turn off power to the Pulser is working as it should, the
via a small hole drilled in an unused circuit and install Ul and U2 in their project is ready to be put into service.
area of the latter. sockets. Make sure that each is prop- To use it, simply connect its output
Note in Fig. 4 that even though erly oriented and that no pins over- to the input of a frequency counter
CRI and CR2 are positioned slightly hang the sockets or fold under be- via the TTL OUT connector or cable,
forward of Q1, energy given off tween ICs and sockets. turn on both instruments and select
from the sides of the cases of these With power on once again and an appropriate range on the counter.
devices can strike and saturate the gain set to minimum (R2 fully coun- Finally, adjust sensitivity as needed.
phototransistor. To prevent this
from happening, slide a '/4 -inch
length of appropriate diameter heat -
IDOES YOUR DIGITAL CAPACITANCE METER oo THIS ?,
shrinkable tubing over CRI and CR2 FULL 4 DIGIT 0.5 INCH LCD DISPLAY COMPLETELY AUTORANGING WITH 10 RANGE MANUAL CAPABILITY

and shrink into place. Make sure that AND THIS AND THIS
RANGE OF 0.0 pF to 1 FARAD (999.9 mF) IDENTIFIES TRANSISTORS (NPN, PNP)
the forward-facing portions of the 0.5% BASIC ACCURACY UP TO 100 uF AND THEIR LEADS (E, B, C, ETC.)

lenses on these IR emitters are not AND THIS AND THIS

READS DIELECTRIC ABSORPTION TESTS ZENER DIODES AND RECTIFIERS.
obstructed. Shrink the tubing until it AND THIS UP TO 20V ZENER WITH AC ADAPTOR,
ZENER VOLTAGE WITH 9V BATTERY
just begins to conform to the shape EXTENDED PSEUDO 5 DIGIT
RESOLUTION ON SOME RANGES ONLY
DEPENDS ON ITS CONDITION

of the diodes. AND THIS AND THIS

AUTOMATICALLY CALCULATES LENGTHS
ABILITY TO ZERO LARGE CAPACITANCE
Wire visible LEDs CR3 and CR4, VALUES UP TO 99.99 uF
OF CABLES IN FEET, METRES, MILES,
KILOMETRES (THEORETICAL RANGE
BNC connector (or cable), switch/ AND THIS OF 9,999 MILES)
CALCULATES TRUE CAPACITANCE
pot assembly and pushbutton switch IF CAPACITOR IS LEAKY
AND THIS
ABILITY TO SORT CAPACITORS IN
to the circuit-board assembly as per AND THIS MANY DIFFERENT MODES
DIODE CLAMP AND FUSED
AND THIS
Figs. 1 and 4. Tightly twist together PROTECTED INPUT.
DISCHARGE RESISTOR IN OFF
ABILITY TO READ LEAKY CAPACITANCE
(INSULATION RESISTANCE OR CURRENT)
the fine wires in each conductor of POSITION AT TERMINAL INPUTS.
POWERED BY 9V BATTERY AND THIS
the battery snap connector and light- ONE YEAR PARTS IS CALCULATES TIME CONSTANTS WITH
LABOUR WARRANTY USER DEFINED RESISTANCE VALUES
ly tin with solder. Pass the free ends AND THIS
FOR ONLY THIS
of these wires into the enclosure HOLD FUNCTION FREEZES DISPLAY
SHIPPING INSTRUCTIONS:
through the battery compartment All units shipped out F.O.B. Buffalo NY via United Parcel Service (except Hawaii & Alaska)
unless otherwise indicated (in which case shipments will be F.O.B. Canada)
and plug the red one into the + BAT-
TERY and black one into the - BAT- PLEASE SEND ME U.S. FUNDS
(QUANTITY) MC300(S) (i $169.95 $
TERY holes in the circuit board and CARRYING CASE $ 16.95 5
AC ADAPTOR $ 9.95 $
solder into place. MODEL SHIPPING AND HANDLING @ $5.00 PER INSTRUMENT $

MC300 [ (CHECK ( ]MONEYORDER $

Checkout & Use

With Ul and U2 still not installed,
[.DAETRON
a division of Bergeron Technologies Inc.
935 THE QUEENS WAY, BOX 641
[

[
(VISA ( (MASTERCARD
] CARD NO.

EXPIRY DATE
NAME
ADDRESS
TOTAL

SIGNATURE
TELEPHONE
$

TORONTO, ONTARIO M82 5Y9

snap the battery into its connector. CANADA (416)676-1600
CITY STATE ZIP CODE

DEALER ENQUIRIES INVITED

CIRCLE NO. 150 ON FREE INFORMATION CARD
Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 37
Project

A Miniature LED Beacon

This easy -to -build project adds more realism to model
airplanes, trains, etc., and can be used as an attention -
getting device in jewelry and sciencefair projects

By Dan Becker

If you operate model railroads,

airplanes, etc., the battery-
powered Miniature LED Bea-
con to be described can enhance their
realism by providing a railroad warn-
ing light or an airplane or rocket
strobe or landing light. Alterna-
tively, the tiny circuit can be used to
draw attention to signs or, with a
wristwatch battery, to create elec-
tronic jewelry. The project is small
and light enough in weight to fit in-
side or on any model. It uses only few
low -cost components and can be as-
sembled in an hour or less. In fact, if
you are an experienced electronics
experimenter or hobbyist, chances are up an RC timing circuit whose time x 1%-inch perforated board that has
good that you have all the compo- constant (charging time) is 2.16 holes in 0.1 -inch centers. For solder-
nents needed in your spare -parts box. seconds. ing convenience, each hole should be
When the charge on CI reaches surrounded by a narrow circle of
About the Circuit about 1.5 volts, the comparator in- copper cladding on one side only.
The Miniature LED Beacon circuit is side ICl switches on. This, in turn, Position the board as shown in
shown schematically in Fig. 1, which switches on transistor Ql. Fig. 2, and install an 8 -pin DIP IC
also illustrates the internal workings Once Ql switches on, it provides a socket inch from the left end, with
1/2

of the LM3909 integrated circuit that low- resistance current path in which pin 1 positioned nearest the lower-
makes up the heart of the project. In the voltages across Bl, RE and Ql right corner of the board. Solder the
this circuit, ICl performs as both a are in series with each other. The ad- socket's pins to the copper circles on
LED driver and an oscillator. The vantage of this arrangement is that the board.
circuit is powered by a No. 357A the 1.5 volts across Bl and the nearly Plug electrolytic capacitor CI into
1.5 -volt cell. Because circuit current 1.5 volts of charge on CI add to put a the holes in the board, route its posi-
drain is less than 1 milliampere, this 3 -volt potential across LEDI. tive ( + ) lead to pin 2 of the socket
cell will provide more than seven The discharge time constant is and solder the connection. Clip off
days of continuous operation. about 6 milliseconds. This yields a any excess capacitor lead length. Si-
Current flows from the positive short, bright flash of light from milarly, route the capacitor's nega-
( +) terminal of BI via pin 5 of ICI LEDI. When LEDI flashes, it dis- tive ( -) lead to pin 8 of the IC sock-
through internal resistors RA and charges CI so that the cycle can re- et, solder the connection and clip off
RB and to the IC's pin 2 output. This peat. This charge /discharge cycle re- any excess lead length. Incidentally,
current charges capacitor CI and peats once every couple of seconds. to keep the circuit assembly as com-
flows through the RC /RD series re- pact as possible, use a capacitor with
sistor combination. Resistors RA Construction a 6.3 -volt rating. Of course, if you
through RD and capacitor Cl make The circuit can be assembled on a cannot find a 6.3 -volt electrolytic,

38 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 rc1 PARTS LIST
LM3909
B -No. 357A battery (Radio Shack
I

Rt,
RA .
Cat. No. 23 -115 or similar) -see
12 text
400:
C1- 220-µF, 6.3- or 16 -volt electrolytic
B1
capacitor with radial leads (see text)
1.5V IC 1 -LM3909 LED flasher /oscillator
400: Comparator (Radio Shack Cat. No. 276 -1705)
LED1 -Any general -purpose red light -
emitting diode.
Rc Ro Misc.- Perforated board with holes on
0.1 -inch centers and thin solder rings

L--------- - -- -- - -- --1
6K 3K
a
around each hole (Radio Shack Cat.
No. 276 -185 or similar) 8 -pin DIP
08 02 socket for ICI; 2-conductor, light
duty cable or individual 26 -gauge
LEDI Cl stranded hookup wire (see text); 24-
220µF gauge solid hookup wire; insulating
plastic tubing; solder; etc.
Fig. 1. Schematic diagram of Miniature LED Beacon.

you can use one that has a 16 -volt socket via an appropriate length of removed. Bend the wire to form a
rating at the penalty of larger assem- two -conductor cable or two separate "U" shape whose "legs" are parallel
bly size. stranded hookup wires loosely to each other and 0.1 inch apart.
When you install CI, position it so twisted together. Plug the legs of the wire U into the
that its negative lead is as close as To prepare the cable or wires, start holes at the center of the battery area
possible to pin 8 of the socket. Be- by removing % inch of insulation in the perforated board.
fore routing and connecting the posi- from both conductors at both ends. Locate the center of the battery
tive lead to the socket, slip over this Then tightly twist together the fine area as follows. First, set the No.
lead a % -inch length of insulating wires in each conductor and sparing- 357A cell with its negative lead fac-
plastic tubing and then route it to pin ly tin with solder. ing toward the board and immediate-
2 of the socket. Separate the conductors at one ly to the right of the socket. Then use
A standard red light-emitting di- end of the cable about 1% inches and a pencil to lightly trace the outline of
ode (LEDI) connects to the circuit then slip over each the 1 -inch length the cell onto the board's surface. Re-
assembly via its cathode lead to pin 8 of insulating plastic tubing. Clip the move and set aside the cell and count
and anode lead to pin 6 of the IC cathode lead of the LED to % inch the number of holes across the out-
and solder to it one of the cable con- line to find the center. Plug the wire
ductors. Similarly, clip the LED's U into the holes that most approxi-
anode lead to 'A inch and solder to it mate the center location. Bend one
the other conductor. Then slide the leg of the wire U flat against the
plastic tubing over the soldered con- board, route it to pin 4 of the IC
nections until it contacts the bottom socket and solder the connection.
of the LED's case. Bend the other leg flat against the
Connect and solder the other end board in the opposite direction and
of the cable to the appropriate pins solder it to any convenient point on
of the IC socket. Make sure that the the board.
cathode conductor goes to pin 8 and Press the part of the U that pro-
the anode lead goes to pin 6. trudes from the top of the board flat
To mount BI on the board, you against the surface so that the cell sits
need some sort of holder, which you as close as possible on the board.
Fig. 2. Assembly details for project, can make from a '/4 -inch length of
which mounts on and is wired to a 24 -gauge solid tinned hookup wire
small perforated board. from which all insulation has been (Continued on page 90)

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 39

Project

A High-Performance
Audible Continuity Tester
A stand -alone instrument that tests circuits and
components for continuity down to 50 milliohms

By Adolph A. Mangieri
Most continuity testers have
a relatively high resis-
tance at which they trip,
severely limiting their utility in many
critical testing applications. With a
trip threshold of 200 ohms, for ex-
ample, any resistance less than this
value will show up as a good indica-
tion, which would make just about
any switch, relay or wire that is not
an open circuit test good. So to be
truly useful, a continuity tester
should be able to tell you when a de-
vice or circuit has too much resis-
tance, even if "too much" is less
than 10 ohms, to adequately do its
job. The continuity tester should
have a trip point that can be adjusted
to between, say, 50 milliohms and 10
ohms, as the high -performance con-
tinuity tester to be described does.
Our tester has a piezo- buzzer that
sounds when continuity measures
between 0 and 10 ohms. For general-
purpose testing, a 10 -ohm trip thres-
hold would be selected. For more
critical tests, the project would be tance directly its dial) and as a good/ bridge are made up of potentiome-
preset against a 50- or 100 -milliohm bad indicator for a variety of solid - ters R5 and R6 and resistors R3 and
resistor to detect resistance differ- state devices. R4. Potentiometer R6 is used to set
ences of as little as 10 or 15 milliohms. the threshold from 0 to 10 ohms on a
A LED indicator is used when testing
About the Circuit calibrated dial, while potentiometer
circuits whose resistance is greater Shown in Fig. 1 is the complete sche- R5 balances the bridge circuit.
than 10 ohms. matic diagram of the High- Perfor- Operational amplifier ICI senses
Only a 0.25 -volt test potential is mance Audible Continuity Tester. the output voltage from the bridge
imposed on the circuit under test, Resistors RI and R2 make up two circuit, Vb, via input pins 2 and 3. In
making this continuity tester safe to arms of a dc Wheatstone bridge, this configuration, the ICI op amp is
use on digital circuits. For maximum with resistor RX in the RI arm repre- operated in the open -loop condition
versatility, the tester can be used as a senting the circuit or device under as a very- high -gain voltage compara-
low -range ohmmeter (you read resis- test. The other two arms of the tor with a dc open -loop gain in excess

40 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 l S1

B1
D2 D3
(see text) 9V
(see text))

cl
47µF

PARTS LIST
Semiconductors R1 ,R2 -220 ohms Shack Cat. No. 273 -065 or similar)
D1- 1N4001 rectifier diode R3,R4- 15,000 ohms S1 -Spst toggle or slide switch
D2,D3 -1- ampere Schottky barrier di- R5- 1,000-ohm trimmer potentiometer Suitable enclosure; printed- circuit
ode (Radio Shack Cat. No. 276-1165 R6 -500 -ohm, linear -taper panel-mount board or perforated board with holes
or equivalent) potentiometer on 0.1 -inch centers and suitable sol-
ICI-741C operational amplifier Miscellaneous dering or Wire Wrap hardware; DIP
LEDI -Red T -1% light- emitting diode B1-9 -volt transistor battery socket for ICI; snap -on connector
Capacitors J1,J2 -5 -way binding post (one red, and clip for B1; pointer -type control
C1-47 -µF, 15 -volt electrolytic one black) knob for R6; machine hardware;
Resistors (1/2-watt, 1% tolerance) PB1- Piezoelectric buzzer (Radio hookup wire; solder; etc.

Fig. 1. Complete schematic diagram of high -performance continuity tester.

of 100,000. Hence, a fraction of a 1-

millivolt difference at pins 2 and 3 of
ICI is sufficient to swing output
voltage Vo at pin 6 from low to high
or high to low, depending on the po-
larity of input Vb.
If Rx is an open circuit, pin 3 of
ICI will be positive with respect to
pin 2, causing Vo to go high and si-
lence piezoelectric buzzer PBI. Con-
versely, if Rx is less than the value set
by R6, input pin 3 goes negative with
respect to pin 2, causing Vo to go low
and sound PBI.
Light- emitting diode LEDI serves
as an on /off indicator, test -current
indicator and visual continuity indi-
cator. It also limits the open- circuit
test potential to 2 volts.
When plugged into JI and J2, Fig. 2. All components can be mounted and wired on perforated board that then
Schottky barrier diodes D2 and D3 mounts on front panel of enclosure.
further limit the open- circuit test po-
tential to 0.25 volt. Rectifier diode In designing the project, the range The range covered by R6 would be
Dl provides circuit protection. The of Rx covered by R6 was calculated doubled to nominally 20 ohms if this
short -circuit test current passed using the formula Rx = (R1 x R6)/ potentiometer's 1,000-ohm value or
through Rx is approximately 12 mil- (R3 + 0.5R5). With the component halved to 5 ohms if the potentio-
liamperes. values specified, Rx is 10.6 ohms. meter's value is 250 ohms.

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 41

 Sensitivity of the bridge circuit to
small diffetences in RX is determined O o O
by the amount of current in arms Rl
and R2. The greater the current, the
higher the sensitivity.
Values for RI and R2 were chosen o st -
PB1

as a compromise between loading of

battery BI and bridge sensitivity. 8
Making Rl and R2 larger in value to
reduce battery drain reduces sensitiv-
o
ity because RI becomes appreciably Fig. 3. Actual -size etching- and- drill- Fig. 4. Wiring guide for printed-cir-
larger than R. Contrariwise, mak- ing guide for making printed- circuit cuit board. Be sure to use a DIP socket
ing RI and R2 appreciably lower in board that can be used instead of using for IC1 and observe proper compo-
value than 330 ohms increases bridge perforated board. nent orientations.
sensitivity but places a greater drain
on Bl. Keep this in mind if you de-
cide to make circuit changes. and J2 exactly 3/4 inch apart to ac- change from + to and vice-versa.
commodate a double banana -jack If you used 1- percent resistors in
Construction assembly. Then drill the holes in the bridge circuit, potentiometer RS
Figure 2 shows how the high- perfor- which to mount LEDI in a panel clip will be near its mid -point setting
mance continuity tester can be as- and POWER switch S1 and potenti- when the bridge is at null setting. If
sembled in a small plastic enclosure ometer R6. Mount the LED, switch you cannot null the bridge circuit,
with all circuitry except the piezo and pot in their respective holes. check the resistors here for possible
buzzer and battery in its holder Wire potentiometer R6 so that its mismatch caused by soldering heat.
mounted on the lid. Component lay- resistance increases with clockwise Power down the circuit and install
out and wiring are not critical, per- rotation of the shaft. File a flat on ICI in its socket, taking care to prop-
mitting you to use any assembly tech- the shaft of this pot so that its knob erly orient it as shown. Make sure
nique that suits you. You can use pointer falls at about the 7 o'clock that no pins overhang the socket or
perforated board with holes on 0.1- position with the control shaft set fold under between IC and socket.
inch centers and suitable soldering or fully counterclockwise. Set R6 fully Use an ohmmeter to set R6 to
Wire Wrap hardware as shown or a counterclockwise and place a small about 25 ohms and mark a tempo-
printed- circuit board on which to dot on the panel at the pointer loca- rary 0 -ohm index on the project's
mount the components, which is tion to serve as the minimum refer- panel. Connect a short, heavy U-
then mounted to the enclosure's lid. ence mark. shaped jumper wire across J1 and J2
Fabricate the pc board using the ac- Install two 40 -volt, 1- ampere and adjust the setting of bridge BAL-
tual -size etching- and -drilling guide Schottky rectifier diodes in parallel ANCE control RS just to the point
shown in Fig. 3. Then install the with each other and back-to -back on where the buzzer sounds.
components on it exactly as shown in a double banana plug. This "acces- Advance the setting of R6 from its
Fig. 4. Use a socket for ICl and sory" can plug either way into the fully counterclockwise reference
make sure that Cl and D1 are prop- J1 /J2 assembly. It is used to limit the mark until the buzzer sounds and
erly polarized before soldering their open- circuit test potential to 0.25 note whether this corresponds with
leads to the copper pads. Do not in- volt for digital circuit tests. the 0 -ohm index. If not, trim the RS
stall the IC in the socket until after Carefully check the polarities of setting slightly and recheck.
initial checkout has been performed. Cl, J1, J2 and PB1 before applying Connect a 10 -ohm resistance
You can use an ohmmeter to select power to the circuit. Connect a volt- across J1 and J2 and advance R6's
matched pairs of 5- percent-tolerance meter, set to its lowest dc voltage setting until the buzzer sounds. If the
resistors for Rl through R4. range, from J2 (common lead) to the value of R6 is too low, maximum
Next, trim V4 inch of insulation wiper lug of RS or to pin 3 of the ICI range may be 8 or 9 ohms.
from both ends of eight 5 -inch hook- socket. Set R6 to its fully counter- To calibrate the BALANCE dial,
up wires. Plug one end into the LEDI, clockwise position. Set POWER you need six 1 -ohm and two 5 -ohm
BI -, SI and R6 holes and solder them switch SI to ON and verify that LEDI resistors to make up all the values be-
into place. lights. Connect a jumper wire across tween 0.5 and 10 ohms in 0.5 -ohm in-
When machining the enclosure's J1 and J2 and adjust RS over its en- crements. Two 1 -ohm resistors in pa-
lid, drill two mounting holes for J1 tire range. The polarity of Vb should rallel make up a 0.5 -ohm resistor.

42 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 With J1 and J2 shorted together, overshot the first setting, the buzzer reed relay may have up to 100 or even
advance the setting of R6 until the should sound, indicating that the res- 200 milliohms of contact resistance.
buzzer just sounds and mark and la- olution of the tester is well under 50 Used toggle, slide and microswitches
bel this as the 0 -ohm index. Connect milliohms. often exhibit much higher contact re-
resistors ranging from 1 to 10 ohms If you cannot obtain the above re- sistance, the result of contact wear
across J1 and J2 and mark off on the sult, try again using the 100-milli- and oxidation.
panel the 1 -ohm intervals. Then, us- ohm resistor instead of the 50- milli- To test switches, flip their toggles
ing the 0.5 -ohm resistance you pre- ohm one. If even this fails to give you or sliders back and forth a number of
pared in series with the 1 -ohm resis- the proper response, the problem is times to burnish their contacts, re-
tors, label the 0.5 -ohm intervals. low open -loop gain of the particular moving oxidation. Then set the test-
Remove the pointer knob from the 741 op amp being used. You will then er's dial well up-scale, say, to 5
potentiometer and label the control have to change chips until you have ohms. Make connections to the
panel as shown in the lead photo. one with sufficient open -loop gain. switch and rotate the control knob
You can use a dry- transfer lettering When you replace an op amp, it may on R6 counterclockwise until the
kit for this. When the panel is ready, be necessary to touch up the setting buzzer stops sounding. If the dial is
spray onto it two or three light coats of RS to reset the 0 -ohm index. at or very near the 0 index, the switch
of clear acrylic to protect the letter- Make a pair of test leads with is in good condition. Many of the
ing. Wait until each coat completely phone tips at one end and collet -type used switches I have tested gave resis-
dries before spraying on the next. test -probe handles at the other end. tance readings of as much as 0.5 ohm
Then replace the knob on the poten- The collet accepts steel phono (500 milliohms), 3 ohms and even 5
tiometer's shaft and double check needles that easily bite into copper ohms. Slide switches can often be re-
that the pointer index properly lines pads and terminals. Check your stored with a shot of lubricating
up with the counterclockwise refer- spare-parts box for old computer ca- cleaner spray.
ence mark. ble connectors that have machined When the resistance of a circuit is
The resistance per foot of solid female pins. You may be able to expected to be extremely low, do the
copper wire is as follows: chuck the pin in the probe collet and following. Give the project a 30-sec-
use the probe to make contact with ond warm-up to stabilize the very
Wire Gauge Milliohms /foot
the top ends of Wire Wrap posts. small drift of ICI. Short together the
12 1.62 Make another pair of test leads, test leads and adjust the dial setting
14 2.56 this time terminating one end in
16 4.10 counterclockwise to the point where
heavy -bite alligator clips and the the buzzer just sounds. Proceed with
18 6.51
20 10.4
other end with phone tips. Jumper - your test. In this case, you will be
22 16.5 wire the two jaws of the alligator working at considerably lower than
24 26.2 clips with copper braid to assure low - 100 -milliohm thresholds, possibly as
26 41.5 resistance connections. low as 50 milliohms or less.
28 66.2 If the above procedure cuts things
30 105 Using the Tester just a bit too close, use the following
32 167 For general- purpose tests, merely set procedure. Short the test leads
Armed with this information, fabri- the dial to a resistance threshold of through the nominally 50- or 100 -
cate a 50- milliohm and a 100- milli- your choice, from 0.25 ohm to 10 milliohm resistor you made earlier.
ohm resistor, using suitable lengths ohms, and proceed with your tests. Adjust the tester's dial just the the
of wire wound onto larger-value The buzzer will sound when the resis- point where the buzzer sounds. The
(100 -ohm or greater) 1- or 2 -watt car- tance of the circuit or component un- actual resistance threshold is equal to
bon resistors. For example, a 6 -inch der test is equal to or less than the the value of the calibrating resistor
length of 30 -gauge wrap wire is 50 value set on the dial. If the buzzer plus just a bit more. This gives you
milliohms, which is close enough for does not sound and LED1 is off, in- more leeway than does the preceding
our purposes. dicating test current flow, you can mode of operation.
Connect the 50- milliohm resistor adjust the setting of R6 until the You can also do the above the oth-
across J1 and J2. With the buzzer buzzer does sound and read off the er way around. With the calibrating
sounding, very slowly rotate the con- indicated resistance from the tester's resistor connected to the test leads,
trol knob on R6 counterclockwise BALANCE dial. adjust the project's dial to the point
until the sound from the buzzer Switch and relay contacts usually where the buzzer just stops sound-
ceases. Replace the resistor with the have contact resistances of 2 to 10 ing. Then remove the calibrating re-
heavy wire jumper. If you have not milliohms or so when new. The small sistor and short together the tester's

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 43

 leads and verify that the buzzer form your tests with no power ap-
sounds to be sure you have not over- LEDI ON LEDI OFF
plied to the circuit-board assembly.
shot the adjustment. This sets the J1
The low 0.25 -volt test potential and
threshold to a point somewhat less . 12- milliampere test current should
than the value of the calibrating not damage any ICs in the circuit, re-
resistor. A
gardless of test lead polarity. Inte-
Multiple-conductor ribbon cables, grated circuits can typically with-
DIP jumpers and similar devices are J2 stand up to 0.6 volt of reverse bias
tested by comparing the lines while ODES current. If there is any doubt about
looking for differences in resistance. J1
this, check the device's specifications.
You decide how close you want to You can also use this continuity
cut this test. tester to measure resistances of up to
For an example of how to use the 10 ohms. When it is used in this man-
tester, assume you are testing a 36- ner, adjust R6 to the threshold point
inch IDC ribbon cable made up of J2 and read the value indicated on the
28-gauge conductors. Armed with NSISTOR control's dial. Another way you can
conductor length and gauge and the J1 use the tester is as a visual continuity
information given above, you know tester in which LEDI is off when the
that the conductors should have a re- resistance between J1 and J2 is less
sistance that is close to 200 milli - than about 100 ohms or so. Use this
ohms. The two IDC contact pins at mode to check continuity of audio
J2
the ends of the conductor may add 40 transformers and the like.
milliohms of resistance at worst. NSISTOR
Using the connection arrange-
Make connections to the IDC ments shown in Fig. 5, the continuity
socket pins of any line selected as a tester handily performs basic good/
standard for comparison. Use two bad tests on a wide variety of semi-
wrap -post pins, preferably gold plat- conductor devices. If the device be-
ed, to make connections. Adjust the ing checked fails the test, it has little
setting of R6 clockwise until the or no chance of meeting its published
(D) SILICON CONTRA LLED RECTIFIER
buzzer sounds. Check two additional specifications. If it passes the test,
lines. If the buzzer sounds, the three the device has a very good chance of
lines are typical; so you can proceed Fig. 5 Connection arrangements to use meeting its specifications.
with testing. If the buzzer does not when testing various types of semicon- To check diodes and rectifiers,
sound, the first selected line may be ductor devices. bridge the device across J1 and J2 in
defective. Select another line as the both directions, as shown in Fig.
standard for comparison and pro- 5(A). With cathode x connected to
ceed in a similar manner. to identify which connector is caus- JI ( +) and anode A connected to J2
A cable that passes this test is in ex- ing the problem. (- ), LEDI should be on to indicate
cellent condition. If you want more To assist in cable testing, dedicate that the diode is blocking the flow of
leeway, nudge R6 a bit more up- a male or female socket with all pins current. Reversing the device's con-
scale, or calibrate the first line with connected together at one end and nections to the jack, the LED should
your 100 -milliohm test resistor tem- probe each line at the other end. Rib- be off, indicating that the diode is
porarily inserted in series with it. bon cables and DIP jumper cables conducting.
Checking an IDC cable suspected of have the same wire gauge on all lines, If LEDI is on when the diode is
causing computer crashes, I found but some bundled cables may have connected across the jacks in both di-
that the resistance of one line was 0.5 several wire gauges and several sock- rections, the diode is either open or
ohm greater than the others. This et pin sizes that you must take into consists of multiple diodes in series
difference would be of little concern account when making tests on them. with each other. If the LED remains
with a low- current signal line. How- When you test populated circuit - off when the diode is connected
ever, as luck would have it, the defec- board assemblies, insert the D2 /D3 across the jacks in both directions, it
tive conductor run was the 5 -volt Schottky diode voltage limiter into is shorted.
power-supply line. When you find a J1 and J2. For good indications, When checking a light-emitting di-
suspicious line, test it several times LEDI should remain off when the ode, the LED should emit some light
and flex the cable at each connector tester is used in this manner. Per- (though it may be faint and difficult

44 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 SUBSCRIBER SERVICE
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nections for checking small- and me- Include your mailing label NAME
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transistors. When using the tester to prompt service on your inquiry
check bipolar transistors, check first Modern Electronics CITY STATE

-1 with base lead B floating or discon- 76 N. Broadway,

Hicksville, NY 11801 ZIP
nected. If the transistor is good, the i
DATE

LED should light, indicating that the

transistor is off and is not shorted.
Connecting a 1,000-ohm resistor
from base B to collector C should
cause LED1 to turn off, indicating
that the transistor has switched on
and is amplifying.
Check photodiodes and transis-
tors as you would any ordinary diode
and transistor. The only exception is
that you should use a flashlight to
switch on the device under test.
Figure 5(D) shows how to check
low- and medium -current silicon
controlled rectifiers (SCRs). With
gate lead G not connected to anode
A, LED1 should be on to indicate
that the SCR is blocking the flow of
current. If the LED is off, try open-
ing and closing S1 on the continuity Now! In America attenuator, full memory backup, and
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With high- current SCRs, the de- For example: sensitivity across all shipping you an AR2002 within 48
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With very-low- current SCRs, the de- Performance Above shipping option, plus our Computer
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Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 45

Typical sensors (above, left to right) that can be interfaced with
computer: photocell for light, thermistor for temperature, toxic
gas sensor. Circuits (like light detector at right) can be wired on a
solderless breadboard.

Interfacing Commodore's
User Port
Using a low -cost serial A /D converter chip and some
simple software, you can use your C-128, C-64 or
VIC-20 to monitor real-world analog events

"language" that can be understood new world of applications for your

By John Iovine computer.
by a digital computer.
In this article, we will be examin- Our focus here will be on sensing
Commodore's series of per- ing serial interfacing and the 60- the real -world analog environment,
sonal computers -the C- Hz interrupt routine used in Com- with the computer serving as a data
128, C -64 and VIC -20 -can modore computers, using a low - "receiver." To illustrate the power
be used to sense and monitor the cost off -the-shelf analog -to-digital of the computer when interfaced
"real- world" environment. To be (A /D) converter. Knowing what with the real -world environment, we
able to use these computers in real - your computer wants and needs and will be discussing such useful appli-
world applications, however, you equipped with the hardware required cations as biofeedback monitoring,
must know a bit about interfacing to to convert real -world analog events monitoring light and heat with trans-
be able to translate real -world ana- to a binary code that the computer ducers and detecting toxic gases. By
log events into the two -state binary can use directly will open up a whole providing these applications and dis-

46 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 Computers

The type of interfacing used is im- cise moment to receive or transmit

portant, too. There are basically two data on the line.
interfacing schemes commonly used Commodore computers have a
> in personal computers today: serial built -in serial register and clocking
and parallel. To be able to success- line that can receive or transmit data
0
0 1 0 fully interface your computer with in such a serial fashion. This greatly
Binary the real -world environment, there- simplifies your programming task.
fore, you must understand the dif- You might be wondering just what
Fig. 1. Binary 1 and 0 are equal to ference between serial and parallel an analog event is. This should be an
+5 volts and 0 volt, respectively. interfacing. easy question to answer, since we
In a parallel interface, eight data deal with analog such events as tem-
bits are transmitted or received si- perature, speed, etc., every day of
cussing them in enough depth to il- multaneously on eight parallel lines our lives. Therefore, an analog event
lustrate the principles of interfac- called a data bus. The details of the is one in which the reading or mea-
ing, you should be able to devise typical parallel interface used in per- surement is infinitely variable be-
your own schemes to detect and sonal computers like those from tween two points. The possible volt-
monitor other physical phenomena, Commodore are given in Fig. 2, age events between 1 and 2 volts, for
such as pressure, voltage, current, which also shows the eight PB lines example, can be virtually any value
etc., among others. of the Commodore User Port. between these two levels, such as 1.1
To read the binary number on the volts, 1.00009 volts and any number
port, you add the decimal values re- up to and including 2 volts, with any
A Brief Refresher presented by the Is under Binary number of decimal places. As you
Before you can consider interfacing Values, reading from bottom to top, can readily see, the voltages can vary
procedures for a computer, you must assigning a 1 for all PB lines that are by infinitesimal amounts, making
be thoroughly familiar with binary at 5 volts and a 0 for all PB lines that the possible number of readings
numbers as they relate to interfacing are at 0 volt. Hence, the binary num- infinite.
voltages. In the Commodore series ber in this example is 10011010. In contrast, a digital event occurs
of computers (indeed, any personal Translating this binary number, you in a discrete, predefined step. A sim-
digital computer currently in use), a would obtain a decimal value of 89 ple example of this is an electrical
binary 1 is equal to 5 volts, while a bi- (1 +0 +0 +8+ 16 +0 +64 +0). light switch that can be either on or
nary 0 is equal to 0 volt, as illustrated As its name implies, in a serial in- off, with no positions in between. A
in Fig. 1. In practice, though, there is terface, the same information can be rising voltage that is digitally plotted
a bit of "play" in each case. That is, transmitted and received over a line against time would not trace a
the 5- and 0 -volt figures are only ap- consisting of only two conductors, smooth, continuous line, as in the
proximate; the actual voltages re- one bit at a time. Figure 3 illustrates case of plotted analog events, but
quired to initiate either binary level how this is accomplished. The first would jump in increments that re-
need approach only a volt or so of bit transmitted or received is bit 7. semble a staircase. The illustration
the + 5- and 0-volt levels. The clocking line correlates the pre- shown in Fig. 4 shows how analog

DECIMAL DATA SIGNAL BINARY

Fig. 2. On a parallel I/O bus, eight data bits are transmitted or
EQUIVALENT BUS LINES VOLTAGES VALUES received simultaneously.
128 PB7 0

64 PB6 1
Fig. 3. On a serial I/O arrangement, one bit is transmitted or re-
32 PB5 0
ceived at a time.
16
8

4
PB4
PB3
PB2
JL 0
1

1
Binary values 1 0 0 1 1 0 1 0

Serial line
2

1
PB1

PBO

10011010 (Binary) = 89 (Decimal)

_L 0

i
Clocking line

0 2 3 4 5 r; 7
Bit number 1

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 47

 Analog event tacts, as illustrated in Fig. 6. Two of connect it between the pot's wiper
Sample rate -e these are the serial and clocking lines lug and circuit ground to compare
for the serial register. Figure 6(A) the computer's displayed voltage
CD
shows the arrangement to use for C- values against those displayed on
ro
o Digital 128 and C -64 computers. The serial the voltmeter.
equivalent
and clocking lines for these two com- The serial register in Commodore
puters are at CNT2 and SP -2, respec- computers and the A/D chip is one
tively, on the User Ports. The ar- byte (eight bits) long. The largest val-
Time rangement to use for the VIC -20 ue one byte can contain is 11111111,
computer is shown in Fig. 6(B), which is decimal 255. With this 8 -bit
Fig. 4. A smooth analog line is repre-
which picks up the serial line at CB2 A/D chip, therefore, you have 255
sented digitally by a staircase-like possible increments between the min-
and clocking line at CB1 on the User
waveform.
Port. The other two lines that pro- imum and maximum voltages being
vide the clocking signal and chip-en- measured.
able function come from the com- The relationship between the max-
and digitally plotted data compare to imum 255 count of the A/D converter
puter's parallel port.
each other. When building the appropriate and Vref tells you what each incre-
Fig. 6 circuit for your particular ment represents with respect to the
Serial A/D Converter Chip computer, be sure to use a socket for voltage being measured. If the range
An analog -to- digital converter does the serial A/D chip. The outer lugs is from 0 to + 5 volts, each incre-
just as its name implies. It "reads" of the 10,000 -ohm potentiometer ment is 5 volts /255 = 0.01960788431
an analog voltage and then converts shown in both circuits must be con- volt per step. Each time the voltage
it to a specific digital (binary) value nected between + 5 volts and ground varies by this amount, the reading of
that the computer can use. This digi- at pins 1 and 4 of the A/D chip. The the serial point will vary one point. If
tal value is then fed into the computer. potentiometer's wiper then wires di- the computer is reading 100, the volt-
A TLC548 serial A/D converter rectly to the chip's analog input at age at pin 2 of the A/D converter
integrated circuit useful for our ap- pin 2. This control is used here for chip is 100 x 0.01960788431 =
plications is readily available at any testing purposes. 1.960788431 volts, or approximately
Radio Shack store (Cat. No. 276- Once you have breadboarded the 2 volts. By substituting different
1796) for just $6.95. This 8 -pin DIP appropriate circuit for your specific transducers for the potentiometer
chip, whose package configuration model Commodore computer, plug shown in the Fig. 6 circuit, you can
and pinout details are given in Fig. 5, the circuit assembly into the comput- have your computer measure levels
is extremely easy to interface to the er's User Port. (Note: Make sure to of light, heat, toxic gas and galvanic
Commodore User Port. It can han- turn off the computer before you at- skin resistance.
dle 40,000 samples per second and tempt to plug the card into or remove The BASIC programs used to de-
has an internal clock and an 8-bit it from the computer's User Port. If monstrate operation of the interface
conversion resolution. you plug or unplug the card while the is slow and cumbersome. Therefore,
To use this chip, you need four computer is running, you can irrepa- later on, we will use a machine -lan-
lines on your experimenter card that rably damage the A/D circuit, the guage program that works with the
has connector fingers that match up computer or both!) 60 -Hz interrupt to speed things up.
with your computer's User Port con- With the A/D card plugged into In the C- 128/C -64 and VIC -20 BASIC
the computer, turn on the power and programs (Listings 1 and 2), two ad-
type in and run the BASIC Loader ditional registers are being used aside
wp.46r Program for your specific computer from the parallel port (56579) that is
REF+ 1 8
Vcc (Program Listing 1 for C -128 and commonly used in interfacing proj-
I/O clock C -64 models or Program Listing 2 ects with Commodore computers.
Analog input 2 TLC548 ' for the VIC -20). Slowly vary the set- They are the 56588 Serial Register
REF - 3 6 Data output
ting of the potentiometer and note and the 56589 Interrupt Control Re-
GND 4 5 CS
the results on the computer's video gister. In the former, you PEEK the
monitor screen. The numbers dis- register to see what number the A/D
(TOP VIEW)
played on the screen represent the di- converter transmitted, while in the
Fig. 5. Case configuration and pin - gital equivalent of the voltage pres- later, you mask all interrupts.
out details for TLC548 serial A/D ent on pin 2 of the A/D converter. If The CRA Control Register, lo-
converter chip. you have a voltmeter handy, you can cated at 56590, controls whether the

/ January 1988 Say You Saw It In Modern Electronics

48 / MODERN ELECTRONICS
 1 8 1 8

10K 2 TLC548 7 2 TLC548 7

Serial A/D Serial A/D 6 NC

3 6 3

4 5
4

(REAR
VIEW)

12 L GND 12 1 L GND

11 K

10 J PB7

9 1 PBG PB6
SP-2
8 H PB5 PB5
CC

-I I
7 0a G PB1 PB4

CNT2 PB3 PB3

6 F
W
N
5 o E PB2 PB2

4 D PB1 PB1
I I. 1

3 C PBO PBO
I I

2 B CB1 r I

+5V
i A IGND

r (REAR VIEW) (REAR VIEW)

(A) (B)

Fig. 6. How a TLC548 serial A/D converter chip is used to interface the C-128 and C-64 (A) and the VIC-20 (B) to the
real-world environment.

serial line will be an input or an out- Listing 1: BASIC Loader for C -128 & C -64
put. This register has the proper con-
figuration needed on power -up; so it 2 REM ** SERIAL ANALOG TO DIGITAL CONVERSION **
REM ** FOR COM -128 AND COM -64 **
is not necessary to change it. You use 4 REM ** JOHN IOVINE 1987 **
the PBO line to provide the clocking 5 POFE56579, 255
pulse to both the CNT line and the 7 POI: E56577,0
A/D converter chip. PB I provides 10 POKE56589,127
12 FORX =0T07
the high -to -low pulse needed every 14 F'OKE56577, 0: POF..E56577, 1
eight clock cycles to start the chip 15 NEXTX
transmitting its latest conversion. 20 IF(PEEK(56589)AND8)= OTHEN20
The program for the VIC -20 oper- 30 X= PEEK(56588)
ates in a similar manner. Detailed in- 40 F'RINTX;
45 F'OKE56577, 2
formation is provided in the Pro-
SO GOT012
grammer's Reference Guide that
came with your computer to help you
to understand the serial register, in- which we will work are in the varia- will cause a change in the voltage
terrupt register and CRA. ble- resistance category. That is, as dropped across the transducer that is
the sensor (transducer) detects a sensed as a varying voltage at the an-
Transducers physical analog event, its resistance alog input at pin 2 of the A/D con-
The first of the transducer types with will change. The change in resistance verter chip. The voltage on pin 2 will

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 49

 Listing 2: BASIC Loader for VIC -20 Resistor RI in Fig. 8, in series with
the thermistor, is used to "scale" the
10 REM VIC SER IRO.PAS reading range of the system. With
15 REM J IOVINE the 47,000 -ohm value shown, the cir-
20 FORD= 7430T07510:READX:POKEJ,X:NEXT cuit will respond to a 0 -to -120- degree
30 SYS7463: NEW F range of temperatures. To change
40 DATA160 ,8,169,0,141,16,145,169.1 041,16.145 the response range, you must change
50 DATA136 ,192,0,208,241,173,29,145 .173,26,145
60 DATA133 ,255,169,2.141,16,145,108 .84.29.173,20,= the values of the voltage- divider re-
70 DATA141,84.29,173.21.3,141,85.29 020,169,6.141 sistors. If you do this, make sure you
80 DATA20 ,3,169.29.141,21,3,169,255 ,141,18.145,169 remain within the range detailed in
90 DATAD ,141.16,145,169,127,141,30, 145,165,122,141 the A/D chip's specifications sheet.
100 DATA27,145,88.96.234.234.234 Calibration of the temperature -
sensing setup is needed before using
the sensor for any critical measuring
applications. One way to do this is to
be displayed as before, with changes graphic analyses to determine what immerse the thermistor "probe" in
in the transducer's resistance track- elements are in an unknown corn- first ice water and then in boiling
ing in much the same manner as oc- pound or even to determine the corn- water and make a note of each read-
curred before with the test poten- position of our Sun or other star. ing obtained. The first number re-
tiometer. Temperature. To measure tern- corded is equivalent to 32 degrees F
Light. A cadmium -sulfide (CdS) perature, you simply substitute a (0 degree C), the second to 212 de-
cell like the Radio Shack Cat. No. thermistor for the CdS photocell in grees F (100 degrees C).
276-1657 changes its resistance in ac- the previous example, as shown in Toxic Gas. A toxic -gas sensor re-
cordance with the intensity of the Fig. 8. The thermistor must have a sponds to a wide variety of air -borne
light that strikes it. Resistance is negative- temperature coefficient toxic and not -so-toxic compounds,
greatest in complete darkness and (NTC) whose resistance decreases as including natural and butane gases,
decreases in proportion to the inten- temperature increases, as shown in kerosene and gasoline, and even per-
sity of the light it detects. Figure 7 the resistance plot in Fig. 8. Using a fumes and colognes. It operates in a
shows the simplest method of con- Digi-Key Cat. No. KCOO6N-ND ther- manner similar to that of of the ther-
necting a CdS cell to the A/D mistor, whose resistance at 25 de- mistor in that as it detects a "toxic"
converter. grees C (77 degrees F) is 10,000 ohms compound its resistance decreases.
There is a disadvantage in this par- and maximum operating tempera- Figure 9 illustrates how a Figaro
ticular arrangement in that only half ture is 150 degrees C (302 degrees F). TGS812 toxic -gas sensor ($12 from
of the converter's possible 255 count
range (128 to 255) is being used. This
is easily corrected with the circuit in
which two 1,000 -ohm resistors in se- CdS
ries make up a voltage- divider net- photocell
(all other circuitry
-
work that changes Vref from 0 volt R1
1K
z
TLC548
Serial ND remains
to 2.5 volts. The voltage -per -step fig- a
the same)
ure also changes to 2.5 volts /255 = R1
R2
22K 4
0.00980392157 volt per step. Thus, 1K

simply by adding the voltage divider

to the basic circuit, potentials be- 800n«m
tween 2.5 volts (- Vref) and 5 volts 255
( + Vref) can be read, providing a Output not linear
throught spectrum
full -scale reading with a simple CdS
photocell. Photocell C
Using the Fig. 7 arrangement, a linear
travel
photographer could use his comput-
er as an exposure meter for his en- o
400 800
larger. In the laboratory, this ar- PRISM 400nm Output (nm)
rangement could be used as a spec-
trophotometer to perform spectro- Fig. 7. Interfacing a photocell to the computer to measure intensities of light.

50 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 minute or so warm -up period before biofeedback device, which makes it

:C
A
it will respond as it should. The necessary to make occasional ad-
warm-up time required thereafter justments to the circuit.
should decrease with successive uses, Because the circuit must have a
a)
until it settles down to a fairly brief very high sensitivity to produce mea-
(7)

7i) R1 interval whenever you fire up the surable voltages, a 741 operational
ai
cc
47K sensor. amplifier is used in conjunction with
B After the warm -up period has a bridge circuit to drive the serial
elapsed, you can test the sensor A/D converter chip. Bipolar power
around your home, workshop and -
(V + and V with respect to circuit
Temperature garage. For example, you can release ground) required by the op -amp por-
the gas form a butane lighter (make tion of the circuit is provided by a
Fig. 8. Interfacing an NTC thermis- sure there is no flame!) into the sen- pair of 9 -volt transistor batteries,
tor to the computer to measure sor and note the reading. As I was while power for the A/D converter
temperatures. performing this test, I noted that the chip is obtained from the computer's
reading immediately jumped from a User Port, as was the case in pre-
base line of 0 to a full 255. Breathing vious circuits.
Figaro Engineering, Inc., P.O. Box on the sensor will register the level of Use a pair of dimes as the elec-
357, 322 Wilshire Dr. East, Wil- carbon dioxide of an exhalation. trodes. Solder the dimes to the wires
mette, IL 60091; tel. 312- 256 -3546) You can also make tests with various at one end of a short (24 -inch or so)
connects to the A/D converter chip. cleaning fluids and solvents and the length of two -conductor cable. Con-
The heater coil between pins 2 and 5 exhaust from your car. nect the other end of the cable into
of the sensor requires 5 volts dc at ap- Biofeedback. The biofeedback the circuit at ground and the negative
proximately 115 milliamperes for the arrangement shown in Fig. 10 has ( -) side of the battery in the bridge
sensor to operate. Because this cur- two obvious uses: lie detection and circuit, as shown. Then wire the rest
rent is somewhat beyond what Com- stress measurement. It is designed to of the circuit exactly as detailed. You
modore computers can provide at detect changes in galvanic skin re- can use either 1N914 or 1N4148 sili-
their User Ports, a separate dc supply sistance. con diodes for Dl, D2 and D3.
must be used. Shown is a 9 -volt bat- A person's galvanic skin resistance To use the biofeedback monitor,
tery that feeds a 7805 fixed + 5 -volt at any particular moment is an indi- place a fairly wide ('''h inch or wider)
regulator to provide the required 5 cator of his current state of rubber band around the wrist of the
volts dc. If you expect heavy usage of stress /tension. This base -line con- subject to be monitored and slip the
this sensor, you might consider using ductance will vary as you use the dimes between the rubber band and
a commonly available plug-in power wrist skin about 2 inches apart, un-
supply that has an output of at least soldered side toward skin. The rub-
7.5 volts dc at 250 milliamperes or OUT
ber band should make a snug fit but
more to avoid having to frequently COM
lora should not be tight enough to cut off
replace spent batteries. blood circulation.
=9V
The Figaro TGS812 toxic -gas sen- Set both potentiometers to about
sor specified contains two sensing el- 4 or 6
the center of rotation and turn on the
ements. When connecting this device system. Depending on whether you
into the circuit, use pins 1 and 4 or 3 47K are using the biofeedback monitor as
and 6. Pins 1 and 3 are connected to a lie detector or stress -level monitor,
each other internally, as are pins 4 1" adjust RI until you reach a point
and 6. Polarity is not important for (approx) where a small amount of rotation
either the heater coil or the sensor produces a reading that jumps up or
elements. down a significant amount; this is
TGS812
When you fire up the toxic-gas (REAR VIEW) the trigger point. How you are using
sensor for the first time, you may no- NOTE: the monitor determines where to
tice that it becomes fairly warm to 1 and 3 = Internally connected
set RI.
the touch. This is the normal operat- 2 and 5 = Heater coil Potentiometer RS is used to adjust
4 and 6 = Internally connected
ing condition. In fact, when you fire the gain of the op -amp stage. Nor-
it up for the very first time, you Fig. 9. Interfacing a Figaro TGS812 mally, you will not have to adjust the
might have to give the sensor a 2- toxic -gas sensor to the computer. setting of this control.

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 51

 56K
R1

B1
9V-
+ 100K
R3
1K
NC
Y2 741
B

7
NC
R5
1M
R6
150K

Op amp
C1 D1 D2 3 6

0.1µF 1N914 1N914 R7

4 6 NC
2.2K (all other
circuitry
= R4
._ TLC548
2
o remains
Electrodes 1K 01+
Serial A/D
R8 3 the same)
B2 B3
9V 9V 2.2K
4

Fig. 10. A biofeedback arrangement for using the computer as a lie detector /stress-measuring device.

To use the monitor as a lie detec- Listing 3: Machine -Language Program for C -128
tor, adjust the setting of RI until you
obtain a reading that is just a bit 100 REM JOHN IOVINE
120 FORJ=4864T04937:READX:POKEJ,X:NEXT
above O. Pressing the electrodes 130 8N/84897: NEW
firmly against the skin of the subject 150 DATA160,8,169,0,141,1,221,169,1,141,1,221,136
being monitored should cause the 160 DATA192,0,208,241,17.3,13,221,173,12,221,133,255
reading to jump to 255. Releasing the 170 DATA169,2,141,1,221,1C)8,16C),19,173,20,3,141,160
pressure should cause the reading to 180 DATA19,173,21,3,141,161,19,120.169,C),141,20,3
19C) DATA169,19,141,21,3,169.255,141,3,221,169,0,141
settle back to about the point from
200 DATA1,221,169,127,141,13,221,88,96,0
which it started. (Remember to at-
tach the electrodes to the subject be-
fore adjusting R1.)
When you ask a question that mind can be in a state of high -level achieve an even greater state of
evokes an emotional response, the awareness, even though your body relaxation.
displayed readings will increase. might be relaxed. With practice, The reason you do not set the bio-
Anything that evokes a strong emo- your ability to quickly reach a state feedback monitor to 0 or 255 when
tional response can be detected by of relaxation will become second - adjusting RI is that you can over-
this device. Be aware, though, that nature even without the biofeed- compensate. This could make read-
the nature of a question, regardless back monitor to keep tabs on your ing the changes occur below or above
of the response given, can cause a progress. 255. Until you become fully familiar
"lie" response. Hence, even if an an- You can also reset the project to with operating the biofeedback mon-
swer is truthful, you can get a lie indi- give a reading of almost 255 after itor, it can be frustrating to set the
cation if the subject is highly charged you have zeroed it out so that you potentiometers for a good reading.
emotionally. Keep this in mind when can try again to lower the readings to The solution, of course, is to give
you use the monitor.
To use the biofeedback monitor to
reduce stress, place the electrodes on Listing 4: Machine- Language Program for C -64
your wrist and adjust RI until the 1.0 REM JOHN IOVINE
displayed reading is almost 255. 20 FORJ= 40710T040785 :READX.:POKEJ,X:NEXT
Then sit back and relax by imagining 30 SYS40743: FOKE56, PEEK (56) +1 NEW :

yourself to be in any place or situa- 40 DATA160,8, 169, 0,141,1,221,169,1,141,1,221,136

tion you find soothing. As your body 50 DATA192,0,208, 241 ,173,13,221,173,12,221,133,255
responds (relaxes) more and more, 60 DATA169,2, 141,1, 221,108,79,159,173,20,3,141,79
70 DATA159,173,21,3 ,141,80,159,12[),169,6,141,20,3
the displayed readings will begin to 80 DATA169,159, 141 ,21,3,169,255,141,3,221,169,0
fall toward O. 90 DATA141,1, 221, 169 ,127,141,12,221,88,96,0,255,74
It is interesting to note that your

52 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 Listing 5: Machine- Language Program for VIC -20 After typing in and SAVEing the
specific version of machine -language
2 REM ** VIC 20 SERIAL A/D BASIC ** Listing for your particular comput-
4 REM ** JOHN IOVINE 1987 ** er, RUN it. Then type in the follow-
10 POK.E37138, 255
20 POKE3715O, 127: REM INTERUPT FLAG ENABL ing line:
30 FOK.E37147 12: REM AUXILIARY CONTROL REG
,
10X = PEEK(255):Print X:GOTO 10
35 F'OKE37136.2
40 FORX =OTO7 This one -line modification will print
50 POKE37136. 1: F'OKEv7136, 0 serial A/D conversions. The pro-
60 NEXT gram is not affected by the RUN/
70 X= (PEEK(37149)AND4):REM SERIAL FG
STOP key, but a RUN /STOP and RE-
80 X= PEEK (37146 )
STORE will reset the vector. To reini-
90 PRINT X;
95 POKE37136,2 tiate the program, SYS the number
100 GOT040 in the program.
Be sure to SAVE the program be-
fore you RUN it because it automati-
cally erases itself from memory!
yourself time to learn the apparatus, memory at location 255. All you Interfacing your computer to the
its capabilities and limitations. need to do is PEEK the location for real -world environment opens up an
the current value. BASIC Listings 1 exciting new area for experimenting
A/D Interrupt and 2 are not needed when using the and practical applications. The few
The A/D interrupt programs read machine -language programs given in applications presented here should
the A/D chip 60 times each second Listings 3, 4 and 5 for the C -128, get you started on devising others of
and place the information read into C -64 and VIC -20, respectively. your own. AE

INNOVATIVE PROJECTS FROM THE

4 PAGES OF "MODERN ELECTRONICS"

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Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 53

Project

A Low -Cost
Function Generator
This project delivers individually adjustable sine,
triangle and square waves simultaneously over a
frequency range of less than 1 Hz to almost 300 kHz
into almost any load impedance
By Anthony J. Caristi
Acommercial multipurpose
signal source that can deliv-
er a wide range of signal
waveforms and frequencies into al-
most any load impedance usually
costs $200 or more. With modern in-
tegrated- circuit technology, how-
ever, high cost need not be the case.
The sine /triangle /square -wave func-
tion generator to be described is such
an example. Built around a relatively
inexpensive precision waveform gen-
erator chip from Intersil, the entire
project costs less than $50 to build,
including enclosure.
Depending on choice of options,
the function generator can be made
to cover a frequency range of less
than 1 Hz to almost 300 kHz. The
square -wave output has a respecta-
ble risetime that is close to 0.1 micro-
second, and sine -wave distortion is
typically less than 2 percent. Output
impedance, at less than 1 ohm, (IC3) that has been designed by In- three overlapping frequency ranges
makes the generator suitable for tersil to serve as a precision wave- covering 15 Hz to 100 kHz can be se-
driving almost any load to be en- form generator /voltage -controlled lected with RANGE switch S2.
countered in modern electronic cir- oscillator with only a minimum of Since the chip's operating fre-
cuits. Hence, except for extremely external components. Operating fre- quency is inversely proportional to
critical applications, this generator is quency is selected externally by the value of capacitance used, the
suitable for use on both a hobbyist's means of a given value of capaci- choice of values can be changed to
and a professional's testbench. tance connected between pin 10 of suit individual requirements. Also, if
the chip and the negative ( -15 -volt) you want a greater range or operat-
supply rail and the voltage applied to ing frequencies, you can add bands
About the Circuit pin 8 by means of potentiometer R2. simply by using a rotary switch with
As shown schematically in Fig. 1, the Possible range from this IC is 0.001 a greater number of positions to ac-
function generator is designed Hz to almost 300 kHz. With the commodate more capacitors.
around a low -cost integrated circuit values specified for C6, C7 and C8, For any given value of capacitance

54 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

inserted between pin 10 of 1C3 and square waveforms appear at pins 2, 3 . R11 and R14) and three output buf-
the 15-volt rail, the frequency ad- and 9 of 1C3. Amplitudes of the sine fer amplifiers (105, IC4B and IC4A,
justment range provided by R2 is and triangular waveforms are about respectively) so that each of the
about 40:1. For the values shown for 6 and 9 volts peak -to -peak, respec- waveforms can be independently ad-
C6, C7 and C8, the frequency bands tively. The square -wave output is justed over a range of at least 12 volts
are 15 Hz to 600 Hz, 500 Hz to 20 about 25 volts peak -to -peak. peak -to -peak. With an amplitude of
kHz and 2.5 kHz to 100 kHz. Note that the circuit contains three 12 volts peak -to-peak, the sine wave
Simultaneous sine, triangle and amplitude adjustment controls (R8, is equal to 4.2 volts rms.

+15V o C10

'-
10pF
D3
1N4148_1
RG,
4 7K :
C9
100µF
I-
R9
R1
R10
R5 < 22K
R4 R8
470 5.11K Ç
5.11K 100K J3
Square
output
C5 LF353N
R2 0.1µF R12
10K R13
IC3 R11
FREQUENCY 15K
ADJUST
8038 20K 7
J2
O
IC4B Triangle
output

R15
R3 11 12 R16
S2 10K
10K RANGE
R14 22 K
1O- 3
20K o J1

C8 4 IC4A Sine
z
C6 0.001 µF LF353N output
0.15µF
R7
C7
82K
T0.0047µF
15V o

PARTS LIST R3,R10,R12,R15- 10,000 ohms T1 -12.6-volt power transformer (Radio

Semiconductors R6 -4,700 ohms Shack Cat. No. 273 -1385A or equiva-
Dl,D2- 1N4001 rectifier diode R7- 82,000 ohms (see text) lent)
D3- 1N4148 diode R9,R16- 22,000 ohms Printed -circuit board or perforated
IC1- LM7815CT + 15 -volt regulator R13- 15,000 ohms board with holes on 0.1 -inch centers
IC2- LM7915CT - 15-volt regulator R4, R5 -5,110-ohm, 1% tolerance metal- and suitable soldering or Wire Wrap
IC3- ICL8038 precision waveform gen- film hardware; suitable enclosure (see text);
erator (Intersil) R2-5,000 -ohm linear -taper panel - ac line cord with plug; pointer -type
IC4,IC5- LF353N high -slew -rate op mount potentiometer control knobs (5); two 8 -pin and one
amp R8- 100,000 -ohm linear -taper panel - 14 -pin DIP IC sockets; dry- transfer
mount potentiometer lettering kit and clear acrylic spray or
Capacitors (25 WV or more) R 11, R 14- 20,000 -ohm linear -taper pan- tape labeler (see text); 1/2-inch spacers;
Cl,C2- 220-µF electrolytic el -mount potentiometer machine hardware; hookup wire; sol-
C3,C4,C5- 0.1 -µF ceramic disc der; etc.
Miscellaneous
C6- 0.15 -µF ceramic disc or paper F1 -1- ampere slow -blow fuse Note: The following items are available from
C7-0.0047 -µF ceramic disc or paper I1 -Panel -mount neon-lamp assembly A. Caristi, 69 White Pond Rd., Waldwick,
C8-0.001 -µF ceramic disc or paper with current -limiting resistor
NJ 07463: Ready-to -wire pc board, $8.95;
C9- 100 -µF, 35 -volt electrolytic 7815 and 7915 regulators, $2.95 each;
C10-10 -pF ceramic disc J1,J2,J3 -Phono jack, binding post or ICL8038 precision waveform generator,
C11- 22 -SF, 35 -volt electrolytic other suitable output connector $9.95; LF353N high -slew -rate op amp,
S1 -Dpdt toggle switch $3.50 each; two 5,110-ohm, 1- percent toler-
Resistors (1/4-watt, 5% tolerance) S2- Single -pole, three -position, non - ance resistors, $1.25. Add $1 P&H. New
RI -470 ohms shorting rotary switch (see text) Jersey residents, please add state sales tax.

Fig. 1. Basic schematic diagram of the sine /triangle/square -wave function generator.

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 55

 IC1 OUT
N
o +15V
H 78 15
D1
COM
1N4001
F1 Cl C3
12.6Vac 0.1µF
1A 220µF
. C11
220µF

S1B C4
C2
220µF COM 0.1µF
117Vac INI 1C2 OUT
o 15V
o o 7915
D2
7815 7915 1N4001

IN I I I OUT (.15V) COMI I I OUT ( -15V)

COM IN

Fig. 2. Bipolar power supply for function generator.

Output impedance of the function conditions of this project, the power rectly on the board without the use of
generator is less than 1 ohm, as pro- transformer specified in the Parts sockets. Since very little power is
vided by operational amplifiers IC4 List for T1 will provide sufficient drawn by the circuit, you do not need
and 105. To preserve the fast rise - output voltage at a 117 -volt ac line heat sinks on the regulators.
time of the square -wave output at J3, potential. Figure 3 shows the component lo-
a high -slew -rate LF353N op amp was Power transformer TI drives a bi- cations and orientations for populat-
chosen. Because ordinary op amps polar voltage doubler to provide the ing the printed- circuit board. Use
will not produce fast risetimes, they necessary positive and negative volt- this illustration as a guide to laying
should not be used in this circuit. ages to the regulators. Ripple voltage out the components on perforated
The low output impedance of this fed to the inputs of ICI and 1C2 is board as well.
generator can source a reasonable kept sufficiently low by filter capaci- Wire the board exactly as shown,
amount of current into virtually any tors Cl and C2. Though larger installing first the IC sockets in the
load impedance. The outputs of the values of filter capacitance can be appropriate locations and then pro-
circuit are direct -coupled to preserve used, avoid using values that are too ceed to the resistors. Next, install the
low- frequency response and should small or power supply ripple will ap- electrolytic capacitors and diodes,
not be connected to any circuit that pear at the outputs of the regulators taking care to properly orient them
has a dc component unless a block- and, ultimately, in the output wave- before soldering their leads to the
ing capacitor is used. forms at Jl, J2 and J3. pads on the bottom of the board.
Since the oscillator chip's output When installing regulators ICI and
waveforms are sensitive to power -
Construction IC2, make certain each goes in its re-
supply ripple voltages, it is necessary This circuit is simple enough to be spective location and is properly
to use stable and pure dc voltages for hard wired on ordinary perforated based. Referring back to Fig. 1, note
the + 15 -volt and - 15 -volt supplies. board with holes on 0.1 -inch centers the differences in pin identification
As shown in Fig. 2, this is accom- and using suitable solder or Wire for the + 15 -volt 7815 and - 15-volt
plished with fixed + 15 -volt ICl and Wrap hardware. Alternatively, you 7915 regulators.
fixed - 15-volt IC2 regulators. can use a printed-circuit board fabri- RANGE switch S2, the output am-
To assure ripple -free outputs, the cated yourself using the actual -size plitude controls, and the SINE, TRI-
unregulated voltages fed into the in- etching- and -drilling guide shown in ANGLE and SQUARE OUTPUT jacks all
puts of the regulators should be at Fig. 3 or a ready -to -wire board from mount off the board, oin the front
not less than 18 volts. The transfor- the source given in the Note at the panel of the selected enclosure.
mer used to power this project end of the Parts List. Whichever way When wiring potentiometers R2, R8,
should deliver at least 14.5 volts rms you choose to go, use sockets for RI and R14 into the circuit, all ad-
at the lowest ac line voltage that will IC3, 1C4 and 105. justments should go in the clockwise
be encountered. Under the light load Regulators ICI and IC2 install di- direction to increase frequency and

56 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

amplitude. If you have any doubts as
to what potentiometer lugs wire to
which holes, you can use an ohmme-
ter to make the final determinations.
Other components that mount off
the board include pilot -lamp assem-
bly Il (which consists of a neon lamp
and current -limiting resistor in a
panel -mount housing), POWER
switch SI and fuse Fl. These also
mount on the project's front panel,
except Fl , which mounts near the en-
try hole for the ac line cord.
Select an enclosure that is large
enough to accommodate the circuit -
board assembly, controls, jacks,
POWER indicator and fuse holder
without crowding. You can use a Fig. 3. Actual-size etching-and -drilling guide offunction generator's printed-
plastic enclosure with a metal front circuit board.
panel or an all -metal enclosure. Ma-
chine the front panel so that the the Place on the shafts of the rotary the components permanently. Tight-
mounting holes for R14, RII and R8 RANGE switch and all potentiometer ly twist together the fine wires in each
form a line across the front of the controls a control knob. Note dis- conductor of the line cord and spar-
panel along its center axis. Strike a tances away from the holes the panel ingly tin with solder. Pass the pre-
line 1 IA inch below the control hole markings are to go. Then remove all pared end of the line cord through its
line and parallel to it and drill the components from the panel and set hole (line the hole with a small rub-
holes for the jacks or binding posts. them aside. ber grommet if you are using a metal
Then the same distance above the Using a dry-transfer lettering kit enclosure) and tie a knot in it about 6
control holes and centered between or a tape labeler, label the panel with inches from the end inside the enclo-
the first and second and the second appropriate legends. If you use a sure to serve as a strain relief. Then
and third drill the holes for mounting dry- transfer lettering kit, follow up mount the fuse holder.
the rotary switch and remaining con- with two or three light coats of clear Wire the neon -lamp assembly
trol. The POWER switch and lamp
assembly mount in two other holes
acrylic spray to protect the legends.
When the panel is ready, mount
across the POWER switch's open
not toggle- contacts but do not sol-
-
drilled in out -of- the -way locations.
When you are finished machining
the front panel, drill the entry hole S1A
for the ac line cord through the en- li COM IN CUT

closure's rear panel. For the fuse IC2

C2 ---C11
holder, you can use either a clip type R2
C4
that mounts via a single machine -R3- I
R11

screw or a more convenient (and ex- -R7- J2F -R13-

-R12-
S114-.
pensive) panel -mount bayonet type.
The size of the mounting hole needed T1 Z IC3 I 104 IC5
will depend on the type of holder
R14
used. Only two more holes remain to
be drilled -for mounting the circuit - I \,/
--R5--
R4
-R10-
R11 -R15-
board assembly on the floor of the R2 -D3-
enclosure, via the same holes that
mount Ti to the circuit board. De-
burr all holes.
sl D1

IN
K D2

COM
IC1
-K 4.

OUT
Cl
R;3

J2
-R16-
i
-R9-
11

Temporarily mount the controls, NOTE: 'Indicates control wiper (center lug). R14 R8
switches and jacks in their respective
locations in the proper orientations. Fig. 4. Wiring diagram for pc board and layout for perforated- board.

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 57

der. Remove 'A inch of insulation OFF if it is properly wired into the cir- charge. Then carefully plug IC3, IC4
from both ends of 22 5 -inch lengths cuit), indicating that ac line power is and IC5 into their respective sockets.
of hookup wire. Plug one end of being delivered to the circuit. Make sure that each is installed in the
these wires into the signal and Now use a dc voltmeter set to mea- proper orientation and that no pins
ground holes for JI, J2 and J3 (six sure at least 25 volts to check the out- overhang the sockets or fold under
wires); the holes for S2 (four wires); puts of the voltage doubler. Connect between ICs and sockets.
and the holes for R2, R8, R11 and the meter's common lead to circuit Use an oscilloscope to check the
R14 (12 wires). Mount the circuit - ground at the negative side of Cl and outputs of the function generator.
board assembly using 'h -inch spac- touch the "hot" meter lead to first Set the generator's amplitude con-
ers and machine hardware. the positive ( + ) side of Cl and then trols to maximum clockwise rotation
Connect and solder the free ends the negative ( -) side of C2, which to obtain maximum output ampli-
of the two wires for Ti's primary to should yield readings of about tude and turn on the project. Exam-
the same lugs of the toggle switch to + 19.5 and -19.5 volts, respective- ine the waveforms at Jl , J2 and J3,
which Il is connected. Wire one side ly. Without removing the common where you should observe sine, trian-
of the fuse holder to one toggle lug of meter lead from where you connect- gular and square waveforms, respec-
the toggle switch and the line cord to ed it, touch the meter's hot lead to tively, of about 12 volts peak -to-
the other toggle lug and the remain- first the positive and then the nega- peak. If you note that any one or all
ing fuse-holder lug. tive leads of Cil, which should give of the waveforms are displayed at
Referring to Fig. 4, connect and readings of between + 14.5 and minimum amplitude, the potentiom-
solder the free ends of wires on the + 15.5 volts and between -14.5 and eter for that output amplifier is wired
circuit -board assembly to the appro- -15.5 volts, respectively. backward and must be rewired for
priate lugs of the panel- mounted po- If you do not obtain the proper proper operation.
tentiometers. Remember that you voltage readings, check for proper Rotating the FREQUENCY ADJUST
want the controls to be wired so that orientation of DI, D2, Cl, C2 and control over its entire range should
clockwise rotation increases fre- Cll. Also, check with Fig. 4 to ascer- cause the frequency to vary over a
quency in the case of R2 and in- tain that IC1 and IC2 are each in 40:1 range, with the frequency in-
creases amplitude of the output sig- their respective locations and are creasing as the control is rotated in
nals for the other potentiometers. Fi- properly wired into the circuit. the clockwise direction. Check each
nally, connect and solder the last of Check the ac potential at the secon- output individually. If you note a de-
the wires to the OUTPUT connectors. dary of T1, which should measure at crease in frequency as this control is
least 14.5 volts rms ac. With the line rotated in the clockwise direction,
cord unplugged, check to see if the the potentiometer is wired back-
Checkout and Use -
+ 15 -volt and 15-volt supply rails wards and must be rewired for prop-
Before you attempt to apply power are shorted to each other. Do not er operation. If the extreme clock-
to the generator, check the circuit - proceed until you have cleared up the wise or counterclockwise settings of
board assembly for poor soldered problem. this control result in a distorted
connections and possible short cir- Plug the project's line cord into an waveform or no waveform at all at
cuits between the closely spaced con- ac receptacle and turn on the power. the outputs, you can tailor the limit
ductors and especially between the Set your meter to measure at least 20 of the adjustment range by increas-
IC socket pads. Reflow the solder on volts dc. Connect its common lead to ing the value of RI or R3 as needed.
any questionable connections. the negative lead of Cl and touch the This generator is capable of pro-
With IC3, IC4 and IC5 still not in- hot meter lead to pin 6 of the IC3 ducing a sine -wave output with a dis-
stalled, check the power supply sec- socket and pin 8 of the IC4 and 105 tortion figure of less than 2 percent.
tion for proper operation. Plug the sockets. You should obtain a reading If you see some distortion, you can
project's line cord into an ac outlet of + 15 volts in all three cases. Simi- increase or decrease the value of R7
and set the POWER switch to ON. (Be larly, you should obtain a - 15-volt to obtain the purest possible wave-
very careful to avoid touching any reading when you touch the meter's form. A variation of 20,000 ohms in
part of the circuit between the ac line hot lead to pin 11 of the IC3 socket either direction should be more than
cord and Tl's primary as you per- and pin 4 of the 1C4 and IC5 sockets. enough to produce an optimum dis-
form your tests. Potentially lethal When you are satisfied that the tortion level.
117 -volt ac line potential appears in power supply is working properly If you do not obtain output wave-
this section of the circuit.) The neon and that the power rails are correctly forms at all, check pins 2, 3 and 9 of
lamp should now be on (it should be wired to the IC sockets, unplug the IC3 to make sure the chip is oscillat-
off when the POWER switch is set to line cord and give Cll time to dis- ing and generating the three wave-

58 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 **

forms. If the waveforms are present

2 CENTS PLAIN
at these pins, the trouble is in output
buffer amplifiers IC4 and /or IC5. * *
If IC3 is oscillating, check the wir-
That's about all it costs subscribers for each page
ing associated with the FREQUENCY of editorial matter in MODERN ELECTRONICS .. .
ADJUST potentiometer and BAND every month. No charge for informative advertisers'
switch. Also make sure that D3 is messages. Or for free information requested on our
properly connected into the circuit. bound -in postpaid Free Information Service card.
To demonstrate the low -impe-
A bargain? You bet! MODERN ELECTRONICS is a
dance characteristics of the function
veritable one -stop source of "hard" information for en-
generator, set the project for a rela- thusiasts whose interests spread across the entire
tively low frequency (say, 1 kHz) spectrum of electronics and computers for work and
that can be easily "read" on an ac play. The latest technical information and news writ-
voltmeter. Set the amplitude of the ten by a galaxy of authoritative writers Forrest Mims
on "Experimenting," Don Lancaster on "Hardware
-
sine -wave output at J1 to 1 volt rms
Hacking," Stan Prentiss on "Video," Len Feldman on
on the voltmeter. Connect a 100 - "Audio," Glenn Hauser on "Communications," and
ohm, '/ - or 1/2-watt resistor across Eric Grevstad on "Personal Computers," to name a
JI and note that the resulting voltage few authors who share their specialized experiences
drop is very low, perhaps on the or- with readers every month.
der of a few millivolts. This indicates
This neat package keeps everyone abreast of the
that the output impedance of the important developments in electronics and comput-
generator is very much less than 100 ers. From new devices and circuits to useful construc-
ohms. A mathematical calculation tion projects to evaluations of the latest products.
of the output impedance using the Both "how to do" and "how it works" information in-
voltage -drop method would yield an creases your technical competence every page of the
way. Two cents a shot. And hands -on product evalua-
impedance of less than ohm.1
tions make you a wiser buyer, whether it's on a test in-
Of course, the generator cannot strument or a video recorder. So whether you're a ser-
drive its full output of 4 volts rms in- vice technician, an engineer, a budding one in a techni-
to a very -low impedance like 100 cal career path, or an active electronics enthusiast,
ohms. However, you will find that it MODERN ELECTRONICS will serve you well. Sub-
scribe and be sure to get every information -packed is-
will be able to drive about 0.5 volt sue delivered to you every month. It's important read-
rms into 50 ohms, which is respecta- ing you can't afford to miss!
ble at that impedance.
The procedure for using the func- Just fill out the coupon and mail with your check,
tion generator is very simple. First money order or credit -card information (Visa or Mas-
terCard) to enter your subscription. Do it today to en-
you select the output waveform(s) sure earliest delivery!
you want to use. Then you select the
band of frequencies needed and ad-
just the amplitude control(s) for a MODERN ELECTRONICS
usable signal level at the output(s). If 76 North Broadway, Hicksville, NY 11801
you are interested in a specific fre-
Please send me Modern Electronics for 3 Years 2 Years Year
quency, you adjust the setting of the 1

FREQUENCY ADJUST control until Name

you obtain that frequency. That is all
Street
there is to it.
City
With this function generator on
State Zip
your testbench, you will find that
whenever you need a variable signal
source to check amplifiers and Charge My Order To: Payment Enclosed S

speakers and for general trouble-

shooting, it is always ready. Best of LI MasterCard 3Years(36issues) $48.00
2 Years (24 issues) $33.00
all, you can build it for only a frac- O VISA 1 Year(12issues) $17.97D
tion of what it would cost you to pur- Account Number
chase a commercial instrument. AE

Say You Saw It In Modern Electronics January 1988 I MODERN ELECTRONICS / 59

 J111/ELECTRONICS NOTEBOOK//IllIll111=1
Touch Tone Remote Control

By Forrest M. Mims III are divided into a low group (679 to 941
Hz) and a high group (1,209 to 1,633 Hz).
1 3
The 1,633 -Hz frequency is omitted from
497 497 497
Though the Bell system developed the 1209 1336 1977 standard telephone keypads.
Touch Tone system specifically for tele- When a telephone key is pressed, one
communications applications, it is also frequency from both the low and high
well suited for use in remote control.
ti S
770 ,7o '770 groups are selected, and the two tones are
Touch Tone signals can be easily trans- 1209 1334 1`+77
superimposed on each other. Since
mitted by means of wire, radio and light. speech, transmission noise and DTMF
They can also be transmitted directly 7 8 tones can be simultaneously present on a
through the air as sound waves. 852 esa 652 telephone line, the Bell system carefully
1477
The Touch Tone system provides up to 1209 1334
designed the DTMF system to avoid in-
16 audio -frequency signals that can be terference from non -DTMF signals. The
used individually or, as when making tel- 0 40 Bell standard for DTMF signals allows a
ephone calls, in sequentially transmitted 941 94L 941
1977
maximum frequency deviation of ± (1.5
1209 1334
combinations. Several integrated circuits percent + 2 Hz). The minimum time re-
designed specifically for generating quired for a tone pair to be recognized is
Touch Tone signals are readily available. 40 milliseconds, and the required pause
These chips are designed to be used in Fig. I . Simultaneous tone frequencies for between tones must be at least 40 milli-
conjunction with a crystal that provides a a Touch Tone keypad. seconds.
highly stable timebase. Here is a complete listing of available
Most tone -based remote-control sys- DTMF frequency pairs in Hertz:
tems use a single frequency for each sig- the possibility of inadvertent false trig-
Signal Low Tone High Tone
nal. While these systems are easy to de- gering by interfering tones.
sign and build, they are very susceptible In the telecommunications industry, 1 697 1,209
to false triggering. For example, several the Touch Tone system is often referred 2 697 1,336
years ago, I developed a remotely con- to to as the Dual Tone Multi-Frequency 3 697 1,477
trolled camera system for taking photo- (DTMF) system. Figure 1 is a diagram of 4 770 1,209
graphs from kites and helium -filled bal- a pushbutton telephone keypad labeled 5 770 1,336
loons. The camera was triggered by with the frequency pair represented by 6 770 1,477
transmitting an audio tone from a hand- each key position. 7 852 1,209
held transmitter. The signal was detected Though not present on standard tele- 8 852 1,336
by a small radio receiver with an integral phone keypads, four additional frequen- 9 852 1,477
tone decoder. When the tone decoder de- cy pairs are available. The frequencies 0 941 1,209
tected the transmitted tone, it actuated 941 1,336
an optoisolator that tripped the camera's 941 1,477
shutter and advanced the film to the next A 697 1,633
frame. TO B 770 1,633
POSIT V8 C 852 1,633
Though I obtained hundreds of aerial
suPPLY D 941 1,633
photos with this system, sometimes the
R2
camera was tripped when no signal was 10
transmitted. The likely cause of this false Touch Tone Generators
triggering was other radio signals that To Q1
just happened to be modulated at the 2n,2t22 A Touch Tone remote -control system re-
SPEAkER
same frequency, if only for a fraction of our Pur quires a DTMF tone generator. DTMF
a second, as the tone from the system's
Ct tones can be generated by a pair of tran-
transmitter. LED sistor or integrated- circuit oscillators
The Touch Tone system was designed that have switchable precision resistor
to be largely immune to such interfer- networks for generating each of the re-
TO
ence. Instead of a single tone, each signal GROUnL D
quired tones. A much more reliable and
in the Touch Tone system is a pair of su- simpler approach is to use a crystal -con-
perimposed tones. While this arrange- trolled DTMF IC. Several such chips are
ment does not provide 100 percent noise Fig. 2. A LED modulator for a pocket available from major electronics parts
immunity, it does substantially reduce Touch Tone dialer. distributors.

60 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

Fig. 3. Two Radio Shack pocket -size Touch Tone (DTMF) dialers. Fig. 4. Internal view of a Touch Tone dialer showing the addition
of an interface socket.

Another solution is to salvage the avoid turning its rotor to either extreme. R /C, a major supplier of radio -control
DTMF tone encoder from a discarded If this should present a problem, add a equipment. These connectors are sup-
telephone. Besides a working DTMF cir- 1,000 -ohm fixed resistor in series with plied in matched plug /socket pairs. The
cuit, the telephone will be equipped with each leg of RI. socket is required for the modified dialer
a keypad. I have used the Fig. 2 circuit with two and the plug for the transmitter circuit.
Still another approach is to use a pock- different Touch Tone dialers purchased Before adding a socket to a tone dialer,
et -size Touch Tone dialer. These devices from Radio Shack, both of which are plan ahead. Make sure there is ample
are designed to permit a rotary telephone shown in Fig. 3. The unit on the left has a room for the socket, and be sure the tone
to access Touch Tone services. Some liquid-crystal display and includes a dialer is compatible with the LED driver.
Touch Tone dialers are equipped with a memory that can store 60 numbers that If you are uncertain about compatibility,
readout and enough memory to store up have up to 16 digits in each. It can also temporarily connect mini -clips or solder
to 60 or more telephone numbers. Mem- store pauses, and it has an automatic short lengths of hookup wire to the ap-
ory- equipped dialers can be used for so- shut -off feature. propriate terminals inside the dialer. You
phisticated remote -control applications. Referring back to Fig. 3, note that a can then connect these wires to the LED
small rectangular object protrudes from driver and determine whether or not the
An Infrared the top of both dialers. These are sockets combination works.
Touch Tone Transmitter that are connected to the dialer's elec- The Fig. 2 driver circuit works well
tronics. I installed these sockets to permit with both of the Touch Tone dialers
Touch Tone circuits can be easily adapt- various LED transmitters to be conve- shown in Fig. 3. The circuits used in these
ed to drive an infrared or high- brightness niently connected and removed. products, however, are subject to
red light-emitting diode. Figure 2 is the It's relatively easy to add an interface change. Nevertheless, should this hap-
schematic for a simple intensity -modu- socket to a commercial Touch Tone dial- pen, it is unlikely that the Fig. 2 driver
lated LED driver that is suitable for use er like the ones shown in Fig. 3. In doing circuit will require modification.
with Touch Tone generators. so, it is important to observe CMOS han- Figure 4 shows a close -up of how a
In operation, the driver biases the LED dling precautions to avoid permanent Dean's three-terminal socket can be in-
with a continuous flow of current. and disabling damage to the dialer's in- stalled inside the basic Fig. 3 tone dialer
DTMF signals arriving at the base of Ql ternal circuitry. Incidentally, you should (Radio Shack Cat. No. 43 -139). Adding
modulate the current through the LED, be aware that, in most cases, modifying a the socket shown in Fig. 4 requires only
changing the intensity of the light the commercial device voids its warranty. about 15 minutes of your time. First, it's
LED emits. Potentiometer RI controls Since the free space inside a dialer is necessary to cut a slot for the socket in
the bias level of QI and is used to allow limited, it is necessary to use a very small the dialer's plastic housing. Open the
the circuit to be tweaked for optimum connector. I have used Dean's three-ter- unit by inserting a thin tool in one of the
operation. When adjusting RI, be sure to minal connector available from Ace thin slots below the battery compartment

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 61

ELECTRONICS NOTEBOOK ..

Fig. 2. Their values were selected after Rl

was adjusted for optimum results when
the LED driver was used with the receiv-
ers to be described.

Touch Tone Receivers

Touch Tone receiver /decoder integrated
circuits are made by several manufactur-
ers. Precision switched capacitor filters
played a key role in the development of
such chips.
Silicon Systems Inc. and Teltone
Corp. both manufacture single -chip
DTMF receivers. I have experimented
with receiver chips made by both com-
panies, both of which require only a 3.58 -
MHz crystal and a single resistor. Both
chips have a single signal input pin and
four three-state binary-encoded output
pins. Let's look at how a receiver made
by each company can be used with a sim-
ple infrared detector /receiver to receive
Fig. 5. Breadboarded infrared LED driver Fig. 6. A miniaturized infrared LED driv-
and decode DTMF signals transmitted by
connected to a modified DTMF dialer. er plugged into a modified DTMF dialer. the Fig. 2 circuit.
Teltone M-957 DTMF Receiver. This
22 -pin DIP chip requires a positive sup-
and carefully pry upward. Repeat with piece of wrapping wire is used to connect ply of from 5 to 16 volts. Incoming sig-
the other slot. the left socket terminal to the positive nals can be directly or capacitively cou-
Before cutting the slot for the socket, power -supply terminal near the lower - pled to pin 12.
be sure it will fit. Ideally, the socket left portion of the circuit board. (Impor- Several control and output pins add to
should be positioned so that one of its tant: Observe CMOS handling precau- the M -957's versatility. A complete de-
terminals can be soldered directly to a tions when making these connections!) scription of this chip is given in its specifi-
power- carrying land or terminal on the A breadboarded version of the Fig. 2 cations sheet. Here are some of its key
circuit board. This is possible with both LED driver connected to the socket of features:
dialers pictured in Fig. 3. As can be seen the modified Touch Tone dialer is shown The A and B inputs at pins 8 and 9, re-
in Fig. 4, it's possible to solder one of the in Fig. 5. Connection to the socket is spectively, can be used to adjust the re-
socket terminals directly to a circuit - made by means of a right -angle MolexTM ceiver's sensitivity to incoming signals
board terminal connected to the negative connector. Using the Touch Tone dialer that have an amplitude of as little as 31
side of this dialer's three-cell battery with a breadboarded version of the LED dBm. Output Enable (OE) at pin 3 con-
power supply. driver permits the driver to be tested be- trols whether the output pins are active or
It is important to make sure that none fore a permanent version of the circuit is placed in a high- impedance state. The
of the socket's terminals touch the wrong assembled. hex input at pin 2 determines whether the
conductors on the circuit board. Refer- The breadboarded version of the four output pins provide a standard 4 -bit
ring back to Fig. 3, note that a small rec- transmitter pictured in Fig. 5 can be in- binary hexadecimal output or a 2 -of -8 bi-
tangle of tape has been placed below the stalled on a tiny perforated board that nary code.
socket's left terminal to isolate it from measures only 0.5 by 0.75 inch. Figure 6 The Strobe output at pin 18 indicates
the adjacent copper land. shows a miniaturized version of the cir- when a valid frequency pair is present at
After the right terminal of the socket is cuit plugged into the socket of the modi- the input. This output can be used to pro-
soldered to the negative supply land on fied Tone Dialer shown in Fig. 4. With vide a shift -left pulse for a digital readout
the circuit board, the center terminal of exception of the LED, all components controlled by shift registers. Normally,
the socket connects to the positive speak- and a three -terminal Dean's plug are in- pin 18 is at logic 0. When a valid DTMF
er terminal (indicated by a red dot) with a stalled on one side of the board. The two signal appears at the input and is verified
short length of wrapping wire. A second resistors shown in the photo replace RI in (decoded), pin 18 goes to logic 1.

62 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 HITACHI SCOPES
15 -25% Discount
V1060
100MHz
.A
.; fie' °' . i \$ 1375
V660 60MHz Dual Trace $990
4 TOr12v V422 40MHz Dual Trace $699
V212 20MHz Dual Trace $475

ELENCO PRODUCTS
AT DISCOUNT PRICES!
a 3 5 te 1'-
R1 R2 14
0
lOM 5.4K

2z. $498
15 M-957 marry
LI. 7 C = MO -1252
3 08 12
20
C1 W 3 B
D
Scopes
.0i 11 19 MO -1253 40MHz Dual Trace $550
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R3 1oOpF R6 1R4. R, 1R6 MO -1252 35MHz Dual Trace $498
5.41(
1K 11c 1K I1K MO -1251 20MHz Dual Trace $349
LEbs 1-4 wl Two lx, 10x 100MHz probes, manual
SOLAR
CELL. S -3000 10MHz fully calibrated $239
yylyl>,; GF -8016 Function Generator
with Freq. Counter

Fig. 7. A Touch Tone remote -control infrared receiver built around the Teltone chip. $239.95
'

Sine, Square, Triangle

Finally, output BD at pin 7 provides an can be decoded to provide 16 individual Pulse, Ramp, .2 to 2MHz
early indication of the presence of a pos- outputs, one for each DTMF tone, is il- Frequency .1 thru 10MHz
sibly valid DTMF signal. Normally, BD lustrated in Fig. 8. The outputs from the GF -8015 without Freq. Meter $179
is at logic O. Within 18 milliseconds of decoder can directly drive low- current Digital Triple Power Supply
receiving a possibly valid DTMF signal, LEDs. A relay driver that permits each Model XP -765
BD goes to logic 1. The Strobe output re- output to control a much larger load than $239.95
quires more than twice this time (40 milli- otherwise possible is shown in Fig. 9. The
seconds). 5V @ 5A
A kit consisting of the M -957 receiver, Fully Regulated, Short Circuit Protected
3.58 -MHz crystal, 10- megohm resistor +5 To .12 with 2 Limit Cont. 3 Separate Supplies
and data sheet can be ordered from High XP -660 w/ Analog Meters $169.95
Technology Semiconductors, 2512 _ Multi- Function Counters F -1000

-
1
O
Chambers Rd., Suite 204, Tustin, CA 2
1.2GHz
92680 (714- 259- 7733). Cost is $14.95 plus
1
. --_ $259.95
1
> 2
$2.30 for UPS shipping in the continental
U.S. California residents must add state A > 23 S y

4 >
3
4
S
' `= F -100
120MHz
$179.95
sales tax. The company accepts tele-
phone credit-card orders. 8 > 22 74C1S`i '
a
- a
'
Frequency, Period, Totalize, Self Check with High -

7 Stabilized Crystal Oven Oscillator, 8 Digit LED Dis

Shown in Fig. 7 is a straightforward a
C> 21
10 9 Digital Multimeter with
DTMF infrared receiver designed around 11 A LCR i Cap. and Trans.
> 20
Teltone's M -957 chip. The circuit's de- D tI
B Meter Tester
tector is a standard silicon solar cell. It is 1Y c
$138.00
IP4PvT5 FROM
25 $59.95
coupled through C/ to the input of an M -957
D
Model
14 . E Model
LM308 operational amplifier, which is 27 F
0
CM -1500A
Measures
operated with a 10- megohm feedback re- 16 Inductors, ,
8 Functions -' ',
Lie coo, Ep
sistor to provide very high gain. The Capacitors,
Resistors tmiummli"
with Case
OUTPUTS
LM308's output is directly coupled to the
C &S Sales Inc., 1245 Rosewood
M -957's signal input. Each of the four
Deerfield, IL 60015 (312) 459 -9040
outputs of the M -957 directly drives an 800- 292 -7711 ASK FOR CATALOG
LED through a 1,000 -ohm series resistor. Fig. 8. A 1 -of-16 decoder for Teltone's
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Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 65

ELECTRONICS NOTEBOOK...

four LEDs in Fig. 7 can be omitted if the less breadboard. The output from a sin-
+9V
outputs are connected to an alternative gle solar -cell receiver was connected to
output device, such as the Fig. 8 decoder. each chip's input so that each would re-
R2
This receiver will respond to the Fig. 2 220 ceive the same signal. These tests re-
transmitter over a range of several hun- vealed that both chips performed nearly
dred feet. If a small fresnel magnifying QI
2Ñ222 2
sL
ovo >
>
>
equally well when coupled to the same in-
lens is placed in front of the solar cell, the frared receiver. Though the M -957 was
TO
receiver can be triggered from across a CONTROLLED slightly more sensitive, the difference
RI
room. Since this narrows the beam from FROM
1K
411:
Ryl# CIRCuiT was so slight as to be negligible.
DECODER
the transmitter, careful pointing will be A more important observation was
4
required. RAb SNACK 215 -oo1 that the base of Ql, the LED driver in
Suitable fresnel lenses are available Fig. 2, required a slight readjustment for
from office supply and department both DTMF receivers to simultaneously
stores. A wide variety of lenses of all Fig. 9. A relay driver circuitfor the Fig. 8 receive incoming signals. For other ad-
kinds is available from Edmund Scientif- decoder chip. justments of RI, neither or only one of
ic, 101 E. Gloucester Pike, Barrington, the two receivers would operate.
NJ 08007.
most identical to the Fig. 7 circuit, the
A high -power near -infrared AlGaAs
202P circuit shown in Fig. 10 is shown to
Going Further
emitter that radiates at 880 nanomoeters
will give the greatest range. A super -
avoid possible errors. The simple DTMF infrared remote -con-
bright AlGaAs red LED will give a short- Operation of the Fig. 10 circuit is es- trol circuits presented here can be modi-
sentially identical to that of the Fig. 7 cir- fied to increase their sensitivity and ver-
er range, but its beam can be seen in a
cuit. Moreover, the Fig. 10 circuit can satility. They can also transmit signals
darkened room.
SSI 202P DTMF Receiver. SSI's 202P
also be connected to the Fig. 8 output de- through optical fibers.
18 -pin DIP DTMF receiver chip can be
coder and Fig. 9 relay driver. The most Though these DTMF remote -control
powered by 5 to 16 volts and is designed important difference between the two circuits use near -infrared or visible light
circuits is that the 202P chip must not be as a transmission medium, there is no
to be powered by a single 5 -volt supply.
operated with a supply that delivers more reason why a twisted -pair cable or radio
Like the M -957, the 202P has several con-
than 7 volts. cannot be used instead. In any event, the
trol and output functions that enhance
operation. A complete description of To test the relative performance of the DTMF system offers a very convenient
these functions is given in the device's M -957 and 202P DTMF infrared receiv- and relatively noise -immune method for
ers, I assembled both on a single solder- achieving reliable remote control. ÁE
data sheet. These include:
The Output Enable (OE) at pin 3 that
controls whether the output pins are ac-
+ SV
tive or placed in a high- impedance state.
The Hex input at pin 2 determines wheth-
er the four output pins provide a stan-
dard 4-bit binary hexadecimal output or
a 2 -to -8 binary code. R1 11
The Detection Valid (DV) output at lOM
pin 14 indicates when a valid frequency 18 6
pair is present at the input. Normally, pin 12. SSI 202.P
14 is at logic 0. When a valid DTMF sig- 1'1 c
nal appears at the input and is verified
a > o'
(decoded), pin 14 goes to logic 1. Cl T 19 10
2 RQ
The SSI 202P tone receiver and data .01
HE- R5 P.6 R1

sheet, complete with sample circuits is C2.

1K 11( LK ik
R3 loo pF
available from Radio Shack for $12.95 5.64
(Cat. No. 276-1303), as is the required SDLAM1
3.58 -MHz crystal (Cat. No. 272 -1310) CELL

for $1.69.
LEDs 1 -'1
The Fig. 7 Teltone M -957 DTMF in-
frared receiver can easily be adapted for
use with the SSI 202P. Though it is al- Fig. 10. A Touch Tone remote -control infrared receiver built around SSI's chip.

66 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

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IIPSOL/D -STATE DEVICES/Ill/IL
A new monthly column on semiconductor technology
and developments

By Harry Helms
+2 -6V

Electronics engineering journals and

trade magazines today are busily beating AO A > B output
the drum for applications -specific ICs Al A - B output
(ASICs), the catch -all term for a host of _c) A2 A < B output
technologies that produce custom and
Z A3
semicustom ICs. Indeed, many predict
that by early in the next decade ASICs BO A > B cascading input
will capture over half of the worldwide Bl A = B cascading input
IC market. B2 A < B cascading input
I happen to think they're right. ASICs z B3
will be a big and important part of elec-
tronics in the 1990s. But they won't be
the whole show by any means. For many
purposes, existing IC designs will be ade- 74HC85 4 -Bit Magnitude Comparator
quate and there will be no need to use an Dc supply (Vcc): + 2 to + 6 volts Propagation delay: 230 ns at 2-volt
ASIC approach. Since ASIC devices in
Dc input voltage: Not to exceed Vcc Vcc, 46 ns at 4.5 -volt Vcc
small quantities are an expensive propo-
Maximum quiescent mode power con- Prime vendors: GE /RCA Solid State,
sition in small quantities, it seems likely Motorola
sumption: 8µA
that cost -conscious engineering manag- Secondary vendors: Hitachi, National
Minimum high -level input voltage: 1.5
ers will urge their design staffs to try to Semiconductor, Signetics, Texas In-
volts for a 2 -volt Vcc, 3.15 volts for a
find solutions using "off the shelf" de- struments
4.5 -volt Vcc
vices before going the ASIC route.
Therefore, keeping up with develop- Fig. 1. Pin diagram and salient specifications and information for the 74HC85
ments in standard ICs will continue to be magnitude comparator.
highly important. A recent one I found
interesting is the explosive growth in
high -speed CMOS devices. I'm so im-
pressed by the capabilities of this logic
family and the range of devices offered in (some frustrated users felt you could Propagation delay times are virtually
it that I'm going to go out on a limb and "zap" a CMOS device simply by looking identical for ALS and HCMOS. HCMOS
predict that HCMOS (as it's known) will at it wrong!). Enhanced versions of noise immunity is greatly superior to
be the dominant logic IC family of the CMOS and TTL were developed to ad- ALS. And HCMOS has a big advantage
next decade, supplanting .standard dress some of these problems, but they in fan -out capability. For example, a typ-
CMOS and TTL (including advanced were more expensive and had some new ical ALS IC can drive inputs of 20 other
low -power Schottky ALS versions). limitations of their own. devices, while HCMOS outputs can drive
What's so special about HCMOS? Ahhh, but HCMOS! Now we're get- over 50 inputs.
Think of it as a marriage between TTL ting somewhere! Let's compare HCMOS HCMOS also has remarkable compat-
and CMOS that produced children with to ALS, the most advanced version of ibility with other logic families. HCMOS
many of the good qualities of the parents TTL. HCMOS can operate from a sup- outputs can directly drive HCMOS, stan-
and few of their shortcomings. For years, ply voltage from + 2 to + 6 volts instead dard CMOS, or up to ten TTL inputs if
the tradeoffs in digital logic were clear. of the fixed + 5 volts needed by ALS. all ICs use the same supply voltage.
TTL was fast and its devices were ALS ICs typically have a quiescent sup- Moreover, HCMOS can accept inputs
"tougher" than CMOS but consumed ply current demand of 0.2 mA per gate, from HCMOS, standard CMOS and
globs of current, was bothered by which HCMOS easily beats with a 0.0005 - NMOS devices. There are even some
"noise," and its power supply had to be mA figure. In speed, there's no real dif- HCMOS devices that can directly accept
+ 5 volts. In contrast, CMOS used little ference between HCMOS and ALS. For TTL inputs.
current and could operate over a wide example, a D flip -flop typically has a You can identify HCMOS devices by
supply voltage range. Unfortunately, maximum speed of 35 MHz in ALS and the "HC" or "HCT" in their part num-
CMOS was very slow compared to TTL. 40 MHz in HCMOS, while a typical bers. "HC" is a "normal" HCMOS de-
A serious problem was CMOS's suscepti- counter IC can operate at up to 45 MHz vice, while "HCT" indicates a device
bility to damage from static discharge in ALS and 40 MHz in HCMOS. with TTL -compatible inputs and out-

68 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

puts. The normal format for part num- thermore, HCMOS is currently more ex- = B cascading input (pin 3) to high and
bers begins with "74" (sometimes, pensive than most other logic families. the other two inputs (pins 2 and 4) to cir-
"54 "), then the "HC" or "HCT," fol- And HCMOS still is vulnerable to dam- cuit ground.
lowed by two to four numbers. One such age from static discharge, requiring the Figure 2 shows how to cascade the
part is the 74HC00, which identifies a same handling and use precautions that 74HC85 to compare two bytes. The first
quad 2 -input NAND gate device. If that ordinary CMOS does. But these short- device is used to compare the least- signif-
number looks familiar, it should; 7400 is comings are more than offset by icant nibbles of the two bytes and the sec-
the part number of the same device in HCMOS's many strengths. On balance, ond 74HC85 compares the most-signifi-
standard TTL. Virtually all TTL devices it's clearly the best existing logic family cant nibbles. Outputs of the first device
have HCMOS equivalents identified by for most purposes. feed the cascading inputs of the second,
"HC" and "HCT." These are identical while the cascading inputs of the first de-
in their pin numbers and functioning. In vice are held to the same logic levels used
addition, a number of standard CMOS
4-Bit Magnitude Comparator with the single device. Additional devices
devices are available in HCMOS ver- One useful new HCMOS device is the can be cascaded in the same manner
sions. This means you can incorporate 74HC85 magnitude comparator. Figure shown in Fig. 2 to compare words of 16,
analog switches, multiplexers /demulti- 1 shows a pin diagram for this device, 32 or more bits. Though it would be easy
plexers, timers, and even phase -locked which takes two 4 -bit (or "nibble") in- to use an ASIC device to compare two
loops (the 74HC4046A) into all-HCMOS puts and compares them. The two nib- bytes, this is one example where using
designs. If you're already familiar with bles are labeled A and B, and three out- standard components can be just as ef-
TTL and CMOS, you won't have to learn puts (at pins 5, 6 and 7) indicate three fective and much less expensive!
a new variety of part numbers, devices possible relationships between them: A
and functions. > B, A = B and A < B.
HCMOS isn't perfect, however. It still The output corresponding to the rela-
An 8 -Bit Equality Comparator
consumes more power and is more sus- tionship between the two nibbles has a There are often cases when all we need to
ceptible to noise than standard CMOS. It high logic level, while the other two out- know is whether or not two bytes are
can't operate over as wide a voltage range puts are low. There are three cascading equal. Figure 3 shows the pin diagram for
as standard CMOS, and "HCT" devices inputs (pins 2, 3 and 4) that are used when the 74HC688 8 -bit equality comparator
must be operated from a constant + 5 two or more devices are cascaded to com- device. The inputs consist of two bytes,
volts like TTL (HCT devices also con- pare "words" larger than four bits. If labeled A and B, and a single A = B out-
sume more power than HC types). Fur- you're using just one 74HC85, set the A put at pin 19. This output is low when-
ever the two bytes are equal; otherwise, it
is high. There is also a cascade input at
pin 1, which should be kept at a low logic
vcc level when only one device is used. (If it is
o o at a high level, pin 19 will be high regard-
less of the inputs.)
16 3 16
The cascade input is used if more than
AO s one 74HC688 is used to compare data
Al 2 6 3 "words" that are longer than one byte.
.0 A2 3 This is done by connecting the A = B
C
E A3 15 AO 10
output of the first device to the cascade
ro
U Al 12 s A> B output input of the second. The pattern is re-
Em BO A2 13
peated for all other devices in the cascade
A -B output chain. The cascade input of the first de-
B1 A3 1s
vice must be connected to ground. The
d B2 7 A < B output
first device accepts the least- significant
J B3 BO 9
4 B 2
11
byte of each word, the last device in the
B1
chain accepts the most -significant bytes.
82 14

B3
8
A 9 -Bit Odd/Even
1 Parity Checker & Generator
Parity checking it a technique to detect
Fig. 2. Details of how to cascade 74HC85s to compare two bytes. Additional 74HC85s errors when data is transmitted serially
can be cascaded in the same manner to compare words of 16, 32 or more bits. from one point to another. Each data

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 69

SOLID-STATE DEVICES ..

word has one bit known as the parity bit,

and odd or even parity can be used. If +2 -6V
odd parity is used, the number of 1 (high 74HC280 9-Bit Odd /Even Parity
logic level) bits in the data word will al- 20 Checker & Generator
ways be an odd number. In even parity, AO 2
Dc supply (Vcc): + 2 to + 6 volts
the number of 1 bits will always be even. Al 4
Dc input voltage: Not to exceed Vcc
The parity bit is usually the first bit in A2 6
Maximum quiescent mode power con-
each data word; in the data word < A3 8
sumption: 8µA
a1
101100011, the first "1" is the parity bit; A4 11
Minimum high -level input voltage: 1.5
co
0 is used for even parity, while 1 is used A5 13
volts for a 2-volt Vcc, 3.15 volts for a
for odd parity. Some parity- checking A6 15
4.5 -volt Vcc
systems "borrow" a bit from a data A7 7 Propagation delay: 205 ns at 2 -volt
word byte, leaving only seven bits for 19 A B output Vcc, 41 ns at 4.5 -volt Vcc
data, while other methods add an extra BO 3 Prime vendors: GE /RCA Solid State,
bit to a byte to form 9-bit words. B1 5 Motorola, Signetics
Figure 4 shows a pin diagram for an 7 Secondary vendors: Hitachi, Mitsubi-
B2
HCMOS device to detect the parity of a shi, National Semiconductor
B3 9
9-bit data word input. The 74HC280 has a)
T B4 12
two outputs, the even parity (pin 5) and m
B5 14
an odd parity (pin 6). Input bit A (pin 8)
B6 16
is the parity bit. Depending on the parity
18 Fig. 3. Pin diagram and salient spe-
of the input, one output will be high B7
10
cifications and information for the
while the other will be low. If the number
Cascade input 74HC688 8-bit equality generator.

"Made in U.S.A."

JAN
CRVSTRLS
of 1 bits in the input is even (0, 2, 4, 6, 8), Integrated devices haven't totally con-
quered the world. For many high -power
pin 5 will be high and pin 6 will be low. If
the number of bits is odd (1, 3, 5, 7, 9),
1 applications, it's tough to beat a MOS-
ISince I then pin 5 will be low and pin 6 will be FET. A valuable collection of MOSFET
1965
high. This allows you to not only deter- circuits is TMOS Power FET Design
We've been supplying quality
crystals since 1965
long before the flood of
- mine the parity of an input signal, but
also to "generate" a parity signal for use
when comparing inputs that are larger
Ideas, available from Motorola Semi-
conductor Products. This book includes
schematics and circuit information for
cheap imports. than nine bits. To cascade 74HC280 de- voltage regulators, motor speed controls,
vices, connect the odd -parity output of lamp switches and dimmers, audio am-
We're still supplying quality the first device to the A bit input of the plifiers, modulators, power supplies, and
crystals with next device in the chain. Leave the even - radio transmitters. This manual runs 7Ó
Quick Turnaround pages and proves that discrete devices are
parity output open. Additional devices
Low Price
can be cascaded in this manner to handle alive and well. (Motorola, P.O. Box
High Quality
33- or 65 -bit inputs. 20912, Phoenix, AZ 85036.)
I started this month's column by men-
TO SOLVE
tioning how ASICs seem destined to
CRYSTAL Good Reading dominate electronics. A good guide to
PROBLEMS,
GET THIS Manufacturer literature is one of the best what an engineer must keep in mind
CATALOG ways to keep up with semiconductor ap- when designing an ASIC is Practical
plications and electronics technology. Considerations for the Design of Semi -
You can obtain literature from their dis- custom ASICs (ICAN- 8740), available
JAN CRYSTALS tributors and sales representatives, or from GE/RCA Solid State. Some of the
Box 06017
P.O.
you can obtain it directly from the manu- advice is surprising, such as suggestions

A Ft. Myers, FL 33906

(813) 936.2397
CALL 1- 800 -237 -3063
facturer if you request it on business or
professional letterhead.
to avoid using on -chip clock signal oscil-
lators and tri -state (high, low and high-

FREE (Except Florida)

CIRCLE 3 ON FREE INFORMATION CARD
70
 LETTERS (from page 7)

Electronics can send $12 to Vontronics, Mismatching

1010 Park Drive, Everett, WA 98203. In "Hardware Hacker," August 1987
Also available from the same source are issue, it's noted that the internal resist-
an undrilled case, the pc board, the three ance of automobile batteries is not "care-
ICs and assembly instructions for the fully matched" to the impedance of the
converter for $35. Please add $2.50 for starter motors they are designed to drive.
5 Even parity output P &H and state sales tax if you are a If the impedance were matched, the ter-
9
Washington resident. minal voltage of the battery would drop
Crady VonPawlak to one -half the unloaded voltage. In
D In the Note at the end of the Parts List practice, the cranking voltage is not ob-
á E 2 in the "Off-Hook Phone Alert" (No- served to drop below about 10 volts in a
F 13 vember 1987), the pc board and kit sup- 12 -volt system.
G plier should read R&R Associates, 3106 Stanley W. Wilson
H 2 Glendon, Los Angeles, CA 90034. Don Lancaster's statement that " ... a
4 6 Odd parity output Peter A. Lovelock car battery's impedance is carefully
7
For benefit of any readers who may be matched to the impedance of the starter
confused by some typographical errors in ... " in your August issue with regard to
74HC688 8-Bit Equality Comparator "A General- Purpose Speech Synthesiz- delivering maximum power during
Dc supply (Vcc): +2 to +6 volts
er" (October 1987), I offer the following cranking can be misleading. I feel certain
Dc input voltage: Not to exceed Vcc
corrections: that such matching is not the case. Al-
In Fig. 2, eliminate the connection
Maximum quiescent mode power con- though there is a correlation between the
from pin 1 of IC4 to pin 1 of IC12; con-
sumption: 8µA impedance of the starter and the battery,
nect pin 16 of IC4 to pin 2 of IC7; con-
Minimum high -level input voltage: 1.5 a match would infer a 1:1 impedance ra-
nect pin 19 of IC4 to pin 1 of IC7; change tio. If this were the case, the output of the
volts for a 2 -volt Vcc, 3.15 volts for a
4.5 -volt Vcc
CI5 to 0.1 microfarad and R2 through battery would fall to half its open- circuit
R7 to 2,700 ohms.
Propagation delay: 210 ns at 2 -volt potential, or about 6.6 volts. However,
Vcc, 42 ns at 4.5 -volt Vcc
If used, Data Out in Fig. 3 goes to the cranking potential should not fall below
Prime vendors: GE/RCA Solid State, RX input on the computer, not CTS.
9 volts during cranking, suggesting a 3:1
Motorola, Signetics, Toshiba Also, pressing the RESET button causes ratio between load and battery. Best
the synthesizer to vocalize "okay" but
Secondary vendor: Hitachi power delivery occurs when load impe-
not print it on the computer screen. dance is much greater than source impe-
Fig. 4. Pin diagram and specifications Barry L. Ives
dance.
and information for the 74HC280 9 -bit
Okay A very large battery that has essentially
odd/even parity checker and generator.
Since Radio Shack introduced the zero impedance would deliver about four
CTS256A-AL2 speech processor, I start- times as much power to a fixed load as
ed building the circuit. The furthest I suc- the same- voltage battery would with a
impedance) outputs. (GE/RCA Solid ceeded is when I hit the RESET button and matched impedance. Therefore, what car
State, P.O. Box 3200, Somerville, NJ the speech processor signaled "OK," manufacturers probably look for is a rea-
08876.) telling me that the wiring is more or less sonable tradeoff between power -delivery
correct. The literature that came with the "efficiency" and weight to optimize
A Personal Note... chip was helpful just to wire it up to say cranking in practice.
"OK." But to interface it with a comput- Wayne Shook
This is my first of what I hope will be a er, it was not. Happily, the October 1987 Marissa, IL
long line of columns. I'm particularly Modern Electronics explains how to wire
glad to once again write for Art Salsberg, and interface it to a computer using serial In the Beginning
for whom I wrote over a decade ago at or parallel outputs. I used the serial out- Some time ago, needing more shelf
Popular Electronics, and to appear in the put option. As I was wiring it up accord- space, I cast my eyes about looking for
same magazine as Forrest Mims, who has ing to the diagram, I noticed the diagram something to throw out. I settled on some
been a good friend since my days in Ra- on page 36 has a misprint. Pin 2 of DB -25 old vacuum -tube TV schematics printed
dio Shacks's technical publications connector J1 should be TxD and pin 3 in blue and taken out of an old magazine
group. My charter is to bring you the should be RxD. After making this correc- called Electronic Technician. Guess whose
most recent developments in semicon- tion, my Speech Synthesizer started vo- name I saw on the masthead ? ? ??
ductor technology and news on the latest calizing any word I typed in. I hope TL Clayton
devices available. I'd appreciate your everyone has as much fun as I did. Meridian, MS
feedback and comments about what John Vartanian Yes, indeed, that's where this editor
you'd like to see in this column! AE Garden City Park, NY started in the magazine business. -Ed.

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 71

Eli/il/PC CAPERS illl
A New Computer- Oriented Column

ple jump right out again! This tends to

By Ted Needleman
keep the BBS situation fluid. New boards
are always popping up, and established
boards disappear overnight. Still, even
Welcome to the first installment of with all this corning and going, BBS (and
"Computer Capers," which is intended the commercial services) are a great place
to help you keep up with the pulse of the to do two things -solve problems and
small- computer field that so many of us find software.
are active in. I've been using a variety of Many Bulletin Boards, especially the
computers (in a variety of sizes) for al- commercial services with their Special In-
most 20 years as a programmer, systems terest Groups (SIGs), serve as forums
analyst, DP manager, consultant, and an where users, both experienced and new,
accountant in public practice. can exchange information. If you're hav-
I love gadgets and gizmos, and enjoy a ing a problem with a piece of hardware or
love /hate relationship with computers. software, it's possible that another mem-
Over the years, I've accumulated a varie- ber has also had the same problem and
ty of computers. My main working ma- solved it (or found out that it is unsolv-
chines are three PC compatibles, but I able). There are boards and SIGs for
also use a 512K Mac, and occasionally most major computers. Moreover, sever-
my Apple IIe. There's a DEC Rainbow al software companies, such as Micro-
over in the corner running a FIDO Bulle- soft, Borland, and Aldus, maintain their
tin Board and a DEC Pro 380, which is as own areas on CompuServe. You'll often
impressive a door stop as you'd ever want get a faster response by leaving a message
Facsimile boards like E.I. T. 's gives PCs
to see. The Apple /// got pawned off on receive /transmit facsimile functions.
on one of these forums than calling the
my brother (he doesn't know much about company. If your message isn't a private
computers, and was thrilled to get it), one to the system operator, other folks
while a Commodore C-64 is in the care of will readily put in their two -cents worth.
a cousin. Add several printers (one for The BBS network and SIGs on the
tion of downloadable public- domain
each system), a variety of review systems, commercial services function as a para-
software and shareware.
and several hundred software packages, In the meantime, you can drop me a user's group. Throw a modem and some
and you'll understand why my wife note, or E -mail me on my CompuServe communications software in your ma-
makes me work down in the basement. chine, and fellow users are as near as
account. One word of warning, though.
What this eclectic collection means to your telephone. This by itself is enough
If you'd like to hear back from me,
you, as a reader, is that I won't concen- to make me strongly recommend them. A
please include a phone number. Like
trate on one particular computer system. many writers, I'm terrible about answer- tremendous side benefit of most BBS's
And you can expect to occasionally see ing mail. I'd much sooner pick up the
are their download libraries. These are
me cover some out -of- the -ordinary ap- phone than fire up the word processor. sections that contain lots of free (or al-
plications here, as they strike my fancy. most free) software. There are all kinds
Of course, much of this depends on your of software programs on these boards,
Bulletin Boards including programming utilities, spread-
feedback to me. As the feedback loop in-
creases over time, a column tends to As the operator (sysop) of a Bulletin sheet templates, word processors, data-
evolve and take on almost a life of its Board System, and an early user of com- base managers, etc. Some of these pro-
own. As I can't call each one of you indi- mercial information services like Com- grams are real dogs, but some are as good
vidually, this leaves the matter in your puServe and The Source, I'm sometimes as their commercial equivalents. Most
hands. surprised at how many people don't are free, except for the cost of the phone
I'll list a couple of ways you can con- know about the tremendous number of call to download them. With others, the
tact me at the end of this column, but I'm BBS systems out there. It doesn't take author asks that you voluntarily send
going to try and improve and expand my much to set up a BBS; just a computer, a them payment, if you like.
computer bulletin-board system over the modem, some software, and an open tel- Considering the amount of time that
next couple of months. Right now, it's ephone line. As a result, lots of people goes into writing, testing, and debugging
primarily for use by owners of Digital's tend to jump right in. a program, you might be a little skeptical
Rainbow systems, but I hope to be add- Naturally, when the amount of work about the quality and/or utility of some-
ing sections for PC and Mac owners. In a needed to keep the board up begins to thing for nothing. After all, we all know
couple of months, when it's ready, I'll dawn on them, or they realize that they that there ain't no free lunch. Maybe so,
give you the details. It will be the best way can only use their own computer when but at the same time, sometimes you get
to get in touch and will also offer a selec- someone's not on the board, lots of peo- treated to lunch by a friend. And there

72 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

still are at least a few people out there (up to 9,600 baud) the system will trans-
who are willing to share the fruits of their mit information at. The scanner allows
labor. In many instances, a program is documents with text and/or graphics to
just as much a work of art to its creator as be captured as fax documents, just like a
paintings or sculptures are to their crea- .cument was produced
standard desktop fax. It sounded great,
tors. And most of us like to feel that our y freehand by Publisher's so I rushed to install it in my main sys-
work is appreciated. rush. tem, an ITT Xtra with an 80 -meg Tall -
For others, who ask for a nominal reg- auboiq zsw tnemuaob zidT grass hard disk.
bnsrieeit yleiitne
istration fee, the "donations" are a way Installation was simple: drop in the pc-
of funding on -going support and im-
a. ."."n" .izu dfnis9
FAX modem board and the scanner con-
provement. After all, it's hard to keep mIauq_'d troller board, close up the machine, run
pouring time into something you "fin- the install program to transfer software
A video screen generated by Z- SOFT's
ished" a year and a half ago. For a few, to the hard disk, and run the set-up pro-
the number of users who actually pay for
Publisher's Paintbrush program. gram to tell the software what kind of
the software is enough to fund a full -time system it was running in. Bingo ... it
business. Quicksoft, the people who put didn't work! The scanner, which is sup-
out PC Write, is a successful, on -going posed to scan at 200, 240, or 300 dots per
business, as is Headlands Press, with its boards for motorcycle riders, fishermen, inch (dpi) resolution would only work at
PC -TALK III communications package. the handicapped, and many others. 200. And the modem refused to talk to
In fact, Headlands has been so widely ac- FIDO BBS's are also running all over any other fax system. It would dial a
cepted as a software publisher that PC- North and South America, Europe, Afri- number and then ignore the other sys-
TALK IV, its latest version, is no longer ca, Asia, and even a few behind the Iron tem's "Hello there" tone.
shareware -it's strictly commercial now. Curtain. For more information on the A call to the company elicited the opin-
Along with the gems, you sometimes FIDO "movement," write to Ken Kap- ion that it might be that I was using an
get rocks. Some of the downloads are lan, President, IFNA, P.O. Box 41143, older version of the software, or it might
just plain poor. You might even get a St. Louis, MO 63141. And if you have a be the outboard hard disk on the ITT, or
program with a worm in it. These are in- favorite board that's something special, it might be .... It turned out that one of
nocuous- looking programs that can drop me a note and I'll spread the word. the E.I.T. people lives about two miles
trash your hard disk's contents. (For ex- from me, so she was nice enough to stop
ample, a hidden FORMAT command The Best -Laid Plans .. .
off at my home the next day with a new
isn't inconceivable.) Most BBS operators set of disks.
are cautious about weeding these out, but One of the benefits of working in the Another two weeks went by (never let
never say never. Therefore, if you're go- computer press is being able to review it be said that I rush into these things),
ing to download software, make sure lots of hardware and software (and get and I transferred the boards to an old PC
your hard disk is backed up. But this is paid for it to boot!). And it's a great ego compatible. When I went to install the
good practice anyway, isn't it? enhancer when people come to you with software, I realized that I had only three
Public-domain software and share- their problems because they consider you disks, while the installation routine ex-
ware are worth looking into. I'll talk "an expert." At least it is until I remem- pected four. Another call to E.I.T. pro-
more about this in future columns and ber my own definition of the word expert duced the fourth disk in the mail two
tell you about some of my favorites. I'd -someone who has fallen flat on his face days later. The software was quickly in-
also like to hear from any of you who use enough times that he has developed cal- stalled and, Bingo ... it still didn't work!
downloads and find out what you're us- luses on his nose. This time the scanner refused to even
ing and your experiences. On this note, about a month or so ago, peek at the document, and the modem,
What's the best way to find a BBS? I received a pc -FAX board and ps -2000 likewise, is incommunicado.
Lots of sources. Some computer -only scanner from E.I.T., Inc. This board and I had the feeling that the problem was
publications list them, and local user's software combination turns an IBM caused by either a) the fact that the Col-
groups may run their own. You can start compatible into a facsimile machine, umbia has an incompatible BIOS (after
with a commercial service and just ask which scans a document and converts it all, it's four years old); b) the TOPS net-
about them in the various SIGs. into a form that can be transmitted over work card I installed the week before; c)
Another place to inquire is the Interna- the phone lines. The receiving fax ma- the E.I.T. equipment needs to be re-
tional FidoNet Association (IFNA). Fi- chine reconstitutes the document and paired/replaced; or d) the moon is in the
doNet is a network of over 1,000 FIDO prints it out. seventh house and Jupiter is aligned with
Bulletin Board systems. Most of these are E.I.T.'s pc -FAX can send and receive Mars or some such nonsense.
"public" boards, which are more or less fax's to and from any other fax machine The next step was to move the modem
(depending on the system operator) open that meets Group I, II, or III standards. and controller cards to the other ITT.
to the public. There are special- interest These standards determine what speed This system has a built -in hard disk, and I

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 73

 PC CAPERS ...

hadn't gotten around yet to installing the really like to hear about some of the tips
TOPS network card in it. The results of and techniques that you've developed to
s
1M111110 the move should narrow the above handle troubleshooting. I'll pass the best
choices down somewhat, I thought. of them on here. It may not make you
When I couldn't get anything to work, rich, but at least you'll be famous.
I decided to take another tack. E.I.T.'s
ps -2000 scanner is basically the same unit
In Times To Come
as the Shape scanner. I recently reviewed I don't need a crystal ball to know what's

`\e000 a great package from Z -SOFT called coming up in near-future columns. All I
o°cs `1p°
ed
P Publisher's Paintbrush. Z -SOFT is well have to do is look at the pile in my "lab."
state
a known for its PC-Paintbrush graphics Apple's Hypercard, OWL's Guide for
h °
ñp°e Q
the PC, Centrum's TOPS network and
1ac program, and Publisher's Paintbrush is
tec0aw eY some nice utilities are all here. And, of
Sos an extension of this. The program lets
you do almost anything you might want course, there's the on -going story with
aa the E.I.T. pc -FAX as well as another fax
eo with a graphic image, including shrink-
5 9 x ing or blowing it up and rotating it. It card from Gammalink. I'll also tell you

t0i1 G:a a tdS about a nice 80386 machine I've been

saatácNe
cAt\ tcte
.

\l0
P
et

free
ode
3 0 also supports a variety of scanners, in-
cluding the Shape. playing with, the ACER 1100, as well as
K the PC- MOS/386 multi -user, multi -task-
Oat oe 93 Dragging the software package home
Pods óó Oy \QS NC08G 421 P
Pec lGG S A\.
g 995 ,
°P
9
from the office, I installed it on the Col- ing operating system. And, of course,
there's always something new showing up.
umbia's hard disk. The next step was to
23 If there's something specific you'd like
MLLE J V IV r 11LL 11n r vn mef r rvi -ri. install a device driver for the Shape into
my MS -DOS config.sys file. Easy enough, to see covered here, drop me a note. If I
can get it, and if it will be of general inter-
Bean FCC except the driver wasn't on any of my
disks. A call to Z -SOFT uncovered that I
had one of the first set of disks shipped,
est, I'll give it a shot. There are several
ways to get in touch. The easiest, though

LICENSED
ELECTRONIC TECHNICIAN!
and that driver probably wasn't available
at that time. I shipped the disks back for
updating, and two weeks later I was back
not necessarily the best, is U.S. Snail. A
card or letter to P.O. Box J, New City
(not NY City), NY 10956 will generally
in business. make it through. Electronic mail can be
tl .1111 Now, however, there is also an install sent via CompuServe 72777,3041.
Earn up to program for the Shape scanner that has If you want to log onto FIDO BBS,
$30 an hour to be run once the device driver has been Rainbow Corner, the phone number is
and more! installed. Want to guess on what set of (914) 425 -2163. When my system an-
disks it wasn't? Shannon, over at Z- swers, wait five seconds and hit RETURN
Learn :u Inenc in spare time.
No previous esperfence needed! SOFT's tech support, promised me he'd a couple of times. Before you dial,
1 mail it right out. Maybe by next column though, set your communications pack-
No costly school. No commuting to class. I'll have some success (or at least some age to emulate a VT -100 terminal. The
The Original Home -Study course pre- answers). sign -on screen uses VT -100 graphics.
pares you for the "FCC Commercial Radio- The whole point of this tale is not to You can access the board without this
telephone License ". This valuable license ability, but the first 20 seconds or so will
is your "ticket" to thousands of exciting convince you what a rough life we re-
jobs in Communications. Radio-TV. Micro- viewers have. Rather, it's just to remind be garbage.
wave. Computers, Radar, Avonics and you that being on the edge of technology Once you get to the point where the
more! You don't need a college degree to means that you sometimes get a few cuts. system asks your name, you'll be OK.
qualify, but you do need an FCC License. The first time you sign on, you won't be
No Need to Quit Your Job or Go To School It's frustrating when things don't work
This proven course is easy, fast and low right the first time out. And more than allowed in the file area. However, you
cost! GUARANTEED PASS - You get your that, it's time consuming. But it's also a can go to the message area, look around,
FCC License or money refunded. Send for and leave me a message. If you'd like file
FREE facts now. MAIL COUPON TODAY! lot of fun most of the time.
I can't help thinking that if it's taking download privileges (there is some IBM
r C®mmanD PRODUCTIOnS me all this time to straighten things out software up on the board), let me know
FCC LICENSE TRAINING, Dept 220 1
when the companies involved know I'm a that you're a Modern Electronics reader
P.O. Bex 2223, San Francisco, CA 94126
reviewer, it chills me to think of what and I'll upgrade your access. Be speaking
Please rush FREE details immediately! I
NAME 1
some of you must be going through. I'd to you.
1

L
ADDRESS
CITY STATE_ZIP_ ,
1

74 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 and you can too!
Andy is a Ham Radio operator and he's having with, Amateur Radio is the hobby for you. The
the time of his life talking to new and old friends world is waiting for you.
in this country and around the world.

You can do it too! Join Andy as he communi- If you'd like to be part of the fun ... if you'd like to
cates with the world. Enjoy the many unique and feel the excitement ... we can help you. We've
exclusive amateur bands ... the millions of fre- got all the information you'll need to get your
quencies that Hams are allowed to use. Choose Ham license. Let us help you join more than a
the frequency and time of day that are just right million other Hams around the world and here at
to talk to anywhere you wish. Only Amateur Ra- home. Who are we? We're the American Radio
dio operators get this kind of freedom of choice. Relay League, a non -profit representative organ-
And if it's friends you're looking to meet and talk ization of Amateur Radio operators.

For information on becoming a Ham operator

circle number 110 on the reader service card or write to:

Street
AMERICAN RADIO RELAY LEAGUE DewtingtOon, Connain

This space donated by this publication in cooperation with the American Radio Relay League.
 d FOCUS ill/It11
Quick Charts By Stella

By Art Salsberg
SBG CRAPS SELECTION NEVI

Stella Systems (Cupertino, CA) upgrad-

ed its Stella Business Graphics package to
MIN
gz01:PS:M:
version 3.01 and, at the same time, an-
11111.11111111111111
nounced that its U.S. management .X

bought the company from its Japanese

owners. Moreover, the $199 package was
reduced in price to $99. This was fol-
lowed by the introduction of a second
Stella graphics software product, called
Business Graphics II, ver. 2.0, priced at
$199. Both are for use with IBM and IBM
compatible computers, come with two
Tm
........f/
Chart
disks, and are not copy protected.
- Praaticalits
The graphics packages work similarly,
with the latest one providing more flexi- ill - Ettiaienoy

bility. BGII, for example, adds the capa-

bility to work with more graphics boards,
AM' - lase of Use

such as IBM's new PS /2 and Vega De- CMla-) C.I.

en
luxe PGA, as well as EGA, CGA and Novo cursor to selection using the arrow keys, then (RETURN].
monochrome ones. Further, the latest, Stella Business Graphics' chart selection screen makes it easy to look at the same data in
more expensive (though less costly than a variety of different ways and allows you to get your first chart in five minutes.
most other graphics packages) software
expands its print device capability, allow-
ing setup for color and ink jet printers, as
well as a wider choice of laser printers, tions are made for printer choice, graph- can be chosen by simply moving the cur-
plotters and dot -matrix printers. Fur- ics card, etc. Loading either program, the sor to the selected one, which displays a
thermore, the newer package enables a first screen display that one sees is a pic- blinking line frame, and pressing RE-
user to position the created graph on one torial bevy of 12 graph types (actually, TURN. These range from bar, column,
of nine different page locations, offers a one is all text that can be modified) that pie, donut (with hole in the center that
choice of three different graph sizes, and
portrait or landscape orientation (verti-
cal or horizontal paper positioning).
Additionally, the more costly program
allows one to choose alternate paper sizes Percent of Satisfied End Users
to as large as 11 x 14 inches, choose the
number of copies, and produce color Percent
Laser
printer output from monochrome moni- 19.7%
tor systems. Default outputs are in high 9 -Pin
16.8%
resolution regardless of what graphics
card is in the system, with a draft resolu- 18 -Pin
16.8%
tion option. A variety of file formats can
24 -Pin
be imported, including ASCII and . WKS Vz 16.8%
and .WK1 Lotus 1 -2-3 files. In contrast,
Ink Jet
the earlier package required DIF file con-
version for Lotus. BGII now provides ex-
® 13.8%
Thermal
tensive Help screens; 100K worth. 11.1%
Daisy
Effl 4.9%
In Use
Setup is a snap, giving the user a choice of
menus from which submenu -listed selec- A BG2- developed pie chart with exploded section, printed with Epson's GQ-3500 laser.

76 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 ATTENTION!
E L1C
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Critical Factors in Printer Purchase B.S.E.E.
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Our New and Highly Effective Advanced- Place-
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1J 1 %/í %11 Through this Special Program you can pull all of
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Over 40 Years! Write for free Descriptive Lit-
Example of a stacked-bar type graph created with Stella systems' BG2 program. erature.

COOK'S INSTITUTE
OF ELECTRONICS ENGINEERING
can accommodate two lines of up to 8 text anywhere he wishes, which is an es- 347 RAYMOND ROAD
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fied if the user wishes to do so. A new The earlier SBG graphics package is cer-
State of the Art Kits by Hal -Tronix, Inc.
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TOUCH -TONE DECODER AND ENCODER KITS
Once a chart selection is made, the user price. It's simple to use, which means HAL- 567 -12 $39 95
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LOW COST METHOD OF ADDING MEMORY TO THE
The graph is subsequently displayed by The later package, BGII, expands on ACCUKEYER. COMES WITH TWO 1101 MEMORIES. GIV-
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Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 77

IIIih/ PRODUCT EVALUATIONS I/Il/It1ENNIr
The Daetron MC300: More Than Just a Capacitance Meter

The Daetron MC300 Digital Capacitance

Meter belies its name. It's not your gar-
den- variety capacitance meter, as you
shall see. Nor is it limited to the typical
capacitor checks. At $169.95, the power-
ful and flexible battery -powered instru-
ment is one of the better bargains
around. (An optional carrying case is
$16.95; an ac adapter, $9.95.) Surpris-
ingly, the meter isn't made in Japan or
Korea; it comes from Canada.
The unit is packaged in a handsome
black square-edged 7 x 4 x 13/a -inch
case that appears to have a terrifyingly
complex four -color 16 -key keyboard.
However, reading the manual and fiddl-
ing with the MC300, it becomes con-
siderably less imposing.
To start with, the basic function of the
MC300 is fully autoranging measure-
ment of capacitance, with a range from
0.1 picofarad to a whopping 1 farad
(1,000,000 microfarads). To measure
most capacitors, you simply turn on the
unit and poke the capacitor's leads into
the instrument's push -in sockets. The
MC300 responds with a four -digit '/c-
inch -high LCD display, and one of four
LEDs lights to indicate the range in use.
To measure capacitors with values great-
er than 10,000 microfarads, the unit must
be turned off, the capacitor inserted (or,
more likely, connected via short cables to
the two banana jacks), and the unit is The MC300 goes far beyond the fore- time periods off. To measure a capaci-
then turned on. The larger the capacitor, going. While you might not ever want to tor's dielectric absorption, you charge
the longer the wait for its value readout. measure a capacitor with a value greater the capacitor for a certain period of time,
The manual indicates a wait of about 50 than 1,000 microfarads, you may wish to discharge it for a like period of time, and
seconds for a 180,000 -microfarad capa- know a few of its other electrical charac- then measure its residual voltage- that's
citor, and this was borne out in my test- teristics, such as its leakage rate and the DA. With the MC300, all you do is
ing. (The largest capacitor tested was dielectric absorption. The MC300 mea- plug the capacitor into the push -in socket
220,000 microfarads, which turned out sures both directly! and press FUNCTION, followed by the
to be 214,700 mikes -pretty close, all The highest test voltage for leakage white DA key. The display changes to dA,
things considered.) tests is about 15 to 18 volts. A lower test and pressing the DA key again starts the
Accuracy of the unit was excellent up voltage, down to about 3.5 volts, can be test. The display indicates UAIt (that is,
through about 33 microfarads, that be- chosen. The display will indicate either wait) and the mF range LED lights to in- r
ing the largest precision capacitor in my nonE (if leakage is negligible) or bAd (if dicate the stabilization period. After
stock. Accuracy on the smaller 1- percent leakage is severe), or will indicate leakage about a minute total, the capacitor's DA
and better capacitors was within their tol- in kilohms. To exit the leakage testing is displayed, expressed as a percentage
erance ranges. mode (actually, to exit any of the special ratio of the charging voltage to the resid-
In addition to full autorange capabili- test modes), you press the FUNCTION key ual voltage. A reading of 0 indicates no
ty, the MC300 allows you to select any of two or three times. absorption.
10 fixed test ranges by pressing the blue Knowing the dielectric absorption of a The MC300 can be used to quickly sort
MANUAL key, followed by one of 10 capacitor is critical in timing circuits, a pile of capacitors in a variety of ways.
range -select keys. since a high DA can throw the calculated The simplest way is to enter the upper

78 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 and lower ranges you want. Thus, if you voltage with a resolution of 0.1 volt. All roses have thorns, and the MC300
want to select all of the 1- percent devices Testing rectifiers is a similar proce- is no exception. For all of its power, the
from a pile of 1-microfarad capacitors, dure, except that the diode is inserted in unit has a few annoying drawbacks, the
you would enter .99 and 1.01 microfa- reverse fashion. Any reading from 0.2 to most glaring of which is the keyboard ac-
rads, then press SORT and poke the caps 1 volt means the diode is good; a reading tion. The keyboard is a flat membrane
into the socket one by one. The display of 0 means a short, and a higher reading type, which wouldn't be too bad except
will show LOU, hiGh or GOOd, depending (usually the maximum) means the diode that no feedback, either tactile or audi-
on whether the capacitor's value is be- is open. ble, is provided. The only feedback
low, above or within the range. Lastly, we come to the MC300's at- comes from the four range LEDs, which
Since the MC300 allows you to enter a tractive ability to test bipolar transistors. flash briefly when the pressed key is read
zero value, you can also sort capacitors "So what ?" you say, "you can get a into the microprocessor. The flash is
by entering the nominal value, say, 1,000 transistor tester for as little as twenty hard to see under the best of circum-
,
microfarads. The display will then show bucks!" That may be true, but you first stances, and the keyboard polling rate is
?
the difference between this value and the have to know the pinout of the transistor, very slow, Therefore, it's best to hold
capacitor's actual value. For example, a and often have to know whether it's npn down a key for a half-second or more to
1.215 -microfarad capacitor would read or pnp. The MC300 not only tells you assure a response. (According to a Dae-
0.215, etc. what type the transistor is and whether tron spokesman, an audible feedback in-
Among other features are true capaci- it's good or bad, but it also identifies all dicator is soon to be added to the unit.)
tance (which tells you the actual capaci- three leads for you! A second complaint is that it's some-
tance of a leaky capacitor), extended res- Transistor leads fit into the top three times difficult to get out of a special test
olution (which allows you to shift the dis- holes of the tester's transistor socket. If mode and back to the regular capaci-
play to read a capacitor's value to one ex- the transistor is good, the display will in- tance- testing mode. According to the
tra decimal place), and time constant dicate either nPn or PnP; if it's not, you'll manual, two presses of the FUNCTION key
(which allows you to enter a resistance get bAd. A second press of TRANS (if the will return you to the initial mode at any
value and determine a capacitor's time device is good) produces a reading of time. In practice, three or four presses
constant with that resistance in seconds). EbC, CbE, bCE, etc., and lines run between are sometimes required, and some por-
One semi-capacitive function that is the display and the socket to tell you tions of the special test modes must be
worth noting is the MC300's ability to which lead is which. Now, is that incredi- first exited by pressing the relevant test
measure cable length, up to a theoretical ble or what? mode key before pressing FUNCTION. It's
limit of 10,000 miles. This is done by en- This function isn't perfect: the display easy to forget which test mode key was
tering a known or measured value of pi- indicates bAd when the transistor is good last pressed, of course, meaning you're
cofarads per foot (or meter), then con- about 25 percent of the time. Switching locked up until you figure it out. I often
necting the MC300 to the cable to be around the leads often helps produce a found myself powering the unit off and
measured. It's uncertain how useful this reading from the MC300. However, then on to get it back to the capacitance -
feature is, as many things can influence some transistors, particularly power measuring mode.
the accuracy of the reading. When it types, just won't generate a reading. A Finally, the manual that accompanied
works, though, it would be a useful sub- fresh battery or the use of the ac adapter the MC300 was less than ideal. The usage
stitute for a very expensive time -domain will produce the most good readings, but information presented is somewhat un-
reflectometer. as the battery weakens the number of bAd clear and sometimes inexact despite a
In addition to all of the above, the indications will increase. Even so, this is careful listing of which keys to press and
MC300 tests transistors, zener diodes, one of the MC300's useful functions. when. Although nicely printed, the text
and rectifiers. To extend its zener testing Since many transistors have leads that of the manual was produced with a non -
range, the MC300 has a dc-to-dc voltage are too large to fit into the socket, Dae- letter- quality dot-matrix printer and is
converter that produces up to 25 volts, tron provides three short leads with alli- difficult to read.
even though the unit is powered from a gator clips on one end and pins that slip Despite these drawbacks, the Daetron
single 9 -volt battery. The voltage isn't into the socket on the other. These can MC300 is an impressive piece of equip-
regulated, though, and drops as battery also be used in the capacitor socket to ac- ment, with a host of imaginative func-
voltage declines. To see what peak testing commodate large capacitors, but they tions that are not ordinarily available at
voltage is at any given time, all you have tend to fall out, so regular banana jack - its price. Lastly, after three weeks of us-
to do is press the ZENER key again with to- alligator clip leads are a better bet for ing it on my (well- equipped) bench, I re-
no diode in the socket, and the display testing more than one or two large capa- fused to part with it, and ended up buy-
will show the voltage. With a zener in- citors at a time. (Such leads are not pro- ing the test sample. I think that says it all!
serted into the transistor socket, the dis- vided with the MC300 but can easily be -J. Daniel Gifford
play will show the diode's breakdown bought or you can make them yourself.) CIRCLE I ON FREE INFORMATION CARD NE

Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 79

111111111BOOKS1111111.
Handbook of Practical I.C. Circuits by category, like desk accessories, fonts, be taken, that portion is highlighted with
Harry L. Helms. (Prentice -Hall. Hard communications, graphics and anima- a tint block.
cover. 163 pages. $34.95.) tion, music and sound, games, utilities
and everything else), it goes much further
Here is a book for everyone who has a
professional, experimenter or hobby in-
in offering quality and value ratings in
addition to description. Each entry is ac- NEW LITERATURE
terest in electronics. Rather than being a
companied by the program title, where it SWL Catalog. The 1988 edition of the
mere "handbook" that lists some IC de-
is available from and for how much (al- Electronic Equipment Bank SWL Cata-
vices and a few typical applications cir-
most free, remember ?) and screen print- log is now available. It contains complete
cuits, this book is collection of "recipes"
outs where appropriate. listings, including descriptions, technical
that let the reader get right to work in
Up front, the first chapter tells the and physical specifications and prices for
breadboarding and building devices
reader where and how to get public -ex- a wide variety of tabletop and portable
without resorting to deep theory, heavy
change software. The where includes shortwave receivers, converters, anten-
mathematics and component-by- compo-
users groups, commercial disk libraries nas, accessories and literature. Brand
nent analyses. As such (as the author
and over the wires. This chapter closes names like Grundig, ICOM, Japan Ra-
states) it is a "cookbook" that is ready to
with a section on how to use the book. dio, Kenwood, Magnavox, Sony, Ten -
be used as soon as a reader opens it.
This is a fun book through which to Tec, Toshiba and Yaesu are represented.
Emphasis is on using readily available
browse. Its contents make fascinating Each product listed is accompanied by a
IC building blocks rather than on design-
and sometimes amusing reading. If you photograph. For a copy, write to: Elec-
ing circuits from scratch. It capitalizes on
own a Mac, you should have this book tronic Equipment Bank, 516 Mill St., Vi-
available building blocks that perform
near it. enna, VA 22180.
specific functions instead of the old-
fashioned method of reinventing each
Build Your Own Working Fiberoptic, In- Test Equipment Catalog. Beckman In-
circuit as it is needed. frared and Laser Space -Age Projects by dustrial's new 52 -page test instruments
The book beings with an introduction
Robert E. Iannini. (Tab Books. Soft cov- catalog describes the company's full line
to integrated circuits with discussions on
er. 262 pages. $15.95.) of heavy -duty digital multimeters, oscil-
IC packaging, pin- numbering schemes,
Leafing through this book is like scan- loscopes, telecommunications test gear,
IC types, logic symbols and construction
ning an electronics technical manual function generators and frequency count-
and powering IC circuits. Following
from the future. Its 14 chapters are chock ers. In addition to providing detailed
chapters individually discuss operational
full of plans for building devices one usu- specifications and full -color photos of
amplifiers, linear ICs, TTL devices and
ally associates with a physics research la- each product, the catalog includes a spe-
CMOS devices. Each chapter includes
boratory and some even with science-fic- cial section on the company's new line of
basic theory, pinouts and tables for the
tion movies and books. Here you will digital temperature- measuring instru-
specific devices mentioned and a number
find such items as solid-state, helium - ments, including hand -held thermome-
of practical schematic diagrams that can neon and CO2 lasers, even a ruby -laser ters, multiple -input digital bench -top
be built.
gun. Other items that will pique your in- thermometers and temperature calibra-
If you are a professional, serious ex- terest are a high -speed laser -light pulse tors. For a copy, write to: Shelly Vickery,
perimenter or just an occasional tinkerer,
detector, an IR night -time viewing de- Beckman Industrial Corp., 3883 Raffin
you should find this book to be a handy
vice, a fiber -optic communication sys- Rd., Dept. ME, San Diego, CA 92123-
source of information and ideas.
tem, and a plasma tornado display lamp/ 1898.
sculpture lamp, among others. All proj-
Free (and Almost Free) Software for the ects are fascinating, to say the least. Interconnection Products Catalog. A 60-
Macintosh by Robert C. Eckhardt. (Di- Many of the projects are also danger- page Interconnection Products Catalog
lithium Press. Soft cover. 413 pages. ous if not built and operated properly. from L -Com lists and describes more
$19.95.) Thus, the author leads off the book with than 2,000 products, many of them new
Free software? You bet! and this large - prefaces on laser safety and general pre- to this issue, for computer, communica-
format book (it measures 8.5 x 11 cautions and project descriptions and tions and electronics applications. Infor-
inches) tells you what it is and how and special precautions. mation supplied includes: unit /quantity
where to get it for the Apple Macintosh Each project presented has a chapter pricing, full specifications, drawings and
computer. Among the free (and almost of its own. All chapters contain theory of photos of the products, dimensions and
free) software items that can be obtained operation sections and detailed construc- other pertinent details. Product cate-
are hundreds of applications and files tion procedures, including assembly gories include: molded coax and data ca-
ranging from sophisticated games to util- drawings. Full schematics and parts lists ble assemblies, baluns and multiplexers,
ities to templates for commercial pro- are also provided. Where circuitry is to data line and surge protection systems,
grams. There is even a complete catalog be assembled, printed- circuit board lay- telecommunications cables /accessories,
of nearly 300 free fonts, most printed out outs are given, and where perforated - RS -232 devices and testers, IEEE -488 ca-
as they would appear on paper. board construction is called for fully de- bles and accessories, and more. For a free
This book is more than just a catalog tailed drawings are provided. Whenever copy, write to: L-Com Data Products,
of software titles. Though it does list a point in construction or operation is 1755 Osgood St., N. Andover, MA
hundreds of titles (arranged according to reached where safety precautions must 01845.

80 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

Electronic Instruments Brochure. A full - ty for both Motorola OPTO 400 and op- tion. New entries include a combination
color brochure published by Hewlett - toisolator "dome "packages. For a copy DMM /storage oscilloscope, 60- and
Packard presents information on 22 bas- of the No. SG87R4 /D guide, write to: 20 -MHz portable scopes, several types of
ic instruments used to make electronic Motorola Literature Distribution Cen- signal generators and waveform moni-
measurements. Instruments covered in- ter, P.O. Box 20924, Phoenix, AZ 85063. tors, and six power supplies. Included is a
clude digital multimeters, counters, pulse new section that gives information on
and function generators and power sup- Test Equipment Catalog. A new eight - programmable RGB generators. For a
plies. Brief descriptions, specifications page, two -color catalog that lists and ful- free copy, write to: Leader Instruments
and prices are provided by each product. ly describes the company's low -cost test Corp., Dept. ME, 380 Oser Ave., Haup-
For a copy of Publication No. equipment is available from Mercer Elec- pauge, NY 11788.
5953 -7040, call any Hewlett- Packard tronics, Division of Simpson Electric.
sales office listed in the white pages of Among the items listed are recently an- ASIC Design Manual. National Semi-
your telephone directory. nounced multifunction frequency count- conductor's 1987 ASIC Design Manual
ers and 20 -MHz sweep /function genera- provides designers with guidelines fqr us-
Optoelectronics Selector Guide. Motor- tor; 3'/ - and 41/2-digit hand -held DMMs; ing the company's application- specific
ola's fourth edition of the "Optoelec- a volt -ohm -ammeter; a high- accuracy, integrated circuits and describes circuit
tronics Selector Guide" lists more than full -range 3'/ -digit capacitance tester; functions available in gate arrays and
20 product families in sections on Emit- and a variety of other digital test instru- standard cells. Packaging data, including
ter /Detectors, Optoisolators, Optointer- ments and probes. For a free copy, write package types, physical dimensions, pin
rupters and Fiber Optic Components. to: Mercer Electronics, 859 Dundee Ave, counts and thermal resistance, are also
Product families new to this edition in- Elgin, IL 60120 -3090. supplied. A general information section
clude Motorola's first hermetic -pack- lists the features of National's ASICs, il-
aged optoisolators (4N22,A Series), the Test Instruments Catalog. An 88 -page lustrates the gate array cell structure and
industry's first 200-volt zero -cross triac test and measurement instruments cata- helps designers calculate delays and
driver (MOC3080 Series) and the com- log from Leader Instruments details "size" chips. Selection tables and alpha-
pany's first visible light- emitting diode complete features, specifications and ap- numeric and function indexes are provid-
(MLED76). Also included are a cross - plications for more than 100 products, ed. For a free copy, call Carmen Valles at
reference guide and a section on reliabili- including 18 new ones in this latest edi- 408 -749 -7372.

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CIRCLE NO. 152 ON FREE INFORMATION CARD 83
NEW PRODUCTS (from page 16)

ule plugs into any available 28- or disk are install programs with full used to capture a window of pulses.
24 -pin ROM IC socket on the instructions and illustrations. The delay mode can acquire data up
computer's motherboard. If no emp- The PC -Clock Calendar module to 50,000 clocks after trigger, and
ty socket is available, the Module can has a built -in (not user -replaceable). non-delay mode can be used to view
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CIRCLE 22 ON FREE INFORMATION CARD Supplied with a standard RS -232
serial cable, the logic analyzer fea-
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can be used to troubleshoot or verify CIRCLE 23 ON FREE INFORMATION CARD
proper operation of digital circuits
that contain sequential and /or com- Motorized Cellular Antenna
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CIRCLE 29 ON FREE INFORMATION CARD
84 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics
 A Career Start in
21st Century Electronics
Text-to- Speech Converter text to speech and accurately speaks
it through its own built-in speaker. It
Smart Speaker from Swisscomp Inc. also has a line output for driving an
(Tampa, FL) is an advanced text -to- external audio device and a facility
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features not available on other con- No programming is required. Num-
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Say You Saw It In Modern Electronics January 1988 / MODERN ELECTRONICS / 85
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to $2,500 projectors ... Total cost less than 46032.
CIRCLE 38 ON FREE INFORMATION CARI) $30.00 ... PLANS AND 8" LENS $21.95 .. .
Illustrated information FREE. Macrocoma-
ME, Washington Crossing, Pennsylvania
COMMUNICATIONS
18977. Credit card orders 24 HRS. (215) "EXPLORE Ham Radio" "VHS" 24.95 +
736 -3979. 3.00 shipping. L.B. Video Productions Inc.,
2509 52nd Ave. Dr. W., Bradenton, FL 34207.
PICKS UP A WHISPER 50 FEET AWAY! ELECTRONICS
The model WAT -50 miniature FM tranmitter uses a POLICE, Fire Scanning Radios. Bearcat Re-
4 -stage circuit NOT to be confused with a simple wire- LINEAR PARTS-Transistors: MRF454 $15, gency Fanon. Harvey Park Radio, Box
less microphone. Simply snap the unit on top of a 9V MRF455 $12, MRF477 $11, MRF492 $16.75, 19224ME, Denver, CO 80219.
battery and you can hear every sound in an entire house
up to 1 mile away! Use with any FM radio. Tunes to any
MRF421 $22.50, SRF2072 $13, SRF3662 $25, DETECTIVES, Experimenters. Exciting New
frequency from 70mhz - 130mhz. Easy to assemble kit 3800 $18.75, 2SC2290 $19.75, 2SC2879 $25. Plans. Hard to find MICRO and RESTRICT-
Includes all parts and instructions. Only 29.98 tax Incl. Tubes: 6KD6 $10.50, 6LQ6 $9.75, 6LF6 ED Devices. Large Catalog $5.00 Refundable
$9.75, 8950 $16.75. Best Prices on Palomar on 1st Order. WILSON, P.O. BOX 5264, Au-
Road Noise Mics, Ranger AR3300. New 16
page Catalog listing radio /amplifier tricks
Channel Modification, PLL- Sliders, Peaking
- gusta, Georgia 30906.
TRANSISTORS -TUBES: MRF421 $24.00,
The WIRELESS TELEPHONE TRANSMITTER model MRF454 $15.00, MRF455- MRF477 $12.00,
WTT-20 is only about the size of a dime, yet transmits
for Range, Hard -to -Find Linear Parts -Mail
both sides of a telephone conversation to any FM radio $1.00 to: RFPC, Box 700, San Marcos, CA MRF492 $16.95, SRF2072 $13.50, 3800
with crystal clarity. Completely automatic. Uses power 92069. For Same Day Parts Shipment, Call $18.95, 2SC2879 $25.00, 6LF6 -6LQ6 -6JS6
from the telephone line Itself - never needs a battery! (619) 744-0728. $10.95, 8950 $15.95. New RANGER AR3500
Up to Vi mile range. Tunes from 70mhz - 130mhz. Easy All Mode 10 Meter Transceiver $319. Quanti-
to assemble kit includes all parts and instructions. On- LASERS Helium Neon 5mw good for visual
ly $29.98 tax incl.
ty Discounts! Best Prices on Hard -to -Find
Call or send MO, VISA, MC for Immediate delivery.
effects use, leveling, holography $175.00. To Parts, Antennas, Mics, Power Supplies, &
Single kit orders include $1.50 S &H. FREE SHIPPING order call 714-956-8497. Orders shipped 2day Equipment! Catalog $1.00 (refundable), or
on orders of 2 cr more. All orders shipped by U.S. Mail. air. free with order. RFPC, Box 700, San Marcos,
COD add $4.00. Personal checks allow 21 days.
FIBER OPTIC CABLE .100" DIA. 10FT- CA 92069. For information or Same Day
DECO INDUSTRIES
BOX 607, BEDFORD HILLS, NY 10507 8.50 100FT- 69.95 JSDIST POB 361 PARCH- Shipment -Call (619) 744 -0728. VISA /MC/
914.232.3878 MENT, MI 49004. C.O.D.
CIRCLE 40 ON FREE INFORMATION CARD

86 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

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are identified by the affix
NO IolbnonO t span number. After writing yo r order.total all new discountable items and eppy the appropriate disoount. To this subtotal,
add the non.ÓIuoun,eblN items Then add in SERVICE CHARGES VOLUME DISCOUNT
charge. We pavan shipping andmaurance to ad 'eases in the U.S.A.. Canada and Mown when check or money order accompanies order.
Hawaii, Canada and McEno.
Dpi -Key only ships orders within the continental U. Se. Aaska, S 0.00 -9 9.99 Add $2.00 9 0.00 -1 99.99 NET
0 10.00 $25.00 Add 90.75 9 100.004249.99 Less 10%
WNE ORDERING BR PHONE, CALL 1.800344.4538 IRK. call 210581 6574). BY MAIL SE50 YOUR ORDER T0: 5151181, P.O. Ow 577, Thief River F01ó, MN 56701. 9 25.00449.99 Add40.50 9 250.00- 9499.99 Law15%
You may pay b check. money order, Master harps. VISA or C.O.D. OIGI -NEV GUARANTEE... Any pans or products
purchased from Din Key Mal prove to be defective mil be replace or r., in,: 9 50.00499.99 Add$0.25 9 500.004999.99 Le. 20%
ed if returned w thin M days from receipt with a copy el your Kona, 'TI9/CES SUBJECT TO CHANGE WITHOUT NOTICE." $10006 Up No Charge $1000 Up Less 25%

CIRCLE 76 ON FREE INFORMATION CARD

SECRET CB PUBLICATIONS (modifica- SAVE MONEY on computer supplies! DO IT YOURSELF
tions, schematics, etc.). KITS, FM, PARTS,
ACCESSORIES, BOOKS. Catalog $1.00 (re-
Bargains galore. FREE Info. Write today!!
CREGS Enterprises, Dept. E, 318 Harper,
REPAIR YOUR OWN TV ITS EASY. ...
Write Research, Rt. 3, Box 601B, Colville, WA
fundable). Selman Enterprises, P.O. Box New Llano, LA 71461.
99114.
8189, Corpus Christi, Texas 78412. 512/853- CHALLENGING games for IBM com-
2935. patibles $8. DNE Math & Spelling tutors, both MISCELLANEOUS
COMMUNICATIONS PLANS, BOOKS, for $29.95. Satisfaction guaranteed! DNE,
Rte 1, Box 136, Pennsboro, WV 26415. ASIAN LADIES want correspondence for
KITS! AM /FM broadcasting (licensed /unli- friendship, marriage, SUNSHINE INTER-
censed), 1750 Meter transceivers, ham /CB NATIONAL, Dept. TW, Box 260, North
ACD1O
amplifiers, surveillance bugs, more! FREE Hollywood, CA 91603.
catalog, PAN-COM, Box 130 -ME 1, Paradise, Find out why we sell more high performance
CA 95967. SATELLITE and cable equipment schemat-
speaker kits than anyone in the U.S. For free cat- ics, service manuals, booklets, diagrams, in-
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formation packages, construction material,
CONCEPTS INC., 1631 Caledonia, La Crosse,
COMMODORE Chips, Distributor, Factory covers ,co nverters, receivers,decoders.Catalog
WI 54601.
Fresh. Low prices. For eg., #652649.95, $3.00. Ponderosa Company, 3624 Citadel
#6581- $12.85, 901227-$10.95 and many, Drive North #289M, Colorado Springs, Colo-
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many others. Just released new C128 ROMS,
AN UPDATE MUST, $39.95 plus postage INVENTORS! Can you profit from your
" . "THE COMMODORE DIAGNOSTI-
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CIAN", a new inexpensive way to diagnose PORATION for free information. Over a de-
faulty chips. This aid is a double sided lami- cade of service, 1-800-338-5656. In Massachu- Use the
Now do I get
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what chip to look for. Over 3,000 sold. $6.95 info card.
plus postage ....
HD Power Supply for C -64, 1 \VE \TORS
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parts /labor ....
Send for complete catalog . .
present ideas to manufacturers - Toll Free
VISA /MC ... Kasara Micro Inc., 31 Murray
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1 -800- 225 -5800.
Hill Drive, Spring Valley, N.Y. 10977 (1 -800-
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1 Information Call
vice. Free Catalog. TYNAMIC, Box 690, (402) -554 -0417. M.D. Electronics Inc., 5078
Hicksville, NY 11801. So. 108th Ste #115, Omaha, Nebraska 68137

MAN8910 - Double Digit 7 Segment Display, Hi

Efficiency Red .56" Comm Ann
50 PIN IDC Ribbon Cable Connector
36 PIN RI Angle "Snap Off" Header
..50
..50
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508 Central Ave. 14 Segment Driver Chip .75 14 PIN Header for Ribbon Cable ..... 3/$1

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Hewlett Packard 7 Seg .4" Red Ann67651 95 7 PIN Male Header 20/$1
Westfield, N.J. 07090 7 Seg .3" Bent Lead (Hobby Grade) 441 IC Storage "Bug" Box $2.45
(201)854.8008 7 Sag .6" Bent Lead (Hobby Grade) 341 Heavy Duty Alligator Clips (10 Sets) $2.30
1.5A 50V Bridge (1.0-5) .50 Regular Alligator Clips (10 Sets) $1.80
4A 50V Bridge (KBUO5) .75 Wire Strippers (Spring Loaded, Adjust.) $2.50
1 00
6A 600V Bridge 5/0" Square 5" Needle Nose Pliers (Spring Loaded) $3.95
10A $00V Bridge 5/8" Square 1 15 4 1/2" Diagonal Cutters (Spring Loaded) ... $3.95
NE555 TRANSISTORS 25A 200 Bridge (Solder Lug Type) 200 Not Driver set for 3/16 ", 1/4 ". 5/16" ,. 3/$2
LINEAR
45 0012
1.10.741 8 DIODES 12VDC SPST Reed Relay PC Mount 60 Jeweler's Screwdrivers (4 pcs) $2.65
TR SERIES 60 ]4L516. LM309R 50 UP798 361 $4.00
74367
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165 60 4013 25 40 M01330 50 SPST PB Switch (Keyboard Type) Oesoldering Pump (Solder Sucker)
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7406 34 741.5195 GO 4024 45 65 Solder Aid Tool Kit (4 pcs) $3.00
7407 35 Nafirn 50
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726 75 LM335N 95 1407005 45
TPDT "Bat" Handle Toggle (On Off On) 1 65 Model 6108 Logic Probe (Pencil Type) $18.95
1406 34 7415240 65 4035 40
7410 60 4040
LM330N 35 4.107806 45 250896 1 2 So DPDT RI Angle PC Toggle (On ON On) 95 Model 620B Logic Pulsar (Pencil Type) $18.95
to 7413 SERIES LM380N 75 807612 45 26011729 211 20/51
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366N 40 807624 11 LED Bar Graph Display. 23/4 ", Rectangular LED's .010F 100V Mylar Cep
HOUSE 4216 15/$1
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20 74L5245 70 40aú BO
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Self Adhesive Rubber Stopping - 741
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You Choose (3M- Bumpon), 3 Feet32, 10 Feet45.00,
7440 30 741514 35 7415290 75 4077 20 8 PIN/.09, 14 PIN /.13, 16 PIN/.15, 18 P151.17, 20 3,200uF 50V Twist Lock .65
7442 25 741515 25 7415293 75 PIN/.19. 22 PIN/.21, 24 PIN/23, 28 PIN/.26, 40 PIN/.28 3,300uF 50V Axial Lytic .85 50 Feet/$2000.
7445 50 741521 20 74L5265 75
4072
4073
26
35 Zero Insertion Test Socket 28 PIN ..... ..... 5.00 60004F 40V Computer Grade (Mallory) 1 50
-
Hi Reliability TO-3 Socket (Augur) as

1451
75
64
25
741521
741622
20

p
7496
162
7412299 7
60
35 .077
4076
50
25
TOKO COILS FOR FEB 1984
Ceramic Monolithic,
330pF, 470pF,
-
0014F.
All $0V or Higher:
.0018uF, .0022uF,.00270F,
Low Fluid Level Detector Kit
Instructions
Parts, PC Board 8
495
745+ 741.526 )41.5356 70 95
.0033uF, .0039uF ((All 30/91).010F -20/$1.0220F Soldering Iron Convenience Stands 5/51.00
7454 30 7 53] 20 74L6365 35 4081 20 TV PROJECT
7474 30 > L52e 26 747.5366 >5 4082 15/91,.11JF 10/$1 .22uF 10/$1 Voltage Mate Switching Regulator Kit S18.95
7475 45 741539 50 7415267 40 4085 35 Toko k's BKAN- K5552AXX(2), kE520HN-3000023 50
Crystal Clock Oscillator 146760 MHZ.
7478
7462
45
BS
741530
741532
20
20
7415366
74`6373
35
65
a006
093
45
45
(.071 uH) 8 L- 2(120H) Fixed. Set of 4 pcs $6.00. 3 Sets
$15.00. 10 Sets $45.00.
1

UCN4116B - OSC /Freq Div Clock IC

AM /FM Radio IC w/Data Sheet (02204) ... 15/51.00
5/1.00
COMMODORE COMPUTER KEYBOARD&MOTHER-
BOARD COMBO, INCLUDES ARTICLE FOR COM-
7483
7489
7485
50
55
40
741533
)4153)
741538
25
25
25
7415374
74L5375
7415377
75
85
70
4160
4163
4416
45

ls
Opto Isolator H11AX(Transistor Type)
Opto Isolator HXXCX(SCR Type)
-65
.85 Slide Pats - 1 Each 50K. 100K, 1.2M.2M,5M -
10/$1
$1 PATIBILITY (INTERFACE) $12.95

] 90 µ26 2.50 74165 (Shift Register) Houser/8095

45 74`540 30 7415378 1 0 4s Hewlett Packard Clock (No Specs)
ULN2231 (Delco DM50) Dual Preamp IC 2/1 705 Digital Multimeter
7491
7492
]
85
45
35
74542
741547
741551
31
90
20
7415393
7415620 1
10
50 4697
9 45
45
Line Cord 6 feet UL Listed SPT 2
Scope Probe Set w /Everything x1/x10
60
24.95 Switching Power Supply - Plus 8 Minus 5812 Volts
MODEL

- 549.95
93 7415670 85 4502 60 200W. by Conver 14V to
7495
796
74107
45
55
75
741554
741655
741573
25
30
25
74SD SERIES
4571
4510 70
Wire Stand Offs
Zoner Asst -
65 pcs Total Includes -Minimum
10/51

$1.95
3 MRF901 (Hobby
Peter PT100 3/8"
You Test)
Horizontal Mount
10/$1
Trimpots 100 OHM.
DC Vo11694
AC Voltage
DC Current
10000
100kV to 750V
0.1 PA to 10A
051 95
-
7450137 50 4517 75 Different 1W Devices
74. 0 74 574 25 745C138 35 45. Resistor Asst 1,000 pcs 35 Values Minimum. 1K, 5K, 10K, 20K, 50K, 100K, 200K. 500K, 1M. AC Current 0.1kÁ to 10A
74116 100 74`,75 30 750139 35 4510 60
Single Turn 4/51 111-LOResistance 0.19 to 20612
7412+ 35 741.576 3v 452e 75 Popular Values (16,106,100K) Included. Mostly 1/4 8 Capacitance MP to 207F
74123 40 741579 40
7450237 60
4532 1/2W. Some 8 2W. Lots of Precisions. Carbon Film. Multi Tum Precision Tnmpote. 50 OHM, 100 OHM, 200 tolvlsrd voltage testing
60
74541239 1
Diode Teei
OHM, 250 OHM, 500 OHM, 1K, 2K, 5K, 10K, 20K, 25K,
-
45
74125 741561 40
7450240 50 4539 75 Taped and Reeled fo/ Easy Sorting $9.95
100/$66
Hen test transistor testing
74126 40 741565 40
7450241 50 4555 75
Jumper Plugs (Cambion) Male to Male for Bread- 50K, 100K, 200K, 250K, 500K, 1Meg .75 Each,
74128 741566 Zenith TV Replacement IC Special Sl Each 221-42,
74145
55
45 741590
26
b 7450244
7460245
65
50
4556
4573
35
45 board 8 Connectors 10/01.25
$2.95 221 -43, 221-48. 221-69, 221 -79, 221 -87, 221 -96, UHF -TV PR MP
9VDC Well Transformer. 200704
74118
74151 50
741593
741510] 30
7450373 50
4584 70 $3.95 221. 104, 221 -105, 221 -106, 221 -140. featured Radio Electronics March/
74374
50 60 9VDC Well Transformer. 5007004 ic e i
articles,
71153 50 7415112 25 4565 70 Motion Detector Module (Includes ULN2232 IC 6 Caps), (As
7450533 50 12VDC Well Transformer, 400ma $6.95
74156
74157
70
50
74151+3
7415++4
30 7460534
30 40060
0
45
6.3V 1.2A Transformer $1.60 $2 Eech, 7410, 25425. This inexpensive antenna mounted pre -
amp can add more than 25 dB of gain to
45
Motion Detect. ULN2232 IC Only 342. 20/$10 Black,
-
7660440 50
$3.50
7416+ 60 7.5123 45
7450563 150 a5í55 45 12.6 VCT IA $2.25
7415125 7 1/2/15VAC Plastic Case for Detector your system. Lots of satisfied customers
74163 60 35
7450564 60 7 (Seven) Amp Tapped Transformer
74+64
74173
74174
80
70
50
741.5126
74L5132
7415136
30
35
30
70,0573 200
7450570 200
EPROWMISO
2216 295
or 9V /18VAC
Muffin/Sprite Style Fan 8802C7 (EG 8 G Rotron).
$8.95 Miniature Speaker for Detector
Model SG -105 Signal Generator
Low 01515980, 46 STEP
- 20Hz to 150 kHz,
045.95
75
and repeat orders for this high quality kit,
which includes all component parts, PC
BD. Case. Power Supply and Baton $34.50
BOOR $5.95
41]5 50 ]415+36 40 ?2'1',.26 2732 -2 395 3 1/2" 59, 115V
22/44 PIN Edgecard Connector .65
)1171 fio 141.Sí39 40 ABOVE s 250276"5 325 Jumbo Red LED's 1541.00. 10046.00 Assembled Version í57.S0
741.5151
CMOS SERIES
nlza25 .w Jumbo Green LED's 1041.30, 100410.00 40 PIN IOC Ribbon Cable Connector . .40
74181 +e0 3 zs 72562 795
74192
74193
74194
70
65
70
7415157
7415150
7415164
30
25
25
70000
4001
4002
25
20
20
8035
2005
070
195
125
I 25
Jumbo Yellow LED's

Features
10/91.40 100411.00
Jumbo Yellow Hi Intensity with RI Angle 8 Black Case
1041.20, 100410 Term: MICRO -MART accepts Visa. MC and telephone COD's Minimum order S10 00 Shipping
applicable
-
U.S. orders. $2.50. Canada and other countries, $3 50 Shipping rate adjusted where
74195 55 741516+ 5 006 20 UDN6127P 50
45 4006 60 Urn 55 Jumbo Amber LED's 1041.40. 100/$11.00
74228 55 7415162
24385 40 )041.5 +63 45 4011 20 U0N61a4P 60 Mini Yellow Hi Intensity with Discreet, Pale Blue N J residents add 6"o sales tax
u0N71e16 Lens/Case Feature 10/1.20, 100/10 LED Clips/Rings
12011654 -6008
65
for Jumbo 15/51, 100/56 MICRO -MART 508 CENTRAL AVE.. WESTFIELD. NJ 07090

88 MODERN ELECTRONICS / January 1988 CIRCLE 51 ON FREE INFORMATION CARD Say You Saw It In Modern Electronics
 IIEStilktailLESS
for your
FREE CATALOG
DIAL 1- 800 -426 -2653
or write:
CABLE
ISTRIBUTORS
PO BOX 1261, DEPT. M
HOPE, AR 71801
89 OA FRF: k: INFORMIA7105 (ARI)
 LED Beacon Wireless Microphone
ADVERTISERS' (from page 39) (from page 31)
INDEX
For the positive battery terminal, phone's r-f carrier loud and clear.
RS# Page #

50 ARRI 67 strip % and h inch of insulation from Then very carefully adjust the spac-
5 AMC Sales 74 opposite ends of a 1%-inch length of ing between the turns of L1. Use an
96 ACE Communications 45
No. 26 solid hookup wire. Plug the insulated tuning wand for this -not
29 Antique Radio Classified 84
Bentley 90 end from which the inch of insula- 33/4 a metal object like a screwdriver or
95 C&S Sales 65 tion has been removed into the board capacitive effects will give false re-
38 CTM 86
from top to bottom and solder it at sults. Just a slight movement of the
89 Cable Distributors 89
98 Cleveland Institute of Elec Coy. III point A, as shown in Fig. 2. Now po- coil's turns is needed. A word of cau-
Command Productions 74 sition the No. 357A cell, positive tion is in order here: Under no cir-
151 Communications Elec 17
electrode up, against the IC socket cumstances should you attempt to
12 Communications Specialty 90
28 Consolidated Electronics 85 and hold it in place as you bend the tune your wireless microphone to a
6 Cook's Institute 77 wire over the top of the cell and frequency beyond 108 MHz. Such
150 Daetron 37
around the outer edge of the board. frequencies are reserved for aircraft
40 Deco Industries 86
76 Digi -Key Corp 87 Route the wire and solder it to pin 5 services and must not be used for any
152 Digital Research 83 of the IC socket. The hookup wire other purpose or be interfered with
Electronic Equip. Bank for any reason.
41 6
should solidly "sandwich" the cell in
Electronics Book Club 3

7 Haltronix 77 place but still permit easy removal of You can house your wireless mi-
3 Jan Crystals 70 the cell. AE crophone in any enclosure that suits
14 Kelvin Electronics 53
your tastes. For general-purpose use
64 Kenwood USA Corp Cov. IV
LT Sound 86 to pick up sounds at a distance, a
PORTASOL
42 MCM Electronics 7
The First Truly Portable Butane Soldering Iron small plastic box with a hole or slot
51 Micromart 88
cut in it directly in line with the mi-
13 NRG 53
NRI Schools 10, 13
{
crophone element will do fine. For
27 National Technical Schools 85 up -close announcing applications, as
8 OptoElectronics Coy. II in a PA system arrangement, use an
Pacific Cable Co., Inc 9

9 Radio Shack 5 Now Solder Anywhere ... Anytime enclosure that is small enough to be
Only 7 Inches Long conveniently hand -held, such as an
Uses Butane, No Cords or Recharging Time
60 Minutes Soldering per Cartridge inexpensive microphone housing or
Built -in Igniter
Heats in 30 Seconds, Cools in Seconds Also
a small project box. Another alterna-
Adjustable 10-60W Power tive is to mount the circuitry inside of
ONLY $34.95 Includes 2.4mm Tip
Other Tips 8 Refills Available. Send MO or Check + $2.00 P8H a box that has a clip on it to permit
NYS Residents Add Applic. Sales Tax
hanging the electronics from your
Bentley Electronics, Inc.
106 Wedgewood Drive P.O. Box 996
belt and locating the microphone ele-
Hauppauge, NY 11788 (516) 265.1325 ment on a tie bar or pocket clip at the
Dealer Inquiries Invited WA2LIC
end of a shielded cable.
To obtain long operating life, use
NO WAITING FOR COMPLETE, LOW a high- energy alkaline battery to
PRICED, CHIP COMPONENT KITS power the wireless microphone. A
CC-1 Capacitor Kit contains 365 pieces, 5 ea. of every
10% value from 1pf to .330. CR -1 Resistor Kit contains single fresh alkaline battery will
1540 pieces; l0ea. of every 5 %value from 100 to 10 meg0.

Free Product Information Sizes are 0805 and 1206. Each kit is ONLY $49.95 and power the microphone continuously
available for Immediate One Day Delivery!
Order by toll -tree phone, FAX, or mail. We accept
for about 30 hours. If your anticipat-
Readers can obtain free information on
VISA, MC, AMEX, COD orders, or company P.O.'s with
approved credit. Call for free detailed brochure.
ed applications call for intermittent
products advertised by the above com- use, such as in paging over a PA sys-
panies, as well as for some editorially tem, you might want to place a nor-
mentioned products. Simply circle the mally open pushbutton switch in
appropriate number printed below an series with the + 9 -volt line to power
advertisement onto the Modern Elec- the circuit only on demand. This will
tronics "Free Information Service" considerably extend battery life. Yet
card bound into this issue. After filling
another alternative is to use a corn-
in your name and address, just mail the
mon spst slide or toggle switch that
postpaid card. Your request will be for-
warded directly to the advertiser with a will allow you to turn off power
mailing label prepared by our reader - whenever the microphone is not be-
WIfMUNICATIQIVS SPECIAL ISTS, NYC.
ing used.
service department to ensure speedy re- 426 Wes1Talt Aven,e
1 prarpe G92665 -4296
,Local (714)998 -3021 FAX17141974-3420

sponse.
Entlr USA. 1µ0a854-0517 AE
CIRCLE 12 ON FREE INFORMATION CARD

90 / MODERN ELECTRONICS / January 1988 Say You Saw It In Modern Electronics

 EXPAND YOUR CAREER HORIZONS...

_....._
--- =
--_i_
i---_
_.y==______
_.._.________
__VINEIMM_._

The CIE Microprocessor Traine- helps you to learn how circuits with
microp ocessors function in computers.

START WITH CIE. the handy reply coupon or card below to:
Cleveland Institute of Elec:tronics,
Microprocessor Technology. Satellite Communications. 1776 East 17th Street, Cleveland, Ohio 44114.
Robotics. Wherever you want to go in electronics...
r
start -irst with CIE.
Why CIE? Because we're the leader in teaching
electronics through independent study. Ccnsider this.
CIE World Headquarters
Cleveland Institute of Electronics, Inc.
AMO-96

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we've been doing it for over 50 years, helping
thousands of men and women get started in
1776 East 17th Street Clevelaid. Ohio 44.
Li Please send your independent stucy catalog.
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For your conven ence, CIE Nill try to rave a representEtiv e

contact you -
there s no cbligation.
electronics careers.
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We offer flexible training to meet your needs.
You can start at the begirner level or, if you already Addres3 Apt
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CIRCLE 98 ON FREE INFORMATION CARD
 KENWOOD
pacesetter in Amateur Radio

Hear itAll! SELECTIVITY SOL &- NOTCH

AUTO
ON
OFF
\ \ lt
s 7 to

'1 i I
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I
I _I
I_I
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LI
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;;;Nny''s._.....YiIAGR ANY I ANtB...._... NOTE:N_.. R4017C

COMMUNICAYIONS RECEIVEq
MODE /KEY
CLOCK I OFF CLOCK 2

A/B4 WOCK

-HFVHF
t Y. 11MHz VU

Versatile programmable scanning,

R-5UUO
High performance receiver
with center -stop tuning.
Choice of either high or low
impedance antenna connections.
THE high performance receiver is Kenwood non -volatile operating
here from the leader in communica- system. Lithium battery backs up
tions technology -the Kenwood memories; all functions remain intact
R -5000. This all -band, all mode even after lithium cell expires.
receiver has superior interference Power supply built -in. Optional
reduction circuits, and has been DCK -2 allows DC operation.
designed with the highest perform- Selectable AGC, RF attenuator,
ance standards in mind. Listen record and headphone jacks, dual
to foreign music, news, and com- 24 -hour clocks with timer, muting
mentary. Tune in local police, fire, terminals.
aircraft, weather, and other public
service channels with the VC -20
VHF converter. All this excitement 100 memory channels. Store mode, Optional Accessories:
and more is yours with a Kenwood frequency, antenna selection. VC -20 VHF converter for 108 -174 MHz
R -5000 receiver! Voice synthesizer option. operation YK -88A-1 6 kHz AM filter
Covers 100 kHz -30 MHz in 30 Computer control option. YK -88S 2.4 kHz SSB filter YK -88SN 1.8
Extremely stable, dual digital kHz narrow SSB filter YK -88C 500 Hz CW
bands, with additional coverage filter YK -88CN 270 Hz narrow filter
from 108 -174 MHz (with VC-20 VFOs. Accurate to ±10 ppm over a
DCK -2 DC power cable HS -5, HS -6,
converter installed). wide temperature range. HS -7 headphones MB -430 mobile bracket
Superior dynamic range. Exclusive Kenwood's superb interference SP -430 external speaker VS -1 voice
Kenwood DynaMix- system ensures reduction. Optional filters further synthesizer IF- 232C/IC -10 computer
an honest 102 dB dynamic range. enhance selectivity. Dual noise interface.
(14 MHz, 500 Hz bandwidth, 50 kHz blankers built -in.
spacing.) Direct keyboard frequency entry. More information on the R -5000 and
R -2000 is available from Authorized
R -2000 150 kHz -30 MHz in 30 bands Kenwood Dealers.
All modes Digital VFOs tune in 50 Hz,
500 Hz, or 5 kHz steps 10 memory channels
Programmable scanning Dual 24 -hour digital
clocks, with timer 3 built -in IF filters (CW filter
optional) All mode squelch, noise blanker, RF
attenuator, AGC switch, S meter 100/120/
KENWOOD
220/240 VAC operation Record, phone jacks
KENWOOD U.S.A. CORPORATION
2201 E. Dominguez St., Long Beach, CA 90810
Muting terminals VC -10 optional VH F
converter (118 -174 MHz) P.O. Box 22745, Long Beach, CA 90801 -5745
CIRCLE 64 ON READER SERVICE CARD
Specifications and prices are subject to change without notice or obligation.