Introduction to DMX
BU Controls
2008
Objective
• Explain simplified functioning of a DMX control system
• Provide basic technical clarification
2008 2
What is DMX
The origin of the abbreviation of DMX is unknown.
However it is often explained as Digital Multiplexed signal DMX
devices
It is a protocol, in which a DMX controller communicates
to DMX luminaires
010110110011
DMX
signal
In other words
DMX
cable
DMX is the language in which DMX controller talks to
DMX
DMX luminaires
controller
2008 3
Examples of DMX products
DMX
devices
Luminaires Switchpacks
010110110011
DMX
controller
DMX controllers
2008 4
History of DMX
DMX originated in the world of theatre was developed by USITT in 1986. DMX
is used mainly for “controlling lighting equipment and accessories” in
entertainment applications (theatre, staging, concerts etc)
Nowadays DMX is used more and more in architectural scene setting
applications as well.
2008 5
The DMX signal explained
A DMX controller sends DMX values.
This is a 8-bit value (value between 0-255)
corresponding to a 0-100% intensity
010110110011
DMX Intensity DMX
Value signal
0 0%
64 25%
255 064 192 248 058 000 128 50%
192 75%
255 100%
DMX
value
2008 6
The DMX signal explained
Strings of 512 values are send 40 times per second.
The location of a DMX value is referred to as “address”
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Address 002
Address 001
Address 512
Address 511
Address 510
Address 004
Address 003
Address 002
Address 001
Address 512
Address 511
128 192 222 255 192
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….000 064 100 105 128 125
DMX string
with 512 values
1/40 sec
2008 7
The DMX signal explained
By addressing the DMX device, it knows which DMX value to use
Address 006
Address 005
Address 004
Address 003
Address 002
Address 001
50% 25% 75% 75% 0% 100%
000 255 255 192 064 128
Address 001
Address 002
Address 003
Address 003
Address 006
Address 005
2008 8
The DMX signal explained
By addressing the DMX device, it knows which DMX value to use
Address 006
Address 005
Address 004
Address 003
Address 002
Address 001
75% 75% 50% 50% 100% 50%
255 128 128 128 192 192
Address 001
Address 002
Address 003
Address 003
Address 006
Address 005
2008 9
The DMX signal explained
By addressing the DMX device, it knows which DMX value to use
Address 006
Address 005
Address 004
Address 003
Address 002
Address 001
100% 0% 100%100% 0% 100%
000 255 000 255 000 255
Address 001
Address 002
Address 003
Address 003
Address 006
Address 005
2008 10
The DMX signal in scene setting
Most DMX devices use more then one DMX-address
In example, the LED LINE2 uses 3 DMX addresses.
1st DMX value determines the intensity of RED,
2nd DMX value determines the intensity of GREEN
3rd DMX value determines the intensity of BLUE
The DMX-start address is the first DMX value used,
(DMX-start address+1) the second value, etc.
Start address: 1 4 22 215
DMX addr. Red intensity: 1 4 22 215
DMX addr. Green intensity: 2 5 23 216
DMX addr. Blue intensity: 3 6 24 217
One DMX line can control 512/3=170 individual RGB units
2008 11
Address 006
Address 005
Address 004
Address 003
Address 002
192 255 000 000 064 255
Address 001
2008
Address 001 Start address: 1
Address 002
Address 003
The DMX signal in scene setting
Start address: 1
Address 001
Address 002
Address 003
Start address: 4
Address 004
Address 005
Address 006
12
Address 006
Address 005
Address 004
Address 003
Address 002
064 192 128 064 192 128
Address 001
2008
Address 001 Start address: 1
Address 002
Address 003
The DMX signal in scene setting
Start address: 1
Address 001
With changing the DMX values, different colours are created
Address 002
Address 003
Start address: 4
Address 004
Address 005
Address 006
13
Address 006
Address 005
Address 004
Address 003
Address 002
000 000 000 255 255 255
Address 001
2008
Address 001 Start address: 1
Address 002
Address 003
The DMX signal in scene setting
Start address: 1
Address 001
With changing the DMX values, different colours are created
Address 002
Address 003
Start address: 4
Address 004
Address 005
Address 006
14
Address 006
Address 005
Address 004
Address 003
Address 002
128 255 128 000 255 064
Address 001
2008
Address 001 Start address: 1
Address 002
Address 003
The DMX signal in scene setting
Start address: 1
Address 001
Address 002
Address 003
Note: luminaires with the same address will always react the same!
Start address: 4
Address 004
Address 005
Address 006
15
Addressing luminaires
2008
Address 001 Start address: 1
Address 002
Address 003
Start address: 4
Address 004
Address 005
How a start address should be changed depends on the luminaire.
Address 006
Start address: 100
Address 100
Address 101
Address 102
16
The DMX cable explained
A good DMX control cable is a RS485 “shielded twisted pair”
This exist of 3 connections; 2 signals and a ground (GND).
Shield = GND Twisted pair
010110110011
Data (+) Data (-)
Shielded CAT.5 (or higher) cable can also be used.
DMX
CAT.5 S/UTP, F/UTP SF/UTP cable
CAT.6 U/UTP, S/FTP, S/STP
CAT.7 S/FTP, S/STP
The data (+) and data (-) signal create the actual DMX signal
Ground must be connected for reference, and to prevent interference.
2008 17
The DMX connector explained
Preferred DMX connectors are RJ45 PIN 1 DATA +
PIN 2 DATA -
PIN 3
PIN 4
PIN 5
PIN 6
PIN 7 GND
010110110011
PIN 8 GND
and Neutrik XLR 5 pin
PIN 1 GND
PIN 2 DATA -
PIN 3 DATA + DMX
PIN 4 cable
PIN 5
XLR make stronger connections and are suitable for thicker cables
(male for incoming signal, female for outgoing signal)
2008 18
DMX topology
Topology with DMX is serial (total DMX length <300m)
serial 9
2008 19
DMX topology
Topology with DMX is serial (total DMX length <300m)
parallel X
2008 20
DMX topology
Notes:
• It is possible to split a DMX line;
this can be done using additional hardware: a DMX-Splitter.
• Every DMX luminaire consumes “DMX energy”
Maximum 30 DMX devices can be connected to one DMX line.
After this the signal needs to be boosted with a DMX-Booster
The “4 way optosplitter” splits and boost the DMX signal.
2008 21
DMX topology
max. 30 pcs max. 30 pcs
max. 30 pcs
max. 30 pcs
Splitted & Boosted Signal 9
2008 22
DMX termination
To create a stable DMX signal the end of each DMX line should be
“terminated” with a 120: resistor
This should be mounted between the Data (+) and Data (-) signal
120ȍ
0,25W
120ȍ
0,25W
120ȍ
0,25W
5 1 5
4 2 4
3 3
2008 23
DMX technical characteristics (1)
Number of units max. 30 (Using boosters: unlimited)
Number of addresses 512 max
Signal level several hunderds of millivolts
Speed 40 times 512 values / second
+/- 250 kbaud
Termination end of the line, 120 Ohm
Cable length max. 500m, (Using boosters: unlimited)
Cable type Shielded twisted pair 100-120 Ohm
Cat.5 S/UPT, F/UTP, SF/UTP
Cat.6 U/FTP, S/FTP, S/STP
Cat.7 S/FTP, S/STP
Cable topology serial (line)
Termination 120 Ohm
Safety DMX is SELV
2008 24
DMX technical characteristics (2)
• A DMX system contains one controller (transmitter) and receiver(s)
• Information is transferred by modulating the two signal wires in opposite way.
Ground is needed as reference
• An receiver has to be given an address. This is a number between 1 and 512.
This address cannot be changed via the DMX connection
• DMX is based on RS485 communication. RS485 is two way communication,
this is not implemented in DMX (one way only)
• DMX is invented to replace a multiplexed analog system
• In DMX communication there is no address info. The receiver counts the
messages
• Random addressing is not possible. Addresses cannot be left out.
• A DMX value can mean anything, depending on receiver. For luminaires with
intensity only most often a linear intensity curve is used.
• Standard: “E1.11, USITT DMX512-A”, maintained by ESTA
2008 25
Summary “Introduction to DMX”
Luminaire settings:
DMX address (start address)
Start address 004
Address 004
Address 005
Address 006
512 addresses
(i.e. 170x individual RGB)
max 30 DMX devices
-terminator
-max. 30 pcs
Unlimited DMX devices using
DMX signal: continuous stream of 512 values
boosters
Each value (0-255) represents an intensity (0-100%)
DMX address 1, 1st value, (i.e. “128” -> int = 50%) Serial topology
DMX address 2, 2nd value (i.e. “194” -> int = 75%)
etc. Special DMX cable
Booster:+
(shielded twisted pair 120:)
4x30pcs
Commissioning:
Booster:+
depends on luminaire /
4x30pcs controller
2008 26
