What is DMX 512?

DMX 512 is a standard protocol by means of which lighting, controllers and control desks can communicate with lighting equipment. It was designed to allow equipment from different companies to be used together easily.

Where did DMX come from?

The first dimmers/fixture functions were actually controlled by levers on the dimmers/fixtures themselves.During a show, it could take several men to move these levers and someone else to coordinate them. This kind of control was quite cumbersome. Later, control wires were run from each dimmer/fixture function to a control console. If you had 300 dimmers/functions, you had to have three hundred control wires! To improve this, manufacturers started using digital signals sent down one control cable. At first each manufacturer used their own protocols, meaning that different manufacturer's equipment could not be combined. Finally, DMX 512 was adopted as the standard lighting control protocol. DMX has 512 individual channels, which can be set to a level between 0 and 255. If a dimmer/function was addressed to be on channel 1, and the level of channel 1 was brought up to 255 (or 100%), the dimmer/function would be sending out full power. Therefore, a color/gobo or other functions are assigned a number from 0 to 255. Example: Channel 1 Gobo 0 = Blackout 10-20 = Gobo 1 20-30 = Gobo 2 30-40 = Gobo 3 This means anywhere between level 10-20 gobo 1 would be visible. DMX512: 512 represent the number of channels one DMX cable can carry. It requires only 3 pins. Older systems, known as 5-core DMX may be seen ? (two pins will not be used and are reserved for 2nd data link). The data is sent serially to 2 pins (the third is the ground pin) known as "positive phase" or "hot" and "negative phase" or "cold". Pins 4 & 5 are reserved for 2nd data signal or talkback. At the console end, the channels are fed into a multiplexer (mux) which takes the individual channel's data and encodes it into a format suitable for sending down the DMX line with all the other channels' data. At the dimmer/fixture end, the data is fed into a demultiplexer (demux) and split up again into the individual channels to be fed to individual dimming/function circuits. In practice, the mux and demux will be incorporated into the console and dimmers respectively, though standalone mux and demux units are available to convert analogue systems into DMX required.

The DMX advantage

DMX is advantageous because the DMX cable is less bulky than a 48-conductor cable and is cheaper and less cumbersome. If the cable were required to run long distances, any repeater/amplifiers would only have to amplify 2 signals instead of 48. DMX also allows control of many different pieces of DMX equipment, such as smoke machine, scanners, dimmers etc. from a central location.

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