Introductory Guide to DMX

DMX is a control protocol, or “language”. If a controller speaks DMX, and a piece of equipment hears DMX, then the controller can affect the operation of the equipment, regardless of who made what and whether it was ever imagined that the two things might be used together.

A DMX controller can be as simple as a little box with one switch and a knob, or as complicated as a multi-screen computer with hundreds of knobs, switches, indicator lights, and faders. DMX equipment can include stage lights, fog machines, and motors to make a screen go up and down. Anything electrical can be programmed to speak or understand DMX. One popular lighting control manufacturer made a DMX coffee pot for fun; now when they want to brew a cup of coffee, they push a button on one of their lighting controllers.

DMX travels over a thin cable, from the controller to the equipment. Several pieces of equipment can be attached to the same cable, in a process known as “daisy-chaining”. A DMX product always has both DMX In and DMX Out connectors, with DMX Out intended to feed any nearby DMX product. A DMX controller only has a DMX Out connector.

Wireless DMX is becoming increasingly popular. You still have a DMX controller and a DMX device, but instead of a wire connecting the two, there is a transmitter at the controller and a receiver at the device. Some controllers and devices even have transmitters and receivers built in.

The DMX language sends 512 channels of information, all at once, with each channel being a level from 0-100%. A small controller might only have knobs or faders for 12 or 24 channels; in this case, the rest of the channels are sent as 0%. Every piece of DMX equipment has a DMX address, a number from 1-512. The address can be changed using switches on the equipment. If you set the DMX address to 118, for example, then that piece of equipment will only pay attention to the % level on channel 118 and will disregard the levels of the other 511 channels. You can have multiple devices set to the same address, and they will react to the % of that channel simultaneously. If you want to control two things separately, then you must assign them different addresses.

Some products require several DMX channels of information to operate. For example, a stage light might use 3 channels: 1 for brightness, 1 for color, and 1 for beam spread. Some products can use 20 channels or more, so you may need more than 512 channels in order to control your entire show. In this case, a DMX range of 1-512 is called a universe, and you will need several universes. You will have one cable going from your multi-universe DMX controller to the devices on the first universe, and a second cable to the devices on the second universe, etc. You might have two devices with the DMX address of 100, but if they’re wired to different DMX universes, then you can still control them separately. The newest control protocol sACN/Artnet can send several DMX universes over one cable.