DMX Basics

Luke Howard

Tags Basics

DMX is a data protocol most commonly used in lighting and stage equipment. DMX or DMX-512 provides control of up to 512 channels per run. A run is commonly known as a universe. Essentially each universe provides you with 512 channels. When connecting DMX, each fixture is daisy chained. This means that the cable comes out of the lighting console or usb module into the first light, then the data comes out of the first light into the second light. Please see diagram below.

Each fixture must also have an address. This address is the starting channel number. You can see in the example above we have a range of fixtures. Some use 4 channels, some use 6 channels, etc. All of this depends on the fixture and parameters, each fixture is different in the amount of channels it uses. The easiest for one of our PRO PAR fixtures is to use the 4 channel profile. You can see that before we add a new fixture, we have to make sure we do not start the address in a channel of a previous fixture. For Fixture 1 there are 4 channels it needs to run so it occupies channels 1, 2, 3, and 4. Which means Fixture 2 will start at channel 5 and take up 4 channels as well. Fixture 2 occupies channels 5, 6, 7, and 8. Fixture 3 will now start at channel 9. Since it uses a profile of 6 channels, it occupies channels 9, 10, 11, 12, 13, and 14. Fixture 4 would then start at 15. Try the next 2 on your own!
Did you get that Fixture 5 should start at channel 25 and Fixture 6 would start at channel 35?

DMX Cable VS Microphone Cable
While microphone cable often gets used in less complex situations, it is never recommended to use 3-Pin microphone cable with our fixtures. While they often look the same and sometimes microphone cable can be subsituted for DMX and work, they are two totally different cables. DMX Cables usually have 110-120 ohm resistance while microphone cable utilizes 75 ohm resistance cable. When using microphone cable, you will see degredation on long runs. You will also notice fixtures doing random things, they are recieving communication but it is not always the right communication.

Further resources can be found here:
What is DMX?
XLR vs DMX Cable

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