I get questions about lighting control almost daily. Most of these questions center around understanding or misunderstanding DMX. Just to clarify I am talking about the lighting protocol DMX512 (often just called DMX) and not the urban contemporary artist Earl Simmons, known as DMX.

I'm not going into extreme detail on the intracacies of DMX. I'd just like to impart a basic understanding. Before we had DMX we often had lights, or strings of lights connected to physical dimmers. If you wanted to dim light number one, you simply turned, or slid dimmer one down to the appropriate level. If you wanted to dim multiple lights, you could grab a broom handle and slide all of the dimmers down at once.

Dimmers weren't easy to deal with. They weren't portable. They created a lot of heat. The operator sometimes couldn't see the stage because the dimmers were tucked away in a corner somewhere.

An Extremely Short History

Here's an extremely abridged version of DMX 512 history. One day a lighting designer or technician had a (pardon the pun) bright idea. "Let's build a remote control dimmer, with sliding fader controls! Then we can put the dimmers in a utility closet closer to the stage and the lighting director can see the stage from the control position." Later another great idea came along, "Let's design some way to record the positions of our faders and save it so we can recall it scene by scene." Then every lighting company began building dimmers and controllers. The only problem was compatibility between manufacturers. If you liked Jim's Lighting Control Company's controller, and Bob's Theatrical System's dimmers, you had problems. They wouldn't talk to each other. Eventually the United States Institute for Theatre Technology developed the DMX512 protocol so that everyone would be on the same page. If you'd like those details, you can check them out here: USITT. Now I know that if I buy an NSI/Leviton controller, and a Chauvet dimmer they'll work together.

What DMX is:

At its most basic level DMX is a control protocol that uses 512 unique addresses to transmit information from the controller, to the lighting device being controlled. In the past this was typically a fader on a lighting console controlling a dimmer in a rack. You move fader one, and it controls the light that was plugged into dimmer one. Now we have lighting instruments that use multiple channels of DMX. Multiple devices can also use the same address. Let's break it down a little more.

How it Works:

Let's pretend I have a walkie-talkie that can select between four channels. I am talking on channel one. Jim is listening to channel one. Ed is listening to channel two. Bryan is on channel three, and Jack is listening to channel four. I pick up my walkie-talkie and say, "If you hear me on this channel, please wave your hands frantically in the air." Jim would be the only person waving his hands about. Ed, Bryan, and Jack would still be standing there waiting for me to tell them what to do. Now, if I switched Ed's walkie-talkie channel to channel one, while leaving Jim's on channel one and said,"If you hear me on this channel, please jump up and down," Jim and Ed would be jumping while Bryan and Jack are still waiting for instructions to come through their channels.

Wrapping it Up:

This is an extremely simplified way to look at DMX, but we all have to start somewhere! Once you understand the concept of how DMX and addressing work, you can take control of your lighting rig. Stay tuned for more posts later!

~Andy

See Illuminating DMX: Part 2- Addressing Here