Why is it So Complicated?

The simple truth is, DMX isn't that complicated. We just need to take some time and understand our equipment. Different lights or dimmers use different quantities of DMX channels. For example a Lightronics AS-40D uses four DMX channels. A Robe Robin DLX Spot moving head fixture uses up to 35 channels.

The trick is to make sure you have enough control channels to control the number of lights you have. For example an NSI/Leviton N7008-D00 is a common 8/16 Channel DMX controller. Maxed out, this little guy will control up to 16 DMX channels. It wouldn't be wise to attempt to control the Robe with this controller. But the Leviton should work just fine for a small band playing at a local bar.

A Look at a Basic System:

As an example let's break down a "Weekend Warrior" rig from a few years ago. This would be the typical bar band set up:

(8) PAR56 Can lights with gels(color filters)

(2) 50 ft DMX Cables

(2) Four Channel Dimmer Packs

(2) Lighting Tree Stands

(1) Eight Channel Lighting Controller

Let's set it up. We've got four lights on each tree. There is one dimmer pack on each tree. The controller is in the back of the room near the audio console. Each fader on the controller controls 1 channel of DMX. So fader 1, is DMX channel 1, fader 2 is DMX channel 2 and so on. Our signal path for our DMX signal would look like this:

Controller => 50ft DMX Cable => 4 Channel Dimmer Pack One => 50ft DMX Cable => 4 Channel Dimmer Pack Two

Example One- Dimmers With the Same Address:

Each dimmer pack has 4 outlets on it connected to one dimmer each.. Each dimmer is controlled by one channel of DMX data. It is also important to note that because of this each dimmer pack uses four channels of DMX. If I give both dimmer packs the address of 001, then when I push fader one on the lighting controller, then light one on both dimmer packs will come on. That patching would look like this:

Example 2- One Fader Controls One Light:

If we want one fader to control one light, then Dimmer Pack One should control lights 1-4, and Dimmer Pack Two should control lights 5-8. So our patching should look like this, if we address the dimmer packs with addresses 001, and 005:

Example 3- Overlapping DMX Addresses:

Here's another example illustrating what might happen if we make a mistake assigning addresses. Let's say we gave Dimmer Pack 1 the address of 001, and Dimmer Pack 2 the address of 003, some of our control channels will overlap like this:

Note that fader channels three and four control lights on both dimmer packs. If I push Fader 3, then it will control lights 3 and 5, and fader 4 will control lights 4 and 6.

Wrapping It Up:

Again, we're taking a very simple look at things right now. We'll continue to look at things more in depth over the next few months.

~Andy

See Illuminating DMX: Part 1- The Basics Here

Continue to Illuminating DMX: Part 3 A- DMX Protocol Charts Here