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Lighting 101: Demystifying DMX

Lighting 101: Demystifying DMX

Next to questions about upgrading their sound system, the most common question churches ask us is how to create an engaging environment through lighting. Before we dive too deep into fixtures and what to do with them, we need to back up a step and discuss one of the more misunderstood topics we come across: DMX. You may know it is key to controlling your lights, but what really is DMX? Let's dive in.

Digital Multiplex

In the early years of lighting, proprietary communication protocols were pretty much the only way to talk to your dimmer racks from your lighting console. Every manufacturer had their own language, which, as you can imagine, made it really hard to mix and match gear without a third "interpreter". While there were some interpreting pieces of gear out there, it wasn't until 1986 when the Engineering Commission of United States Institute for Theatre Technology (USITT) created Digital Multiplex, or DMX for short. Driven by the emergence of new "intelligent lights" and the desire to have different brands play nice with each other, we finally had a standard language for all lighting products to speak.

DMX in More Detail

DMX communicates 512 channels of information to everything it is connected to. Every channel is communicating a simple value somewhere between 0 and 255 which we often convert to a percentage of 0-100%.

We tell a fixture or dimmer rack what channels we want it to listen to by addressing the fixture/dimmer. For example, if you have a 4 channel dimmer pack addressed to channel 1, it will look for the values on channels 1-4 and provide power to the fixtures plugged in at the value you've sent it. An LED fixture in 4 channel mode (Red, Green, Blue, Intensity) addressed to channel 101 will look for data in channels 101-104. Depending on how the manufacturer sets up their firmware, it may see a value for Red in channel 101, Green in 102, Blue in 103 and overall intensity in 104. You tell any given fixture or dimmer which channels it should take its values from and it will, simple as that.

DMX travels to fixtures or dimmers via DMX cable which has 120 ohm resistance (as opposed to mic cable which has 75 ohm resistance) and uses either 3 pin or 5 pin XLR connectors. DMX is digital data, so we use cable designed for digital data, not analog mic cables.

DMX Controllers

So if DMX is just a conduit of information, what generates those values for each of the 512 channels? Your lighting console handles that job, and sort of serves as a highly sophisticated universal remote. A lighting controller works the same way except it simply says, "OK input 1, set your value to 255. Input 2, to 128. Input 3, to 0." It does this for all 512 channels constantly, updating the values it sends as you tell it to. And if a fixture has multiple channels of information, it's just like having more features available on the remote for that specific source.

Practical Applications

One of the beautiful things about DMX is that you can hook up your fixtures in any order and as long as they are all addressed properly, they'll all get the values they are looking for. DMX is meant to be daisy-chained, though it's recommended that you don't daisy chain more than 30 fixtures together. If you have more than 30 fixtures or your fixtures are spread out so far that daisy-chaining them isn't practical, you can buy an opti-splitter to distribute DMX safely and completely to all of your fixtures. It's also highly recommended that you terminate your DMX line with a DMX terminator. DMX moves information at a high speed so it's critical to give it the best signal path possible free from interference and the possibility of getting bogged down. Too many fixtures on one chain, not having your line terminated and using microphone cable instead of DMX (both DMX and microphone cables use the same 3-pin connectors) are all things that can cause interference in your communication. Interference results in lights doing "interesting" things. Your fixtures may still be receiving data, it's just not always the correct data.

Hopefully, that clears up any questions or confusion that revolves around DMX for you. It's really as simple as being a conduit of 512 channels of information, and it's a critical component to making your lighting systems work. Set up correctly, you will have the power and control to do great things with your lighting.

We're always here to assist if you need help setting up or building a new lighting system.

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