Implementing Wireless DMX. By Stephen Ellison

How can you get the best experience when using wireless DMX? First, you should ask yourself if/why you need wireless. The answer to this questions drives the implementation.

In wired vs. wireless, wired always wins out for reliability, no matter what the signal. With a wired signal you don’t experience dropouts, the signal strength is stronger, and the amount of data that is transmitted is greater. That being said, we live in a wireless world now and everybody has cell phones, and we are all familiar with wireless – we all complain when we can’t get a good signal or when streaming is too slow. And this is why I favor wired more than wireless: it comes down to reliability in the moment. During an event, losing the control of the lights affects everybody at the same time – your inability to stream something is a negligible issue comparatively.

However, there are times when you can’t run the wire and you need to get the signal to the light. The lighting world – and in fact all the AVL world –is able to go wireless. Another reason to go wired is because of all the signals already in the room before DMX is even added, and that’s just one reason running wire can be a problem. The time of the dimmer controlling your lights is over, now you need to supply power and data to a fixture, and the power comes from a relay or breaker. Data is a digital signal called DMX 512, which is based on RS485.

I worked with a church on changing the congregation lighting from incandescent to LED. Power was not a problem; the power wires were already in place. All that had to be done was to remove the old dimmers and move the wires to breakers. However, data was a problem. The ceiling was divided into sections by wood beams and the fixtures were in the middle of the sections. The electrician was able to swap the fixtures in the room in half a day and spent another day removing the dimmers and moving the wires. Running data, which has to daisy chain from fixture to fixture, was going to take several days. The ceiling did not have a space between the inner ceiling and the outer layer, so all the data wiring would be exposed in wire mold channels. Wireless DMX took an hour to implement. The fixtures came with the wireless receiver built in, which made connection almost instantaneous – you only needed to install a wire from the control system to the transmitter and do a little programming.

Once the decision has been made to go wireless, what’s the best way to do that? The first step is to choose the gear, and to do that you need to understand frequency options. There are three available frequencies available: 900 MHz, 2.4 GHz, and 5 GHZ.

The 2.4 GHz spectrum is the most versatile for the majority of installations. The 2.4 GHZ spectrum is divided up into 13 slots going from 2412 to 2472. Most devices can only see or work in the first eleven, while some devices can be setup to choose twelve or thirteen. However, it’s important to note all of the other devices in the space on the 2.4 GHz range, such as cell phones. This is a busy spectrum, so most gear is designed to employ some method of switching which slot they are using, also known as frequency hopping.

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