What is DMX?
A DMX, digital multiplex, is a standard protocol for stage lighting, e.g moving lights, LED’s. It was originally developed to allow stage lighting technicians to control a large number of lighting channels on the stage using a control desk that could be positioned away from the stage, without the need to run large lengths of mains electrical cable for each lighting channel. The DMX uses a small voltage control cable, which connects the lighting desk and dimmer packs. Each DMX link can control up to 512 channels. This is what makes a DMX universe.
DMX was first designed to adjust the brightness and intensity of each channel from 0 – 100%. The data which would be sent from the DMX cable for each channel is measured in bytes, which represents the brightness value. The dimmer pack will receive the values, which will then adjust the values to each light.
A decoder is built into the dimmer pack. The dimmer must be set onto the desired channel, (i.e 1 2 3 etc.) This will then allow you use that specific fixture. This is usually accomplished by using a DIP switch, or LED/LCD display. This desired channel is known as the DMX address.
Planning your addressing:
Before you start addressing your fixtures, you need to put the fixtures in a logical order. This will help you figure out which fixture is which later on. You need to find out how many channels it will take to use each fixture. In the theatre at Rotherham College, you will need 6 channels for each fixture. So the starting address will be on 1 and end on 6. The next fixture will start on 7 and end on 12, and so on until the 512 channels are used, or until a terminal plug is used to end the chain. Each channel will control a different light in an LED fixture, or control the movements of an Imove/Mac.
The LED fixtures will need a number of channels, as they have different coloured bulbs in them. In the studio theatre, each bar of LED Parcans is set to the same address. This is useful as if the lighting designer wanted red LED lights, they would just have to push the fader for that channel up. This would then turn on the red LED’s. It would be the same for the other colours that are available.
For the Imove and Mac’s, it would be the same procedure as the LED Parcans, only it would be for GOBO’s, pan, tilt, colour etc. Each effect will have their own channel, like the LED’s with different colours. Each Imove and Mac will be on their own address, as if they were on the same ones, the Imoves will go in the same direction of each other instead of opposite.