Understanding DMX

What is it?

Quite simply, it is a way of controlling lighting remotely.

How does it work?

DMX (also known as DMX512) is used to link a controller (e.g. a lighting controller) to a fixture such as a disco light, moving light, or even a dimmer. We use the term fixture rather than lights as smoke machines and other none-lighting can also run on DMX.

DMX Controller

The controller will have a minimum of one ‘OUT’ port; this is usually in the form of a XLR connector. This is called a ‘Universe’. You can run up to 512 channels on one universe (see details on channels below). On larger shows you may exceed 512 channels and will require a larger controller that has several outputs/Universes. The more Ports you have available the more fixtures you can control using DMX.  Each light then has its own unique channel address so it knows what to listen to from the controller.

The best way to think of a DMX controller is as a printer (Controller) that writes a list of instructions for each light (DMX). The lights then look at the list as to what they’re supposed to be doing and pass the instructions to the next light that looks for its name on the list to see what it should be doing. A DMX light doesn’t communicate with others when it’s in its DMX mode; it only listens to what it’s been told.

 

Linking DMX

Linking DMXDMX runs in a daisy chain formation. From the ‘OUT’ port you would feed a DMX cable to the fixture which will have an ‘IN’ port, hence creating a link between the two.

The fixture will also have an ‘OUT’ port from which, using another DMX cable, you can link another fixture allowing control to each individual fixture.

You can link up to 30 fixtures providing you only use up to 512 channels per universe as each ‘Universe’ only contains 512 channels.

Sometimes you need a DMX terminator at the end of the DMX line, this tells the signal it’s at the end of the line.

 

What is a Channel?

A ‘Channel’ controls a certain attribute (see attributes) of a fixture, e.g. Intensity or colour. Each different type of fixture will therefore require a set number of channels.

So in short – DMX allows you to have 512 channels per universe running from your controller but given that different types of fixtures will require the use of different amounts of channels this doesn’t necessarily mean you can control 512 fixtures.

 

What is an Attribute?

An attribute is a function/feature of a fixture. Here is a list of common attributes relating to intelligent lighting:

Intensity – The brightness of the light.

Pan – The ability to rotate the light.

Tilt – The ability to move the light beam up and down.

Shutter – This allows light to be shut out. It used commonly to create a strobe effect.

Iris – The ability to widen and shrink the light beam.

Colour – The colour of your light.

Gobo – This allows you to add shape to your light. Most intelligent lights include standard Gobos however you can add your own.

Zoom – This allows you to make the beam bigger or smaller.

Focus – This can give a sharp or blurred edge to your beam and will be used commonly alongside the use of Gobos.

 

Basic set up for DMX

As explained previously, a controller is linked to the fixture to enable control. That fixture may then need ‘Patching’ into the desk – depending on the desk.

Patching means to give each light a channel/ the set number of channels it requires. This will result in the fixture having a start ‘Address’.

If an intelligent light has 16 attributes therefore requiring 16 channels its start address is 1. The next lighting fixtures start address would then be 17 as the first fixture is using the first 16 channels. Assuming the next fixture again requires 16 channels means that the next fixture would have an address of 33 and so on. The product manual will tell you how many channels each fixtures uses and what attribute is on each channel.

When you have patched your fixtures into your controller you need to then physically address your fixtures. This is usually done manually using a digital display found on the fixtures or by using dipswitches (see dipswitch page).

 

What types of moving lighting are there?Moving Head spot

There are two different types of intelligent lighting. One is known as a ‘Wash’ and the other is known as a ‘Spot’.

A wash is used to light a general area; wash lights would not have a gobo.

A spot allows you to focus and manipulate beams of light, a profile would create a strong beam of light.

 

DMX Cables

There are a few different types of DMX cables;

XLR- Perhaps the most commonly used due to its robustness, these have a male end which will plug into your controller and a female end which will plug into your fixture. These come in two types, 3pin and 5pin. 5Pin if found mainly in high end equipment; 3 pin in the disco and lower end range. A male end has pins, the female end has holes.

Cat 5 – More commonly used for networking these have been tested and are in use with DMX.

Wireless DMX

The signal is carried wirelessly from the controller to the fixtures. We stock a range of wireless DMX. You require both a transmitter and receiver to use wireless DMX.

 

Splitting DMXDMX Splitter

DMX cannot be split using a standard Y Cord (where two cables are joined together to split the signal into two). To split DMX you must use a digital device to split the signal known as DMX splitters. Due to the way DMX works Y-Cords can cause lots of issues.