Ordinary Lightings
Standard lightings consists of a variety of light bulbs connected to dimmers, and chase modules. The lights maybe anything from PAR Cans to theatrical lanterns. A typical light controller for standard lighting setup has a set of sliders, and each slider controls3intensity of one dimmer using a low voltage control signal of 0 to 10 volts. The standard way to link the sliders to the dimmers is by using a multicore cable with one core for each channel dimmer.
Intelligent Lighting
Intelligent lighting usually contains more functions than just intensity; a typical intelligent light, often called a FIXTURE, can also change in color, create different patterns ( called GOBOS ) and direct the light beam in any direction using a movable mirror, or by a motorized control of the lighting unit itself. The FIXTURES are called intelligent because they contain a samll computer or a microprocessor inside it which controls the movements of the internal motors and mechanisms in response to the control signals. Most fixtures can also listen to music and produce their own light show, sometimes synchronizing themselves with other intelligent fixtures. However they are actually not at all intelligent and they usually need another controller or a user, to make them do something interesting.
Controlling
Each function of an intelligent fixture requires its own control signal, so the user can select the color, position, gobo etc. You can use 0 to 10 volt control signal on some fixtures, but the cable carrying the control signals again has to be multicore with one core for each function, so each fixture might need 8 or more cores in the control signal cable.
DMX Control System
There is an easy to use system for controlling intelligent lighting systems and dimmers. It is called DMX-512, which stands for DIGITAL MULTIPLEX, and it sends up to 512 control signals through a 2 core screened cable. The cable can simply be DAISY-CHAINED from each fixture to the next. Microphone style XLR Connectors are usually used, sometimes 3-pin, and some are 5-pin.
The DMX system sends out the level for channel 1, followed by the level for channel 2, then 3, then 4, then so on, all the way up to the maximum of 512, though not all DMX systems send out all the channels. It then goes back to channel 1 again. All the units connected to the DMX receive all the channels, and you tell them which channel to respond to by setting the BASE CHANNEL or DMX ADDRESS on each unit. The computer inside the fixture waits for the correct channels to come up, then reads in the levels for those channels.
DIMMERS can also understand DMX; some dimmers can read it directly, others use a DEMULTIPLEXER or DEMUX to convert the DMX into the normal 0 to 10 volt analog signals they are used to.
Moving Light Control Desk
Sliders are ideal for controlling dimmers. More complicated dimmer controller desks have memories to record the level of all the dimmers, so yo can recall a setting without having to set all the sliders again during a show. However once you start controlling lights that move and change color, sliders become less ideal, because it is the movement rather than the end level which is important. Dedicated moving light desks include many helpful functions which makes the programming of intelligent lighting much easier, such as pallettes of pre-programmed colors and positions, and a shape generator to create movements.
FEW CAUTIONS ABOUT USING DMX
DMX is a robust system which normally works very well, but sometimes it can be problematic. Here are few tips for making DMX work well.
1. DMX Cabling should be TWISTED PAIR DATA CABLE. Microphone cable is not recommended because it does not transmit the signal very well. You will probably get away with it, but equally, you might have problems.
2. Always connect a TERMINATOR PLUG on the last fixture.
3. Dont split the DMX Cable. Loop it from one unit to the next. If you have to split, use a PROPER ACTIVE SPLITTER unit.
4. Dont try to run more than 16 fixtures from one DMX line. Either use several DMX lines or use a DMX Repeater Unit. Using more than 16 may weaken the signal.
5. Dont run your DMX lines near high voltage cables or neons. They may pick up interference which may stop the system from working, or worse, blow up the receiving electronic unit inside the fixture.
