subject: How Dmx Lighting Took Over The Theatrical World [print this page] One of the most pleasing things about DMX lighting is the nomenclatures used when you talk about DMX setup. A DMX network is referred to as a DMX universe. While the physical layout or stringing together of the devices in that universe is referred to as a daisy chain.
Thats only the beginning, too. Massive DMX installations are referred to as multiple universes, with master consoles controlling all of them through a series of parallel OUT ports.
The point of DMX is to enable control of a multitude of different devices and effects from a single location hence the master unit, controlling all the universes. Commonly the devices controlled in a DMX lighting rig will also include audio; dimmers; moving lights; fog machines; foam machines; and lasers.
One thing the DMX rig doesnt control is pyrotechnics. These require a more rigidly protected control unit to work off the DMX master unit doesnt have thecapacity to automatically check and repair errors, and may occasionally suffer from random triggering. The operator must diagnose any problems and fix them manually.
The DMX lighting controller only has out connectors while all the slave devices in the universe or daisy chain have both IN and OUT. Sometimes, the OUT connector on a slave device is marked THRU a nod to the fact that the device becomes a link in a signal chain starting at the master controller. When you get to the final link in the chain, you plug a terminator into the THRU port, thus closing the universe off.
Some devices designed for use in a DMX lighting rig have built in terminator functions. Rather than plugging a physical terminator into the THRU port, you simply throw a switch to nominate the device in question as the final link in the chain.
DMX can support extremely complex setups, with DMX splitters used to chop the network up into parallel bus configuration. The standard DMX lighting setup supports 32 devices per bus if you need more than 32 units, you bring in the splitter and double up the bus power.
Generally speaking a DMX connector is 5 pin though some equipment manufacturers have disregarded this and manufacture DMX lighting gear with a 3 pin connection.
The longer the chain, and the more complex the setup, the more imperative it is that the system designer follows the standards set out by DMX for cable impedance and proper termination at the end of the chain. You can get away with setting up a DMX lighting rig without paying too much attention to termination and impedance if your whole setup is small and has relatively grew tasks to perform. But if you go big, its essential to follow the code.
Its also important to be sure about the connections you use before you plug them into a chain. For example, if you plug a 3 pin connector carrying a DMX signal into a normal audio installation, you may risk damaging the equipment. Where you find 3 pin apparent DMX connectors on your equipment you may also have to test for polarity before everything works properly.
