Monday, December 26, 2011

DMX512 Lighting System Protocol


I have mentioned the DMX512 light control protocol a few times on Rex and the Bass, and thought a brief explanation might be in order.

If you have ever been to a concert and seen the huge arrays of stage lights and effects, you may have noticed that they are usually independently controlled. But there are not separate controls and wiring going to each one, as they are on a multiplex network. This means that there is only one communication line that goes from component to component, and they can all be controlled from a single panel.

This makes for a more simple set-up, and reduces the number of costly cables that have to be purchased.

The DMX512 digital communication standard was introduced in 1986 to provide a single protocol for stage lighting, thus allowing compatibility of equipment from different manufacturers. It was designed to control light dimmers, but has also proven to be a godsend for effects, such as lasers, spot lights, moving lights and fog machines. I have even seen people using these networks for their Christmas lighting displays.

If you purchase DMX-compatible components, you can assign discrete addresses for each one, and use a single controller to operate them. There will be DMX IN and DMX OUT ports on each device.

DMX512 is able to control 512 dimmable channels and up to 32 devices with just one cable. The cable can be up to 1200 to 1500 meters long, which is pretty far if you think about it.

These communication cables are standardized, sort of. DMX512 systems are supposed to use 5-pin XLR connectors. These have the following pins: Signal Common, Data 1-, Data 1+, Data 2-, and Data 2+. The Data 2 circuits are optional; so many times regular 3-pin XLR microphone cables are substituted. Some manufacturers have dropped the 5-pin requirement altogether and just use 3-pin XLR connectors. So much for standardization, huh?

Some people discourage the use of microphone cables, as they are not the best choice for data transmission, but for the short runs I do I’ve not had any problems. And always be careful not to accidentally plug a lighting 3-pin XLR into your audio mixing board, as 48 volts of phantom power through the data circuits can wreck your lights.

There is a lot more to the DMX512 story of course, and it can get really confusing if you are running a lot of effects over long distances. But if you are running small shows, or are looking for lights and effects to enhance your band or DJ service, it is easy enough to get started.

If you have just a few lights, a cheap light controller running DMX controls will provide a lot more versatility and more professional transitions and fades. Just make sure that as you collect new effects and lights that they are DMX512 compatible, as some manufacturers still use proprietary communication protocols. You will be able to find them easily, as major music retailers carry a lot of this gear.


1 comment:

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