DMX 512 Protocol

I only know a little bit of the theory. The one project I started to work on was cancelled before the customer purchased any hardware.

The DMX protocol is a unicast (one way) protocol. It sends a series bytes out in ascending address order. You set the address of the slave unit (0 - 255) and send the command (0-255). The command is different for each unit. You need a DMX master unit or sequencer to send the commands. The units you want to control will have a way to set their address, usually a pair of hexadecimal rotary switches. They are all daisy-chained on the same pair of wires. You need the manual to find out the command format. Some units break up the bits to cover multiple functions and you need to add the binary values to determine the proper command number. The unit knows its address and the master sends a start command that indicates the start of a new sequence. The controlled unit counts commands until it sees its own number then acts on the command. Timing is very precise and part of the command is usually a delay. Knowing the address and timing you can program several slave units to act at the same time.

This wikipedia article might help http://en.wikipedia.org/wiki/DMX512-A. A google search of DMX 512 has a lot of good hits as well. The units you have should have some documentation online if what came with it wasn't much. Sometimes those manufacturers assume you already know all about what you want it to do even if you don't.

Thanks Andrew..

Big help.. plus finally I got a manual from these dudes...

Also, I just wondered, is it a big advantage to use software with these units?

Thanks again

Donald

I don't know about that. Like I said, I never actually got to use it, just did a lot of groundwork for a project that never went anywhere. The application the customer had in mind was to control a hardware master with a Windows Mobile handheld. The hardware master would control various lighting and A/V equipment in a showroom.

And as a correction to my earlier post, the protocol can control 512 devices not 256.

I hope this helps for starters:

The DMX protocol is great by the way, but lighting is either DMX ready or not. We use it in club, home, theater and restaurant installations, and use many standard products that accept it. Each unit has a set of dip switches, which allows each fixture to run in a certain mode and configure an address.

Just remember that your settings are "channel dependent", so as you have 16 channels (old MIDI protocol base), your fixture can only be controlled to do so many things or even how many it is capable of. Just a quick example, each channel would control a different function like on, off, dim, strobe, color, or open a shutter. The fixtures you want to control together will have the same address.

And yes, I also use computers and software programs (light jockey) or standard DMX control controllers (with faders, etc.) to have my lighting do my bidding. (Cue Dr. Evil laugh).

Donald, I even used wireless dmx before too, on a bunch of color blasts, very expensive but veeeery convenient. Are you looking to control existing fixtures ? Do they have XLR input and outputs ? Do they have dipswitches ? Is it standard RGB LED rope light ?

Standard dmx protocol uses three pin xlr connections. When I install the RGB LED "flat rope" it is actually four pin, and the unit itself (different types available) controls the color changing. it's output to the rope light is the four pin (3 power, 1 ground ?) and the unit itself has controls and dmx input and output (not all units have XLR), female and male xlr. Many these days come with extremely simple 8 option controllers.

It depends on what you are controlling that determines how many channels. You have red, green, blue, on (full), off (blackout mode), strobe, dim, (7 channels so far) what else do you want it to do ?