DMX

DMX is a digital lighting control protocol, in which instead of 1 core for each channel used & a common gorund (like on the Lighting Desk), 512 channels of control are transmitted down 3 wires: Data+, Data-, Gnd, with ground usually being the sheild or braid, Data+ & Data- are a twisted pair.

Current supported devices

• All dimmers in current use
• Lighting Desk

Infrastructure

YSTV runs 2 lines (one each way)down a single Cat5e cable, from the control room's Master patch panel, to the LX patch panel in the studio. Currently unused.

Connections

These are on 3 or 5 pin XLR.

DO NOT plug dmx into any sound gear - something will be unhappy!

Technical

• DMX requires a cable impedance of 120ohms.
  • try not to use mic cable, however it will suffice for short runs (<40m)
• Equipment is "daisy chained" together, using each device's input and an output ports.
• Data+ and Data- must be a twisted pair.
• Multiple types of cable will do the job:

Sheilded Twisted pair:

• This is the "defacto-standard"
• You can get it almost anywhere, below are some retailers (no links because they inevitably die! - just go googling)
  • Canford
  • 10outoften
  • Usedlighting / stagelighting (lighting Partners Ltd)

Cat5e:

• Impedance of 110 ohms (approx) makes it suitable.
• Use any twister pair, and pick another as ground.

Useful Notes

• Don't run DMX right next to audio cables of any kind unless completely unavoidable, even if everything is balanced. You may hear the DMX data - The sync pulses manifest as an intermittent clicks...