Can XLR work instead of DMX?

[rePete]

I have recently used a permanent audio cable run to handle dmx. Worked fine for about 6 months and then went squirrelly. The addition of a dmx terminator brought things back to working again.

Pete

[daver2]

For a while...

Always use a DMX terminator. All they are are a standard fixture plug with an inbuilt resistor that you can buy for a few pence/cents from your local electronics shop. A bit of soldering and the job is done.

For permanent installs - use the proper cable. Audio cable, bell wire, barbed wire etc. may work today - but tomorrow is another story. If you extend the install in the future - or the venue installs additional electronic / electrical equipment - this may break your system for no apparent reason.

Dave

[Steve Vanciel]

Originally Posted by daver2

For a while...

resistor that you can buy for a few pence/cents from your local electronics shop.

A 120 ohm, 0.25 watt resistor is recommended by the standard.

SteveV

[daver2]

Thanks Steve - I forget to put that little snippet of information in!

An excellent website for how to make both a DMX terminator and a DMX activity monitor is at http://www.bigclive.com/dmxtest.htm.

Another very useful document to read for new folk into the land of DMX512 is found at http://www.elationlighting.com/pdffi...1-handbook.pdf.

I have seen reference to 120 Ohm 0.5 Watt resistors rather than 0.25W.

Dave

[Steve Vanciel]

Originally Posted by daver2

...reference to 120 Ohm 0.5 Watt resistors rather than 0.25W.

I was using the value published in Recommended Practice for DMX512 by Adam Bennette. Most important, a high quality resistor should be used.
In an ideal world, the value of the termination resistor would match the impedance of the cable which can vary by design, conductor gauge and length of run. Looking at the charts of Cable Types, the characteristic impedance of some common EIA485 type cables can be anywhere from 95 to 150 ohms. In the real world, 120 ohms has become a sort of default norm.

SteveV, ETCP-CEE
Orlando, FL