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#177816 05/12/08 10:52 PM
Joined: Mar 2004
Posts: 947
T
twh Offline OP
Member
I have an installation where three DMX controlled lights failed at the same time, at about the time welding was done near one of the lights. The DMX cable is shielded and the lights are daisy-chained with separate inputs and outputs. I'm guessing the welder was the culprit.

What precautions should be taken when welding near equipment that is so sensitive that its signal cable must be shielded?

Is there a wiring method that will reduce the risk?

Joined: Jul 2004
Posts: 787
L
Member
You did not state what kind of welding was performed, but I will guess it was TIG. TIG uses a high voltage high frequency signal to initiate the arc. The high voltage leaks out of welding leads and that is probably what did the units in. Keep the welding leads at least 1 foot from the control cables. If the welding leads have to cross the control lines, make the crossing at right angles. Otherwise the usual items, minimize lead length, maximize distance between welding leads and suseptable cables, and if possible, have shielding (magnetic and electrostatic) between the welding leads and the victims.

Best protection would be to unplug the cables from the electronics before welding.

Larry

Joined: Feb 2002
Posts: 183
N
Member
Most DMX lights have the input and output connector tied in parallel. Electrically, DMX is just RS485 (5V differential) signalling.


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