woody74 Posted February 1, 2006 Share Posted February 1, 2006 Figured I'd better start a new Behringer thread, lest I receive the Mod wrath... :unsure: I have an LC2412 that seems to put out weak DMX, for lack of a better description. I use it in conjunction with ETC's Unison system, so the signal goes into a wallplate and to the main brains. The problem comes when I try to use a DMX cable longer than 75' (23m): the rack doesn't respond. And an ETC console with the same cabling and set-up works fine. So my question is two-fold: has anyone else experienced this, and, is there different "strengths" of DMX? Thanks,-w Link to comment Share on other sites More sharing options...
paulears Posted February 1, 2006 Share Posted February 1, 2006 As far as I'm aware, DMX isn't limited in the same way that midi is. So although it's quite common for some midi drivers to be a little short in the current department, and not be able to manage distance well, I've never come accross DMX having source issues. Is there any chance you could tey another behringer and see if the problem remains. not beyond possibility that it's duff - but swapping it for another is the only sensible method of moving forwards. Link to comment Share on other sites More sharing options...
woody74 Posted February 1, 2006 Author Share Posted February 1, 2006 I should add that if I use a shorter cable, it works fine. Link to comment Share on other sites More sharing options...
bruce Posted February 1, 2006 Share Posted February 1, 2006 Is it properly terminated? Link to comment Share on other sites More sharing options...
si_cole Posted February 1, 2006 Share Posted February 1, 2006 I had a sort of similar problem with my old Sirius 24. It was fine with cable runs less than 30m, anything over that it couldn't handle. Replaced DMX card and all was ok. So it may be a case of replacing the DMX board (unless its all integral). HTH Link to comment Share on other sites More sharing options...
Doug kelly Posted February 1, 2006 Share Posted February 1, 2006 hi There can be interface problems between a desk and a dimmer on the DMX front. The Hog 2 used to have trouble talking to older Avo FD series racks when the termination switch was switched in on the decoder. I believe it was a problem with the older Avo decoders and the termination resister value. I have come across a problem with a Sirius as well were one of the data pins on the output XLR was unconnected and the desk would work on some receivers but not others and on some runs of cable but not longer ones. If you have a tester check that both the + and - of the data signal is being sent. It could be the output driver on it's way out as well. Hope some of this helps Doug Link to comment Share on other sites More sharing options...
Modge Posted February 1, 2006 Share Posted February 1, 2006 I had a sort of similar problem with my old Sirius 24. It was fine with cable runs less than 30m, anything over that it couldn't handle.HTHFunny you should say that, when ever I used to use a serius 48 I had to remember not to use the massive long drum of DMX cable we had laying about. Got a feeling that the problem could be solved by remembering to terminate the DMX line, something that didn't usally get done (and wasn't necessary with other desks \ shorter cables). Link to comment Share on other sites More sharing options...
woody74 Posted February 1, 2006 Author Share Posted February 1, 2006 Is it properly terminated? I can only assume so; the signal ends up at (3) 108ch installed Sensor Racks, and this is the only console that has ever given us trouble. So I am understanding that DMX is DMX is DMX, and potentially I just have a hardware issue? :unsure: I agree, I should slap a meter on the back of the desk and at the end of a long run and check the difference. Thanks for the tips! -w Link to comment Share on other sites More sharing options...
jfitzpat Posted February 1, 2006 Share Posted February 1, 2006 FWIW, not all RS-485 drivers can source the same amount of current. It is possible that Behringer is using a lower current RS-422 output, or even no standard communications driver at all (to keep down costs). However, dramatic and obvious cable length problems are usually improper grounding of pin 1/shield or wave shape. It may be that Behringer is not even using an off the shelf or built in microcontroller UART, but an output constructed in programmable logic, etc., again to keep the unit low cost. One problem I've seen with designs that do this are fast, noisy edges in the generated signal, which can turn into problems in cable over distance. If the cable is properly wired and of good quality and the load is properly terminated, your only remaining alternative is to use a splitter or buffer close to your controller. -jjf Link to comment Share on other sites More sharing options...
Dale Posted February 1, 2006 Share Posted February 1, 2006 DMX should be able to run 100s of meters. I've run over 200m and it's been fine. Link to comment Share on other sites More sharing options...
Tomo Posted February 1, 2006 Share Posted February 1, 2006 I'd suggest putting the signal on an oscilloscope while in operation.That will pick up any oddities in the waveform. One other thing they may have done is ground the cold and only drive the hot.This works on short runs, but can't handle noise. Link to comment Share on other sites More sharing options...
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