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Discussion in 'Lighting and Electrics' started by Tyler, Oct 11, 2006.
Terminator and check and see if they still flash when they are not plugged into the board. The light board could be sending out bad information on the DMX line.
line. Make sure that your terminator is made correctly (pins 2/3 120 or 100 ohm resistor) and that all your cables are legit DMX cable, not microphone cable.
connector on the end of the cable. Both DMX and Microphones use XLR Connectors. Cables used for DMX should be of a higher quality cable, usually a twisted pair, shielded cable to prevent interference and cancel out any that does occur. Microphone cable should also use sheilded cable, but often unshielded cable is used due to cost concerns. Microphone cables are also easily confused with DMX cables and can be swapped in a pinch but the problems you experiencing are one reason that its not ideal.
DMX cable was a Belden 5432 ,I believe, The specs are specific and for a reason. Mic cable is not a substitute for DMX line. Thats sort of like wirring an home computer network with zip-cord , (huh ? You cain't do that there either ? )
There's another post discussing termination, do a search for termination to find it since you can't search for DMX. I think you will find several useful insights as to what might be the cause of you problem. Personally I'd gues a capacitence build up in the shield of the mic cable that was intermittantly discharging cause the lights to flicker, even though they were not plugged in. Remember, a wire, sitting all by itself doing nothing what so ever can build up a charge from bombardment by radio waves, <and alien mind beams>. Enough of a charge that you can actually detect it with a meter, or if you're board hook up a cyrstal diode and a coil and you can listen to the radio on it. The point I'm making here is, yes there is one, Read the specs there really is a reason they are written. Terminate everything on a dmx line that is not self terminating. Double check solder connections on the XLR's double check pins on the XLR's, It's a digital world and and as My very first Programming class taught me, on a TRS-80 I might add, Garbage in garbage out, Crappy cables , crappy light, Poor maintenance, poor performance ........ Ok stopping now
Good luck ! Have Fun, that is what it's all about !.
address range for DMX. It is possible that you have something else in the same address range? If I recall these use 6 dmx channels so is it possible that you have an address set incorrectly?
DMX cable is rated at 120 Ohms and is constructed using twisted pairs. We build our DMX cables using Duraflex cable which is also double shielded - both a braid and foil shields. Never had a problem.
Just cause I'm a dmx cable Nazi. The braid is properly refered to as a drain, as it drains away the static build up in the exterior of the cable "sheilding" the twisted pairs on the interior. The foil shield is a sheild and should not be connected, in any way, to any of the connectors.
Tyler in response to your last, I think if it's enough of a problem that your asking about here, and it's enough of a problem to cause a degradation of performance in your fixtures. Then yes I think it's worth the time to go back and wire the fixtures properly. If you used mic cable then your lucky that it's only an intermittent problem and the lights aren't just freaking like daffy duck all the time.
Dave fixed that. You can now search on DMX. The thread in question has been active within the past week or two and so should be towards the top of the list.
DMX thread is my fault
Use the 120 (not 100) ohm resistor if in doubt and as above, make sure it is properly terminated. However, I am having no problems using no terminator, but we're using the highest-quality DMX cable.
Martin's gear for instance they say you can use mic cable but insist on the termination resistor
I think you will find that using the 120ohm resistor terminator cleans up a lot of the problems with mic cable, and that using "proper" dmx cable, reduces the need for the terminator
Now that more and more people are going cat5 it is getting to be less of an issue
dmx detected. Since the power draw on those is so low, maybe you could just run them into a power strip or something and shut them off when not needed.
It's funny you should mention Martin. Technically speaking, Martin, and I love their stuff, worked for a company that had some of thier first gear in America, doesn't use DMX. Ok now let out your breath. Martins insistance on using three pin XLR instead of the specified 5 pin xlr and their insistance on sending spurious data returns on the third pin actually mean that thier fixtures don't comply with the international standards that govern DMX. I'll stick by my original statement. You could wire your home ethernet with zip cord, but why would you ?
The new 250 series all has 3 and 5 pin connections. The 700 series probably does, too. I don't know about data returns on pin 3, but they do use 5 pin connections.
And the HES StudioSpot 250 doesn't have a 5 pin connection, either.
ohm resistor compensates for the 80 ohm mic cable. It would be interesting to have a lab do a sweep on the cables and really do an analysis. It is like networking as you say, I remember when unless you used rg58 coax thin net as it was called then would not work, but it was the early work with Synoptics with a product called lattis net that showed that adding filtering and compensation could be effective.
DMX is digital and Audio is analogue cable. DMX cable makes great Audio cables but the same is not always the case when using Audio cable for DMX.
That being said, it can be used and I do it if I am short on DMX cable. Main problem I have seen is "twitching" on a channel but nothing too drastic.
Search the fora for "DMX cable" and you will find several post that go into this in greater detail.
OK. My first 2 thots would be bad data getting there (some hidden thing emanating from your desk) or bad cabling somewhere.
As an intermediate solution, maybe you could write a cue to take all of them to 0% when not in use?
Edit: One other thot is that you have them addressed too high. If memory serves, the ADJ LED Par can't be addressed higher than 126 or something.
current position and plug them directly into the desk? If it still does it, try a different DMX cable. The other thought is that these may not have been designed for anything more than being held on a single colour (for truss warming), for slow colour changes or for sound to light mode. I am not bagging ADJ gear, just pointing out that in order to produce budget equipment, there are often things that get missed out.
If you cannot find a solution then the cue that Len suggested will probably be your best bet.
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