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Author Topic: Erratic LED flickering issue  (Read 7268 times)

Bill Hinds

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Erratic LED flickering issue
« on: November 30, 2012, 06:17:42 pm »

We are having one heck of an issue with a lighting rig.  Show designer 3 console and 18 chauvet 144 batten LED fixtures.  Here is the issue.  If you turn off the console the fixtures will start to do erratic strobing.  Not all of them and not the same fixture.  Turn the console back on and it USUALLY re gains control.  Now I know that once DMX is lost this may be the nature of the fixtures so we told them to leave the console on.  However, even when the console is left on it seems the fixtures will still become unstable. When this happens with the fixture on, we have no control and will usually have to power down the fixture to regain DMX control.  We have replace DMX cable. Moved power to another circuit etc.  I am out of ideas.  Before anyone ask, yes we are using true DMX cable with 5 pin.  We did make up the the home run and even replaced it with another verified good cable.  All the linking cables were bought from whirlwind and are true DMX as well 5 pin.  And yes we have termination plug on the last fixture.  What am I missing? Tech is now verifying the whirlwind cables.

Thanks,

Bill
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Bob Charest

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Re: Erratic LED flickering issue
« Reply #1 on: November 30, 2012, 07:40:59 pm »

We are having one heck of an issue with a lighting rig.  Show designer 3 console and 18 chauvet 144 batten LED fixtures.  Here is the issue.  If you turn off the console the fixtures will start to do erratic strobing.  Not all of them and not the same fixture.  Turn the console back on and it USUALLY re gains control.  Now I know that once DMX is lost this may be the nature of the fixtures so we told them to leave the console on.  However, even when the console is left on it seems the fixtures will still become unstable. When this happens with the fixture on, we have no control and will usually have to power down the fixture to regain DMX control.  We have replace DMX cable. Moved power to another circuit etc.  I am out of ideas.  Before anyone ask, yes we are using true DMX cable with 5 pin.  We did make up the the home run and even replaced it with another verified good cable.  All the linking cables were bought from whirlwind and are true DMX as well 5 pin.  And yes we have termination plug on the last fixture.  What am I missing? Tech is now verifying the whirlwind cables.

Thanks,

Bill
Hi Bill,
Sounds like you've covered everything you should. A DMX Handheld analyzer inserted prior to the 1st misbehaving fixture might yield good diagnositc info. It also might be possible that one of the fixtures is going bad and si transmitting bad DMX downstream. Symptoms sound like reflected signal, but you've got the terminator installed. You might want to test the terminator to ensure that the proper resistance is present.

Best regards,
Bob Charest
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Bill Hinds

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Re: Erratic LED flickering issue
« Reply #2 on: November 30, 2012, 09:24:56 pm »

Hi Bill,
Sounds like you've covered everything you should. A DMX Handheld analyzer inserted prior to the 1st misbehaving fixture might yield good diagnositc info. It also might be possible that one of the fixtures is going bad and si transmitting bad DMX downstream. Symptoms sound like reflected signal, but you've got the terminator installed. You might want to test the terminator to ensure that the proper resistance is present.

Best regards,
Bob Charest

Thanks Bob, I will try that.  I guess it looks like we will have to try and remove one fixture at a time out of the DMX chain to see if we can get it to quite mis-behaving :(. We did have an analyzer just prior to the 1st fixture in the chain. Both lights on the analyzer seem to indicate DMX signal was good so that kind of leaves a possible bad cable linking fixtures or like you said a possible fixture issue.  I will report back with some more findings.
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Ray Cerwinski

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Re: Erratic LED flickering issue
« Reply #3 on: December 01, 2012, 04:11:05 am »

First, try removing the terminator.

If you drop Data+ or Data- somewhere along the daisy-chained path of cables due to a broken conductor, and have a terminator in place, all the devices past the point of the break will not work correctly or at all.

After the conductor break, the remaining data signal (+ or -) flows to the end of the line, through the terminator and back up the other data line. You no longer have correct differential data as D+ and D- are the same minus a little amplitude and a crazy amount of timing. This results in erratic behavior. Temporarily removing the terminator may fix the issue because one of the data signals and data common are still in place and most receiver chips will still work with this.

A terminator at the end of line only causes problems if there are wiring issues, too many unit loads on the line or weak driver/receiver chips.
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Ray Cerwinski

Bill Hinds

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Re: Erratic LED flickering issue
« Reply #4 on: December 01, 2012, 09:27:41 am »

First, try removing the terminator.

If you drop Data+ or Data- somewhere along the daisy-chained path of cables due to a broken conductor, and have a terminator in place, all the devices past the point of the break will not work correctly or at all.

After the conductor break, the remaining data signal (+ or -) flows to the end of the line, through the terminator and back up the other data line. You no longer have correct differential data as D+ and D- are the same minus a little amplitude and a crazy amount of timing. This results in erratic behavior. Temporarily removing the terminator may fix the issue because one of the data signals and data common are still in place and most receiver chips will still work with this.

A terminator at the end of line only causes problems if there are wiring issues, too many unit loads on the line or weak driver/receiver chips.

Hi Ray,

When we first started trouble shooting the plug was not in place.  We added it as part of the trouble shooting method. Good info though and I certainly would not have thought the termination plug could actually mask issues.

Thanks,

Bill
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Ted Christensen

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Re: Erratic LED flickering issue
« Reply #5 on: December 01, 2012, 12:48:25 pm »

We are having one heck of an issue with a lighting rig.  Show designer 3 console and 18 chauvet 144 batten LED fixtures.  Here is the issue.  If you turn off the console the fixtures will start to do erratic strobing.  Not all of them and not the same fixture.  Turn the console back on and it USUALLY re gains control.  Now I know that once DMX is lost this may be the nature of the fixtures so we told them to leave the console on.  However, even when the console is left on it seems the fixtures will still become unstable. When this happens with the fixture on, we have no control and will usually have to power down the fixture to regain DMX control.  We have replace DMX cable. Moved power to another circuit etc.  I am out of ideas.  Before anyone ask, yes we are using true DMX cable with 5 pin.  We did make up the the home run and even replaced it with another verified good cable.  All the linking cables were bought from whirlwind and are true DMX as well 5 pin.  And yes we have termination plug on the last fixture.  What am I missing? Tech is now verifying the whirlwind cables.

Thanks,

Bill

Curious to know the problem...my guess is an actual connection on the fixture itself. Either dmx in or out. I had this problem on one fixture that described your symptoms
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Bill Hinds

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Re: Erratic LED flickering issue
« Reply #6 on: December 01, 2012, 03:59:18 pm »

Curious to know the problem...my guess is an actual connection on the fixture itself. Either dmx in or out. I had this problem on one fixture that described your symptoms

Man I hope not! There are 18 of them and is really making the trouble shooting process difficult enough as it is.  Right now we are using all 5 pin. If I cannot isolate it after verifying all the cables are good, I may temporarily switch to the 3 pin connection using DMX cable of course.

I am also going to re-verify all the settings on the fixture to ensure there is not some crazy mode on or something.  There are a lot of settings on the Chauvet 144 Battens. 

One thing I still really don't understand yet is when we unplug the DMX cable from the console the fixture will stay exactly like its' last command ( if they are on a color then you have the same color, or if blacked out, then they stay blacked out) BUT if we turn the console off then some of the fixtures (and random fixtures) will strobe. Not always the same fixtures either.  It is like there is a signal being sent from the controller or some sort of bounce that makes them go crazy when the switch is hit.  This seems to me to be a design flaw in the console.  Elation says no but it seems to me some resister or filtr should prevent this from happening.  Anyone have any thoughts on this?
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duane massey

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Re: Erratic LED flickering issue
« Reply #7 on: December 02, 2012, 08:49:10 pm »

You may have more than one issue here. It could be a defective fixture sending random noise out when there is no DMX present (I've found this problem many times), could be one bad cable, could be a gremlin in the power chain.
(1) Is this a new problem or something that just started happening?
(2) Have you tried disconnecting all of the fixtures and checked one at a time?
(3) Have you tried a different controller?
There should be no difference between the 5-pin and 3-pin connectors as far as performance. I couldn't confirm this from the Chauvet manual, but some fixtures will go into a self-run mode when there is no DMX present. I doubt if that is the case here, but you might verify that none of the fixtures are in "Master" mode. I would be surprised if the controller is the culprit, but lately I have been "surprised" by things that the manufacturer said "could not happen".
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Duane Massey
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Bill Hinds

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Re: Erratic LED flickering issue
« Reply #8 on: December 02, 2012, 09:18:47 pm »

You may have more than one issue here. It could be a defective fixture sending random noise out when there is no DMX present (I've found this problem many times), could be one bad cable, could be a gremlin in the power chain.
(1) Is this a new problem or something that just started happening?
(2) Have you tried disconnecting all of the fixtures and checked one at a time?
(3) Have you tried a different controller?
There should be no difference between the 5-pin and 3-pin connectors as far as performance. I couldn't confirm this from the Chauvet manual, but some fixtures will go into a self-run mode when there is no DMX present. I doubt if that is the case here, but you might verify that none of the fixtures are in "Master" mode. I would be surprised if the controller is the culprit, but lately I have been "surprised" by things that the manufacturer said "could not happen".

Hi Duane!

It is somewhat a new problem.  When we first installed the batten 144 it did not seem to have this issue at all.  Seems the trouble started when we added the 6 Qwash560 but they are on a different universe AND we totally disconnected them in the trouble shooting method.  When we first noticed the strobing it was very minimal and just very occasional and it progressively kept getting worse over a two week period.  To the point where it would freeze up the DMX control when the console was on and we had to hard reset the fixtures by powering down to regain DMX control.

We have tried another controller.  We tried a show designer 2 and thought we narrowed it down to the controller as it did not start to strobe when we turned the SD2 off, BUT on day two it did  :( So back to the trouble shooting process.  We did not try one fixture at a time but will after we verify the remaining cables that is the next move.  I also have a handheld analyzer due tomorrow to help assist!  This is such a pain in the butt as there are 18 and they are part of an install.  No scissor lift either. Single man lift only :( which really slows it down.

We are also going to verify all the fixtures are in DMX mode and not master/slave.

I will definitely post back what we find. Until then if anyone has any other suggestions I am very open to any suggestions.

Thanks,

Bill
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Scott Hofmann

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Re: Erratic LED flickering issue
« Reply #9 on: December 03, 2012, 09:02:43 am »

I had a similar problem with Chauvet LED PAR Tri-B fixtures several weeks after the initial install. Turned out one fixture went bad (was replaced under warranty). Thankfully there were only 7 fixtures in the chain but drove everyone crazy for a while as it was in the middle.
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Scott Hofmann

ProSoundWeb Community

Re: Erratic LED flickering issue
« Reply #9 on: December 03, 2012, 09:02:43 am »


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