What would you say the problem is?

[Brentgi]

We just purchased 18 Chroma-Q Inspire's to replace 14" scoops that were used for house lighting. First of all, I'd like to state that I couldn't be happier with the product. It is RGBW and I love being able to dial in a decent color temp.

So here's the deal: I read through the documentation to see if there was a limitation to dmx addressing or if there were a certain number that I could put in the DMX line. Se as there were none, I went ahead and drew a plan that would connect all 18 fixtures together, obviously terminating the end.

The job required me to create my own cable terminations, and I checked each cable as I went along. The cable was attached to the ceiling and various beams using a mixture of cable staples and straps. The longest run was the initial run from the console (where we have an optobox) to the first fixture. Approx. 70'. From there, the average runs were between 16'-25'. Nothing too crazy.

The fixtures were tested and addressed on the ground before they were bolted to the ceiling. But once the installation was complete, only the first 3 fixtures would respond appropriately to commands. Other lights would flicker, while others would simply not do anything. This sounded like a terminator issue, but keep in mind that I made sure to put a terminator on the last fixture.

I called my sales rep to see if she new anything specific regarding these fixtures. She replied with an email: "Fleenor said he thinks it might be a cable only 8 units should be fine in 1 run under 1500ft." First glance, I agreed that it might be the cable. But then I don't know if I was confused by the lack of punctuation or what, but I thought it was strange that she said "only 8 units should be fine" and I was curious as to whether or not she meant to write 18 instead of 8.

Nonetheless, I started with the 8th fixture in and disconnected the remaining fixtures from the line. No dice. I did this with the 7th fixture as well... still only the first 3 fixtures responding. Finally, I disconnected the output of the 6th fixture and was able to gain control over the first six fixtures. My initial thought was that only six fixtures could be connected together. This was close to the "8" that I was thinking.

Meanwhile, I had decided to run them in sets of six. So I needed to go pick up some more DMX cable to get this working. On the way there, I got a call from the service dept. of Chroma-Q or AC lighting (I think they are the same?). The tech told me that there shouldn't be a problem with running all 18 fixtures in one sequence.

When I got back on campus, I got the bright idea of inspecting the cable between the 6th and 7th fixture. Sure enough, the person I had helping me had stapled through the cable in a couple of places. So the first thing that I did was replace the cable. To my disappointment, there was no change in behavior and the problem presented itself again.

So I ran a new line from the optobox to the 7th fixture, and I would not believe it, but I had no problem controlling fixtures 7 - 18 on the same run. So this pretty much put a wrench in the theory of only 6 lights in a run.

Being the good LD that I am, I put a terminator on the 6th fixture, and it started acting erratically. Took the terminator of, and it was fine.

Drawing my own conclusions, I would say that the 6th fixture has something wrong with the DMX out port and I am going to see if I can get the fixture replaced.

What are you thoughts?


p.s. the console is an ETC Element.

 

[Les]

I believe up to 32 devices/units can be daisy-chained per DMX spec, so you should be fine on that. Admittedly, I got a little confused here. Have you narrowed it down to one fixture? If so, when you remove that fixture from the chain, what happens? It could be that fixture in particular. Do these have any self-termination features?

Also, try disabling RDM on the Element if you haven't already done so. It's a long shot, but I've had flashing lights because the fixtures didn't know what to do with the signal. That *should* only be an issue for cheaper equipment, and it would generally be "all or nothing", but it's worth trying.

 

[techieman33]

I would guess that you have a bad cable or one wasn't properly terminated at some point in the line. You should check all of them, sometimes a cable further down the line can cause issues.

Here is some good info about DMX from Doug Fleenor
http://www.dfd.com/primer.html

 

[Brentgi]

I believe up to 32 devices/units can be daisy-chained per DMX spec, so you should be fine on that. Admittedly, I got a little confused here. Have you narrowed it down to one fixture? If so, when you remove that fixture from the chain, what happens? It could be that fixture in particular. Do these have any self-termination features?

Also, try disabling RDM on the Element if you haven't already done so. It's a long shot, but I've had flashing lights because the fixtures didn't know what to do with the signal. That *should* only be an issue for cheaper equipment, and it would generally be "all or nothing", but it's worth trying.

You know, in the hustle of it all, I didn't think to just eliminate that one from the chain all together. I will try that in the morning. Thanks for the heads up on the RDM. I'll also check into that.

 

[Brentgi]

I would guess that you have a bad cable or one wasn't properly terminated at some point in the line. You should check all of them, sometimes a cable further down the line can cause issues.

Here is some good info about DMX from Doug Fleenor
http://www.dfd.com/primer.html

I don't think that this is an issue since all fixtures down stream of #6 work fine on their own (collectively). Thanks for the link to dfd. I've actually read the papers several times.

 

[microstar]

A while back, I had some vexing difficulties installing a different brand of LED houselights. I first tested all of the pre-made DMX cables. I "tested" the fixtures by setting the necessary parameters and DMX address on each and sending each one a DMX signal, making sure it dimmed properly. I then decided to check the DMX OUT pigtails by sending DMX to the input and placing the DMX tester on the output. Found one with a reversed sex 5-pin XLR and another one with the pigtail wired incorrectly. Luckily I did all of this on the ground and not in the air. In retrospect it would have been wise for both of us to have hooked up the entire system on the ground... much easier to troubleshoot there. Never assume.

 

[DavidNorth]

I don't think that this is an issue since all fixtures down stream of #6 work fine on their own (collectively). Thanks for the link to dfd. I've actually read the papers several times.

Ah, but you posted above that with a terminator in #6, things acted erratically so you took it back out. There should be no reason a terminator causes a problem. In fact, if a terminator is used and a problem appears, either the DMX cable or the fixture is faulty. Right now, it is probably much easier to test the DMX cable.

I will say, however, that a shorted DMX cable might cause a DMX receiver chip partial failure. This is extremely rare and as such should be assumed or proven last. Yes, receiver chips can be weak and work only under high amplitude and perfect timing conditions....oh so rare.

But it does look like you found the original issue which was the stapled cable. Now we just need to finish cleaning it up.

David

 

[derekleffew]

... Being the good LD that I am, I put a terminator on the 6th fixture, and it started acting erratically. Took the terminator of, and it was fine. ...

It may have seemed fine, but I suspect it really wasn't.

From https://www.controlbooth.com/threads/moving-light-freakout-terminator-was-the-problem.28635/ :

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. Seen it quite a few times and is a tricky one.

What happens here is that after the conductor break, the remaining data signal [D+ or D-] goes down to the end of the line, through the terminator and back up the other data line. This means that you no longer have correct differential data as D+ and D- are the same minus a little amplitude and a crazy amount of timing. So the light wigs out. When you remove the terminator, the light works fine 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.

See if bypassing fixture #6 solves the issue. Possibly a bad solder joint at the output receptacle of the fixture.

(Posted concurrently with the above.)

 

[bclighting]

Once I had an entire truss of moving lights misbehaving. After hours of trouble shooting and puling cables the culprit was found. The DMX cable between the last two lights had dropped down from the top of the truss and was laying on the back of a Shakespeare. There was the perfect fin pattern of the light melted into the cable. Changed that and the whole truss began to work again.

I learned that a DMX issue anywhere in the chain can pretty much affect everything.

I would check the rest of the cabling as well just to make sure that wasn't the only staple in it.