Strange Mac/PC RGB Strip Problem

[sigilwig44]

Dear QLC community, I have a strange problem, here it is:

Last night, I was setting up our DMX system at church. We use the Open DMX USB by Enttec, and QLC+. I was going through setting up the fixtures, they all worked beautifully, until I got to the last one, which is our DMX decoder for RGB LED Strips. When I tested the lights, they wouldn't turn on, and I was very confused, as my laptop had worked just a couple nights earlier. So I ran home, and grabbed my laptop (which is a mac,) and plugged it into the Open DMX USB, and the decoder works just as it's supposed to. The computer that we use at church is a PC. I haven't had a chance to test it with any other computers, but the Mac works, and the PC doesn't.

I checked to make sure I was running the same version of QLC on both computers, I made sure the settings for the Open Dmx USB were the same, they were (Open TX), and beyond that I don't know much. I contacted Enttec support and they thought the issue was just as strange as I think it is. They told me to try a different PC, and a different lighting software on the PC that doesn't work right now. I'll get in there soon to try that, but can't right now. Is there any other suggestions that you guys would have before I'm at the church again? Any suggestions are appreciated.

Thanks!

[janosvitok]

Can you post details of the DMX decoder?

Was the fixture order and cabling the same for PC/MAC?

[sigilwig44]

Can you post details of the DMX decoder?

I picked the decoder up off eBay... You can see it here: http://ebay.to/2cApEqz

Was the fixture order and cabling the same for PC/MAC?

Everything was the same except for the computer. I literally unplugged the USB->DMX interface from one computer and plugged it directly into the other.

[janosvitok]

I don't know what can be the problem. Here are couple of ideas to try, but I'm not sure if they would help:

- there are per machine settings for QLC+, check those. http://www.qlcplus.org/docs/parameterstuning.html
- perhaps USB port doesn't give enough power - try to plug into different port or powered usb hub (what kind of computer is it? laptop/dektop?, how many other USB devices are plugged?)
- when the lights stop working (I assume all of them stop), if you unplug something in the middle, will it start working again?
- if you plug only the strips controller, would it work?
- if you swap order of the fixtures, what happens?
- maybe there's a faulty cable - which means either it has too big resistance, or has ground somewhere where it should not be, and mac has better power source/usb power so it can somehow cope with that,
and PC not?

Either way, it looks strange and I wish you good luck with finding the problem. Don't forget to tell us the result!

Jano

[sigilwig44]

Ok, here's everything I've tried.

Multiple Windows PCs: none work
One Mac (does anyone know how to get QLC/Open DMX USB to work on OS X 10.11?): works beautifully
PC Running Ubuntu (Linux): works OK, but is very delayed. Takes about 5-15 seconds to turn on a light after adjusting its level in simple desk. ONLY that fixture is delayed though, everything else is fine. Literally if you plug the DMX cable into a different fixture it works perfectly.

Another note: On the specsheet of the DMX Decoder it says "650HZ DMX Frequency." Could this have anything to do with it?

And that's it... I am SO confused as to what's going on here... Ideally I'd like to get the Linux machine to work, as that would be easiest. Any insights anyone?

[sigilwig44]

Alright everyone, I'm bringing this one back. I hate to do it, but it needs to be done. Each year we redo the stage at church, and it's that time of year again. Once again, we're going to be using LED Strip lights. What I ended up doing last year was just living with the linux computer since it worked. It went from "Oh yeah, we'll fix that problem once we have time." to, "I guess there's really no point in fixing that anymore." You see, until now we've just used the computer to change the color of the lights, we've never done anything crazy with scenes or pre-programmed things; so there was really no need to have a computer that worked 100% properly, just as long as we could get the colors set at the beginning of the night we would be fine. This year, I'd like to get into some of the more advanced stuff, and hopefully even sync up the lights with the music. Of course, if I want to do that, I need to have a computer that works properly.

I have a couple options: First, use the Mac we already have. This is an option, but is definitely not ideal since that computer is already being used for projection. Second, just stick with what we have. This would be ok, but as I stated above I would like to do some more advanced stuff with our lights so the problem will definitely need to be fixed. Third, somehow get these decoders to work with a PC.

I was in once again today and tried many different things. I bought a brand new DMX Decoder to see if that would fix the problem. Plugged it into a Windows PC. Nothing. Plugged it into a Linux machine. Horribly delayed (no better than the old decoder). Plugged it into a mac. Worked perfectly. So I'm not sure that it's the decoder that's in question anymore; but we'll come back to that later.

Second bit of important information: The DMX Decoder has a flashing light on it, presumably that either turns on or off when it receives a DMX signal. When nothing is plugged into the decoder, the light flashes rapidly bright. When I plug the PC in, the light remains in the same state. When I plug the Linux machine in, the light stops flashing and becomes solid (for the most part; occasionally it will start to flash). When I plug the Mac in it stops flashing entirely and turns completely off. This all made me think that it might be an issue with my cable, and that for some odd reason the Mac puts out a higher voltage signal than the Linux machine, and the Linux machine puts out a higher voltage signal than the Windows PC. I thought that maybe my cable was of very high resistance and only the Mac machine was truly capable of pushing the signal through my cable; but I attached a voltmeter to the DMX cable, and there appeared to be no difference between the three. The only difference was that when the PC was connected, the voltmeter's needle was moving back and forth rapidly, as if the signal was being terminated and then re-established about 30 times per second. There was no such effect when the Mac was connected; the needle remained rock solid. Here is a video of the needle when attached to the Windows PC: http://www.youtube.com/watch?v=wv9RAlq1ek4 I believe that the occasional spikes in voltage may be from a poor connection between the voltmeter and the DMX terminals.

We can safely deduce that it's either a problem with the decoder, the computer, the software, or the USB to DMX interface. It could be the decoder, but I've already tried two of those. It seems to me that if these things are sold (even if they're sold on eBay) they should work with most DMX signals, so I don't think that it's the decoder. The computer is probably the most likely possibility right now. There is likely some software difference between the three operating systems that is causing the problem since NO Windows PCs work (yes, I've tried to use multiple PCs), all (I guess I've only tried one, but in this case it seems safe to assume) Linux PCs are delayed, and ALL Macs work (I've tried multiple Macs as well). It's just a matter of figuring out what that difference is. It would seem that the problem is not directly related to the USB to DMX interface since it works with a Mac. Chances are that the USB to DMX interface is not the problem. It also could be a cable, but I've tried countless configurations of DMX and XLR cables, not to mention wiring it in a chain with other fixtures and just plugging it directly into the USB->DMX interface.

So this is what it's come down to. I think that somehow the frequency of the DMX signal that the Mac sends out must be different than the one the PC sends out, which is also different from the one the Linux Machine sends out. The different blinking of the DMX signal indicator light and the shimmying of the voltmeter needle points me to this. The only problem is that I don't know how to check what this frequency is nor do I know how to change it. Could it be possible that the windows frequency is the lowest because it is the least efficient OS, whereas the Mac's is the highest since it's the most efficient OS, and that there's simply nothing I can do about this? Or is it a setting that I could change somewhere? I've tried the "Parameters tuning" as outlined on this page (http://qlcplus.org/docs/parameterstuning.html); but I've never been able to find any of the actual parameters listed in the parameters list within the config files or regedit. Could you please post either a video of how to find these things or a more detailed description of how to find them? Because the instruction on the page linked above never seems to work for me.

Thank you so much, please respond as soon as possible as I am trying to solve this issue ASAP so I can get started on the rest of the stage!

[GGGss]

Running into troubles means start very very small.

As you already explained you did already a hell of a job deducing the problem.
Voltmeter issues: are you truly measuring on the +5 and GND points? If you measure on the data ports you might see some needle movement (if your volt-meter is fast enough to keep up with the USB data-stream) - the needle heavily moving could indicate that your usb is draining a the power the port can give which is bad...

With the Open DMX interface it IS the computer which is responsible doing all the DMX math. So if the parameters in the software are bad - DMX signal is bad. (And the CPU is loaded with the 'make the DMX signal-train' job which is sent 1-1 on the USB bus and is sent 1-1 into DMX. If timing is bad - DMX is bad.
(If you'd use a DMX converter with processor built in - the job making the DMX-train pulses is done by the processor inside the converter. The only messages the computers CPU is loaded with is. 'Send value 52 to channel 2' and the converter does it job making this into a DMX-train.)
=> the difference in latency of your Linux computer makes me think of a very high CPU load.

If I'm not wrong the Open DMX interface not galvanically shielded - which is bad on long lines. Speaking of long lines ... DO TERMINATE it (otherwise you'll get reflections back into the wire and that is again very bad). And again : I am suspicious about your Led-drivers? Are the galvanical isolated? (A fault in the led-fixture = bad DMX-signal)

Start small: 1 computer + 1 converter + 1m cable + 1 fixture on address 1
if succes have the fixture addressed to 253 (that is half way the DMX universe) If timing is bad (no response from the fixture) then you have a timing problem.
if succes have the software to run the whole show (sending out signals to all fixtures but only 1 fixture attached to DMX) -> if no or bad response => CPU load problem OR timing problem under load. Very difficult to solve.
if succes you might have a cable problem or faulty fixture in the line. Start using the original cables and 3-4 fixtures (and the one on 253)
if succes grudually expand the DMX line with more fixtures ... to somewhere where you discover a faulty piece of cable / a bad fixture.
If a bad fixture at least try to have it on address 1 and see if this works and see if the others still work. (Internal timing can be off spec of this fixture OR it disturbs the DMX-train)

Remember the DMX specs: it runs at 250kbits/s, max. 32 fixtures, line-length up to 1200m, use a terminator and please please: NO audio cables.

Finding faults can be cumbersome and especially under production-pressure. (This weekend I needed 3hours to fix a problem with a DMX line with only 6 heads - 30m line length) DMX-interface vs old laptop. Solved it by using Enttec DMX PRO (no more CPU load) and installing the right drivers (had to change the .inf file with notepad to have it discovered correctly)

Good luck