Uwanted flicker

Generic issues not specifically related to a QLC+ area.
Post here only if you can't really find the reason of an issue
Post Reply
Posts: 1
Joined: Mon Mar 13, 2017 9:19 am
Real Name:

Uwanted flicker

Post by mp76 » Mon Mar 13, 2017 9:29 am


I'm using QLC+ on windows 7 trough Enttec Open DMX interface. My problem is that there is a short flicker when I change scenes using the virtual console. Besides that there is also a more random flicker when in design mode and editing scenes. Sometimes the problem goes away, but I can't seem to find the reason why. Any ideas anyone?


Posts: 69
Joined: Wed Jun 15, 2016 8:51 am
Real Name: Matt Mayfield

Re: Uwanted flicker

Post by mdmayfield » Mon Mar 13, 2017 5:11 pm

There could be many possible sources for this issue. Can you please upload your project file? I and others could then take a look to see if there is anything obvious that might cause it.

It could also be hardware-related. If I'm not mistaken, the Open DMX interface does not have its own CPU and relies on the host computer's processing power to keep the DMX data flowing to the light fixtures. Can you test the lights on a different computer?

Also, in my experience, large lighting setups are extremely sensitive to static electricity, ground loops, and voltage drops - that is, if the complete wiring plan is not set up EXTREMELY carefully to avoid any earth/ground differential (sometimes called "ground loops," though that can be a misleading term). This is kind of a pain, but it is necessary to do in order to get near-100% reliability. A comprehensive guide on this is here (PDF): http://mickpeterson.org/2014design/Info ... andout.pdf

As an example, to get the large light setup working for my band (45+ fixtures), we had to install optical isolators on the DMX lines and then ensure that all computer equipment was attached to the same AC mains ground. Then I started running into issues where, every hour or so, the DMX interface would stop being recognized and show garbage characters in its Serial Number in the Inputs/Outputs section of QLC+. I had to disconnect it from USB and reconnect it to get it recognized again.

It turned out that the cause of this was that I had a USB cable connecting my computer to a laser printer that was not on the same AC circuit as the rest of the computer equipment. That printer shared a circuit with a small office refrigerator, and whenever the fridge's compressor stopped, it somehow disrupted the USB communication between the DMX interface and the computer. After changing to wireless printing, that problem went away.

The moral of the story is: one careless connection, even over a seemingly-innocent data line, to an AC ground at a different voltage potential, has the ability to completely ruin a whole show.

Post Reply