Flickering Issues

Posted on November 1, 2020

I found a strange issue with my desk controller the other day when I was working under my desk. I noticed a dimming indicator flickering when there wasn’t a dimming channel selected. I took everything apart and started to troubleshoot. There wasn’t any voltage coming out of the selected outlet, so it wasn’t turning on an output, but the channel was erratically flickering.

At first, I thought it was a programming bug I missed, but upon further digging, I found that it was signal interference on the I/O pins from the fans that use the same power supply. When one of the three on/off channels are turned on, there are two fans that turn on to keep the heat sinks cool. The interference of those motors create noise and the selected dimming pin to think there is a signal, which causes the LED to flicker. It doesn't turn the channel for more than 30+- microseconds at a time but it shouldn't turn on at all.

I put some caps on the fans and that seemed to almost get rid of the flicker all together. I tried to include a flyback diode, but it still persisted when I turned on both fans. I was surprised that the caps didn't work to be honest, that normally does the trick. I tried to just use just one fan and immediately the problem stopped. I initially put two in the project to be symetrical and it looked better to me. The fan is blowing on the A/C controller that controls the highest load demands and keeps cool even with 10A being pulled. I tested the heat produces with higher loads using a duel heater and fan and used 12A fuses; everything ran great and kept cool. I will revisit adding the other fan at a later date if needed, but I dont think it will be.

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#interference #flickering #spinstamp #capacitors