I've been playing with LEDs for video work for a while. I made some LED panels using strips and off the shelve controllers which always worked nicely while on full brightness. Everytime I dim then down, I start to get some weird "scanline" flickering. That happens to all sorts of leds and dimmers (Arduino included) Ive ever played with.
Yesterday a friend told me he got a modded 12-24V 8A Dimmer which extinguish this kind of problem. Once I got it on hands I was surprised it looked just like a 12-24 Dimmer I got from eBay. Googling around I found out it's a very popular circuit, with MANY different PCB layouts and different vendors.
I tried to find Flicker related mods online but couldn't find anything. Obviously I opened his circuit and it's surprisingly similar to mine, apart from 3 differences I spotted:
I tried to follow the trails but they go underneath the LM358 and the 3 pinned connector. The other IC is a 555.
I have two questions regarding this situation, which my restrict electric engineering knowledge is not helping me out:
- Where I should interrupt the board on my PCB Layout?
- What exactly this MOD did that eliminated the flickering on video?
Here are a few other pics of the boards:
Any help or tips are extremely appreciated! Docs and Papers regarding LEDs and Flickering are also welcome :D
Thanks in advance!
EDIT: I managed to unsolder the pot conector and the two ICs so I can get a better view of the board. I did destroyed one pad on the U1, which apparently didn't connect anything, just the jumped pins.
There's also a solder blob between U1 and the middle pot pin. It's a jumper to rejoin a track I manually interrupted and repaired afterwards.
I'll be posting demos of both circuits working so I can show you the visual difference too.