| Electronics > Beginners |
| Trouble reverse engineering PCB to schematic - capacitor to nowhere? |
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| jpyeron:
I am reverse engineering a commercial (constant current) LED ceiling panel, to make an open source replacement / improvement. The PCB has two capacitors on the PCB near the wires. They are 10.3uF. The board contains two circuits of LEDs 3k white, 5k white. The capacitors are only on one of the circuits. I have been unable to probe out where the other pad goes. Any thoughts on where to go next |
| KL27x:
Doh. Better check IP address to see if this is Treez opening a fake account. |
| jpyeron:
I am not trez, I am easy to google if you care/need |
| Nusa:
See what the voltage is across the capacitors when the panel is in operation. That'll at least tell you that it's not open-circuit. Which is an idea you shouldn't discard until proven otherwise. Beyond that, you haven't given us enough information. Your schematic of something you can't explain is probably less useful than some pictures of actual traces and components on the board. How is the light used with the two circuits? Both on always? Each one independently? One always on before the other? |
| jpyeron:
The solder mask is a bit difficult to see through, my apologies. Here is a key photo: Here is a a video of the whole boards (1 with the capacitor still on, the other with them removed): https://youtu.be/gSdic5ZpIjU Here are photos of the the power supply shipped with the unit - it is being replaced. Sorry, I omitted the readings across the component. I get a transient spike of +/- 0.007v at power up on the circuit, then it stabilizes to 0v. I am powering it directly with a constant current bench supply. As to the function, at the end of the second board it uses a common +, power supply (should) allocate 0-100% on one set and 100-0% on the other - so yes they can both be on at the same time. The commercial specs are (if you want to google the product): Tunable White LED Panel Light - 2x2 - 4,300 Lumens - 40W Dimmable Light Fixture Part Number: LPD-TWR22-40 CRI 80 CRI Current Draw 0.33A (330mA) Efficacy 108 lm/w Intensity 4300 Lumen Total Power Consumption 40 Watts |
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