I have one of these: http://www.ebay.com/itm/331098605750
But I have seen this same driver, in a dimmable version...
But no idea what the external pot is connected to on the underside. Here's the relevant part of the board with the bottom heatsink plate removed:
Anybody see the likely spot where the pot wiring would go?
And a related question: Would this driver freak out if something, say a BLF-DD driver :bigsmile: , were placed inline on the LED- output? With the BLF driver powered by a separate adjustable DC-DC board set to ~4v?
What does the R33 pads do?
If that was a variable resistor would it make it dimmable?
Per the ebay listing of the dimmable one
*Item is incompatible with PWM controller
That’s a pretty hefty pot, sure it isn’t the “load resistor” for dimming?
R33 is just an unused pad in parallel with the sense resistor at R36. I'm sure the same board is used for different wattage versions, so there are different resistor combos for the different output currents.
I have a dimmable 50W, it's the sealed type in an aluminum housing but it has the same pot-with-only-2-wires-used (in variable resistor mode). It does not do any kind of PWM on the LED outputs, but the wires to the pot are way too skinny to be inline with the outputs. The LED voltage only covers a range from around 29-31.5v from full dim to full bright, I'm not sure exactly how it's doing the dimming. I would think based on Vf curves of other LEDs the voltage would change more than that.
Is it even remotely possible to use a pot like that to “short” across one of the transformer windings to control the output? Or would that be too much for the pot to handle?