.:madworm:.'s photos with the keyword: resistor

Available on tindie.com

Color balancing is done with these as well.

For GREEN.

For RED.

For BLUE.

I couldn't get hold of a precision shunt resistor, so I had to do with this 10% 5W one here. It didn't turn out too bad at all. This one doesn't affect the current displayed on the power supply's display (the display measures the current itself), but the current set-point in the opamp feedback loop. I have a schematic, but it is not quite matching the PCB revision I have, so I couldn't instantly figure out which pot to tweak to compensate for small deviations. Reverse engineering a schematic from a given PCB sucks. I compared the current set on the power supply (via a keypad) and the current measured by a good multimeter and it wasn't off by more than 5% worst case. That's good enough for me right now.

I've retired this one, but kept it. Just in case ;-) It was replaced by a standard 10% 5W 390mΩ resistor. Not perfect, but it works good enough for me. The worst deviation I've measured is less than 5%.

The left one got too hot. It was running a few hours at maximum current (about 2.8A). As I found out later, it ran in unregulated mode, as two fuses were blown. The power to the microcontroller was cut off. After replacing the two 100mA fuses with 160mA ones it works again. I just happened to have them, but I'll need to get proper ones. The shunt resistor will have to be replaced as well, as its insulation is breaking down. I've measured it to be 0.4Ω, but I can't trust that value. Maybe the manufacturer will tell me the correct resistance.