Hello
I'm trying to dim two strings of 6 LEDs through a CAT4101. The schematic is attached. I have a 24V PSU supplying the LED power, a 5 V supply off that sam PSU acting as the input for Vin. Then I have the Arduino attached to ON/OFF PWM for PWM. And I know I have the correct resistor for RSET. Now this is where things get funky. When I bypass the Arduino by making the GND pin off the CAT4101 go to the GND of the PSU (rather than the Arduino) lights turn on to full brightness and everything is cool, but obviously no PWM. (Not weird yet) So then I detach the GND CAT4101 wire from GND PSU and attach it to arduino GND. Now I get PWM but the lights are dimmed to about half brightness even at 255.(Sort of weird) This is where things gets really WEIRD, I then remove the all GND (no Arduino or PSU GND), and a string of lights REMAINS ON!! WTF??? It must be grounding somewhere within the system?!?
When I've been in the sort of r/d getting things working stage. I have witnessed on more than one occasion what seemed to be led's lighting up with only one half of a supply. I put it down to an explanation i don't yet have as i sort of thought it was impossible. A bit like a perpetual motion device or something. It did seem very weird though. Tesla did have a way of sending electrical energy with one wire so they say.
Check the voltage between the CAT4101 LED pin and ground. If it is anywhere near 25 volts, you are probably getting an avalanche current through the transistor/fet to the Vin power supply.
While you are at it, check the 24v power supply. Is the output 24 volts? Or higher?
