In a nutshell a student is using a single output pin to run LEDs of 2 different colours. There are 3 yellow LEDs connected in parallel and 2 red LEDs connected in parallel. The 2 parallel circuits are soldered into one wire that connect to the output pin. The 2 negative lines are soldered together and, via a resistor, connect to the negative rail on the breadboard. The LEDs didn’t work so I suggested separating the two negative lines and using a separate 1k pot on each line. I also inserted a test LED on the breadboard for each line. Both test LEDs were working fine. I plug in the red LED line and it works. I plug in the yellow LED and it works. Plug in both and they don’t work. Also noticed that when the yellow circuit was plugged in, the red pot affected the yellow LED. There seems to be some feedback happening but not sure exactly what is happening. Can anyone please explain this?
I have thought of separating the red and yellow lines for different pin outs but this would mean using the 0 and 1 pins as the others are used. Can this be done? Am using Uno and there is only a stepper driver in use as an add on module.