Sebastian,
I’m sorry about this late reply. The last 2 days were very busy and hectic around here.
Thanks for answering my previous questions. I’m going to assume that your LDR pair is matched (because we matched them when we assembled your kit) so the issue has to be that the LED is not getting bright enough to cause the LDR to lower it’s resistance to a reasonable value.
-Check everything in the circuit between the microcontroller pwm output and the LED. They are: Q1, VR8, and R8.
-Check to make sure the solder joints on these components are good and there are no shorts between any of their solder pads.
-Check to make sure all these components are correct values.
-Make sure R8 is getting 5V on the correct pin (as shown in the trouble shooting guide) and compare the voltage of the other pin on R8 to the same pin on R7.
-Test to make sure the trim pot is working by measuring it’s resistance….from the middle pin to the one of the side pins. Then turn the trim pot about 10 or 12 full turns and re-measure the same pins.
-You should also compare the optocoupler LED voltage (as in the trouble shooting guide…the yellow pads in the voltage chart)…both of them should be around 1.8V.
Look into all that stuff and let me know what you find.
Good luck!
-Brach