I'm having an issue with this PWM controller circuit. In this circuit the potentiometer comes with a on/off switch.
The way it should work is: As the potentiometer resistance value varies the output voltage varies (with the help of a 555 timer chip). When the output voltage increases the red LED increases in intensity and the the green LED decreases in intensity.
The problem that is happening when test the PCB is that:
1- The circuit is always "ON" the switch circuit doesn't seem to work
2- The output voltage doesn't vary as I turn the potentiometer, it is always at full intensity
3- The red LED is always at full intensity, the green LED never turn on
This PCB has 12VDC input.
Q1 and Q2 are N-Channel Mosfet (https://octopart.com/buk7y08-40b%2C115-nxp+semiconductors-19677921)
Q3 is a PNP transistor (//octopart.com/bcx5316ta-diodes+inc.-13152586)
U1 is a 555 timer chip.
Is there a problem with the schematic? Or is it that something went wrong during the PCB design?
I'm a hobbyist so forgive any mistake or oversight. Any help would be appreciated