I have a fairly frustrating problem with my 555 PWM circuit. Above is the circuit I'm using. In my simulator the PWM function works well, I get a good range of duty cycle and the frequency is very regular.
In the actual circuit, starting the potentiometer from the most clockwise position, and rotating it counter clockwise the frequency decreases as I do so, and the duty cycle remains constant. As I approach the center of the pot's travel the frequency reaches its lowest value. As I continue rotating the pot the frequency increases again until it reaches a similarly high frequency as before. I've tried 3 different pots, different capacitor values, different resistor values, I've swapped out the 555 chip for a spare one, nothing seems to work. The result is always the same. Any ideas as to a way to fix this? The output of the circuit is connected to an AND gate so there's little load on the output I would assume.