So I think I’m just being stupid, but I thought I’d ask on here to confirm. I wanted to just play around with some simple circuits just have some fun. I thought that an adjustable PWM output would be nice for some LED lighting for… Something.
After some googling I found a circuit on EEVblog’s forums that I thought I would try to replicate. I put the parts on a breadboard and it doesn’t work as I thought. When I adjust the pot, there is a large band (maybe from 10-90% of the pot range) of little to no change in the brightness of the LED. The main issue though would be that either direction I go with the pot, I get this behavior. The brightness increases in both directions and when I measure the duty cycle (with a DMM) I never get lower than ~50%. So basically from 50% to 90% regardless of which direction I move the pot.
I don’t show the LED on the output, but one is there on the board. Although I get the same issue without a load on the 555. Everything simulates okay (but of course it would). I also attached the simulation file.
PWM_v1_NoLoad.zip (669 Bytes)