Hello, I''ve been working with this PWM circuit on a car's electrical system provided by Bill:
The problem is that the sawtooth wave output from the 555 varies with the car's RPM. If I use a multi-meter to measure average voltage on the sawtooth wave, V goes down when car's RPMs increase. I have both the 555 and 339 connected directly to the 5v supply and ground. Other than the small caps on the input and output of the 7805 5v regulator and the one cap in the above circuit, no other caps were used.
How might I stabilize the 555 output?
Thanks,
Rey
Differences are I'm powering the circuit with 5v from a 7805 plus needed caps.
The problem is that the sawtooth wave output from the 555 varies with the car's RPM. If I use a multi-meter to measure average voltage on the sawtooth wave, V goes down when car's RPMs increase. I have both the 555 and 339 connected directly to the 5v supply and ground. Other than the small caps on the input and output of the 7805 5v regulator and the one cap in the above circuit, no other caps were used.
How might I stabilize the 555 output?
Thanks,
Rey