Quote:
|
Would that be pin 4 perhaps?
|
Yes
Quote:
|
Is Z1 some kind of varister perhaps
|
Yes, that's my assumption too
Quote:
|
Still not sure how it works though.
|
Square tach pulse from Q2 triggers monostable Q3/4 to produce one identical rectangular pulse per tach coil cycle, ie. duty cycle depends on speed, smoothed by LPF to give actual speed value. U1 compares this to target speed, output flips back and forth increasing mean drive period of Q5 when speed is too low etc. U1 switching and loop constants set by RC's in feedback path.