Is it possible to fix the PWM frequency with which Pololu A4988 driver chops the current to the motor windings?
I have one motor that I’d like to use (omc-stepperonline.com/nema-1 … -p-19.html), but it makes this disturbing whining noise. Hooking up a scope to one of the windings, I can see the usual PWM cycle (jumping from 0 to 12v, which is where my supply voltage is at). However, the frequency of that PWM changes depending on the microstep phase (I’m in 1/16 mode, ROSC pin grounded). I get from 5KHz to 15KHz - and I get a headache within 10 min of being near the thing
I thought the PWM frequency of chopper drivers was fixed, and the only thing that changed was the duty cycle, obviously, that’s not the case.
Another motor I have, also shows variable PWM frequency, but its higher pitch (17KHZ to 22KHZ) and not nearly as disturbing.