Stepper motor making noise at low rpms

Audible, maybe but electrical, i think not. Slow down the risetime of each step, so the motor makes a smooth(er) transition from one position to the next.

I am guessing that the pulses the drive is producing to regulate the current are not uniform in duty cycle, and you are hearing the low frequency dither as the controller struggles to find the correct average pulse duty cycle. I have had to design this effect out of a growling stepper motor drive combination that should have had a high enough pulse frequency to be silent.

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Regards,

John Popelish

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Robert, The noise is almost musical - funny. I am sending a square wave using the PWM out function from a Parallax SX chip. How does one slow down the rise time independent of the frequency?

John, the duty cycle is 50% as with my square wave signal.

so I assume your tailoring the carry frequency and keeping the duty at 50% ?

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How are you micro stepping by applying a 50% duty cycle square wave to your motor?

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Regards,

John Popelish

Some kind of filter..LC network might do the trick.

I used to be able to play Amazing Grace on a stepper motor drive test rig, sounded just like little bagpipes.

John, I am using a driver to 1/8th step my square wave. I have 1600 pulses per revolution.

So you are not hitting the motor with a square wave, but stepping the driver with it?

The sub cycle oscillations I mentioned have little to do with the step rate and have everything to do with how the driver regulates the individual step current level.

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Regards,

John Popelish

Are you bragging, ot complaining? ;-)

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