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Date: Fri, 12 Feb 2016 16:55:33 -0500 (EST)
From: "Stuart Brorson (sdb AT cloud9 DOT net) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
To: "Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Subject: Re: [geda-user] Stepper Driver Question
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I understand that windings in transformers and coils can vibrate at
the drive frequency.  If the windings are not held perfectly still
(hard to do), then they will vibrate slightly due to the time-varying
drive iteracting with the magnetic field surrounding them, causing
sound.

Old-timers will recall the low hum emitted by 60 Hz transformers in
old radio equipment.

If you stepper motors themselves are making the noise, then it's
likely the windings in the stepper.  If your circuit is making the
noise, it's likely your inductors or transformers.  If the noise
doesn't bother you, ignore it.  If it bothers you, make sure your
inductors and transformers are potted in something.  Of course, this
lowers the current rating 'cause they can't be cooled effectively....

Hope this is useful,

Stuart


On Fri, 12 Feb 2016, Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:

>> Could be the PWM it uses to control current through the coils
>> (remember, steppers have to be powered all the time to avoid losing
>> steps, even when stopped).  Check with a scope and see if it matches
>> the spec.
>>
>> You might be able to silence it with some extra inductance in the
>> wires, either a LC low-pass filter or a ferrite, depending on your
>> design needs.
>
> It is normal for switched power electronics to make sound. Either from the switching or the control loop.
>