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Date: Fri, 12 Feb 2016 15:40:15 -0500
Message-Id: <201602122040.u1CKeFdl011276@envy.delorie.com>
From: DJ Delorie <dj AT delorie DOT com>
To: geda-user AT delorie DOT com
In-reply-to:
	<CALSZ9grFdpWEWyU2LFhoDfSYCmXatFohBFyxNGfXdS-SnZ7pBw AT mail DOT gmail DOT com>
	(geda-user AT delorie DOT com)
Subject: Re: [geda-user] Stepper Driver Question
References: <CALSZ9grFdpWEWyU2LFhoDfSYCmXatFohBFyxNGfXdS-SnZ7pBw AT mail DOT gmail DOT com>
Reply-To: geda-user AT delorie DOT com


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.