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Posted by Clifford Heath on June 16, 2006, 9:47 pm
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Couldbeflying wrote:
> I just purchased four (6mm shaft) 7.2V gearhead motors for an ATV robot
> project. Just wondering what caps I need across the motor's positive
> and negative terminals?
Not possible to know without knowing your motor's inductance and
resistance.
> Is they a way to calculate this for furture reference?
The capacitor will resonate with the inductance, and the ringing will
be damped by the motor's resistance. If it has very low resistance,
you'll need to add a resister, usually in series with the cap. The
objective is to ensure that the ringing is at a frequency where it
will cause minimal problems of getting into other circuits, and to
damp it out as quickly as possible consistent with not losing too
much efficiency in your drive circuit.
Google for some tutorial on damped tuned circuits and you'll get the
idea quickly.
Clifford Heath.
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> project. Just wondering what caps I need across the motor's positive
> and negative terminals?