It seems common practice to put a protection diode upstream of a quickly-switching mosfet, in parallel with an inductor (motor, relay):
This Mechanical Engineering class page recommends adding a small 1 nF to 0.1 uF cap in parallel with small motors to reduce motor voltage spikes:
Would having both the protection diode and cap be counter-productive when PWM-controlling a 12VDC, 1-2A motor? Or would both be good?
Thanks,
Michael
You wouldn't normally use a capacitor with PWM.
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The caps are for reducing noise, like the ME paper says. I've used caps across the diodes in a 60 Hz bridge rectifier to reduce interference coming from the commutating diodes, but I've never seen it suggested that you should do such a thing across the freewheel diode in a pwm circuit. It's a different animal. You might get ringing or some unwanted effect. Scoping a working circuit might be edifying.
Are you going to reverse the motor?
Ed
nope.
Michael
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