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PWM control of 25amp motor
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PWM control of 25amp motor

by shobley on Thu Sep 30, 2010 6:00 pm

I have a project that requires the PWM control of a 25amp fan (in a car dash) - is there any problem with wiring the gate of a suitable mosfet (or pair) through a an optoisolator to an arduino pin?

I've done this successfully in the past, but only with about 10amp loads.

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Re: PWM control of 25amp motor

by franklin97355 on Thu Sep 30, 2010 8:08 pm

I would say you would be OK as long as the frequency response of the opto can handle your PWM frequency and the mosfet is sized correctly.

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Re: PWM control of 25amp motor

by zener on Fri Oct 01, 2010 1:32 am

You will need a pretty beefy mosfet. Something 3 or 4 mOhm might work, and you will need a heatsink.

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Re: PWM control of 25amp motor

by Entropy on Fri Oct 01, 2010 11:06 am

Might want to look at Charles Guan's blog (etotheipiplusone.net) for ideas. He and Shane Colton (scolton.blogspot.com) do a lot of work involving controlling BIG motors.
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Re: PWM control of 25amp motor

by shobley on Fri Oct 01, 2010 4:43 pm

Thanks - I will check that out.
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Re: PWM control of 25amp motor

by zener on Fri Oct 01, 2010 5:26 pm

Historically this was done with two or more fets in parallel. But you might get away with a single one with very low RDSon. Just a follow up to my previous post.

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