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Unread 04-05-2012, 12:43
rbmj rbmj is offline
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Re: Non-FRC Motor Controller?

Yes, at some point the PWM has to be digitally processed - I think 1-49% is reverse, 50% is neutral, 51-100% is forward (based off of reading the WPILib source a while back, so might be a bit off). The code on the microcontroller must be very tightly optimized if they're generating the pulses on the fly - no interrupt timer will give you the time resolution you need - they must be relying on the actual instruction processing speed of the microprocessor. That manual talks about delays in microseconds...

So those diodes are part of the MOSFET? That manual says they're arranged in a circle under the fan - those heat sinks must dissipate a lot of power. I don't quite grok how the synchronous rectification works - seems like black magic to me. The energy in the motor has to go *somewhere*. It's just a matter of where and how quickly (right?). Maybe if they had all that current switched to a capacitor or something, it would make sense, but I don't understand how they get an order of magnitude less dissipated energy without channeling that energy TO somewhere.