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Old 05-01-2009, 08:25 AM   #1110 (permalink)
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Originally Posted by Roger Heuckeroth View Post

OK. Let me see if I understand. You are going to have the capacitors and the diodes,
It may be one cap and one FRED, like this one:

MEO450-12DA IXYS 1200V 450A Fast Recovery Epitaxial Diode Module at The - Electronic Surplus Parts & Equipment

and still need a micro controller to manage the servos.
Actually I said I was going to build one without it by using the accelerator cable to draw the assembly back and forth across the brushes. I was thinking out loud about the micro/servos as a current control mechanism.

So the whole mechanical contraption only hakes the place of the MOSFETs.

Wow! MOSFETS look a whole lot simpler to me.
A prototype is buildable with no control electronics whatsoever.

The biggest problem with MOSFETs is that they blow up. You overvolt, overcurrent, or overheat a MOSFET bank and they go POOF!

The second problem is that mounting a MOSFET bank is a major undertaking, milling/etching/drilling/soldering a board.
It's one of the reasons that folks keep asking about IGBT's as an alternative.

Seriously, the only advantage I can see is using this for drag racing when you want to handle thousands of amps for a 10 second run. It should be cheaper than IGBT modules. But for your average car, this seams like a really complicated way to go.
As wonderful as this thread is, it also has shown the pitfalls of putting together a reliable PWM MOSFET motor controller. There are significant design/programming challenges.

The alternative is simple, cheap, and easy to build with common household tools. More importantly it will be reliable because it isn't relying on a ton of interconnected complex parts to pull off.

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