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Old 12-28-2008, 01:55 PM   #52 (permalink)
MPaulHolmes
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Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
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Capacitors added, and a few wires

The power board is nearing completion. I need to add the mosfets and diodes, but first I need to attach them to a heat sink, since there would be no room for screwing them in if I soldered them in first.

Then all that's left is the weenieboard, where the ATMega8 microcontroller will be. Those long red wires (which will be shortened later) will each be connected to it's own 30 ohm resistor which will be attached to the output of the gate driver (on the weenieboard).

One of the senior design engineers of brushless DC motors that writes on the EV Tech list suggested that I only need 2 of those mosfets to get 40 amps continuous out of this controller. So, I think we'll use 5! haha! A 72v 100 amp bike controller. haha! Well, the 13 gauge wire "bus bars" will probably be one of the weak links, so I'll still keep it under 50 amps, and just get practice with paralleling mosfets and making sure everything turns on at the same time.

EDIT: Safety resistors added from mosfets' gates to ground (22kOhm) just in case the mosfet driver breaks down. Without them, the mosfets' gate voltage would drop to around 5-7 volts if the driver quit working. This would mean that they would stay ON! So, power would start dumping from the battery pack until the mosfets burned themselves up. That's not good. This way, their voltage would settle at 0v after a very short time, shutting the current off from the battery pack, saving them to switch another day!
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Last edited by MPaulHolmes; 12-28-2008 at 04:21 PM..
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