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Old 04-19-2009, 01:20 AM   #985 (permalink)
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Originally Posted by edown View Post
Iíve been thinking about multiple gate drivers, and it seems that if one fails, you wouldnít know until you let the smoke out of the remaining fetís . So I was wondering if you could take each driver output to an input of an AND gate (like a DM7415) and signal a shut down? As long as the drivers are in sink the AND gate will stay high..
Let's see. If the driver fails, (and this is personal experience talking! haha!) make darn sure you have a path from the driver output to ground through a (OOOOHH LET'S SAY...) 1 kOhm resistor. That will keep those fets off, and prevent the fet gates from floating and settling at around 4 volts, which is bad. hehe. In that scenario, you would lose half of your current carrying capacity, which could cause major problems if you are pulling a lot of amps, because the good driver would still be running his (or her!) mosfets really hard, because they would now also be doing all the work of the other mosfets that are relaxing with their gate at 0 volts.

So, now I see the purpose of your AND gate. You could have each driver output (limited back down to 5v through a voltage divider? since the driver output is like 12-15v) connect to an AND gate that would disable both drivers somehow or other. Maybe send the signal to the micro-controller, and based on a number of possibilities, the microcontroller has an enable line that gets ANDed with the PWM signal, whos output goes to the mosfet drivers! Git 'r done! hahaha!

You are some kind of crazy Maguyver with your wood based motor controller! I love it!
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