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Old 01-01-2012, 11:44 PM   #5375 (permalink)
MPaulHolmes's Avatar
Join Date: Feb 2008
Location: Maricopa, AZ (sort of. Actually outside of town)
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Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
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Someone told me that it's possible that some of that noise is probably from the probes picking up noise, so I attached the positive lead and ground to the same point, and it was oscillating and ringing like crazy. So it's possible that I'm chasing phantoms. haha. It's such a menace that it's happening. The Phantom Menace.

The control board, driver board, and power board needed very minor changes, but since the control board has so much room left on it, I added undervoltage lockout for the 12v signal now too. So now it disables if 15v supply to the driver board drops below 12.5v, 12v supply drops below 10.1v, and 5v supply drops below 4.49v.

It could still be a problem if the microcontroller crashed and didn't restart from the watchdog timer, so I took 2 unused pins on the micro, and am pulsing them from 0v to 5v to 0v. When one pin is zero, the other pin is 5v. They are driving the primary side of a small line filter (transformer). On the secondary, I rectify the signal and have a capacitor there. Then I have a load resistor that is constantly sucking the current from the capacitor. So... If the microcontroller freezes, it will certainly stop pulsing those 2 pins, which will cut the power to the primary of the line filter. The output of the line filter will drop to zero volts. I'm choosing the output capacitor and load resistor so the output falls in about 1 millisecond. That will trigger a comparator, which will then disable the mosfet driver. ya! You can't teach that. Pure instinct. hahaha.
kits and boards
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