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Fan controller

posted May 4, 2011, 5:50 PM by Nicholas Leesam   [ updated May 5, 2011, 6:34 PM ]
Had some time to breadboard tonight.

Current issue:
When pwm is fully off the mosfet doesn't switch fully off. Disconnecting MCU allows full off but high freq (32kHz if i'm reading that correctly) switching 90% off only seems to drop the voltage to 10-ish volts (12v source). The Off voltage stayed the same even under heavier load. It's now running four fans at .6 amps each.

I think i may be switching too fast. I had cranked the pwm frequency to get it out of hearing range. I've got to see what i can lower it to.

Scope reading while MCU outputs below signal.

Scope reading at lowest knob setting.