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Kenmore 158: Motor Flyback Diode

Although small power diodes make fine flyback diodes for relays, the motor can draw several amps during the startup pulse, which will be a bit out of spec for the usual 1N4007-class diodes. Pressing an old 5 A / 200 V stud diode into service produces the ungainly black-and-blue lump eating the end of the green wire:

Motor flyback diode - installed

Motor flyback diode – installed

For completeness, here’s the entire AC line interface part of the schematic:

AC Power Interface

AC Power Interface

The diode’s 200 V limit should suffice, even for cold starts at high line peaks, but, when you build this with new parts, get something rated a bit higher, OK?

The four NTC power thermistors lie just to the right of the relay, before the bridge rectifier.

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