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:
For completeness, here’s the entire AC line interface part of the schematic:
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.
The Smell of Molten Projects in the Morning 