[chbot] Wax Motor

[Mark Atherton]

There was some interest in the wax-motor I passed around Monday eve 
(brown plastic assembly, with actuator).

Quite surprised taking apart; a small metal WM assembly with retracted 
metal actuator. This part is heat-driven.

Thermally and electrically attached to it was a 10mm dia, 2200 ohm, PTC 
thermistor.

Apply mains to the whole thing; the thermistor heats up, which in turn 
heats up the WM causing actuation. As the thermistor heats up, 
resistance increases, dropping final drive power to around 3W.

Wonderfully elegant and simple.

-mark

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