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I am wondering if there is a circuit I can add to a low voltage DC motor or a 110VAC motor that will cut the power if the motor stalls. I service coin op redemption games and on a few games these small AC/DC gear motors will jam and sit there and burn up. I know about thermal protection but was wondering if there was something else simple that I can wire into the power leads of the motor that can detect a stall. Is there some type of fuse?? that would do this? I did an experiment and jammed a motor while monitoring the current draw and it didn't make much of a difference. I would also like to avoid adding a optical wheel encoder type of thing because of the difficulty of mounting the device. One motor uses a Hall effect setup but it might be hard to mount it on other motors. Anything come to mind?

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For the DC motors a PTC resettable fuse can be put in series with the motor. You'll have to find one that has hold current high enough to run the motor as normal, but trip current low enough to stop the current if it stalls AND also have maximum voltage greater to the maximum applied motor voltage. An example of a PTC is here: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=F2152TR-ND

Digikey has lots of PTCs available. Take a look.

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