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How fast is this motor???


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I need a working motor for a Seth Thomas electric.  The bad motor is a sangamo that runs (I think) at 7.5 RPS.  So I am buying motors on ebay in hopes of coming up with a retrofit.  But I need to measure the speed.

Aha!!  I wired an LED to my arbitrary waveform generator and used it as a strobe.  Dial up the frequency until the rotor stops!  This one is 12 RPS.

Voila!!

setup.png

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