Sensorless Controllers- (Dept. of Who Knew?)

In the process of doing my hub motor repair, someone mentioned something that I’d never heard of- a sensorless controller.  That is, a controller that doesn’t rely on Hall sensors to determine where the rotor is, and when to feed what to where to make the motor spin.  Magic, pure and simple.  Here’s a link to one of the controllers available on EBAY.

Apparently the controller can tell where the rotor is directly from the drive wires.  To quote Bruce in the ElMoto thread: “They either look at the third leg while driving the other two if it is a two phase at a time type or they can measure the back emf on all three to infer the position of the rotor. This type of controller could care less if you originally had sensors, the more compicated circuit internal to the controller makes the sensor unnecesary.”

I don’t know what EMF is.  Wait.  Google.  EMF = electromagnetic field.  OK, that makes sense.

Unfortunately the item on EBAY ships from China- and the shipping is almost the same as the item itself, at $24.  I had a bad experience with China EBAY purchases, the last one I bought took 6 months to show up.  It would be a fun little twist on my repair project, though…  stay tuned!

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