E-Bike Repairs - Hub Motor Hall Sensors

One of the apparent "benefits" of owning an e-bike is the opportunity to learn as much as you might care to know about e-bike electronics.  There are plenty of regular bike things to deal with - tires, tubes, bearings, chains, brakes and such, but the electronics of e-bikes adds a whole new level of complexity.

We've been having a few issues recently and mine began a week or so ago while out on a ride.  A sudden decrease in power accompanied by a noise that reminded me of a cold or dry bearing.  I've heard them before in old cars coming from the inside fan when it's really cold.

I ended up replacing the clutch/planetary gear assembly in my bike which might have solved the problem (that's another story), but I wanted to learn how to test Hall Effect sensors because someone had mentioned that they could cause problems and I wanted to know what to expect.

I managed to find this video which explain what Hall sensors do.  Many e-bike motors have 3 (sometimes 4) of these sensors which are used to detect a moving magnetic field and send that information to the bike's controller.  The video explained how to test these sensors very nicely.  I used the procedure near the end of the video because I had an old motor that I could practice on.

This shows the motor and the circuit board the sensors are attached to.  Note the coloured wires in the middle.  These supply power (+5v red), ground (black) and the 3 Hall sensor output wires (blue, green and yellow).  There is a fourth wire coming from another Hall sensor that I believe has something to do with speed measurement.

I set up my test equipment the way the video described, complete with a 10K ohm resistor, tack soldered the power leads from an old USB cable to the circuit board and proceeded to test.  As the video described, as I moved the inner part of the motor so that the sensors were moved past the outer ring of magnets, the output voltage from each sensor changed from +5v to 0v and back.  This change indicated that the sensor was good.  This particular motor was replaced because it had other problems.  It appears the Hall sensors were fine.  I haven't yet figured out what the original problem was.  

This photo shows the power supply I used, an old USB cable (red is +5v and white was 0v) and a wall charger.  I also made a quick circuit diagram from the video to remind me of the proper connections.

More ebike discussions likely to come.