Sounds reasonable... except, the wheel is always going to turn the same speed as the cassette unless you stop pedaling. So it seems the cassette lockring magnets could detect both speed and pedaling.
You're correct, it does not turn
faster in any case, but it can turn slower. Thats why I wrote that if its at (nearly) the same speed as the wheel (therefore there has to be a second way of measuring the wheel speed), the motor will turn up.
[Update]
Ohh, now I've got it. Because the speed is only relevant ,if your pedaling that could be used.. tricky.
Then pedaling slow enough would let the motor still be running, even if its too fast. I will check that with the bike in my working stand.
How do you like your bike? Does it have enough power and have the max speed limit of 20 mph?
I love it
It feels really lightwheigth and handy. Actually when I'm not commuting, the motor is mostley turned of. Even then it feels lighter then my steel Randonneur. I'd say you don't realize the e- if you are not using it. In germany the speed limit for e-bikes is 25kmh (roughly 15mph), otherwise you need a license plate..
So its limited to this. Its hard to tell when its shut down, because the transition is very smooth, but it seems to assist until 27kmh (17mph) ..
On the minus side, the motor starts a little bit late, due to the way of measuring discussed before. The motor starts up after around a half turn of the crank and stops after around half a second after stopping the crank. Thats something you have to get used to and it makes starting at a steep hill harder.
Speaking of the motor. It feels strong enough for me, not really less then the bosch whatever I tried once. In full power mode and without assisting the motor (just fake pedaling) I reach around 17kmh (11mph). The turn on is reasonable smooth in full power mode. In that mode you hear the motor humming, but its not loud and a nice tone imho. In the lower modes (I use it usually at 60% max power) you feel or hear almost nothing, it just feels easier