Need to Pedal Extremely Slowly for PAS to work

[lichKing]

I installed a cheap 24 pole PAS I bought from aliexpress. When I pedal the bike at a natrual cadence, the motor does not spin. I have to be pedalling unnatrually slow for the motor to start spinning. Then it works perfectly, just that I have to pedal at this slow cadence. Any faster and the motor stops again. Is my controller not sensitive enough for 24 poles or is it something else?

 

[E-HP]

link to the unit?

 

[lichKing]

It's similar to this, but the disc has 24 poles.

 

[LeftieBiker]

My guess is that the sensor is too far from the magnets (too large a gap) and that the signal only crosses the gap when the two are in proximity for longer times, i.e. when you are pedaling slowly. The problem may also be magnets that are too weak to work properly.

 

[E-HP]

It's similar to this, but the disc has 24 poles.

Likely the sensor is too far from the disc, but it could also be a poor design. In my experimenting with PAS sensors, I tried adding additional small neodymium magnets to my disc. It worked, until I added too many and the sensor couldn't resolve the pulses between magnets as the spacing in between became closer. 24 is a lot a magnets on a disc that size (and doesn't really offer any benefits).

 

[lichKing]

I’ve reduced the number of magnets on the disc to 12 by poking half of them out. I now don’t have to pedal as slow for the motor to kick in but it’s still slower than I’m comfortable with. I feel like I have to pedal at a specific RPM, any slower or faster and the motor shuts off. Is that how these cadence PAS works?

 

[E-HP]

I’ve reduced the number of magnets on the disc to 12 by poking half of them out. I now don’t have to pedal as slow for the motor to kick in but it’s still slower than I’m comfortable with. I feel like I have to pedal at a specific RPM, any slower or faster and the motor shuts off. Is that how these cadence PAS works?

What controller are you using. Many have settings for the number of magnets, so possibly the controller is set for a certain number of magnets.

 

[lichKing]

I’m using a Chinese controller that I bought on aliexpress. Doesn’t seem to have any programming wires on it. The controller that I’m using is similar to this one.

 

[LeftieBiker]

I’ve reduced the number of magnets on the disc to 12 by poking half of them out. I now don’t have to pedal as slow for the motor to kick in but it’s still slower than I’m comfortable with. I feel like I have to pedal at a specific RPM, any slower or faster and the motor shuts off. Is that how these cadence PAS works?

Not usually. You should be able to pedal at any speed you want, and after a short lag, it should start PAS.

 

[lichKing]

I tried a different PAS sensor, it's a smaller sensor with only one hall sensor (just found out that the original one has 2 hall sensors), and everything seems to work fine, using 8 poles and the motor kicks in after 1 crank rotation and I can pedal at any speed I want. I guess the PAS with 2 hall sensors just doesn't work very well with my controller due to some sensitivity setting.