Installing pas sensor on sprocket side...

Would guess that most readers here are less interested about pas, but its my preference for two reasons:
1) local eu laws reques using one
2) it gives a smooth response to pedalling in terrain

Now to the point that thought to be worth of sharing...

During last 2 months i have been struggling to get pas sensor working properly. Instead of using a normal pas wheel i decided to put magents on the sprocket side of the crank. There is some hex bolts on the sprocket side so it was just a natural decision to make a clean install ( this is full suspension kona four deluxe mtb ).

During thest rides the pas sensor just seemed to give intermittent pulse, until it hit me. The sensor send a reversed pulse as on crank side the sensor is wrong way round. In practise this means that the duty cycle from sensor is reversed.

After reversing the sensor the pas started to work flawlessy. Felt so dum after this discovery that took two months to realize !

Thanks PetriK,

I thought those PAS devices had to be directional. Just wouldn't make sense otherwise.
--
Bill

if this is the case with PAS (peddle adjusted sensor), then we may need to forget about it for a while.... keep it manual on the frame is my guess...

ekline309 said:

if this is the case with PAS (peddle adjusted sensor), then we may need to forget about it for a while.... keep it manual on the frame is my guess...

Click to expand...

Eh?

Don't know what a "pedal adjusted sensor" is but a "pedal assist sensor" produces a stream of pulses when the pedals are rotated in the forward direction. The controller looks at the incoming stream and determines if the rider is pedaling fast enough to turn the motor on.

--
Bill

I don't think it cares how you pedal, although the sensor may be sensitive to the installation direction. I say this because pedaling a PAS bike backwards engages the motor, or you can just rock the pedals back and forth until it comes on.

yes, i thought there is no difference either and its only because my wheel is somewhat uneven - until saw a signal from a motorcycle cam sensor that had been installed 180degrees of.

During these 2 months I have tried several pas sensors, magnets with reversed polarity for some magnets on the wheel etc. Welding magnets (obviously lost the polarity), supergluing magnets, playing with the distance to the sensor etc. Funny thing was that I could make the bike engage the motor when reverse pedalling very systematically, but forward pedalling was very unreliable method to engage the motor.

Here is some scope signals from different situations. The two topmost are from my pas sensor, the bottom is from a couple of motorcycles which were able to keep a steady rpm.

I'm quite curious about this. On my PAS it definitely only kicks the motor if I rotate the pedals one way, not the other. And I can get it to power the motor when reverse pedalling (not very useful !) by reversing the magnet disk on the left crank arm. So what's the orientation of the magnets? And how does this result in a different output from the Hall sensor when turning the crank in each direction?

There are some PAS that output a throttle signal rather than a pulse stream. So if the crank is moving in the right direction they output a constant +5v. The integration of the magnet pulses, start delay and end delay are all happening in the PAS itself.