pas sensor problem.

[fill]

I am installing a 250w rear hub motor to a cycle and have hit a snag.
I suspect i have killed my pas sensor (SM-A3).

i have the cheap Yose Power 250w rear hub kit.
sensor manual
Following the many vids of installation the pas sensor seemed like a simple push fit. However my crank wanted to argue.


its a Chinhaur 122.5 mm bottom bracket and with the pas sensor fitted the crank offers noticeable resistance to movement and when it finally turns is quite scratchy (forward - bike on its bars n seat) It appears as if the square shaft end is shorter with my crank revealing a larger diameter shaft about 1cm before the hub which the sensor is too tight a fit on, I will attempt to pry off again and perhaps file down the inner race perhaps??

working on the assumption i have killed the pas sensor is there an alternative sensor option there appears to be at least one other type (2 part clamp around type) - Are these interchangeable? replacing the bottom bracket seems a bit ott to get a sensor working?


all encouragement and help appreciated. i can post pics if needed ( charging atm)

 

[amberwolf]

All that's in the sensor unit is a hall sensor module up where the calble is, and a bunch of magnets ona plastic ring inside the shell. So if you're willing to open it up you can fit the magnets to your chainring in a circle, then fit the sensor on the frame so that it detects them passing by.

There are quite a few other PAS sensors, but they are not all intercompatible with all controllers, as there are several types of signals and wiring. Pedal Assist Systems - Learn

But if you find hte right type, and the magnet wheel wont' fit on your crankshaft in the space avaialble, you can still take the magnets off and put them on the chainring. (just keep them all in the same orientation they were in the plastic ring; you can draw marks on them with a marker, etc). As long as they are at the right distance from the sensor it doesn't matter what they're on, as long as the magnets pass it and trigger it.

 

[rick_p]

What amberwolf said and pictures wouldn’t hurt.

 

[fill]

Thank you both for the input, After posting i returned to the project and coaxed the sensor into place as per all the vids and illustrations suggested, it took some effort and it results in a stiff crank as it appears the inner race has now pushed out into the outer static body, its not right, and probably the result of my kit living at the extremes of tolerances.

on its Back testing indicated no pas signal, but a ride resulted in pas input and motor drive after 10m or so traveled (low gear so started slow.. my bad habits and ignorant expectations of when a pas sensor signal is considered 'on' perhaps..

The ebike rides, though i have only gone round the block the once as that ride revealed some brake and gear tuning was required.

So I will order a cheap ebay plug in replacement (less than a tenner) and if the current set up fails to wear the tight fit loose with the aid of a drop of oil and the airborne grit that will pick up I may attempt a dissection and refit. confident i can refit a replacement when it goes pear shaped and be no worse off than now ?

Thanks again..

 

[fill]

Well the pas sensor didnt fail before i replaced it But I did discover the reason behind the variable start of the pedal assist,

When pulling to a stop i will try to balance and maintain feet on pedals as long as possible and often get to pull off again before i need to put a foot down, well sometimes, its happened at least once .. anyway my balance attempts often involve a pedal backwards, and pedaling backwards has been rotating the sensor until its cable snags it and stops it turning, and as i pedal forward.

First the sensor just rotates with the crank until its flex snags it again at which point the sensor engages and starts to turn initializing the trigger of power on after a variable delay.. So Now i have the chainring side disk fitted with the sensor secured by the bottom bracket itself. And consistent pedal assist startup..

 

[richj8990]

One thing you could do if you really want PAS is get a longer square-tapered bottom bracket. They have 142mm out there, that will be plenty of room on the non-drive side to fit the sensor.

Another thing is that they now have $50 Hollowtech knockoff cranksets including bottom bracket.

Hollowtech knockoff crankset and bb



You can then buy a large-hole (I think it's 35mm) sensor and put it right up against the frame, then thread in the external bottom bracket bearing on that side. That will hold the sensor very nicely and out of the way. And you'll feel a difference with the hollowtech crankset, even on an e-bike.

Right (crankset) side big hole PAS sensor

 

[Ecyclist]

Well the pas sensor didnt fail before i replaced it But I did discover the reason behind the variable start of the pedal assist,

When pulling to a stop i will try to balance and maintain feet on pedals as long as possible and often get to pull off again before i need to put a foot down, well sometimes, its happened at least once .. anyway my balance attempts often involve a pedal backwards, and pedaling backwards has been rotating the sensor until its cable snags it and stops it turning, and as i pedal forward.

First the sensor just rotates with the crank until its flex snags it again at which point the sensor engages and starts to turn initializing the trigger of power on after a variable delay.. So Now i have the chainring side disk fitted with the sensor secured by the bottom bracket itself. And consistent pedal assist startup..

Picture is worth a thousand words.
Post photos so we can see it. You are making it more complicated than it is.

 

[YOSE POWER]

I am installing a 250w rear hub motor to a cycle and have hit a snag.
I suspect i have killed my pas sensor (SM-A3).

i have the cheap Yose Power 250w rear hub kit.
sensor manual
Following the many vids of installation the pas sensor seemed like a simple push fit. However my crank wanted to argue.


its a Chinhaur 122.5 mm bottom bracket and with the pas sensor fitted the crank offers noticeable resistance to movement and when it finally turns is quite scratchy (forward - bike on its bars n seat) It appears as if the square shaft end is shorter with my crank revealing a larger diameter shaft about 1cm before the hub which the sensor is too tight a fit on, I will attempt to pry off again and perhaps file down the inner race perhaps??

working on the assumption i have killed the pas sensor is there an alternative sensor option there appears to be at least one other type (2 part clamp around type) - Are these interchangeable? replacing the bottom bracket seems a bit ott to get a sensor working?


all encouragement and help appreciated. i can post pics if needed ( charging atm)

Hi, could you please send the photo of the crank to our service team at service@yosepower.com and let them know your confusion so that they can provide help? Thanks for your cooperation.

 

[fill]

Hi, could you please send the photo of the crank to our service team at service@yosepower.com and let them know your confusion so that they can provide help? Thanks for your cooperation.

Thank you for your latent interest, however the issue is resolved by fitting a replacement sensor.