Failed cadence sensor

[spokewrench]

More than 3 years ago, I got an aftermarket controller for my Radmission. One advantage was that I could have the throttle available while pedaling without PAS. Today I tried PAS on a hill. It cut out for about a third of each cycle.

I pulled the left crank arm and removed the sensor. It's labeled P14 and has 7 magnets. I saw no problem except maybe dirt, which I polished away with toilet paper. That didn't fix it. This time I measured.

At 2.5 mph (cadence of 10), the transistor senses all but 2 adjacent magnets. At 7 mph (cadence of 29), it senses all but 1. At 9 mph (cadence of 38), I begin getting PAS through the pedal cycle.

One possibility is that 2 magnets have become weaker than the others. I don't know why. Another is that 2 somehow don't pass as close to the transistor as others. I didn't see anything to suggest that.

I went to Amazon. It seems that the replacements these days all have 12 magnets. I ordered one. If it works, maybe I'll start to like PAS.

I still don't know why the original sensor doesn't respond equally to all 7 magnets.

 

[PCeBiker]

I went to Amazon. It seems that the replacements these days all have 12 magnets. I ordered one. If it works, maybe I'll start to like PAS.

I'm pretty sure that it will work, but you'll have less crank rotation (number of pulses) before the PAS engages/disengages.
Your controller should just think you're pedaling faster.

I still don't know why the original sensor doesn't respond equally to all 7 magnets.

I'm thinking it's mostly a clearance issue.
My PAS sensor was wearing inside, and the housing was separating a bit, lifting the sensor away from the magnets.

I'm pretty sure the two magnets give a stronger pulse as they move faster, so they start working at a higher cadence?

 

[PedalUma]

More than 3 years ago, I got an aftermarket controller for my Radmission. One advantage was that I could have the throttle available while pedaling without PAS. Today I tried PAS on a hill. It cut out for about a third of each cycle.

I pulled the left crank arm and removed the sensor. It's labeled P14 and has 7 magnets. I saw no problem except maybe dirt, which I polished away with toilet paper. That didn't fix it. This time I measured.

At 2.5 mph (cadence of 10), the transistor senses all but 2 adjacent magnets. At 7 mph (cadence of 29), it senses all but 1. At 9 mph (cadence of 38), I begin getting PAS through the pedal cycle.

One possibility is that 2 magnets have become weaker than the others. I don't know why. Another is that 2 somehow don't pass as close to the transistor as others. I didn't see anything to suggest that.

I went to Amazon. It seems that the replacements these days all have 12 magnets. I ordered one. If it works, maybe I'll start to like PAS.

I still don't know why the original sensor doesn't respond equally to all 7 magnets.

View attachment 210939

The problem as I see it is that the controller is programmed for seven magnets per revolution not 12. If it is the weaking of magnets then see if you can pop them out of the new one and Crazy glue them in to the old one. They are directionally polarized. Check directionality by placing a new magnet on an old one that is in place on the ring, remembering that opposites attract, or you will go full speed pedaling backwards. Which is kind of fun.

 

[PCeBiker]

Someone replaced the controller on my old POS ebike before I bought it.

Now the PAS only works when I pedal backwards.

They tried installing a PAS sensor on the opposite crank, but it never worked.

 

[PCeBiker]

The problem as I see it is that the controller is programmed for seven magnets per revolution not 12.

I don't think that should matter.
The controller will probably just react with less crank rotation?

Unless the controller detects a cadence of 12/7'ths of what is humanly possible and shuts down??

 

[PedalUma]

I don't think that should matter.
The controller will probably just react with less crank rotation?

Unless the controller detects a cadence of 12/7'ths of what is humanly possible and shuts down??

One guy had a 'jumpy' bike. Half the magnets had been reversed. You could pedal backwards and then forwards again 60 degrees each way to make it fly. Reversing the polarity of magnets is almost as good a practical joke as glueing a BB to the inside of a valve cap. I kind of wish it was June the Third all year, the light so is nice. Another good one is three BBs in the interior of a double walled rim. If it passes an anti-theft security set-up at a bike shop daily, insert security tags way down inside the handle bars. The alarm sounds each time.

 

[RunForTheHills]

You can buy a Cycle Analyst, attach the PAS sensor and throttle to the CAv3 and the CAv3 to the throttle input of your controller. The CAv3 can be programed for any number of poles on the PAS sensor. You will have to use the CAv3 to program and control your PAS levels though.

https://ebikes.ca/ebike-parts/control-stuff/cycle-analysts/ca-sa.html

 

[PCeBiker]

My KT controller allows for 5, 8, 10, and 12 magnet PAS sensors.

No 7 magnet version though, and the only 5, 8, and 10 magnet versions that I could find on Aliexpress are the old-school Huge ring types,..

 

[PCeBiker]

,..It's labeled P14 and has 7 magnets.

That's odd??
Must be proprietary.

I still dont think that it matters though, but your PAS might be a little twitchy??