Strange 12v throttle line

[mr.electric]

Working on another rental bike repair.
This one has a pas sensor and small geared hub - 36v system.
I measure a little over 12v going to the pas sensor. I remember checking this signal on another similar bike and finding a typical around 5v pas sensor. This bike cuts out if you pedal too fast. You must pedal very very slowly to get the motor to stay on. I tested with a potentiometer and got reliable motor operation under load when I dropped the 12v pas power to around 4 volts going back to the pas signal wire. As soon as I go over 5v it cuts out.
So why is this controller sending 12v not 5v to the pas sensor. It seems to be expecting a typical 1-4 v throttle signal. I tried a new spare controller and a used pas sensors the rental co gave me - no change.

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[mr.electric]

Pic inside two disassembled pas sensors. A toothed wheel (not shown) spins past the optical sensor. Mostly I wonder if this little board has 12v power and outputs 0-5v like throttle signal.

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[fechter]

Can't make out the numbers on the chips, but those are probably something that needs 12v to work. It probably gets divided back down to a 5v range just before going to the MCU in the controller.

 

[mr.electric]

I think they must have two versions of the e-moto controller. The last one I repaired had 5v on the pas sensor power line and worked with a regular hall throttle in place of the pas sensor.
What would be the simplest way to drop the 12v pas sensor power to 5v so I can use standard, cheap throttles. There are about 30 of these bikes in service. They all have sensorless geared hub motors (some bafang some no name) and have been tge most reliable bikes in the large fleet. I believe the version 1 has cantilever brakes and 12v feed to pas sensors. Version 2 has disk brakes and 5 v feed to pas sensor. Both versions seem to need typical 5v signal coming back from pas sensors to controllers. There are no extra pas sensors on hand. Parts are difficult to find since there is confusion among versions and typical crappy Chinese supplier parts support. It seems like dogman's suggestion of just replacing controllers might be a sourcing time suck if I hope to have matching plugs for motor , battery and other components. I would like to start replacing pas sensors with throttles since throttles are inherently easier to install. New or different pas sensors may need complicated mechanical adapters to fit existing cranks.


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[fechter]

You could try picking up 5v from somewhere else if it exists. Otherwise, a LM7805 regulator could drop the 12v down to 5v.

 

[mr.electric]

That worked!!
I snipped the red wire to the pas sensor plug and replaced it with the red wire from the plug shown in the pic.
I wonder if these unused 3 wire plugs are brake cut offs. I have only seen two wire brake cut offs. There are no two wire plugs on the controller and the brake lever switches are not plugged into anything.

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[mr.electric]

So the red white and yellow plugs are the brake cut offs. Shorting the white and yellow cuts the motor. Now that all the wiring is figured out I will be better prepared for maintaining the fleet of e-moto bikes


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[fechter]

So did you borrow 5V from that cut off wire?

 

[mr.electric]

So did you borrow 5V from that cut off wire?

Yes I borrowed the 5v power from the brake cut off.


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