How does a PAS sensor work, exactly?

[edrift.eu]

This might be obvious for some but i cant find any explanation online how it actually works. It has 3 wires just like a gas/trottle but

Both RED and GREEN carry positive volt. The Green 5.0 Volt and the RED 4.69V.
The black is ground.

On the Wheel there is magnet that when close to the sensor lets the current PASS through.

Why is there TWO wires with DIFFERENT volt needed?


Part 2:

http://eldrift.nu/temp/ARDU.jpg

I've tried all possible combinations of these wires thru my arduino to get the PAS working but i think it is waiting for some other response/signal (maby what assistance setting? is required) before letting the wheel get power. The PAS wires from the sensor in the wheel is YELLOW/RED/BLUE.

This is my controller:

http://eldrift.nu/temp/36VCONT.jpg

I would really like to get help understanding HOW the PAS system works and and what can be wrong with my setup.

 

[nieles]

the signal on the green wire should change when the magnet is near the sensor

*edit*

the wheel does not have 'PAS' sensors. it has hall sensors which are used for position feedback

the PAS sensor also has hall sensors, but are used to detect pedal movement

 

[docw009]

My PAS device contains a Hall sensor. This is an epoxy encapsulated circuit with a hall effect device and a transistor output. It has three wires. Usually, red and black are power, which is +5 and ground. The third color is the output signal, which toggles between high voltage and ground when the device senses a magnetic field. The result is a digital signal that varies in frequency with the rotation speed of the disk carrying the magnets. In your case, I would expect yellow to be the signal. Hook up power, pass a magnet near the sensor and yellow should change between 4.X volts and 0 volts.


Your controller applies motor power based on the frequency. So the PAS sensor just tells you how fast the pedals are spinning. You need a more complex system if you want to read the rider's pedal pressure. Still, I believe some controllers do a nice job with a PAS. Others are more primitive.

 

[d8veh]

Not all PAS sensors work the same, though all the common ones use hall effect sensors in them. Some have one and some have two hall sensors. The output is mostly the same - a signal that pulses 5v when the pedals are turned. Some are handed and all are directional, so the direction that you pass the magnet and the orientation of the magnet is important. If you mount the magnet disk the wrong way up, it won't work when you pedal forwards, nor will it work by pedalling backwards with it mounted the right way up. The handed ones won't work when you fit it to the wrong side of the bike. There's 4 combinations of magnet disk orientation and rotation direction. If they're handed, only one works. If they're not handed, two will work.

Only a few controllers relate power to crank speed. Most only respond to pulsing or not, in which case they give a fixed power, which would be adjustable through a control panel of it has one.

 

[harysinh99]

what kind of Hall sensor is used in the PAS sensor is it Latching Hall sensor/ Magnetometer hall sensor. I opened up the PAS sensor and in some of them I found single HALL sensor and in another one, I found two HALL sensor. do anyone has any datasheet or HALL sensor number.

Thanks in advance.

 

[spinningmagnets]

Somehow, it also has to sense when the pedals are spinning backwards, instead of forwards.

If you are spinning the pedals backwards, the sensor can tell that the pedals are spinning, but it does not apply power. It only applies power when it senses that the pedals are spinning forwards.

 

[harysinh99]

so thats it? How does Hall sensor know it pedals forwards or reverses? is there is a circuit inside? In new PAS i found 2 hall sensor with some IC. But old PAS has one sensor only with no IC attached.

 

[docw009]

Yes, there can be circuits inside.

Grin tech has a nice explanation, which you can read, but his picture show several ways for how these sensors work. If your sensor uses the middle method, your arduino program will have to (a) determine the initial frequency and (b) determine if the signal is up more than it is down. All in the first turn of the crank.

https://www.ebikes.ca/learn/pedal-assist.html

 

[Parastools]

which model of IC used in double hall sensor type 3 wire PAS, if any one have idea, please share, i have double hall sensor PAS in my e bike which is malfunctuning, i want to replace IC but it has no identification number o it,
please share if any one have details, parasomicron@gmail.com

 

[docw009]

You got a 4 wire sensor? Maybe you can buy the complete unit from Grin.

https://ebikes.ca/shop/electric-bicycle-parts/torque-sensors.html

Al this about 4 wires being better, etc? You need a controller that can handle it, and you have to find someone that sells both. Stuck on the side of the road, I'll take the simpler design.