Hall Sensor Question

[Stryder]

Hi All,
I have an Ancheer 26" E-bike. Just recently when using pedal assist, motor seems to kick in for 3-4 seconds, stops, runs 3-4 seconds, stops, runs 3-4 seconds...... and this continues. Throttle makes motor run 3-4 seconds then it stops and won't kick in again unless I nudge the wheel backwards a bit and then throttle will make it run 3-4 seconds again.
I read lots of info on here and followed troubleshooting and when I got to the 3 hall sensors there seems to be an issue with sensor 1.
Sensors 2 and 3 seem good and cycle from 5/0/5v but sensor 1 cycles from 5/4.2/5v

Is that a typical way a sensor could fail and could that cause the weird motor behaviour I'm seeing or could the controller or something else be contributing to the 5/4.2/5v reading? I can't see any obvious shorts or damage on the board and wiring continuity seems good. Don't think I would be able to replace the sensor, it looks pretty tricky to do so just wanted some opinions before spending on new hub or new controller etc.
PS - tried two batteries including one brand new and fully charged.
Thanks

 

[fechter]

You did well to find the faulty hall signal. For sure it could cause the strange behavior you are seeing.

It may be something fixable like a bad solder joint on the sensor. There is a remote chance the problem is with the controller since the sensor seems to be trying to do something. It's possible to test the sensors separately without the controller connected. You can power them with a small 9v battery and look at the signals. Depending on the sensor type, you may need a resistor from the signal like to +5v when testing, but I would try without one first.

If the sensor still tests bad with the controller disconnected, then time to take apart the motor. Your other option is to replace the motor, so you don't have much to risk by trying.

If the sensors seem OK with the controller disconnected, time to take apart the controller and look for a wiring problem. I've seen this kind of failure when a little blob of solder was bridging the connection points on the board. Again, low risk as your other option is to replace the controller.

 

[amberwolf]

Since the sensors work by grounding a voltage output from the controller (the sensors don't output a voltage of their own), then any sensor that does not fully ground the signal when active either are not well-connected to the signal line or have failed internally.

A poor connection can be anywhere from the point you measure all the way to the body of the sensor itself, but not at the controller end (as that is where the voltage on the signal line comes from). Poor crimps in contacts at connectors, poor solder joints at the PCB the halls are mounted on (if any) or wires soldered to the sensor legs (if no PCB), or even a broken-off leg on the hall itself that is just barely touching the hall still.

Alternately, an extra low-resistance connection (not a full short) can exist (like Fechter said, solder bridges, etc) anywhere in the path from signal to the 5v line.

 

[Stryder]

You did well to find the faulty hall signal. For sure it could cause the strange behavior you are seeing.

It may be something fixable like a bad solder joint on the sensor. There is a remote chance the problem is with the controller since the sensor seems to be trying to do something. It's possible to test the sensors separately without the controller connected. You can power them with a small 9v battery and look at the signals. Depending on the sensor type, you may need a resistor from the signal like to +5v when testing, but I would try without one first.

If the sensor still tests bad with the controller disconnected, then time to take apart the motor. Your other option is to replace the motor, so you don't have much to risk by trying.

If the sensors seem OK with the controller disconnected, time to take apart the controller and look for a wiring problem. I've seen this kind of failure when a little blob of solder was bridging the connection points on the board. Again, low risk as your other option is to replace the controller.

Thanks both for the info

Since the sensors work by grounding a voltage output from the controller (the sensors don't output a voltage of their own), then any sensor that does not fully ground the signal when active either are not well-connected to the signal line or have failed internally.

A poor connection can be anywhere from the point you measure all the way to the body of the sensor itself, but not at the controller end (as that is where the voltage on the signal line comes from). Poor crimps in contacts at connectors, poor solder joints at the PCB the halls are mounted on (if any) or wires soldered to the sensor legs (if no PCB), or even a broken-off leg on the hall itself that is just barely touching the hall still.

Alternately, an extra low-resistance connection (not a full short) can exist (like Fechter said, solder bridges, etc) anywhere in the path from signal to the 5v line.

Thanks @fechter and @amberwolf for the useful info.
I have one of the brushless motor testers arriving later this week - not sure but hoping it lets me do an "offline" test with it's own power supply. If not I will figure out how to put 5v on it and test again.

 

[Stryder]

Thanks both for the info

Thanks @fechter and @amberwolf for the useful info.
I have one of the brushless motor testers arriving later this week - not sure but hoping it lets me do an "offline" test with it's own power supply. If not I will figure out how to put 5v on it and test again.

UPDATE: Received the tester and it showed same result - one of the hall sensor tester LEDs was showing 50% dimmer than the others.

Unfortunately I couldn't see any useful identification marks on the sensors. The centre one is white and the other two black, the white one says "426AN" on it - couldn't see anything on the black ones due to the glue covering it. I couldn't find anything on the web to help me get correct replacements and eventually I decided to order a couple of replacement PCBs with the sensors already soldered in, there were plenty of these on Amazon and eBay but the descriptions don't really give much info. fortunately they are pretty cheap so nothing to lose.

They arrived from China last week, one had 3 black sensors and one had a white centre one and black outer ones. I found it really difficult to get the old ones out of their slots but managed after a lot of work with a Dremmel tool with tiny grinding attachment. Don't know why but I tried the black ones first. Unfortunately the PCB was slightly smaller than the original and the sensors didn't line up with the slots, I tried bending them but they kept breaking the legs. I tried removing the sensors from the new board and soldering back onto the original, after about 5 attempts at bending the legs to the required angles I managed to do it without breaking them. Did a quick test on the motor before putting everything back together and pedal assist worked but throttle did not. Repeated the process with the white and black sensors and it ran perfectly! I've now order 2 more sets of those to keep back for any future problems. Really happy and thanks for your assistance!

 

[E-HP]

Glad you went for it; had to be a confidence booster. You know you're a DIYer when you start keeping spare parts around

 

[richj8990]

For this level of bike (I think they are around $600 USD for the complete bike), it would be good to simply get a new controller. And don't be shy about going way up on the max amps. I kept buying 22A controllers and finally ordered KT sine wave 45A max for $80, it looks like the toughest controller I can get that is a match for the 48V battery cable. For your...wow they are down to $389!...bike it was upgraded to 48V so you can do 22, 26, 30, or 45A max controller. They used to be 250W. Trust me it will help a lot to get a better controller. I'm pretty surprised that the bike comes with a 500W geared hub motor too, that's actually pretty decent. Freewheel, no comment. I also know this frame; I've had it before. I hated it. But the bike w/o the motor and battery used to be around $300, so you got a freaking good deal. You actually may want to buy a new frame later for maybe $100, a 27.5. You can run a 26" wheel in the back and be fine. A larger frame is also going to help in a lot of ways, it will be night and day for comfort and handling bumps.