PAS activation when back pedalling

[Bizzertdog]

Hi.

I’m a mechanic but very much a novice re eBikes. I’ve been looking at a tandem eBike with an unbranded electric assist on the front wheel (and installed by someone else). His PAS pickup has been working very inconsistently and today I took it off and tested showing it seems to pick up very intermittently, so I’ve replaced it with a new one from Amazon.

Now it works very well , except.... it also activates when back pedalling (installed acc to arrows on magnet wheel and sensor). Is this a sensor problem or an issue with the controller? Actually when test riding it hardly seems an issue, but I assume generally it shouldn’t do this?

Many thanks, Keith Slater.

 

[Gringo]

Well I have no experience of this type of system but surely it’s just a magnet or series of magnets passing a sensor, the sensor won’t know (or care) in what direction the magnets are going, just that they are moving
Its the same for any bike with a magnetic speed pickup, on any of the pedelpecs I’ve owned if I spin the wheel backwards it still registers the speed as if it’s going forward.
I think you’re looking for a problem that doesn’t exist.

 

[vfr400]

The sensor does indeed care which way the magnets go. You'll have to take of the magnet disc, then flip it to make it work in the correct direction.

Some sensors are handed too, so they only work on one side, i.e. if you flip the disc, it won't work at all unless you move everything to the other side of the bike. Let's hope you haven't got one of those.

 

[Nealh]

One of my bikes activates backwards as well, so I always make sure the PAS is at 0 at start so when I push the bike back it doesn't kick in. I think that one is the D12 model.

 

[Bizzertdog]

Sorry @vfr400 it works perfectly well in the right direction and I did install it with arrows in both disc and sensor orientated correctly. The point is, it also activates on back pedalling.
@Gringo surely the reason it has xx sorrows is because it is directional?

 

[vfr400]

Sorry @vfr400 it works perfectly well in the right direction and I did install it with arrows in both disc and sensor orientated correctly. The point is, it also activates on back pedalling.
@Gringo surely the reason it has xx sorrows is because it is directional?

I've never known one to work in both directions, except the crappy ones from 15 years ago before they figured it out.

Can you show us which one it is?

 

[Bizzertdog]

It might well be a crappy one! From m Amazon apparently sold by MAGT-EU.

 

[Bizzertdog]

Presuming from your reply that the directionality is controlled by the sensor, rather than the controller (which makes sense as the stimulus is only a signal from the sensor)?

 

[vfr400]

I might have guessed it would be a 12 magnet one. You could try pushing out every other magnet to see if that fixes it.

 

[vfr400]

Presuming from your reply that the directionality is controlled by the sensor, rather than the controller (which makes sense as the stimulus is only a signal from the sensor)?

It's controlled by the magnetic field. A south facing magnet coming from the right has the same effect as a north facing one coming from the left.

 

[Woosh]

there are two types of pedal sensors, simple and dual hall/intelligent.
the simple type (usually in red case) triggers when the magnet passes in front of it, whether you pedal forward or backward. The intelligent type (Dual Hall, usually in black case) only triggers when you pedal forward, you can mount it anyway you like. It magically knows when you pedal forward! That's the type I use in my kits because it avoids flipping the magnet disc.
If your particular controller was programmed to see the intelligent type, it will trigger in both forward and backward directions if you fit a simple (red) sensor. The solution is to replace your (red) sensor with a 'Dual Hall' pedal sensor.
That's the usual situation when after flipping the magnet, the motor is still turned on when pedalling in both directions.
If you have a KT controller, you can reset the pedal sensor type yourself.

 

[vfr400]

there are two types of pedal sensors, simple and dual hall/intelligent.
the simple type (usually in red case) triggers when the magnet passes in front of it, whether you pedal forward or backward. The intelligent type (Dual Hall, usually in black case) only triggers when you pedal forward, you can mount it anyway you like. It magically knows when you pedal forward! That's the type I use in my kits because it avoids flipping the magnet disc.
If your particular controller was programmed to see the intelligent type, it will trigger in both forward and backward directions if you fit a simple (red) sensor. The solution is to replace your (red) sensor with a 'Dual Hall' pedal sensor.
That's the usual situation when after flipping the magnet, the motor is still turned on when pedalling in both directions.
If you have a KT controller, you can reset the pedal sensor type yourself.

That's not true. Even the cheapest single sensor ones are directional. I've never seen or heard of one that works in both directions in 10 years of working with ebikes - until this thread started. Has anybody else ever seen one work in both directions before?

The one thing I do know is that the 12 magnet ones often give problems. I'm pretty sure that it's because the magnets are too close together and the hall sensor gets swamped by the magnetic fields. I've sorted a couple by removing every other magnet.

 

[Bizzertdog]

Thanks for all your replies and a much better insight, if not complete agreement, into pedal sensors! I’ll maybe try out the alternate magnet theory, if no good replace with a dual hall sensor.

Any advice on connector types? I had to utilise the existing cable and solder the three wires (good advice on here re colour mismatch). I’ve been unable to find any source for good waterproof connectors on line.

 

[vfr400]

Thanks for all your replies and a much better insight, if not complete agreement, into pedal sensors! I’ll maybe try out the alternate magnet theory, if no good replace with a dual hall sensor.

Any advice on connector types? I had to utilise the existing cable and solder the three wires (good advice on here re colour mismatch). I’ve been unable to find any source for good waterproof connectors on line.

You shouldn't get a dual sensor one. The most compatible are the cheapo 8 or 10 magnet ones. Your problem is very unusual and related to the exact PAS that you have. No normal PAS would do that. Forget what Woosh says above. He probably hadn't woken up properly when he wrote that. Now that he's had his coffee, he should be fully recovered.

 

[sjpt]

Actually when test riding it hardly seems an issue, but I assume generally it shouldn’t do this?

It could certainly be an issue while parking. Push the bike back onto where it's going to rest, the pedals turn backwards as you push and the bike suddenly kicks forwards. Probably not that serious, but could do damage to you, the bike or a passer by.

 

[Woosh]

That's not true. Even the cheapest single sensor ones are directional. I've never seen or heard of one that works in both directions in 10 years of working with ebikes - until this thread started. Has anybody else ever seen one work in both directions before?

The one thing I do know is that the 12 magnet ones often give problems. I'm pretty sure that it's because the magnets are too close together and the hall sensor gets swamped by the magnetic fields. I've sorted a couple by removing every other magnet.

I have half a dozen PAS models in my workshop - you can see for yourself on the test bench next time you visit.
The main thing is how the controller was programmed.

 

[Nealh]

My KT 12 pole DL PAS activates ( briefly) if the cranks rotate when I push the bike backwards so I always make sure PAS in 0.