Do any cadence sensored hub motor controllers activate pedal assist when ghost pedalling backwards as well as forwards?

Prompted by this thread:

 

https://www.pedelecs.co.uk/forum/threads/technical-question.47911/#post-726998

 

...I'm wondering if any cadence sensored hub motor controllers are capable of activating pedal assist when ghost pedalling backwards as well as forwards, because it strikes me this would be an advatage for hill starts - one reason why many are keen on throttles. Anyone can pedal backwards with ease. Legal too perhaps, because effort however small is required to backpedal? Also, standing starts would be easier if you've happened to have stopped on too high a gear, which is another situation when a throttle would come in handy (not a problem for my Dahon 20" wheeled BBS01B mid-drive folding bike conversion). Would ghostly backpedalling be easier on the knees, for those with severe knee problems? Could a huge boost of up to a legal 2000W be activated from a standing start by backpedalling fast? Drivetrain would last ages with low force backpedalling. Could get by with one gear? Ebrake cutoff would make things safer in case of accidental motor activation. Made safe by ebrakes, with a sufficiently powerful controller and large capacity battery, very long motor run-on for effortless forward travel, with the occasional ghostly extremely low effort backpedal to keep pedal "Assist" activated would be possible regardless of incline. Sounds to me a relaxing prospect, for when I inevitably in time become too feeble to put even the small amount of effort required to activate the pedal assist of my present ebike. Can KT controllers do this, or will it require custom firmware and/or controller? If ghost pedalling a cadence sensored hub motor is only possible in one direction, perhaps a Golden Age of extremely low effort ghost backpedalling ebikes could commence? Ideally backwards and forwards. Asking because I don't know anything whatsoever about these mysterious hub motor things, with their arcane WTF PLC settings.

 

The Guerney Throttleless Bi-directional Superlazy Pushmepullyou GhostPedallator™®©℠ is invented!

 

 

Edited October 11, 20241 yr by guerney

Prompted by this thread:

 

https://www.pedelecs.co.uk/forum/threads/technical-question.47911/#post-726998

 

...I'm wondering if any cadence sensored hub motor controllers are capable of activating pedal assist when ghost pedalling backwards as well as forwards, because it strikes me this would be an advatage for hill starts - one reason why many are keen on throttles. Anyone can pedal backwards with ease. Legal too perhaps, because effort however small is required to backpedal? Also, standing starts would be easier if you've happened to have stopped on too high a gear, which is another situation when a throttle would come in handy (not a problem for my 20" wheeled BBS01B mid-drive conversion). Would ghostly backpedalling be easier on the knees, for those with severe knee problems? Could a huge boost be activated from a standing start by backpedalling fast? Can KT controllers do this, or will it require custom firmware and/or controller? If ghost pedalling a cadence sensored hub motor is only possible in one direction, perhaps a Golden Age of extremely low effort ghost backpedalling ebikes could commence? Ideally backwards and forwards. Asking because I don't know anything whatsoever about these mysterious hub motor things, with their arcane WTF PLC settings.

If the cadence sensor has just the three wires, then my guess is that there are two Hall effect sensors, which produce a quadrature signal as the pedals turn, and there is a little bit of internal logic which gates one of the quadrature waveforms with the derived direction signal, so there's no pulse train output when pedalling in reverse.

If the cadence sensor has just the three wires, then my guess is that there are two Hall effect sensors, which produce a quadrature signal as the pedals turn, and there is a little bit of internal logic which gates one of the quadrature waveforms with the derived direction signal, so there's no pulse train output when pedalling in reverse.

Most pedal sensors only have one hall sensor. There are sensors with dual halls, but none of my bikes have one.

 

Three wires are necessary for a single hall sensor to work: 5v and ground to power the sensor, and the signal wire to send the pulse.

Most pedal sensors only have one hall sensor. There are sensors with dual halls, but none of my bikes have one.

 

Three wires are necessary for a single hall sensor to work: 5v and ground to power the sensor, and the signal wire to send the pulse.

Interesting. How do they avoid working when reverse pedalling?

Prompted by this thread:

 

https://www.pedelecs.co.uk/forum/threads/technical-question.47911/#post-726998

 

...I'm wondering if any cadence sensored hub motor controllers are capable of activating pedal assist when ghost pedalling backwards as well as forwards, because it strikes me this would be an advatage for hill starts - one reason why many are keen on throttles. Anyone can pedal backwards with ease. Legal too perhaps, because effort however small is required to backpedal? Also, standing starts would be easier if you've happened to have stopped on too high a gear, which is another situation when a throttle would come in handy (not a problem for my 20" wheeled BBS01B mid-drive conversion). Would ghostly backpedalling be easier on the knees, for those with severe knee problems? Could a huge boost of up to a legal 2000W be activated from a standing start by backpedalling fast? Could get by with a fixie? Can KT controllers do this, or will it require custom firmware and/or controller? If ghost pedalling a cadence sensored hub motor is only possible in one direction, perhaps a Golden Age of extremely low effort ghost backpedalling ebikes could commence? Ideally backwards and forwards. Asking because I don't know anything whatsoever about these mysterious hub motor things, with their arcane WTF PLC settings.

 

The Guerney Bidirectional GhostPedallator™®©℠ is invented!

There are some controllers that don't seem to be able to differentiate between the forward and reverse pattern. You could adapt many by sticking reverse polarity magnets beween the normal ones, then you'd get the correct signal whichever way you pedalled unless you had a dual hall sensor. Alternatively, in a 10 magnet disc, you could try pressing out and reversing every other magnet so that you have alternating N and S.

Edited October 10, 20241 yr by saneagle

Interesting. How do they avoid working when reverse pedalling?

Let's say the signal wire is held high by a pull-up resistor. The hall sensor will switch to low when say a south facing magnet passes in the forward direction. It will also switch low when a north facing magnet passes in the opposite direction. That's why you have to flip the magnet disc when you swap the sensor from one side of the bike to the other. You can't do that with dual hall sensors. They only work on one side of the bike when the magnets pass in the right direction.

 

Basically there are four combinations of magnet direction and orientation They're forwards, backwards, N and S, so you can have FN, FS, BN, BS. For a single hall, BS is the same as FN, so two combinations will work. A dual hall will only switch with one of the four combinations.

Let's say the signal wire is held high by a pull-up resistor. The hall sensor will switch to low when say a south facing magnet passes in the forward direction. It will also switch low when a north facing magnet passes in the opposite direction. That's why you have to flip the magnet disc when you swap the sensor from one side of the bike to the other. You can't do that with dual hall sensors. They only work on one side of the bike when the magnets pass in the right direction.

 

Basically there are four combinations of magnet direction and orientation They're forwards, backwards, N and S, so you can have FN, FS, BN, BS. For a single hall, BS is the same as FN, so two combinations will work. A dual hall will only switch with one of the four combinations.

I'm not sure about that. I don't think a single Hall effect sensor can determine the direction of travel of a magnet. I know there are some chips that can do this, but as far as I know, they have two Hall effect sensors integrated in the one chip.

I may be very new to eBikes, but I've been active in electronics for 60 years.

I may be wrong, but I'd also question why the sensor that came with my cheapo PAS is the size of half a KitKat finger, if it only contains 1 Hall effect sensor.

There is no way to detect direction of rotation with just one hall sensor, so they have to be dual hall. To see this, think of discrete images of a circle with dots on them --- from that info alone one cannot know whether the circle is rotating clockwise or anticlockwise. One needs the derivative signal as well and that is what two Hall sensors with a small spatial separation can effectively provide. One can generate the derivative or simply the difference signal from those two. If the first one triggers just before the second we know the magnet moved from 1st to second, if not in reverse. The dual hall could be in a single package so may not look any different. One can still have a single signal wire that output the pulsed waveform only for forward rotation or two wires outputting pulse forms with a phase difference.

 

As for tricking the controller to operate in both forward and backward, it must be possible to devise a sensor that generates the same pulse train irrespective of the rotation direction.

I'm not sure about that. I don't think a single Hall effect sensor can determine the direction of travel of a magnet. I know there are some chips that can do this, but as far as I know, they have two Hall effect sensors integrated in the one chip.

I may be very new to eBikes, but I've been active in electronics for 60 years.

I may be wrong, but I'd also question why the sensor that came with my cheapo PAS is the size of half a KitKat finger, if it only contains 1 Hall effect sensor.

I bow to your superior knowledge, I've only been working on ebikes for 14 years, so what do I know? According to the theory of multiple universes, after every event, the universe splits into an infinite number of universes, where every possibility plays out. I must have missed the bit where it split into one where pedal sensors start acting differently. Thanks for the heads-up. I'll look out for it when i install my next pedal sensor in a few days time.

There is no way to detect direction of rotation with just one hall sensor, so they have to be dual hall. To see this, think of discrete images of a circle with dots on them --- from that info alone one cannot know whether the circle is rotating clockwise or anticlockwise. One needs the derivative signal as well and that is what two Hall sensors with a small spatial separation can effectively provide. One can generate the derivative or simply the difference signal from those two. If the first one triggers just before the second we know the magnet moved from 1st to second, if not in reverse. The dual hall could be in a single package so may not look any different. One can still have a single signal wire that output the pulsed waveform only for forward rotation or two wires outputting pulse forms with a phase difference.

 

As for tricking the controller to operate in both forward and backward, it must be possible to devise a sensor that generates the same pulse train irrespective of the rotation direction.

I would agree, but I guess the aim is to only generate the pulse train in the forward direction.

And I was about to respond to the now disappeared post showing the use of an Allegro device, which actually incorporates three Hall effect sensors.

But sorry, saneagle, I didn't want to upset anybody, just getting my head round how this stuff works.

I would agree, but I guess the aim is to only generate the pulse train in the forward direction.

Of course yes.

I was referring to the question at start of this thread which asked whether we can have a sensor that works for pedalling in both directions.

I'm not saying it's practicable; but with an irregular pattern of magnets a single sensor can detect rotation direction. Probably bad for response time.

(I thought I'd seen that mentioned somewhere above, but can't see it.)

I'm not saying it's practicable; but with an irregular pattern of magnets a single sensor can detect rotation direction. Probably bad for response time.

(I thought I'd seen that mentioned somewhere above, but can't see it.)

In theory yes, but hard to implement. An easier one with single Hall would be to use pairs of opposite polarity magnets with different spacing among and between pairs. But poor response time and complicated.

I'm not saying it's practicable; but with an irregular pattern of magnets a single sensor can detect rotation direction. Probably bad for response time.

(I thought I'd seen that mentioned somewhere above, but can't see it.)

Agreed. With an irregular pattern.

Lets make it simple. We don't need any complicated theory. We know that a normal simple 5, 8 or 10 magnet single hall (they're all single hall) sensor works backwards when you put the magnet disc on the wrong way up, and it works in the forward direction when you put the magnet disc the correct way up. The only difference is the orientation of the magnets from N to S or vice versa. Therefore, if you take an 8 or 10 magnet disc, push out every other magnet and put them back in the other way up, it'll work in both directions. Simples!

 

That will not work with a dual hall sensor (normally 12 magnet disc), nor will it work with a magnet disc that has fore-and-aft magnet direction, though I haven't seen one of those for 10 years apart from the spare parts in my storage.

https://www.techmezine.com/allegro-product-news/magnetic-position-sensors-efficiently-drive-e-bike-pedal-assistsystems/

 

This is the link that some kindly soul posted yesterday, before swiftly deleting it.

https://www.techmezine.com/allegro-product-news/magnetic-position-sensors-efficiently-drive-e-bike-pedal-assistsystems/

 

This is the link that some kindly soul posted yesterday, before swiftly deleting it.

Most of the pedal sensors that have been used on ebikes don't work like that. It's a specific bit of theory to get a specific solution. It does partly explain why people have so many problems when they buy a 12 magnet sensor.

There was a specific requirement under the 2009 EN15194 standard which I assume probably still applies that pedaling backwards will not activate the motor as below.

 

There was a specific requirement under the 2009 EN15194 standard which I assume probably still applies that pedaling backwards will not activate the motor as below.

 

[ATTACH=full]60175[/ATTACH]

It's also a requirement that the bike has the correct lights, reflectors and a strength test. That's if you want to sell an ebike with a CE mark. It's not a legal requirement to ride the bike.

 

When the motor activates by pedalling backwards, it's a bit dodgy because you have to lift the pedal to get ready to ride. That's going to be a bit awkward when the bike surges forward each time you attempt to move the pedals. It would require a bit more sophistication in the control system to make sure that it didn't go when you didn't want it to. Also, pedalling backwards to start up a hill is going to be a nightmare.

Edited October 11, 20241 yr by saneagle

You could adapt many by sticking reverse polarity magnets beween the normal ones, then you'd get the correct signal whichever way you pedalled unless you had a dual hall sensor. Alternatively, in a 10 magnet disc, you could try pressing out and reversing every other magnet so that you have alternating N and S.

 

Thank you. Unless some intrepid soul on this forum tries this first, I will, if I ever convert using a hub motor kit. Can you recall which controllers? Were they current controlled or the crappier speed controlled?

 

 

There was a specific requirement under the 2009 EN15194 standard which I assume probably still applies that pedaling backwards will not activate the motor as below.

 

[ATTACH=full]60175[/ATTACH]

 

Thanks for answering my question. When stopped by the rozzers, simply switch off the PAS senor? Could claim the bike had broken down shortly before - who knows, you might be believed if you weren't bombing down the road? Or switch to the second PAS disc on the opposite side, which has magnets oriented for forward pedal assist? Or fashion some mechanism which can swiftly click one set of magnets too far away and bring the other set closer, or flip the required magnets over with a sneaky kick of a heel? If caught somehow, surely backpedalling pedal assist is less illegal than an independently operating throttle faster than 6kph? Can they throw the book at you for operating a motorbike without insurance etc, if all you have is a backpedal activated EAPC? Would it be more of a pamphlet? A pamphlet wouldn't hurt as much.

 

 

When the motor activates by pedalling backwards, it's a bit dodgy because you have to lift the pedal to get ready to ride. That's going to be a bit awkward when the bike surges forward each time you attempt to move the pedals. It would require a bit more sophistication in the control system to make sure that it didn't go when you didn't want it to. Also, pedalling backwards to start up a hill is going to be a nightmare.

 

Might not be too bad? Start with ebrake+brakes on, pedal backwards to activate the motor, having let go of brakes a split second before... then continue pedalling backwards temporarily, until you're travelling forward fast enough to easily pedal forwards? Could end up rolling downhill of course once the ebrakes are let go, if there's a huge preset pause between ebrake and the start of pedal assist.

 

 

If the cadence sensor has just the three wires, then my guess is that there are two Hall effect sensors, which produce a quadrature signal as the pedals turn, and there is a little bit of internal logic which gates one of the quadrature waveforms with the derived direction signal, so there's no pulse train output when pedalling in reverse.

 

Replacing the internal logic is something I hope to avoid.

Edited October 11, 20241 yr by guerney

Thank you. Unless some intrepid soul on this forum tries this first, I will, if I ever convert using a hub motor kit. Can you recall which controllers? Were they current controlled or the crappier speed controlled?

 

 

 

 

Thanks for answering my question. When stopped by the rozzers, simply switch off the PAS senor? Could claim the bike had broken down shortly before - who knows, you might be believed if you weren't bombing down the road? Or switch to the second PAS disc on the opposite side, which has magnets oriented for forward pedal assist? Or fashion some mechanism which can swiftly click one set of magnets too far away and bring the other set closer, or flip the required magnets over with a sneaky kick of a heel? If caught somehow, surely backpedalling pedal assist is less illegal than an independently operating throttle faster than 6kph? Can they throw the book at you for operating a motorbike without insurance etc, if all you have is a backpedal activated EAPC? Would it be more of a pamphlet? A pamphlet wouldn't hurt as much.

 

 

 

 

Might not be too bad? Start with ebrake+brakes on, pedal backwards to activate the motor, having let go of brakes a split second before... then continue pedalling backwards temporarily, until you're travelling forward fast enough to easily pedal forwards? Could end up rolling downhill of course once the ebrakes are let go, if there's a huge preset pause between ebrake and the start of pedal assist.

 

 

 

 

Replacing the internal logic is something I hope to avoid.

All I know is that a couple of months or so agao there was a guy on this forum that mentioned that his PAS worked forwards and backwards. The problem he wanted solved was something else, so nobody paid any attention to it. I just made a mental note of it at the time because it's unusual.

 

This isn't it, but it's the same. See post #26 onwards.

https://www.pedelecs.co.uk/forum/threads/alternatives-to-flipping-pas-disc.40349/page-2#post-602882

Perhaps? with a small dc motor and a cheap all in one pas sensor, you could rig up a push button to turn the motor to rotate the pas sensor, box it up somewhere and hide it on the bike, route the button to the handle bars and the pas signal wire and ground to the pas sensor input of your controller and press the button when needed.

Perhaps? with a small dc motor and a cheap all in one pas sensor, you could rig up a push button to turn the motor to rotate the pas sensor, box it up somewhere and hide it on the bike, route the button to the handle bars and the pas signal wire and ground to the pas sensor input of your controller and press the button when needed.

If back pedalling is not a requirement, just use a 555 Timer IC to generate a pulse train. About 10Hz with 1:2 ratio for on/off would work perfectly. Pretty easy and cheap.

Slightly off topic but I have noticed the power output on the display varies with cadence, am I imagining that ?