How does the cadence sensor work?

scrambler

Active Member
That's not the case with at least my Espin Sport.

I have a power output setting on my display and the power output varies based on how fast/slow I am pedaling, when I pedal slower, power output is higher, when I pedal faster, power output is lower.

The way this works is similar to a torque sensor... when you pedal slower, the assumption is that you are having a harder time pedaling so it increases the power to the motor... like when you first start pedaling or when you start pedaling up an incline. As you pedal faster, it reduces the power which follows the logic that you are having an "easier" time so the motor needs less power.
This matches my understanding of the best approximation a Cadence sensor can make.

Assuming you always wish to pedal at 80rpm for example, if you are pedaling slower, it assumes you are struggling to reach that cadence and raises the assist, as you are able to pedal faster it reduces the assist assuming you are having an easier time

That scenario is a valid one, but it is not the only one. There will be cases, where you are pedaling slowly with little effort because of leisurely pedaling, and in that case the fact that it will push the assist wont be a good thing.
But once you know this is how your assist is programmed, you can adjust your gear and pedaling habit to match its assumption.

It is definitely not as good and exact as a torque sensor, but can get closer for a majority of situation.
 

Timpo

Well-Known Member
This matches my understanding of the best approximation a Cadence sensor can make.

Assuming you always wish to pedal at 80rpm for example, if you are pedaling slower, it assumes you are struggling to reach that cadence and raises the assist, as you are able to pedal faster it reduces the assist assuming you are having an easier time

That scenario is a valid one, but it is not the only one. There will be cases, where you are pedaling slowly with little effort because of leisurely pedaling, and in that case the fact that it will push the assist wont be a good thing.
But once you know this is how your assist is programmed, you can adjust your gear and pedaling habit to match its assumption.

It is definitely not as good and exact as a torque sensor, but can get closer for a majority of situation.
Yeah as I noted on example I just gave, I'm not convinced that that's how cadence sensor works.

If you decide to pedal slowly on parking lot, now all the sudden bike will boost up the assist? It doesn't make sense.
 

scrambler

Active Member
Yeah as I noted on example I just gave, I'm not convinced that that's how cadence sensor works.

If you decide to pedal slowly on parking lot, now all the sudden bike will boost up the assist? It doesn't make sense.
There is no such thing as "how a cadence sensor works"
A cadence sensor just provides one information to the controller.
It is then then up to the bike manufacturer to decide what to do with that information. Controllers are programmable, and can use a signal to do all sort of things with that information. This is how a controller can blend a torque sensor signal and a cadence sensor signal, to provide the best possible response to specific scenarios.

With a cadence sensor only signal, some only switch on or off the assist on a set level causing a burst of assist as soon as you start pedaling and then keeping it constant (on/off switch behavior)
Some improve the start by ramping up the assist power progressively, but still keeping it constant. It is still an on/off behavior but with a smoothed ON.
And some as mentioned above could modulate the Assist power based on pedaling speed to try and provide a modulated assist, similar in a way to a torque sensor, but that would only matches one usage scenario, and would therefore be imperfect.
 
Last edited:

Timpo

Well-Known Member
There is no such thing as "how a cadence sensor works"
A cadence sensor just provides one information to the controller.
It is then then up to the bike manufacturer to decide what to do with that information. Controllers are programmable, and can use a signal to do all sort of things with that information. This is how a controller can blend a torque sensor signal and a cadence sensor signal, to provide the best possible response to specific scenarios.

With a cadence sensor only signal, some only switch on or off the assist on a set level causing a burst of assist as soon as you start pedaling and then keeping it constant (on/off switch behavior)
Some improve the start by ramping up the assist power progressively, but still keeping it constant. It is still an on/off behavior but with a smoothed ON.
And some as mentioned above could modulate the Assist power based on pedaling speed to try and provide a modulated assist, similar in a way to a torque sensor, but that would only matches one usage scenario, and would therefore be imperfect.
Okay well maybe I should rephrase the question.

Why would any manufacture program in the way that slower the cadence, more assist you get?

It really doesn't make sense to me, because cadence doesn't tell you the whole story.
 

scrambler

Active Member
I cant answer for them, but it may be because it matches a majority of scenarios.
You still have the ability to change the level of assist for the situation that do not match that scenario, but if they studied it and found that in a majority of situations, when people pedal slowly it is because they are applying more pressure to reach a faster cadence, then it is worth making the the controller behave that way.

You should ask people like @BigNerd what his experience is with a bike that supposedly is using the Cadence sensor that way, and find out from him how he deals with the situations where the programming does not match the reality, and how often that is.
 

Gionnirocket

Well-Known Member
Region
USA
City
Y. O.
Okay well maybe I should rephrase the question.

Why would any manufacture program in the way that slower the cadence, more assist you get?

It really doesn't make sense to me, because cadence doesn't tell you the whole story.
I think scrambler hit it.
Think about when you ride... No matter the gear, it always gets easier to pedal the bike as the cadence increases.
 

Timpo

Well-Known Member
I cant answer for them, but it may be because it matches a majority of scenarios.
You still have the ability to change the level of assist for the situation that do not match that scenario, but if they studied it and found that in a majority of situations, when people pedal slowly it is because they are applying more pressure to reach a faster cadence, then it is worth making the the controller behave that way.

You should ask people like @BigNerd what his experience is with a bike that supposedly is using the Cadence sensor that way, and find out from him how he deals with the situations where the programming does not match the reality, and how often that is.
okay so, I just tested it.
You were right all along, I didn't know that :oops:

I just put my gear at the lowest, and pedaled slowly...then I pedaled fast, the assist really tapered off. (slowing the bike down)

I thought cadence sensor was on-off switch, I learned something new.
 

BigNerd

Well-Known Member
I’ve explained this before but think of a non ebike with gears. When it’s harder/slower to pedal, like going up a hill, what do you do? You gear down to make it easier to pedal. That’s the same thing a true cadence sensor programmed ebike will do... increase the power to make it easier to pedal.