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Author Topic: torque sensor on a bike  (Read 2483 times)
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hi, I want to put a torque sensor on my bike, but it's too much ironworks and too expensive to put a rotative sensor. does any one has a idea? I thougt on a force sensor on the pedal, but it doesn't work.
thank you
Pilou
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I thougt on a force sensor on the pedal, but it doesn't work.

In what way does it not work?- what did you actually do?

Sounds like an interesting project.
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Dee Why NSW
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I guess it doesn't work because, to measure torque, you have to compare it to a resistance, and the resistance is what you have to find first.  A good place to start would be to try riding your bike through a brick wall with the brakes applied. It would then be quite easy to measure the torque at the pedals with an Arduino monitoring a deflection device on the crank.
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to measure torque, you have to compare it to a resistance

¿Que?
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Dee Why NSW
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Think about it. Then try to measure some without any. 

On second thoughts, it might be quicker to try measuring torque against no resistance first, and then thinking about it.

Let us know how you go.
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Nick is just trying to say that your drive train has to resist your foot otherwise you aren't producing any torque, i.e. freewheeling.  Also remember that your pedals always stay mostly horizontal so you will also need to measure what the angle between the pedal and shaft is somehow.  So when your pedal is all the way forward the force on the pedal is giving maximum torque.  When the pedal is all the way down or all the way up you are producing no torque at all.
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you will also need to measure what the angle between the pedal and shaft is somehow.  So when your pedal is all the way forward the force on the pedal is giving maximum torque.  When the pedal is all the way down or all the way up you are producing no torque at all.

LoL. I wasn't quite ready to add that stage of complexity......

And what happened to those bikes with oval front sprockets?
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http://keithhack.blogspot.ca/2013/01/v3power-meterthe-complete-how-to.html
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Or a modificatin to your bike so that the rear axle i mounted so there is some movement that could be measured with a strain gage. You could then corrolate that eading to torque.
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Nick is just trying to say that your drive train has to resist your foot otherwise you aren't producing any torque

Maybe that's what he was trying to say, but what he really said was that to measure torque you need to compare it to a resistance, and that's what I was questioning because the use of the word compare doesn't make sense.

I agree that without a load indeed the mechanism will not require a torque to turn it and there would be no force provided to the pedal of a freewheeling mechanism.

But it's still true to say that the force applied to a pedal is an analog for the torque since the crank is of fixed length. Even under freewheeling that would work, since the force measured would be zero and that's still a correct analog for the torque of zero.

My original question to the OP was, what went wrong with trying to use a force sensor on the pedal?- he didn't elaborate and I wondered if that was a mechanical problem of having some kind of FSR on the pedal and all sorts of wiring complications in a rotating system. Not to mention the FSR getting destroyed by the cleats under the shoes.



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hi, I want to put a torque sensor on my bike, but it's too much ironworks and too expensive to put a rotative sensor. does any one has a idea? I thougt on a force sensor on the pedal, but it doesn't work.
thank you
Pilou

How did the force sensor not work? Wires wrapping?
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I guess one option would be to measure the top chain tension using an additional derailleur?
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I think a load cell on the pedal would be the way to go.   To get the signal off the pedal either use Bluetooth or a slip ring to directly get the electrical signals, power and ground off the rotating pedal.
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If you put the bike on a rack with some resistive things on the rear wheel, then you just keep arduino on the ground with a wire going to the force sensor on the pedal.
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If you put the bike on a rack with some resistive things on the rear wheel

This should do the trick  smiley-cool
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