[LAU] A crazy idea

[Karl Hammar]

Jonathan Gazeley:
...
> I want to measure how fast I'm turning the pedals on my bike (the 
> "cadence") and synthesize/sample the sound of an internal combustion engine.
...

Sounds 
like fun.

> 1. A sensor that can measure my cadence. A simple magnet switch that 
> triggers once a revolution won't be enough to measure the cadence with 
> sufficient resolution, since my cadence is usually between 50 and 80 
> rpm. I would probably need to mount multiple magnets spaced equally 
> around the chainwheel and have a single sensor on the frame. Then I have 
> to get it to supply this information to my control program.
...

Why don't you put an inductive sensor [1] at the pedal gear teeth?
You could probably mount it at the chain protective cover if the
tolerances are the right.  Have a look at Omron "E2E-X5MF1 2M" [2,3]
(you might have to paint it to protect it from water). For that one
you need 12-24V DC.

Regards,
/Karl

[1] http://en.wikipedia.org/wiki/Inductive_sensor
[2] http://www.ia.omron.com/product/family/449/index_fea.html
[3] http://www.ia.omron.com/product/item/e2e_7258d/index.html

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Karl Hammar                    Aspö Data               karl at aspodata.se
Lilla Aspö 148                                                 Networks
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