linuxaudio.org

On Thu, 4 Mar 2010, Karl Hammar wrote:
> Why don't you put an inductive sensor [1] at the pedal gear teeth?

quoted text
> 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.

This is a good idea... as long as your sensor and your uC

can keep up with the pulses.  I didn't look into the sensors

that you picked, but they usually publish their response

times... so you need to check that out.
How many teeth does a typ. sprocket have?  Say about 40T.

Lance Armstrong spins his cranks at 80RPM.  That would be

53.3 pulses/sec (or 1 pulse every 18.75 ms).
Sometimes the sprockets have spokes or holes in them to make

them lighter.  Like 6 or 8.  Perhaps sensing those would

provide a more sensible signal if 18ms is too fast for your

sensor/uC.
-gabriel
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