4 Mar
2010
4 Mar
'10
10:09 a.m.
On Thu, 4 Mar 2010, Karl Hammar wrote:
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.
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