4 Mar
2010
4 Mar
'10
8:30 p.m.
On Thu, 4 Mar 2010, Folderol wrote:
Also, use a short range photocell on the spokes (say
50mm). Easy to
mount, reliable results with minimal effort. As these can usually
respond up to 10-30kHz you won't have to worry about pedalling too
fast :)
Sensing the spokes measures vehicle speed, not pedaling speed, you'd want
your synth to drop to idle while you're coasting. I'm for a photocell
watching the crank sprocket teeth in the rear interval where there's no
chain.
You also need to measure torque, or chain tension, to drive your synth's
volume. An idler with a load cell on the top of the chain between the
crank and the wheel can be used for a single-speed or three-speed in-hub
transmission, but if you have a rear derailleur, you'll need another fixed
idler between the sensor and the rear wheel. If you have a front
derailleur as well, it just gets too complicated...
Maybe the accelerometer is simpler after all, even if you have to
compensate for incline. That's just math, not hardware.
--
Rick Green
"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
-Benjamin Franklin
"As for our common defense, we reject as false the choice between our
safety and our ideals."
-President Barack Obama 20 Jan 2009