[LAU] A crazy idea

Charles Henry czhenry at gmail.com
Thu Mar 4 10:04:47 EST 2010

> 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.

Once per revolution is okay.  b/c what you've really asked for it not
that the estimation be accurate to some threshold throughout the
cycle, but that the output be smooth and continuous.

An F/V converter takes pulses, irregularly spaced, and creates
identical pulses of current.  Those pulses get integrated across an RC
network.  It's not accurate during the time between pulses, but it
doesn't have to be.  It just has to have smooth response when the
pulses start to get faster or slower.  You choose a RC time constant
that is long compared to the slowest cycle you want to use and is
small compared to the time over which the pulses


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