Turn FR into bike meter

[Al Johnson]

On Friday 03 July 2009, Paul Fertser wrote:
> Cameron Frazier <frazier.cameron at gmail.com> writes:
> >> 1) I'm missing the cadence display = the number of revolutions of the
> >> crank per minute; roughly speaking, this is the speed at which a
> >> cyclist is pedalling/turning the pedals.
> >
> > For cadence detection, a hall effect sensor and a small magnet would
> > cover it and have no moving parts/contacts ( see [1] for an
> > example),
>
> Hm, i was always under the impression that most bike systems use a
> simple magnet and a reed switch (no need for hall effect sensor) for
> both cadence and speed measurements. So any sensor from a regular
> "bike computer" can be directly attached to the mic line of FR.

They do, and they eventually fail, hence the "no moving parts/contacts" bit. 
Both will work, but hall effect should last longer.