On Thu, 01 May 2014 23:55:27 -0300, Mike Spencer wrote:

snip

Take apart an old (computer) mouse and get the LED and sensor. Should
be far more responsive than a reed switch. (But I'm only guessing.
Electronics weenies to the bridge, please. Is there such a thing as a
high-speed, solid state magnetic switch?)

Yes there is -- they're called Hall switches, or Hall sensors (they work
by the Hall effect. You get one guess as to the last name of the guy who
wrote it up first.)

I just don't feel that doing this optically will be robust.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com