> The emitters and detectors I used looked sort of like the attached
> picture but only had two wires each

Bob,

Over the past few days I've tried various methods and think I've
decided what will be best for my application

First thing I tried was a standard reflective opto, OPB702. OK,
but coarse resolution, even when restricting the apertures and using
matte laser printing on shiny paper to give it the best contrast

So I made my own reflective sensor with 0.1mm optic fibre + IR
LED and an optic fibre channelling the reflection to an RPM1700
IR receiver. OK, fussy to set up and still coarse resolution

>From The Drawer Of Parts That'll Come In Handy One Day came
a Siemens SFH551V fibreoptic housing, like the one you posted,
complete with a couple of inches of 1mm plastic fibre. Same result
as before unfortunately

But it was easy to do a quick test with light transmitted through the
paper, and it worked very well. I'll make an adapter to use 0.1mm
fibre. I'm assuming the RPM1700 will work equally well. It seems
to be a lot more sensitive than the SFH551V, which may or may not
be an advantage

This means a sheet of glass with the IR receiver on top tracked
by an IR transmitter below, something I instinctively thought from
the gitgo might the most reliable. A little bit more mechanics but
not a big deal for getting a better result

Joe
--=20
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