Mike,

You 'black' spirit pen may be black in the visible wavelengths, but may
be quite reflective in the IR band. You just have to find a black
paint/ink that absorbs IR. Since your eyes cannot detect IR, this is
difficult!

Maybe try various pieces of card painted with various black inks/paints,
and see which ones reflect the IR from your TV remote control? Or lay
them out in the sun, and see which ones get hot (= absorb IR)

Regards, Peter Moreton



-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Mike W
Sent: 15 September 2003 10:05
To: PICLIST@MITVMA.MIT.EDU
Subject: [EE]:Homebrew Opto Encoder advise pse.

GM folks,
I'm trying to find the 'proper' stuff to make a reflective opto
quadrature rotary encoder.
 I'm having problems in as much as the black ( spirit based felt tip
pen ) is reflecting as much IR as the white

Please share your experience ..

I'm using an old VCR head for the mechanics, with two OPB706a
reflective opto couplers as the detectors. they are mounted inside
the head assembly and shine on the inside of the VCR head which has a
computer drawn wotzit ( can't think of its name ) stuck on the head.
spaceing is about 1mm from opto's to wotzit.

thanks v much
mike

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