why opto and not a stepper in reversed way ? It's there, its cheap and
it's easy to use with two comparators. More robust and clean than any
homebrew optical encoder.


top 10 wishes,
Vasile
http://surducan.netfirms.com


On Mon, 15 Sep 2003, Hulatt, Jon wrote:

> Laser toner is good for this. You could get a shiny metal disk, print your
> encoder onto transparency on a laser printer, and stick it together. Ensure
> the toner side of the transparency is on the outside- the other side of the
> transparency may reflect.
>
> -----Original Message-----
> From: Peter Moreton [mailto:peter@RIL.ORG.UK]
> Sent: 15 September 2003 12:01
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]:Homebrew Opto Encoder advise pse.
>
>
> 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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