'Look' at the problem a different way - you are shining a light onto a
reflector and measuring when you get a little / lot back.  In ambient
conditions there is already a *LOT* of light around so you have to get close
to to be able to pick up the *SMALL* increase when the reflector passes.

So - how can you get more light?
  1. use different light to the ambient - ultra violet is good (otherwise
your TV remote wouldn't work in a brightly lit room).
  2. increase the concentration of the light onto the reflector with a
focusing system (don't forget to re-calculate the focal length of your
selected lens from 'natural' light to UV wavelengths).
  3. eliminate the ambient light by collimation (put a shade tube over your
reciever to make it highly directional).

Bye.

> -----Original Message-----
> From: Geoff Child [SMTP:geoffchild@HOTMAIL.COM]
> Sent: Tuesday, 26 October 1999 14:37
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Optical pickup
>
> I am making a no contact tachometer using a pic for a model airplane and
> am
> trying to find a reflective sensor for the pickup. The ones that I have
> looked at have to be to close ~.150 inches and I would like to be several
> inches away. Does any one know of any any sensors?
>
> Thanks
>
> ______________________________________________________
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