Shoot a modulated beam of light into the screw hole at an angle.  If the screw
is there the beam will bounce back with a certian strength.  If it is not there,
the bulk of the light will be 'lost' in the screw hole, and the strength on the
sensor will be significantly less.

-Adam

"Kosmerchock, Steve" wrote:
>
> Friends,
> First, Sorry for the Off Topic question.
> Second, I need to design a fixture that will "sense" if a
> screw is missing on a product. The device in question goes
> into a test fixture. I would like to have a way of checking
> for missing screws. Any suggestions?
> And yes, it will have a PIC in it!
> Thanks in advance.
>
> Best regards,
> Steve
>
> Steven Kosmerchock
> RFS CELWAVE
> Phoenix  Az  USA
> Email: steve.kosmerchock@rfsworld.com
> Personal: www.geocities.com/researchtriangle/lab/6584