Angus,
  No cover huh?
  Well I don't know if you'll get a correct laser class safety rating
without a mechanical interlock, but that's outside my experience.
  Short range IR should be simple, especially with something as IR
reflective as a cd.

Just get a reflective ir photosensor.
Digikey has them, Mouser has them, everybody has them.
Modulate the TX (not at 50/60hz)  led, look for correlation on the receiver
to avoid confusion with ambient room light.
  Limit the output power on the TX led down to decrease range to a couple
of mm.

If you want a closer approximation to a real interlock, use the output of
your sensor with some hardware to enable the laser on the cd player.

good luck,
carl



At 07:52 PM 3/28/2002, you wrote:
>Thanks for the leads... unfortunatly these are out of range, ill tell you
>the app. to make
>things clearer.
>
>Im hanging a CDROM drive on a wall... (dont ask why! - cos it looks good..)
>and
>I want to avoid the laser firing off into the room, whilst the drive is
>finding out if there
>is a CD there... Im sure the power of the laser is v. small, however,
>I cant take risks on other peoples behalfs..
>
>So the i thought it would be okay to attach a infrared measuring device
>connected to a PIC which is constantly scanning, and when something arrives
>at a suitable distance (i.e. hopefully a CDROM, and not someones eye!), then
>it communicates via RS232 to the PC COM port, and the software tells the CD
>etc...
>
>So i think I need a infrared/sonar ranger that will be accurate from about
>8mm - 30mm.. unless anyone has a better idea.
>
>angus.

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads