007 style

I think this link shows the general thing you are talking about, and you can peel enough key words from it to look further:

Use google and look for "laser trip wire"....

or build your own

Radio Shack sells these - eBay too. Look for Door Minder.

Just to throw a monkey wrench at you, I think it would be cooler to have a capacitive proximity sensor. Invisible.

Of course, in some movies the lasers aren't just covering the doors, they create a full pattern in the room, so movement is nearly impossible, especially if the lasers are infrared so they can't be seen normally.

Michael

And in some movies the 'lasers' are just an excuse for Catherine Zeta-Jones to wriggle around in skin tight clothes!

I'm fine with it too. Halle Berry has made a lot of bad movies wearing very little - I wish we could have just the good parts of those!

Not that that's a BAD thing, mind you....

Bob M.

An ORP12 light dependant resistor in a potential divider circuit and a dc amp of some kind with perhaps a relay output stage to switch whatever you need to switch would do the trick. My website has a system for working out all kinds of simple circuits, which is intended for beginners, and your cicuit can easily be assembled from these kits. Visit

Ed

photocell, phototransistor, light dependant resistor,

try google-ing these phrases

light beam sensor schematic

photointerruptor schematic

phototransistor datasheet

investigate the first 10 hits on each.

Bye. Jasen

A laser beam is invisible from the side, unless there's dust or smoke in the air. If your burglar is a smoker, he might see it and run away. ;-)

(or step over it - better use several of them.) ;-)

Cheers! Rich

Detection of humans is most commonly done these days by sensing body heat.