LED - Lens - Lens - Photocell Question

Hi, everybody, first post so I hope I'm in the right place.

I'm working on a project where I need to make a specialized proximity sensor (well, I suppose a proximity switch).

It will work about like the failsafe on a garage door opener. There is going to be a beam (probably infrared) that is pointed at a photocell. When someone stands in front of it, the beam won't hit the photocell and from there I can condition the signal so that it operates like a switch. Proximity switch should be able to work at around 3 feet.

I'm wondering if anyone know how to select lenses or other parts in order to make an IR LED into a beam.

This should be pretty cheap and nothing too fancy.

Anyone have any thoughts?
Thanks

I have several remote controls for my TV's, and they all work at 3 feet without a lens. I think that qualifies as pretty cheap and not too fancy. Try it.

Measuring the behavior of parts and circuits is often a good substitute for trying to "math out" every aspect of the design.

Be sure to limit ambient light to the sensor, so that doesn't swamp the IR signal since standard silicon IR sensors are also sensitive to visible light. Mount the sensor in a tube to limit the light it gets. Also may need a dark red filter the minimizes visible light transmission, but allows IR to pass.

crutschow said:

... may need a dark red filter the minimizes visible light transmission, but allows IR to pass.

Click to expand...

I'm sure you can buy better, but I've found bin-bag material, or old camera film to be excellent for this.

Andrew