IR Sensor for Occupancy Detection

Bruce's post in my arduino turnout thread reminded me I've been meaning to do a separate post on the IR detectors I used, as I think they could be pretty handy for general purpose occupancy sensing. The sensor is a self-contained unit consisting of an IR emitter, IR detector, and logic circuitry. When a train passes over the sensor, the detector picks up the reflected IR from the underside of the train, and the output of the detector circuit goes low, indicating that a train is present. All that is needed is a 5vdc supply, and something to monitor the output.

The sensor is Sharp part number GP2A200LCS0F. The datasheet from Sharp is here. I got mine from Mouser, here. Here is what it looks like 'out of the box':

And after popping it out of the outer gray housing, which is necessary to fit between the ties of ross/gargraves stuff:

With the housing removed, just tuck them between the rails and secure with a couple drops of CA glue. You may need to shave a couple corners if you are using them on the curved leg of a turnout. Here's a pic of two of them installed on one of my turnouts:

For hookup, you can either desolder the connector and solder your wires directly to the PCB, or use a mating connector. I used connectors on my turnout installations, but I've done it both ways and either works well. If you want to use connectors, here are the parts for the contacts and housings:

Housing

Contacts