reading IR photoresistor

[mbw123]

Hello everyone,

I am using a PIC18F4550 and I am trying to measure the strength of an IR beam (translating to distance). I am using this [http://www.phidgetsusa.com/tutorials...ue_sensors.asp] setup (at the bottom of the page) because I have this [http://www.radioshack.com/sm-infrare...i-2049724.html] photo transistor. I am using ADCIN to read the values of the photo transistor with a 2200 ohm resistor hooked up to it. I am unsure, however, about what resistor value to use with it because when I hook everything up, it doesn't seem to be working well. Usually it will print a value around one or two (with 8 bits conversion for ADCIN) with no IR light on. When I turn an IR led on I am getting the same value (I am positive the IR emitter is working). Please help.

PS: I know there was a recent post similar to this on this [http://www.picbasic.co.uk/forum/showthread.php?t=5592] but it doesn't have what I am looking for.

Thank you,

-Mike