IR obstacle sensor question

[arunbhaskar]

I found this circuit on some website.
**broken link removed**
Can someone explain how exactly this circuit operates.
The phototransistor is located right next to the IR led and it receives the light reflected from the obstacle.
I need to know what outputs i obtain under what conditions.

 

[keith1200rs]

I guess it just detects reflected light. It might also try to use the brightness to determine distance, although that would be pretty unreliable. More likely it is just modulating the light source to try to eliminate ambient light effects.

Keith.

 

[karesz]

Maybe its a sort of "light curtain" system/sensor...
K.

 

[pranam77]

Looks like a reflective type IR obastacle detector where the LED's are driven with the frequency generated by one Picaxe, and detected by another on the other side...cheers