Simple beam break sensor

[Archangel]

I don't want people to be able to see the beam, but if I cant get IR working then that might be the only option.

Thanks for the links. Ill have a read through them

red laser / infrared filter might work . . .

[The Master]

This seems to be working now. The calculators ive used say that RA (or R1) should be 0K. The circuit doesnt work unless i put a 1K resistor in. Ive tried a few lower values but the LED will go off after a set amount of time then not come back on. 1K doesnt give me a 50% duty cycle but it seems to be alright.

Once it was flashing correctly i changed the other values to what the calculator said and the LED came on but dimmer than usual so i assume its flashing really fast. I replaced with an IR LED and it now works over 2M

I hope it keeps working once its all soldered into a PCB :P