I'm trying to make a simple IR break-beam circuit to activate an LED. So when someone breaks the beam, it will activate an LED on a timer (simple 555) and the LED will turn off once the timer has expired. I understand the timer part, but I have no idea how to go about using IR LEDs to activate separate circuits. I suppose a phototransistor would be the receiver, but I don't know how to use it in this context. Can anyone supply a diagram or some information on how to approach this? I'm trying to make this very simple so that I can understand the basics and then go from there. Thanks.