Great how to on detecting a laser pointer “break” using a serial port – Chard writes “Ever wanted to make your own laser beam security system. You know the kind they have in the movies, with dozens of lasers and the thief has to limbo through them. Well, I just made a simple laser beam break detector. My computer can now tell when the beam is broken. The parts I used are: 5.6k resistor, photo diode, Digikey part #PDB-V107-ND, serial port from my PC…” Link.