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:
1. 5.6k resistor
2. photo diode, Digikey part #PDB-V107-ND
3. serial port from my PC
You set the RTS pin of the serial port high. You then use the CTS pin to track the state of the photodiode. When the beam hits the diode, current from RTS will flow into CTS and the CTS pin will show high. When the beam is broken, the diode stops the current flow and the CTS pin goes low. Below is the circuit: