Want to send secret messages over a distance but are wary of your communiqué being intercepted? After all, transmissions can be listened to with the right equipment, and you don’t want to run entire spools of wire to say “Hello world.” I know, how about a Simple Laser Communicator! This Weekend Project is quite simple, and relies on two parts: an audio transformer and laser for sending, and a photoresistor and crystal earpiece for receiving. Most of you probably already have a laser (or lasers) in your possession, so how you wire up that component (see diagram below) will vary, but the premise is the same: the laser will interpret the output from the audio transformer as pulses of light. Those laser pulses hit a photoresistor or solar cell, which in turn causes the diaphragm inside the piezoelectric earphone to vibrate, making light audible! This does of course require very precise line of sight, and communication is only one-way, but is a great combination of two generations of technology into a contemporary Weekend Project.
The transmitter consists of a microphone, mini-amp, audio transformer and laser.
The receiver consists of a photoresistor and crystal earpiece.
See all of the RadioShack Weekend Projects posts (to date)