Spies need ways to secretly communicate with their partners. This can be a simple signal like a chalk mark on a wall or a newspaper left on a park bench. But the best kind of signal is completely invisible. In this project, I am going to show you how to make a simple invisible beacon that you can use to signal your friends and accomplices.
Step 1: How the Invisible Beacon Works
By using an infrared LED and a digital camera, you can send and detect signals that will be invisible to everyone else.