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
This design uses an infrared LED as the signally device. Infrared light is invisible to the human eye. However, digital cameras are able to detect these wavelengths. You can observe this by pointing your TV remote at a digital camera and pressing a button. To the camera, the infrared LED will appear to light up bright purple.
By using an infrared LED and a digital camera, you can send and detect signals that will be invisible to everyone else.
Step 2: Materials
Here are the materials that you will need for this project:
1.5V Button Cell Battery
Small Magnet (optional)
Step 3: Bend the Leads of the LED to Fit the Battery
The first thing that you need to do is bend the leads of the LED so that the button cell battery can fit between them. This works best if you leave the shorter lead straight and bend the longer lead to match the shape of the battery.
Step 4: Insert the Battery Between the Leads of the LED
Insert the battery between the leads with the positive side touching the longer bent lead and the negative side touching the shorter straight lead. Use your fingers to squeeze the leads against the sides of the battery. Hold the LED in front of a digital camera to verify that it is working. It should appear as bright purple on the screen.
Step 5: Trim the Leads of the LED
Next you need to trim the leads of the LED so that they don't stick out past the battery.
Step 6: Wrap the Battery in Electrical Tape
To hold the battery and the leads in place, wrap them with electrical tape.
Step 7: Stick a Magnet to the Side of the Beacon (optional)
The simplest way to set up your beacon is to just set it on a flat surface. However, this gives you limited options to work with. Another option is to mount the signal beacon with a magnet. This will let you attach it to any metal object. Just take a strong magnet and stick it to the side of the battery. You can then stick it to any metal object that you come across. Not only does this give you more locations to work with but it also lets you point the LED in more directions.
Step 8: Use the Invisible Beacon to Signal Your Accomplices
This beacon is small and difficult to see (especially at night). You can set it up just about anywhere without attracting attention. Your accomplices will be able to see it with any digital camera. Cell phone cameras are ideal for this. To anyone watching, it will just look like they are texting or surfing the internet. This is a fun tool to add to your spy kit.
Also, please remember to retrieve you beacon later so that it doesn't litter the ground.