Picture of Invisible Signally Beacon (Infrared LED Throwie)

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.

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Step 1: How the Invisible Beacon Works

Picture of 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

Picture of Materials
Here are the materials that you will need for this project:

Infrared LED
1.5V Button Cell Battery
Electrical Tape
Small Magnet  (optional)
Digital Camera

Wire Cutters

Step 3: Bend the Leads of the LED to Fit the Battery

Picture of 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

Picture of 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

Picture of 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

Picture of Wrap the Battery in Electrical Tape
To hold the battery and the leads in place, wrap them with electrical tape. 
kevsaul1 year ago
The camera trick does not work on my iPhone 5s but does work on iPad 2
Tanmayg kevsaul3 months ago
It doesn't work with my iPod too. I don't know why.
DIY Hacks and How Tos (author)  kevsaul1 year ago
There are a few cameras that have an infrared filter to try to block more of the near infrared spectrum.

You I-Phone has an Infrared block filter, which blocks infrared Light! Most DSLR´S have them :)

Throw that in a battlefield and watch the laser guided missile hit it.lol

Gula1 year ago
Look at is with the camera on the screen side, it does not have a ir filter.
Ploopy1 year ago