Passing Secrets

Any proper spy will find the need on occasion to pass secret information along to an ally securely. There are many techniques to do so — sometimes, they can be highly technical, such as an encrypted digital message, but other times they may need to be decidedly simple and low tech -- hiding information just outside of plain sight can be very effective.

For example, you can write an innocuous-looking letter that will pass scrutiny should it be seen by enemy eyes, yet have top secret information written in invisible fluorescent ink! Your intended recipient can use an ultraviolet (UV) light to read the message!!

In this project we'll use your Gemma M0 to create a touch-sensitive UV light illuminator. Plus, you'll learn a little coding with so this is a great way to make your first spy project

Materials and Parts

You'll need some paper and an invisible UV marking pen, as well as the parts listed below.

1 x Gemma M0
Tiny microcontroller
1 x UV LED
UVA/Purple 5mm LED
1 x USB Cable
Micro USB to USB A
1 x 3x AAA Battery Holder
with JST connector and ON/OFF switch
1 x USB Cable
A/MicroB - 6"

Additionally, you'll use two M3 x 8mm screws and nuts to connect the LED to the Gemma M0.

This guide was first published on Mar 16, 2018. It was last updated on Mar 08, 2024.

This page (Overview) was last updated on Mar 08, 2024.

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