Picture this: You are a Cold War-era spymaster, stationed in West Germany. One of your operatives has risked life and limb to get her hands on this mysterious case. You inspect and then carefully open it to be greeted by an array of toggle switches, a countdown timer, and a power switch. Disarm it, and you'll have your hands on the vital launch code for a captured missile. Fail, and, well, it's best not to consider failure...

Your best cryptographers have intercepted the following transmission:

    кра́сный - бе́лый - си́ний - зелёный - жёлтый

Thinking back to your language training at Langley, you translate this to:

    RED - WHITE - BLUE - GREEN - YELLOW

That's it! These colors must be the secret to disarming the case!

You dare to turn on the power, the case arms itself, and a three minute countdown begins. You enter in the toggle switches, hopefully in the correct order.

The timer stops. Whew.

A secret code scrolls onto the display. The launch codes you needed! A job well done.

Countdown to fun

Countdown timers with switches, lights, and beeps are a staple of action thrillers. This is a fun and fairly simple prop to build using a briefcase or other similar container.

You could use it for a spy-themed escape room or mystery dinner, or as a prop for a movie or play. Better yet, use it to deliver a message to someone you know who likes solving puzzles. 

You can easily customize the timer, switch combination, and secret message in the included Arduino sketch, or you can add different, complex behaviors, create your own Mastermind-like game, and more.

Parts & Materials

In addition to the parts listed on the right side of this guide, you'll want an interesting case in which to mount the electronics. I used this one which is similar to a Pelican case, albeit lower strength and lower cost. If you happen to have a Halliburton aluminum attaché case, that would be perfect!

If you'd like to follow this guide exactly, that one's a good choice, as I've included CAD files for panels that fit that case. You can laser cut and etch two sheets of 3mm acrylic to make the panel, or print the template and use it as a guide for hand cutting cardboard or thin plywood with a band saw, coping saw, or knife.

Additionally, you'll need some wire for making connections, a soldering iron and solder, and a small screwdriver.

To distress the case I used watered-down black acrylic paint, the kind you can get at a craft or hobby store. I also used gray spray primer and red glossy spray paint for the star. You'll want some cardboard, or better yet, Mylar stencil sheet to make the start stencil, and access to a laser cutter (or use a hobby knife) to cut the pattern.