Nixie tubes are essentially an old school method of displaying digits before LCDs. They’re primarily famous for being used in Soviet Russia but are now a favorite among the DIY community. Most people use them to make clocks, but occasionally they’re used for more unique purposes such as this keychain.
With a bit of brainstorming and ingenuity, this elegant design was conceived as a contest entry for a 555 Timer Contest (it flashes ‘555’). Composed of a double-sided circuit board, and powered by a standard battery, the Nixie Tube is powered by increasing the battery voltage to 170v.
Additionally, you can also buy larger displays (shown above) which are cheaper, run at about 60v, and display more digits.
Using a custom PCB, the assembly is inspiring and fun for anyone searching for a new, challenging project. You can buy the nixie tubes used in this project pretty cheap on eBay.