Vacuum Fluorescent Displays (VFDs) aren’t something you work with every day. They are often found in car radios and emit a green or blue light with high levels of contrast. Given these characteristics, it’s not a stretch to think they would make a great display for a clock.
The folks at Akafugu Corporation are selling a kit for this concept in the form of the VFD Modular Clock version IV-6. VFDs, which are similar to vacuum tubes, each contain a single digit so this modular kit includes six IV-6 tubes. You can also opt for an option without the tubes if you have them already. The baseboard is powered by an ATMega32U4 microcontroller with a high-voltage VFD driver that lights up the display shield above the board.
The kit comes pre-programmed with the Arduino Leonardo bootloader and firmware. If you would like, it can be reprogrammed from the Arduino IDE open-source firmware. The finished clock is powered by a 5V USB mini-b connector that works with a computer.
You can also utilize Four Letter Word functionality. It comes with the word association database EEPROM if you would rather display words instead of numbers. Finally, an acrylic enclosure is available separately for those who would like to opt for it.