While LEDs have more or less taken over the indicator lighting game, other more now-exotic indicators were once used to output numbers and symbols. Although Nixie tubes are fairly common in new vintage-style builds, this four-digit clock instead uses beautifully bluish-white VFD tubes to tell the time.
Per the build’s photo log, the tubes in question are “very rare DT-1704A” units, which have neither a grid or segment supports. This design produces a simple and unique appearance, but also means that multiplexing is out of the question. Driving the four tubes therefore required a total of 28 2N3904 transistors and a Mega Pro Embed with an ample number of GPIO pins. A custom power supply setup is used to produce 27V for the tube segments, 1.3V for the filaments, and 6V for the Arduino board
The time is set via a GPS unit, and when powered up it displays noon + the time zone offset before being synchronized. The wide array of connections needed to control the clock are laid out on perfboard, with wires organized in a way that will make maintenance easier. All of this circuitry takes up a bit more room than a normal clock, meaning to a bit of a redesign during the build process, and a sizable enclosure when done.