VFD clock – A home-built clock from recycled calculator parts runs an ATmega328P on a 32.768 kHz crystal, drives a harvested vacuum fluorescent display with an HV5812 high-voltage driver, and keeps time with a steady 1 Hz pulse—all powered by a single AA battery or USB 5
The moment you notice it, the clock doesn’t look like it belongs on a workbench. It’s got the glow of a vacuum fluorescent display pulled from an old calculator. framed by copper pipe elbows for a deliberately handmade look. Underneath it, addressable RGB LEDs add a soft underglow—pretty enough to distract you from the real trick happening underneath.
The project centers on an ATmega328P microcontroller, running from a 32.768 kHz crystal. That crystal isn’t a styling choice; it’s the timing backbone. The chip’s counters divide the incoming frequency down to produce a steady 1 Hz pulse. the kind of regular beat that makes accurate timekeeping possible.
Time shows up on a VFD harvested from an old calculator. VFDs have a catch: they need rather high voltages to run. In this build, those voltages are generated using an HV5812 driver chip and supporting circuitry. The result is a display that behaves like old-school electronics—except it’s being fed by a surprisingly simple power plan.
Power comes from a single AA battery, using a transformer-based low voltage converter. If you’d rather keep it plugged in, the clock can also run off a USB 5 V power supply. That same USB setup charges the NiMH AA cell while it’s available, with help from an LM2576-ADJ buck converter.
There’s a practical lesson running through the whole build: the clock isn’t just telling time. It’s also showing what you can squeeze out of parts that already exist—an approach the maker says taught [Sciter_] plenty during construction. It’s also not the first time someone has put together a clock using second-hand VFDs. suggesting this isn’t a one-off curiosity so much as a recurring kind of home tinkering.
If you’re the type to keep seeing old display tech and thinking it could become something else, the invitation is clear. Send tips, and keep reusing what still has life in it—because in this case, the life is literal: one AA cell, a 32.768 kHz crystal, and a recycled VFD lighting up the seconds.
VFD clock ATmega328P 32.768 kHz crystal HV5812 driver homebrew electronics single AA power USB 5V charging LM2576-ADJ NiMH vacuum fluorescent display
So it’s just a calculator display clock but with like a AA battery? Kinda cool.
I don’t get how one AA can power a whole high voltage VFD like that. Also the RGB underglow seems unnecessary, but I guess people like the glow.
Wait, the 32.768 kHz crystal is what keeps time right? My buddy’s watch uses quartz too so I’m thinking it’s basically the same thing, just with extra steps and more wires. Still wild it charges the NiMH off USB at the same time though.
This is gonna sound dumb but isn’t 5 volts basically enough to run the VFD directly? Like why do they need that HV5812 driver unless they’re doing it wrong. Also copper pipe elbows??? feels like it’s gonna short out if you look at it wrong, lol.