Nixie tubes have been the go-to option for makers looking for retro display aesthetics for many years, because their distinct orange glow carries a lot of vintage appeal. But VFD (vacuum fluorescent display) tubes have been gaining in popularity recently and have different — though similar — appeal. Oskar took advantage of IV-12 VFD tubes to build this beautiful custom calculator.

VFDs work like a cross between Nixie tubes and CRTs (cathode-ray tube). These IV-12 VFD tubes have seven segments that glow in a teal/cyan blue color (thanks to phosphor) and work at lower (and safer) voltages than Nixie tubes. They are bright and readable, which is why VFD technology was popular for automotive dashboards for decades. In this case, Oskar used five of these IV-12 VFD tubes for a custom calculator.

Aside from those very distinct VFD tubes, this calculator also has a lovely wood enclosure and a nice-looking set of key caps for the mechanical Cherry MX Brown key switches. The enclosure is laser-cut plywood with a walnut veneer. Oskar mounted the switches on a 3D-printed base plate.

An Arduino Nano board reads the keypad input, performs the calculations, and displays the results on the VFD tubes. A custom PCB simplifies the wiring, including for multiplexing to the VFD tubes, power connections from a lithium battery charger module, and altering voltage through boost and buck converters.

This looks fantastic, but there is a caveat: it can’t display a decimal point. Some VFD tubes include a segment for that purpose, but the IV-12 model does not. Even so, the calculator is usable for people who can deduce where the decimal point should go.