The Ultra-Satisfying Flapulator Split-Flap Calculator

There is something incredibly satisfying about clicky mechanical movement that you just don’t get from digital equivalents. Split-flap displays are the perfect example. Are they practical? Not even a little bit. But they are just so gratifying to see and hear in action. Knowing that, Applepie1928 used a split-flap display to build the Flapulator calculator.

Flapulator is a calculator, like the app on your phone. But instead of a boring LCD or OLED, it has a mechanical split-flap display. It has six positions, so it can display whole numbers as high as 999,999. I don’t know about you, but that is generous enough to cover all of my finances.

That split-flap display is certainly the star of the show, but Flapulator does have some other nifty features. The entire thing, including the key caps, is 3D-printable. The Gateron mechanical key switches are hand-wired. And there are colorful LEDs (red, yellow, green, and blue) that act as indicators for the current mathematical operation, since the display has such limited real estate.

A Raspberry Pi Pico 2 monitors the keypad input and does the number-crunching. It also drives six FS90R continuous rotation servo motors, which spin the split-flap assemblies. Six Hall effect sensors detect magnets for the home positions of those assemblies. An Adafruit PowerBoost 1000 Basic deals with the 18650 lithium battery and its charging.

Aside from those quirks, Flapulator is still a calculator that does calculations. Using it is like using any other calculator, just a lot more satisfying (and maybe a bit slower).