If you’d like a split-flap display with numbers and letters, options tend to be quite expensive. This though was no problem for hacker “scottbez1” who reports that after “only” two-plus years of work, he has produced a split-flap assembly that plugs into an Arduino Uno as a sort of external shield.

The device employs inexpensive stepper motors to click through letters, numbers, and even some punctuation, using cutout PVC ID display stock to show the characters. Cleverly, the PCB he designed for it can function as a motor driver or be split in two to function as a sensor board.

I’ve always loved these electro-mechanical displays, but you can’t buy them for a reasonable price, so I figured I’d try making them myself (plus it’s more fun that way!). Ultimately I wanted to design a split-flap display that can be built at home in small/single quantities and can be customized and put together by an intermediate hobbyist for not too much money.

The design I settled on uses PVC ID badge cards for the flaps, store-bought vinyl stickers for the letters, and is driven by a cheap 28BYJ-48 stepper motor. The enclosure and moving parts are all made from laser-cut MDF, which can be easily ordered online. To control them, I designed a driver board that can be hand-soldered and plugs into an Arduino like a shield.

The entire build story can be found here and more details including Arduino code are available on GitHub. If you’d just like to see and hear it flapping away, check out the video below!

Let’s face it, there’s something magical about split flap displays. Common throughout older airports and train stations, the electromechanical devices are used to show changeable alphanumeric text (e.g. arrival and departures), fixed graphics, or in Jonathan Odom’s case, Internet slang.

With three-letter abbreviations like BRB, LOL, OMG and SMH commonplace in today’s smartphone and online conversations, the Maker decided to bring text and animation back to its mechanical roots with his own split flap display. As you can see in the video below, an arcade button under each frame enables him to cycle through all 26 letters to spell out his thoughts in acronym form, while a fourth frame reveals an animation of the very first cat video (by Eadweard Muybridge).

Structurally, the DIY gadget consists of 3D-printed parts, laser-cut acrylic for the tongue, flaps, brackets, wheels and spars, and plywood for the base. Everything is assembled by hand using screws and nuts. In terms of electronics, an Arduino Uno and Adafruit Motor Shield control a set of servo motors.

The configuration I built has four modules, but you could build as many as you want and connect them. The Arduino motor shield has 16 channels, so if you want more than than that you’ll have to find another means of controlling the rotation.

Want one for your desk? You can find all the necessary files and code on its project page, and see the final product in action below!