How to build a split flap display

Split flap displays are the boards that used to greet you at train stations and airports — rows of mechanical flaps that spin and snap into place to show departures, arrivals, destinations. That sound, that motion, that slight impermanence. They disappeared from public spaces decades ago because LCD screens are cheaper and more flexible. But they never stopped being beautiful. And now that 3D printing and cheap stepper motors exist, building your own is genuinely within reach.

flip forward is a project to make that happen. It covers everything: the mechanical design for individual modules and full installations, the electronics and firmware to drive them, and a platform to control them remotely. It's a side project, built by one person in Germany — not a company, not a product. The goal is to make building this possible for as many people as it can.

What you can build

The design scales across a wide range of budgets and ambitions.

At the low end: a 3D printer, a 28BYJ48 stepper motor, and a handful of screws. That's genuinely everything you need to build a working module. All the models and instructions are here.

At the high end: NEMA stepper motors (roughly ten times more powerful, faster, more reliable), sheet metal cases manufactured to spec, professionally printed flaps, and modules mounted on a metal backboard. That's what the displays on the flip forward YouTube channel look like — finished, not prototype.

You can start at the bottom and move up piece by piece. The design is the same throughout.

How it connects

Scaling a multi-module installation is clean by design. Modules connect via small connector boards that snap between them, with no cable runs and no wiring harness. Four modules or forty, the installation stays tidy.

Every module runs firmware with a small web UI, so a display can be controlled from a browser on your phone over WiFi without installing anything. Two other ways exist. play.flipforward.de runs virtual twins that behave exactly like real hardware, so a display can be built, its content tested and its alphabet designed before any modules exist. local-control is an open-source desktop app for macOS, Windows and Linux that finds displays on your local network and handles firmware updates, logs and calibration. All three work out of the box and all three are free. Controlling Displays compares them.

Using this guide

In a hurry? TL;DR condenses the whole system onto one page. Otherwise the docs follow the order you'll build in.

Specifications has the numbers on one page: dimensions, weight, power, temperature, flap counts.

Build a module covers one module from parts to first power-up: Sourcing, Flaps, Parts Preparation, Module Assembly, Electronics and Helpers & Accessories.

Build a display is everything that only matters once there's more than one: Planning an Installation for enclosures, load, service access and failure behaviour, Connector Boards for the three boards that link modules, and Wiring & Power for backboards, power groups and addressing.

Control is Controlling Displays: the module's own web UI, play.flipforward.de, and local-control.

Built in Germany, open to the world

flip forward is designed and built in Germany. Parts are sourced from European suppliers where possible, and the shop (coming soon at shop.flipforward.de) will ship PCBs, hardware kits, and flap sets from within the EU — no customs for European builders, fast shipping.

Until the shop is live, modules, boards and flap sets can be ordered directly by mail at hello@flipforward.de. That's also the address for installations, custom alphabets and anything that needs a quote.

Licensing

The hardware design, published parts, and interfaces are licensed under CC BY-SA 4.0. You can use, adapt, and redistribute everything freely — including commercially — as long as you give attribution by linking to flipforward.de and naming flip forward as the source.

The firmware is not open source at this time, as it contains logic tied to play.flipforward.de. Pin-out headers for both board versions and a minimal firmware example will be published in the future. The firmware itself is and will remain free to use.