This Guy Built His Own XXL Split-Flap Display

Split-flap displays used to be mundane vessels of information located in places like train stations and airports. They were popular because they served a utilitarian purpose relatively reliably at a reasonable price. But they became obsolete once CRTs and then LCDs reached low enough prices. Today, split-flap displays are no longer mundane or utilitarian, they’re hip. Adam G wanted to be hip, so he created his own supersized split-flap display.

You can still get new split-flap displays, but there are only a couple of companies manufacturing them. Most that you see are vintage. In both cases, they tend to be pretty expensive. Adam G didn’t want to spend a lot of money, so instead he spent a vast amount of time building this.

Split-flap projects like this have become pretty common, but most are small. Adam G even built a small one himself, based on existing design. But this new one is big — similar in size to what would have shown train departure and arrival times back in the day. This new one has 3 lines and 15 characters per line. I’ll save you from doing the calculations: that is 45 flappy wheels in total. On top of that, Adam G added lots of extra characters beyond the typical alphanumeric set.

Each character requires two important components to work: a stepper motor for rotation and a Hall effect sensor to find the home position. To simplify wiring and construction, Adam G designed the display to be modular. Each module contains a flap wheel, a stepper motor, a Hall effect sensor, a custom PCB with stepper driver and sensor connection, and a 3D-printed enclosure.

Those modules all attached to a DIN rail on a backing board. The rail provides power and also a data bus that connects to the central controller: a Raspberry Pi single-board computer. The Pi hosts a web interface that Adam G can access to set the message on the display.

Best of all, this whole project is open-source and you can build your own. Adam G targeted a build cost below $1,000, which is very reasonable for a display of this size and capability.