This Unique Seven-Segment Display Uses a Single Motor to Change Its Digits
For many years now, hobbyists have been trying to come up with increasingly unique and novel ways to display information. These have ranged from giant LED matrices to fun machines that rotate plastic panels in order to create various shapes.
In this project created by Instructables user gzumwalt, he was able to build a large seven-segment panel that utilizes seven plastic panels which raise up or down to show a digits. However, unlike many other designs, this one only requires a single stepper motor instead of seven, making it much more easily scaled and cheaper overall.
The core of the single motor electro-mechanical seven-segment display is a pair of rotating wheels at the center. Each one contains a special track that has ridges and valleys that move an arm further up or further down, similar to a record player's stylus.
A mere deflection of 3.5mm in this grove causes the corresponding panel to flip its orientation by 90 degrees. There is a total of ten individual positions that allow for the device to show numbers between zero and nine in that order. The rate at which the panels move is controlled by adjusting how quickly the wheels rotate.
With the design in Fusion 360 completed, it was time for gzumwalt to move onto the task of fabricating everything. He began by 3D printing each part, and after painstakingly filing down each ridge on every gear, he moved onto the assembly step.
The two grooved gears had bearing installed to reduce the friction they experience whilst spinning. Next, pins made from music wire were slid through each panel and their socket in the chassis to anchor them in place. And finally, a single 5V stepper motor was set in the middle in order to rotate the drive cog.
Once the seven-segment display had been constructed, the next and final step was getting the stepper motor to move at the correct rate. An ESP32 advances the motor's rotors by setting certain coils high based on the current position. This process continues indefinitely within a while loop until power is removed from the system.
This demonstration video below showcases how smoothly this display works considering its simplicity. You can also view its write-up for more information on how it was built, along with the files used to create each piece.