Watch Television the Old Way with an Arduino-Powered Mechanical TV

What is a mechanical television?

Before the advent of display technologies such as liquid crystal, organic LED, and even cathode ray tubes, viewing moving pictures was a lot more mechanical in nature. One of the earliest methods for displaying an image was by using a rapidly changing light that shines through a series of holes to create a persistence of vision effect. Since each hole on the spinning disc is slightly lower than the other, the illusion of horizontal lines can be generated. Columns are created by rapidly changing the light's color as the hole passes over it.

Previous mechanical TVs used analog technology that essentially used a reverse process to capture areas that were lighter or darker on a subject and then transmit the analog values over a wire. However, the YouTuber who goes by Science 'n' Stuff wanted to create a much more advanced version that uses an Arduino Due and RGB LED to display movies in crisp, colorful detail.

Designing the machine

The main component of a mechanical television is the spinning disc, and this project's creator constructed his out of a thin plastic panel by cutting several center mounting points, a single synchronization hole, and then 32 holes around the outside to produce the image. A small DC motor sits at the center of the wheel to spin it, while an IR sensor is positioned along the path of the synchronization hole as mentioned previously to send a signal whenever the wheel has made a full rotation. An Arduino Due is connected to the motor via a brushless driver and it also outputs 12-bit audio via one of its two onboard DACs. "Movies" are read from an SD card and shown with a single high-powered RGB LED.

Producing an image

After an image is read from the SD card, it needs to get converted into a series of light pulses. Starting with the pixels at the top left, this first row is broken up into 96 columns. Because each row corresponds to a single hole in the disc, every pixel gets shown for a very brief amount of time. Sound also plays while this happens via the mono speaker on the front of the enclosure.

Watching TV

This mechanical television runs at 25 fps and spins the disc at 1500 RPM in order to match the digital camera's framerate. Once the machine is running, the resulting images look incredible for something that just pulses light quickly through a series of cutouts in a disc. You can see a demonstration of how this device works here, and you can also view a more in-depth look in this video.