Computers & Mobile Craft & Design Technology
An actual Turing machine

Well, almost. Mike Davey wanted to outfit his gorgeous realization of Alan Turing’s foundational computer-science thought experiment (Wikipedia) with an infinitely long tape, but couldn’t afford to buy one. So he settled on a 1000-ft roll of white 35mm film leader. Can’t say I blame him. Have you priced infinitely long tapes recently?

All joking aside, this thing may be the most beautiful piece of kinetic art I have ever seen. It has a Cartesian robot to draw 1s or 0s on the tape as needed, a rolling felt-covered drum for erasing symbols, a camera that can recognize what symbols have already been written, a bank of white LEDs to provide illumination for the camera, and a beautiful custom control panel.

Mike himself says:

My goal in building this project was to create a machine that embodied the classic look and feel of the machine presented in Turing’s paper. I wanted to build a machine that would be immediately recognizable as a Turing machine to someone familiar with Turing’s work.

Although this Turing machine is controlled by a Parallax Propeller microcontroller, its operation while running is based only on a set of state transformations loaded from an SD card and what is written to and read from the tape. While it may seem as if the tape is merely the input and output of the machine, it is not! Nor is the tape just the memory of the machine. In a way the tape is the computer. As the symbols on the tape are manipulated by simple rules, the computing happens. The output is really more of an artifact of the machine using the tape as the computer.

So, in summation: Wow, Mike. You win. I’m never making anything again. [Thanks, David Jakopac!]


I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and My work has also appeared in ReadyMade, c't – Magazin für Computertechnik, and The Wall Street Journal.

View more articles by Sean Michael Ragan