Relay square root machine
This is the project kickoff page for the Relay Square Root Machine project.
Project Description
Modern computers perform billions of operations very fast on devices that are vanishingly small. All this is beyond everyday comprehension. This has not always been the case. In the 1940s computers were built to compute mathematical functions and decode secret wartime messages using vacuum tubes and electromechanical relays. One example is Konrad Zuse’s Z3. Relays are more appealing than modern devices becuase they can be seen to change and they make a lot of noise. In this project I will construct a machine to calculate square roots, an operation that has long been available on any calculator, using relays, a technology that has long been outmoded. In doing so I bring this common operation into a human scale where every part of the process can be sensed directly, and in doing so I provide an opportunity for learning.
Background
I have long desired to use relays to carry out some computational operation. The machine in this project is a floating point unit that can calculate square roots to 8 digit precision using a floating point binary coded decimal representation. Numbers are entered using a rotary phone dial and displayed on an 8-digit nixie tube display, common in the 1960s. Each of the 400 or so relays in the system is associated with a light which lights up orange when the relay is energised. In that way a large matrix of lights will be seen to change along with an onslaught of clicking. In many ways this is an excercise for my ingenuity; I am designing math and logic operations using switches and this challenge will be rewarded in lights, sound and the fun that people have interacting with the unit.
I hope to display the finished unit at a number of art/tech venues.

I too am designing and building a relay computer. I don’t know how far I’ll go with the design or how complex I’ll make it, but I just have a burning desire to start doing it and expand on it. I’d be interested in learning how your project(s) have been going and how I can view them on the internet.
Dan.