A Butterfly in an Analogue Computer

by Wolfgang Spahn
20 Nov 2021
Piksel 21

A workshop for an Chua Circuit with in an analog computer to generate chaotic signals, noise and sound. This circuit generates chaotic signals over a wide range of frequency therefore it is an interesting device for noise and sound art, performances and installations.

In the 1970th Edward Lorenz developed a mathematical model for the weather and climate prediction, the Lorenz Attractor, a strange attractor with chaotic and fractal behavior and sensible initials conditions, that in the end could lead for example to a tornado in Brazil - the so called Butterfly Effect. At that time it was not possible to compute this module with in an analog computer, the chips for doing the multiplication were to noisy. That’s why in 1983 Leon O. Chua introduced a much simpler circuit (no multiplication) with the same chaotic behavior, the Chua Circuit.

The Analog Computer Confetti is a modular system that makes it possible to perform all kind of computations and operations on base of electrical voltage. This stack able modular electronic analog computation system was and is still developed by Wolfgang Spahn since 2015.

Chua’s Circuit can be made out of two modules of the analog computer Confetti, aGyrator and the Chuas Diode. The analogue computer Confetti is a modular system that makes it possible to perform all kind of electronic computations.

In the workshop we will learn the basic functions of an analog computer. We also will build the two main components for an Chua Circuit as modules of the analog computer Confetti: a Gyrator and a Chua Diode. With these two modules we will create the Chua Circuit to listen to the butterfly in our tornado.

Part 1: Background, Introduction and Build

About Anlogue Computation
... and Chua's Circuit

(graphic by Chetvorno, CC0)

Build an Analogue Computer

Part 2: See, Listen and Discover

writing a progrmm for an analogue computer

“patching is thre new programming”“

X-Y-Z Visualisation

Voltage Control