System 7

System 7 is a musical instrument that creates sounds based on light. The entire unit can be explained in two parts – ‘torch’ and ‘beepers’. The beepers are units that produce sounds according to the intensity of light from the torch or ambient light.




There are seven beepers in System 7. Each of them is an individual circuit that comprises a light dependant resistor (LDR), a relay and an ATtiny85 chip. The ATtiny is programmed using a custom made programmer. The LDR picks up any light and the relay is activated and deactivated rapidly according to the value the LDR gives.



The seven beepers are placed equidistant from each other on a meter long platform. The torch is attached to a motor and can move on a track that it sits on. The track is 20 cm above the platform on which the beepers sit. The torch’s light intensity and movement on the track are controlled via a raspberry pi that listens for UDP signals on a local network.


System 7 allows users to generate sounds either by adjusting the ambient light or my controlling the torch via the network.

The track was a challenge. I decided to use a design by peter_ from thingiverse, but had to modify it to due to the material not being strong enough to hold the motor’s weight at the centre. My modification was to add support bars for each side of the track.
The picture below shows the original problem.


System 7 was part of Performing the System, a new media music performance at Lasalle College of the Arts by Brian O’Reilly and Andreas Schlegel.