My installation DIVE
, in its ideal setup, requires hundreds (or even thousands) of speakers, each one emitting its tone, variable in frequency sensing the light reaching the speaker. Every 'pixel' of the grid then should be indipendent.
Doing all of this digitally (connect sensors to a pc, and then send the audio through thousands of channels, to thousands of amplified speakers) would have been hard and very expensive.
So i needed to find the cheapest, smallest light-controlled oscillator that could drive a speaker with a minimum power consumption.
After some research on the web i've found lots of schematics. None was completely suitable for my situation, but I easily designed the square/triangle wave oscillator needed out of them.
It is NE555 timer chip based, it has a LDR (Light-Depending-Resistor) that controls the frequency, and a trimmer for tuning (because every speaker should deliver slightly different frequencies). The global frequency range is determined by the capacitor value, so it is the only component that may change.
The first oscillator I built, for testing purpouses, had a power supply and speaker plug, an on/off switch, a socket for the capacitor (to mark down all the useful values) and two potentiometers: one for tuning, to adjust the volume, because this tiny thing is LOUD!!!.
I kept this prototype for demonstrational purpouses during exhibitions.
The final osc has not all of these features. It is directly soldered to the speaker and the power supply, has a fixed output volume. This way could fit in a 6x8 or 6x7 holes perfboard and attached behind the speaker.
All this sound generators so are sticked to the speaker and connected in parallel to a standard desktop-pc