Project 1: Photoresistor Instrument

For sometime now, I have been very fond of this pen-type light fan, using it in performances to play guitars or xylophones,

...or mandolines.

But I had never been able to utilize its lighting aspect, except as a beautiful luminous ornament that lights up the often dark spaces of concert halls. So for the first short project of my physical computing class, I decided to use what I have learnt so far and build an instrument which takes advantage of all the features of this light fan-pen. What I came up with is an instrument that uses photoresistors to make sound. It looks like this from outside:

and when you open the top lid, it looks like this:

The circuitry is pretty simple. It connects five photoresistors to the digital inputs of an Arduino via a breadboard. There is also a potentiometer to control the volume, a speaker which extends out from a hole in the lid, and 9v battery as the power source.

The program I wrote assigns a specific pitch to each of the photoresistors. Since there are five of them, I used a pentatonic scale.

The case is a cheap plastic box that you can buy in any 99c shop. I made five holes in its rear to stick the resistors out.

In order to control the sensitivity of the resistors (so that it won't start sounding every time the room light is turned on), I made little covers using a pencil eraser (using different colors for each resistor/pitch):

And that's it!

The rhythm pattern changes according to the light pattern of the fan.

Overall it plays well, but the sensitivity of the sensors is still a problem. Although it is basically functional in a dark room, where the only light source is the fan, it becomes very unstable in other conditions. I attempted to adjust that by changing the threshold for each of the resistors in the program, but maybe distancing the holes in the case could be another solution.

Also, the next step would be to program the light pattern of the fan, which consequently determines the possible rhythm patterns. It would be like implementing the score into the instrument itself -- with different combinations of pitch pattern for the resistors, and rhythm pattern for the fan, one could obtain an instrument to which the overall structural boundaries of a piece is embedded, while still being open to improvisational possibilities