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Signing UpStep 1: Materials
Electronic flickering candles, about $3 each from a hardware or department store
Photocells, one per candle
Toggle switches, one per candle plus one for power
Nine volt battery and holder
Speaker or output jack
Alligator clips, for testing
Enclosure, I used a junction box
Heatshrink tubing









































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http://www.instructables.com/id/How-to-Listen-to-Light/
The amplifier module helps a lot. With the setup I am using there is no need to put the light source and sensor in intimate contact inside a light tight box. Just a few cm of distance between the light source and the sensor is usually close enough to get a clear, audible, signal.
The fact that they all produce different tones makes me suspect that they have a lot of analog circuitry to them. I'm gonna try and pick some up tomorrow and see what they've got inside them.