The Venn diagram of objects you can eat, and objects from which digital synthesizers have been made is one with minimal overlap. But thanks to Gadget Gangster's Jeff Ledger and his Bananaphone touch capacitance synthesizer, that union has gotten a little bigger.
Apparently inspired by a recent Kickstarter project (almost certainly the MaKey MaKey, which enables bananas and other objects to be put to use as a computer interface devices), the Bananaphone is instead built using some of Gadget Gangster's own add-on kits based around the Parallax Propeller microcontroller.
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With the addition of some bananas, an amplified speaker, as well as a 220-ohm resistor and some alligator jump wires from Radio Shack, Ledger was ready to construct the Bananaphone.
Employing an identical principle to the MaKey MaKey, touching the banana keys increase the capacitance in the connection points, increasing the resistor-capacitor time constant monitored by the microcontroller, which in turn decides if the synth should play tones accordingly. A line of code can be altered to establish a cutoff frequency according to the length of the jump wires and the ripeness of the bananas, so that sounds are heard when the bananas are touched.
Though obviously less versatile than the MaKey MaKey, the Bananaphone ably demonstrates how capacitive sensing can be put to use with relatively few electronics.
You can see and hear the Banaphone in action using your own in-built auditory and visual sensors via the exceedingly brief video presentation below.
Source: Gadget Gangster