I've been working on the circuitry to operate the solenoids as well. The circuit is essentially a 48-bit shift register (but I am only using 41 of the bits). It accepts a serial signal and converts it to a parallel signal that goes out to the Darlington transistor array that operates the solenoids. The shift register has a latch on the output that allows me to control when the signal gets output to the solenoids.
This is how it works: A string of bits is sent into the circuit, instructing it about which solenoids to activate. For example, to activate the 2nd and 24th solenoids, the string of 48-bits (0's and 1's) would be sent in with a '1' located in the 2nd and 24th position, and '0's' everywhere else. Once all the bits are sent into the device, the latch is activated to output the signals, turning on only the 2nd and 24th solenoids.
I am using the Arduino microcontroller as a bridge between the Pure Data software and the shift register circuit. I've modified and added to the Arduino code from this page to accept up to six notes and convert those notes into a string of bits to send to the shift register to turn on the appropriate solenoids. The Arduino USB board I am using powers itself through the computer's USB connection and is able to provide enough juice to power the shift register as well.
Over the winter break I upgraded the RAM on the $8 computer I had bought from Value Village. I've installed Ubuntu Linux, Pure Data and Arduino software on it (all open source and free). The computer will be integrated into the device to run the Pure Data code that will listen to the room and determine which notes the device should play.
I bought a car window motor and a windshield wiper motor from Princess Auto. Both motors provide quite a bit of tourque, so I'm hoping one of them will be able to power the bellows.
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