The simplest thing to do might be to use a relay to energize your solenoids. That way you don’t have to monkey around with electronics. The relays from SainSmart don’t require any special wiring and can be powered from an arduino or RaspberryPi. If you’re just using the solenoids for a quick on/off you can wire the solenoid through the relay to the power source without any other wiring. If the solenoid is going to be “on” for a while you will probably need a resistor in line to dissipate some the power. You can probably find a relay board (e.g. SainSmart) that can control 8 things for under $10. The problem is that a relay makes a small click sound, but a solenoid does as well. If you listen to the video below, you can here the relays/solenoids in the background. I’m currently using the Sparkfun 5V relays for a music projects, they’re pretty small but work quite well. “Push” type solenoids are often easier to use for music stuff.
Here is a project I did using a RaspberryPi, relay board, solenoids and a Korg Koass Pad. This would work just the same with an Arduino. I’ve used various solenoids as percussion sources, they work very well.
Picture: RaspberryPi->Relay->Solenoid->KorgKaossPad
youtube video of above project
If you want to get really simple, scrap the arduino and get a doepfer midi to gate, then you can get a usb to midi and camera connection kit and run the whole thing from your iPad! No software to write, just midi (you can sequence your solenoids using Ableton Live or MaxMsp. I have this setup working with the 5V sparkfun relays.
