I always liked the way relays make sounds when clicking on and off. That gave me the idea of using them as a drum machine. I gave it a try and Percussus was born. To control the relays I used a midi interface with a drum sequencer program. One relay is wired as a buzzer, that is, you connect a normally closed contact in series with the coil. A capacitor across the coil softens the tone. The relays are all different sizes and each make there own distinctive click-clack sound. A guitar tuner pickup amplifies the sounds through a homemade guitar amp. Now I just have to learn how to play the drums. A sample of the click clack of little relays can be downloaded here. Website on the project is here. I also did something similar with hard drives. A Instructable (Hard drive after life) shows the process with a different midi interface.
