[tvst] has an interesting take on a sequencer. His design uses coins on a turn table to trigger midi events in a loop. There are four tracks available, each having its own sensor above the spinning platform. The sensors consist of an IR transmitter and receiver setup as a voltage divider. When something passes below the IR transmitter and reflects the infrared waves back up to the receiver, the output of the sensor moves to digital high. The four sensors are connected to an Arduino which is used in conjunction with ttymidi, which converts the Arduino data into midi events.
We like projects that provide a more tangible interface for the user. Coins work well for this setup. They reflect infrared enough to trigger the sensors, and they’re easy to pick up and move without upsetting the rest of the tracks. It would be great if this could be expanded to differentiate between coins (pennies versus dimes, etc.) in order to increase the resolution from four different events to eight or more. Check out the video after the break.