Creator Måns Jonasson wanted to make an automated musical device, so he obtained (what else?) a toy piano, with the requirement that it could play at least two octaves. After stripping it down to its components to find 30 “strings,” or in reality tuned metal rods, he then designed and built holders for 30 corresponding tiny 5V solenoids. Each solenoid was set up with a MOSFET, diode, and resistor, allowing the project’s Arduino Mega controller to activate everything with the help of a MIDI shield.
With the concept proven, the instrument was seemingly done, or at least in its final stages. However, with a rather messy electronics setup and 30 individual solenoid mounts, the machine was quite glitchy. Instead of shoving components into the little piano, slamming the lid and calling it done, Jonasson went back to the drawing board. He created holders for the solenoids in sets of eight, and found out how to control eight of them with a single motor driver board — outlined in this separate write-up. These modifications improved both the mechanical and electrical assembly, resulting in something that can play plinky tunes automatically under MIDI control.
Be sure to check out the build process, along with a short concert featuring the Super Mario Brothers theme song in the video above.