If you like to listen to those “deep focus” soundtracks that are all ambient and relaxing, then you’ve heard a tongue drum in action.A tongue drum, or tank drum, is a unique percussion instrument traditionally made from an empty propane cylinder — though purpose-built models are now common.Several tongues are cut into one end cap and weighted to produce specific notes when struck.
As with all instruments, playing a tongue drum is an art.To simplify that, Jeremy Cook built a robot capable of playing a small tongue drum.When robotizing a percussion instrument, it is common to use solenoids and that is what Cook did here.
Solenoid actuators like these move linearly and can strike with pretty decent force, which makes them a good choice.Cook’s drum has eight tongues, so his robot has eight solenoids held by flexible friction arms mounted onto a C-shaped laser-cut MDF frame.PVC pipes actual as the vertical structural supports on that frame.
An Arduino Opta Lite micro PLC sends power to the solenoids through an Arduino Pro Opta Ext D1608S solid-state relay expansion module, which contains eight SSRs that can each handle 24VDC at 2A.To tell the robot what tunes to play, Cook added a MIDI input that comes through an Opta-compatible I2C and serial adapter of his own design.That adapter is available for sale on Tindie if you want one. The MIDI input can come from a something like a keyboard for real-time manual control, or it can come from a PC for playing pre-written (or algorithm-generated) ambient hits.
If you attended the Orlando Maker Faire last year, you may have had a chance to try this robotic tongue drummer for yourself.