Arduino MIDI Glockenspiel with TIP120 Transistors
Motivation
This was a project done in collaboration with Enrico de Trizio, a New York based pianist, composer, and music producer. Similar in many ways to a project I did a couple years ago with a smaller glockenspiel, this iteration allowed me to improve on many ideas. Working closely with Enrico, a musician, helped me keep a focus on musicality and not just the engineering challenges.
Some of the notable differences from my previous build include:
Using “Hiduino” to make the Arduino Mega a “class compliant USB-MIDI device.” Meaning you just plug it in and it pops up as a MIDI instrument; no more using Loop MIDI and Hairless MIDI.
Using transistors to fire the solenoids versus relays, meaning much less clicking noise.
Adding multiple features to increase the musicality of the instrument, such as damping and dynamic control.
Process
Strikers
The components that strike the keys of the glockenspiel were very similar to the design used in my previous two builds. Small 5V solenoids from Digikey.com are clipped into 3D printed holders that then slide over an L-shaped piece of angle aluminum. Unlike in past builds where these were held to the aluminum with set screws, I just designed the slot smaller so it is held in place with friction. Since I switched from PLA plastic to PETG, there will be less deformation of the plastic overtime and this will hopefully remain secure.
Other differences include the inclusion of an LED on each of the strikers. These are wired, with a series resistor, in parallel with the two wires leading to each solenoid. The LED is mostly contained in the 3D printed plastic, so when they blink, the light is directed downward on to the key. The resistor and legs of the LED face up, so I printed a small cap that slips over the top, hiding the wiring. The inclusion of this LED allowed me to also make an arch in the middle of each component, which all the wires from the solenoids run through, keeping them from dropping down on the keys.
Transistors
In previous builds I’d used relay modules to trigger the solenoids, mostly for the simplicity of wiring. A huge downside of the relays however is the loud click they make each time they fire. For this build I used TIP120 transistors instead, eliminating all the noise, but increasing the build complexity.
Damper Bar
.
Hiduino
.
