MU 2801 – Making Music with Machines – A Term, 2022
By: Elliot Trilling, Colin Lysaght, Jack Aylesworth, Lillian Gallinoto, & Margaret Johnston
Rachael is a multipurpose player machine, mainly used to play the xylophone or marimba. Rachael is a series of servos attached to an angle iron welded frame. An important function of Rachael is that it is transportable. The frame is elevated above the instrument so as to not scratch the surface or damp the sound. With rubber feet underneath that sit on the keys outside of Rachael‘s range, the machine can be lifted with ease to relocate to another instrument. Rachael has an array of laser cut pieces, 3D printed mounts, and handmade mallets with colorful bouncy balls at the end. There are several screws holding the wood, metal, printed mounts, and servos together. The frame itself was measured out to fit to each key within the needed range, causing the mallets to strike each key. Any user of Rachael needs to be knowledgeable on MIDI in order to provide music for the machine.
The Process
There were several difficulties with building Rachael. For instance, the original plan involved 25 servos along the frame but the end result counted a total of 23 working servos. This is due to the quality of the servos purchased. Even though there were plenty of extras, many could not function as needed. Additionally, drilling holes into the iron, and the bouncy balls proved to be more difficult than anticipated. There were several split mallets, and misaligned iron corners. Once again, plenty of extras were purchased in the event of these errors.
Rachael was inspired due to several factors. For one, a team member had experience in percussion instruments and provided guidance through musical challenges. Within the time frame given, it also seemed that percussion style machines would be the most achievable while also being able to expand upon topics discussed within the class.
BOM for Rachael:
| Item | Quantity | Total Cost |
|---|---|---|
| Angle Iron Metal | 4 | $40 |
| Adafruit PCA9685 16-Channel Servo Driver | 2 | $34 |
| UL Listed 5V 3A power supply | 1 | $15 |
| Smraza 10 Pcs SG90 9G Micro Servo | 2 | $42 |
| 20 Pieces 3-pin Servo Extension Cable Wire | 2 | $22 |
| Wood Dowel Rods 12 Inch x 1/4 Inch, 50 Pack | 1 | $11 |
| Bouncy Balls, 100 pack | 1 | $15 |
| J-B Weld ClearWeld, 2 Pack | 1 | $13 |
| Zipties 40 pack | 1 | $5 |
| Total Cost (not including tax) | $197 |