12/9 - 12/15

A project log for Bot-thoven: A Robot Musician

Designing a Servo Motor Based Mallet System to Generate Musical Expression in Instrument Playing Robots

Jason P.Jason P. 12/12/2019 at 14:210 Comments


I will need to take what I have learned from familiarizing myself with the PCA9685 library and write code to have the servos appropriately strike a xylophone key. 


I used the example “Servo” code from the Adafruit Library as a baseline to add upon it and write my own code. I had to find the correct PWM values for my servos to correctly strike the keys and update the code to play a tune at varying dynamics/articulations. 


After familiarizing myself with the PCA9685 library last week, I was able to write a code to control multiple servos (2 as of now) using a single Arduino pin. After being able to strike a xylophone key with my servo-mallet system, I added improvements to my code to achieve the following:  

A video can be found here where a robot is playing a two-note passage with a mix of single notes and chords (two notes at once). The passage is played four times, with the articulation changing from a lot of ringing to a muted sound, the tempo getting slower, and the dynamics becoming softer.

In terms of my budget, I have used $114.70 so far. The table above shows the details of my purchases I have made for my project as of now. Once I order an additional PCA9685 in the Spring, my total budget should sum up to $129.65.


I will now need to build more servo-mallet systems so that I can test my code with more keys (and therefore play more interesting musical passages). While testing, I also realized that the zip ties may not be the best option to attach the mallets on the servo, so I will need to try using other methods such as a rubber band.