The future of music?
Musical Swings, Version 1
with Gemma Ward
and Melissa Norelli Hassan
For More on this Project
Cultural life in downtown West Palm Beach was considerably enlivened for a short period last year when a vacant lot on Clematis Street hosted a traveling exhibition titled The Swings. This interactive art project is a swingset with nine seats, each of which triggers a different set of sounds when a person swings on them. The result of nine people swinging at once can be a sort of a collaborative musical performance.
Inspired by this, a motivated student, Gemma Ward, and her teacher, Melissa Norelli Hassan, of Delray Beach's Unity School wanted to reproduce the project with their school's own playground swingset, and experiment with how cooperating to make interactive art can have an effect on those using the swings. Mrs. Hassan was one of my students in last year's Introduction to 3D Design class at Hacklab North Boynton and thought I might be able to help them realize their project.
They proposed that Gemma would create the software using the Scratch visual programming environment if I could figure out a way to capture the action of the swing and provide inputs to Scratch. I did a bit of research and discovered a project named S4A, or Scratch 4 Arduino, that uses an Arduino with S4A's firmware to act as an intermediary between the physical world and Scratch code running on a PC. The Arduino reads its inputs continuously and sends values up the USB connection to the PC, and listens for values sent by the PC with which it updates its outputs.
The original traveling installation was a custom-made set of rigid-arm swings, which simplifies sensing their motion somewhat. Since the rigid-arm swings are confined to moving on a plane, it's easy to detect angle by, say, optical or Hall-effect sensors without needing to worry about the arm crashing into anything. But at Unity School we had an ordinary set of eight identical swings on chains, which permit twisting and out-of-plane motion. So I decided to detect swinging with an old favorite of mine: solid-state accelerometers.
Given that I could easily read up to five ADCs using S4A, it made sense to buy some accelerometer breakout boards that provide acceleration signals as analog voltage levels. I chose Adafruit's ADXL335 board, using the Analog Devices chip of the same part number, which also includes a LDO regulator so that it can accept 5V power. Sparkfun has a similar product without the LDO.
To attach the accelerometers to the swing chains in a robust way, I designed a small plastic pod with a boss extending through a link of the chain and secured with a 1/4-20 bolt. These pods were 3D printed on Unity School's Makerbots.