Jon Bumstead has created an awesome Arduino powered 13 note midi harp after receiving funding from the optics group Spectra at Washington University in Saint Louis.
Watch the video below to learn more about the midi harp’s construction and design. Full instructions on how to creat the harp have been published to the Instructables website, via the link below.
This laser harp has thirteen strings. To generate these strings, a laser beam is moved to thirteen different position (for thirteen different strings/notes) by moving a mirror galvanometer. The mirror galvanometer, or galvo for short, is a mirror that can quickly move to different positions depending on a control voltage that is sent to it. At the end of each laser beam is a photoresistor that is used to detect if a beam is blocked. When this is detected, a note is played. I also needed the laser beam to be turned off when moving positions so that it appeared as though there were thirteen distinct positions and not a continuous sheet of light.
To generate these signals, I used an Arduino. One of the greatest challenges of the project was creating an analog output that was fast enough to move the galvo (and laser beam) so that it appeared like there were really thirteen different beams and not a single beam being moved to different positions. I constructed a 4-bit R2R digital to analog converter (DAC). The digital output of pins 8-11 incremented thirteen times (for the thirteen positions), and the DAC generated an analog voltage ranging from 0 to 4V. I then amplified this signal and ran it through a differential amplifier to get an analog voltage from around -7 to 7 volts for the galvo. The laser diode was synchronized with the galvo using the Arduino.
If you enjoyed this article you are sure to enjoy how to build your very own Arduino wind speed meter or anemometer project which is easy to build with basic Arduino skills.