How is it controlled?
A tiny computer called "Raspberry Pi Zero W" is the brains of this laser harp. It is wired up to the lasers and sensors. We have written scripts to control the lasers, sensors, and speakers, which you will download onto your Pi Zero.
Do I need to hook it up to a computer to play music?
This project is entirely self-contained -- no external computer is required. The Pi Zero and your circuits handle everything! You will want to hook up the Pi Zero to a display, keyboard, and mouse while you build things. Once it's all set up, you can unplug your peripherals, connect the Pi Zero to a USB battery pack, and take this instrument on the road!
How powerful are the lasers?
The laser beams used for 'strings' are cheap and of similar quality to laser pointers (e.g. those used in pet toys and for business presentations). So, not very powerful! Just like with laser pointers, you won't be able to see the beams without some kind of fog or dust. But, don't worry, you will see the dots on your fingers while "strumming". Practice laser safety -- do not look directly into the beams! Children should not build or use the harp unattended.
How should I practice laser safety during use?
As mentioned, adult supervision is a must for any project involving lasers. Do not let children build or play this harp unattended. Young children especially might be tempted to "explore" by sticking their eyeballs into the path of the laser beams. Do not let anyone look directly into the beams, or reflect the beams with shiny objects. In our harp frame design, we chose to point the beams down (rather than up) for safety reasons.
Getting the Python scripts
I have written Python scripts for testing circuits as you build, and for running the laser harp. These scripts will need to be installed on your Pi Zero. Follow instructions at https://github.com/phyzicist/twang. The bundle of scripts are called "twang". It includes tests you run while building the harp, as well as a script to turn your harp into a playable instrument.
Building the wooden harp frame
The laser harp frame itself is cut in wood using a CNC router. CAD designs coming soon!
Connections and circuits diagram
Connections and circuits diagrams are included in our "twang" GitHub project, in the "diagrams" folder. Here's a direct link to the connections and circuit diagrams PDF: https://github.com/phyzicist/twang/raw/master/diagrams/FiveStringCircuitDiagram.pdf.