Laser Harp

/Engineering

Jacob Thompson Spring 2015

Photos

Final Harp Photos

Inspiration

I think it was during Fall of Junior year in high school that I decided I wanted to make a laser harp. I thought lasers were cool, and I wanted to make a bigger project using Arduinos. I looked around on the internet for a while, and eventually found and liked "laser harps." These use laser beams in place of harp strings, and software to play notes. Some of my inspiration pictures are below

Wooden Frame

My dad has a lot of experience with building things with wood, so I asked if he would be able to make the frame for the laser harp. He said he would be happy to, so we sat down and talked about designs.

I knew I needed a good amount of space in the base to fit all the electronic components and batteries. The biggest requirement was a way to run wires up the side of the harp to the laser diode modules. I also needed access to the top area so that I could put in the laser diodes and fine tune them so they point straight down.

I was expecting a simple 3/4 rectangle design with maybe some smooth edges, but my dad went above and beyond with his design. You can see pictures of it below.

The majority of the frame is made of Hawaiian Koa wood. the white parts are Maple wood, and the whole thing was rubbed in Tung oil for its finish.

The frame was made by cutting out an identical shape from three different 3/8" thick boards, removing parts of the middle section to allow for wire runs, then gluing them together and extensively sanding the edges.

On the right you can see pictures of the removable top section to allow for wire access.

The front panel was removable to allow for easy access when I set up the wires and buttons for controls.

The bottom is open so that you can easily change the batteries out, and because we didn't see a huge need for a bottom.

Laser harp wooden frame with removable section for wire access

Electronics

Once the frame was built, it was my turn to work on the project. I had previously ordered all the parts I thought I would need, so that I wouldn't have many delays in putting it together. Below is a parts list of what I used. Most of the parts were ordered on Ebay from China, because it's cheaper.

1 Arduino Mega
2 speakers from old office phones
2 potentiometers for the speakers
6 pushbuttons
3 indicator LED's
1 LCD display
13 red laser diode modules (3-5mW each)
13 photoresistors
1 7-segment LED display
6 rechargable batteries
Lots of wire
Various resistors
Hot glue and solder

The harp is constructed with the 13 laser diodes on top, and 13 photoresistors on the base. All of those are held in with hot glue, because I found that it had a convenient setting time where I could aim the laser.

In the last two pictures of the above gallery, you can see that I put some foam above each of the photoresistors. That way no matter where the laser beam hit the foam, the photoresistor would be able to sense the brightness. I had trouble aiming the lasers perfectly, and this allowed me a little more leeway with it.

Features and Code

You can download the source code here [link] if you want. The code is very messy and poorly written, sorry ¯\_(ツ)_/¯

Feature list

Scale select (Chromatic scale, B-flat, A-flat, C scale
Octave select (Each scale up or down an octave. The upper octave can be painfully loud/sharp)
Volume control
LCD display of the current scale, and current note being played
The 7-segment display shows the name of the current note (Ex "B"). It displays a dot (ex B .) for a flat note
Buttons to move between scales and octaves
Blue lights on the bottom to look cool

Improvements I'd like to do but haven't found the time to

Use a sound shield for Arduino or sound library to play notes that aren't just buzzer tones
Dry ice or smoke/fog system so that you can see the laser beams in a bright room
Learn to actually play a song on it
Cable management

Video

I don't normally do videos, but I took a short video of me using the laser harp. I plan on making a better video and taking better pictures some time later this summer.