A laser harp is a nifty contraption that replaces the physical strings in a harp with laser beams which are connected to sensors, each of which stand for a particular musical note, which enables the harp to produce a sound whenever the laser beam is cut.
There are infinite possibilities when you combine dazzling lasers, melodious sounds and Arduino and top it off with a healthy jolt of ingenuity. This genius came to play when Rituparna and Suryansh built a stunning life-size laser harp with a wooden frame.
They built this at RHC in Pune and at RiiDL at KJ Somaiya College, Mumbai. The harp was initially displayed at Maker Mela held at Somaiya Vidyavihar, where it managed to capture the imagination of all the visitors, and delighted children that came to visit.
Here’s how to get started.
Gather the Tools:
Here’s the list of items that you will require:
· Wooden structure of the harp
· 12 - 3mm red laser diodes
· 5 V power supply for the Laser
· 1 Tah board (you can use any other Arduino as well)
· 12 - LDR and 12 - 1K Ohm Resistors
· Set of speakers
· Play Doh / Thermocol
· Prototyping circuit board
· Male header pins
· Wires (red and black to help distinguish)
A list of tools you will need:
· Soldering iron
· Wire stripper and pliers
· Glue gun
Making your Wooden Harp Frame
To make your laser harp, you will first need a wooden structure. We suggest you do not compromise on the size of this wooden harp to get best results. The following are the specifications to make your own wooden harp. All dimensions are in (inches).
Tip: If you’re not into woodworking or are going to outsource this part of the build to a carpenter, we suggest taking a print out on a full sized sheet with actual dimensions and pasting on the wooden sheet. Then you can instruct the carpenter to make the harp into the same shape as your cut out.
Remember that the cover of the slit be wide enough to house the LDR sensors that you will be using. (Make sure the slit is wide enough but not too wide)
Getting the circuits ready
To make the circuits, use your protoboard to make a break out board of the arduino that you are using. They used 2 Tah Boards to make our harp work. (A Tah Board is a BLE - Arduino Leonardo variant that is designed and sold by RHC, Pune. For more information log onto: www.tah.io)
Make sure you include the Analog pins from your Arduino in the proto board. You will be needing a total of 10 Analog pins which will be reading the inputs from the LDRs which constitute your strings.
To wire up the LDRs, first take one end and connect each LDR to an Analog pin of the Tah. Continue this connection by attaching it in series to a 1K ohm resistor which will in turn go to GND (top left). Next connect a wire to the other end of each LDR which goes to 5V. This will form a simple voltage divider circuit (top right). To make the laser strings, connect all the laser diodes in parallel with one end of each laser going to 5V and the other to GND. To power up the circuit, attach a 5V wall adapter using an appropriate connector onto the proto board. Remember to give a common GND to both the Tahs as well as to all the resistors and the laser diodes.
Align Lasers and place LDRs
Attach laser in the top cavity of the harp using thermocol/play dough so that they fit snugly and align them to fall onto the LDR faces.
Once this is done, you will have laser ’strings’ which can be played by moving your hand across the air
Next, we upload the code to the Tahs.
Upload the Arduino Code
Now we need to upload the code that will get the harp working. This is the piece of code we wrote:
You can use the same code or write it on your own as per your preference. You will have to modify it as per the number of strings and the board you are using for the harp.
Set up the Raspberry Pi
Clone this repository in the home directory of your raspberry pi:
Next make the launcher.sh file run when the Raspberry Pi reboots. To do this change the permissions:
on the launcher.sh
· chmod 755 launcher.sh
Now test it, by typing in:
· sh launcher.sh
This should run your Python code. Add logs directory
· mkdir logs
· sudo crontab -e
add the following line to the end of the file
· @reboot sh /home/pi/harp/launcher.sh >/home/pi/logs/cronlog 2>&1
Then restart the Raspberry Pi
· sudo reboot
Connect the Powers and Speakers
If you have followed through, at this stage you will have a working laser harp!
We encourage you to try it out, and if you have any questions, feel free to comment below and we shall help you out!