The first harp that I built, it was the frame type. 8 rays and each had a sensor. Additionally was installed tracking circuit which followed the movements of the hand. Thanks to this I could get a change of modulation or filter for sound.
This worked pretty well. However frame harp has limitations, use it is problematic. Moving, folding and positioning of sensors each time it was so tiring. I thought that comes time to build a real harp frameless.
It was not a very difficult task. Simple stepper motor control circuit and circuit that recognizes which radius is touched. Simple idea :) Then, improved circuit tracking hand and processing of a all data to MIDI. I added protection circuit, modulation 15kHz for the laser. This causes the harp does not respond to other light which reaches the sensor. And if I use laser with an output exceeding 1 Watt, it prevents burns the hand by a laser. Harp works well. I used it during my Lasershow which I organized recently. Was any trouble.
The new my harp has a few improvements. Circuit tracking hand was rebuild. Under the inspiration from Stephen Hobley, I decided to use motion sensor removed from Xbox :) of course I had to build for them the interface. Originally Stephen used the sensors from the Nintento Wii.
I also added the ability to change octave, CC parameters for circuit tracking hand. I added a small LED display that tells me which is the octave. Harp is polyphonic. It also has the ability to connect foot keypad. This allows you to play additional accompaniment. Octave and functions is carried out by the foot switch pedal.
The new version of the harp use a blue laser with a power 2 Watts.