Light Controlled Electronic Harp

This project is an audio oscillator that allows you to play musical tunes by waving your hand over the board. The method of obtaining musical arrangements like this has been used since the early days of vacuum tube radios. The first instrument of this type was invented by a man named Leon Theremin, so the instrument was named the Theremin in his honor.

This might be called a "hands-off" instrument, for once you turn the oscillator ON you need not touch it to play a tune. The tones are obtained by changing the amount of light that reaches the CdS Cell. If a bright light is placed over the board without the shadow of your hand, the pitch is high in frequency. As you block the light more by moving your hand, the pitch decreases.

After a little practice you will be able to play many tunes with this musical instrument. The oscillator circuit used for this project is the basic pulse type (which is used time and gain). The only change in this circuit is the addition of the CdS Cell in the base-bias circuit. A fixed 47K Resistor is also included in series with the Cell to provide a protective limit on base-bias. Have fun!

Hear is a another version