Author: LUKA MAJNARIC

Mentor: RUZICA KAMENJASEVIC

Company/Institution: Rijeka High School for Electrical Engineering and Computing

Country: Croatia

web: http://web2.ss-elektrotehnicka-ri.skole.hr/

The laser harp is a virtual musical instrument that has laser beams instead of strings and produces eight tones of different frequencies. Melodies such as “The yellow house at the end of the village”, other children’s songs or any composition composed within one octave can be played on it. The central part of the device is the Arduino Uno, which processes the input signals and, based on them, issues appropriate commands to obtain output tones. Laser diodes are placed above the photo-transistor so that each laser diode illuminates one photo-transistor. When the light beam is interrupted, the photo-transistor goes from the conducting state to the blocked state, so that in this case the voltage on the resistor that is important between its emitter and ground is low (logical zero). The Arduino detects this change as a signal to send commands to the buzzer for a specific tone. The frequency of this depends on the location, or position, of the phototransistor from which the change was detected.