This photoelectric piano has a total of 7 strings, and the buzzer emits the corresponding sound level when cutting the strings. Equipped with LED lights, the corresponding LED lights up when cutting the strings, totaling 7 LEDs. Optoelectronic pianos do not have strings, but are replaced by bright beams of light. Users only need to pluck the beam, as if plucking the strings, and can still play a melody. This production consists of two parts: a photosensitive circuit and a microcontroller. It can arouse interest in music and technology, and for friends who enjoy DIY, this is a good creative small production. I used to see a harp without strings, which is widely recognized by many visitors as the most interesting exhibit in the Iran Pavilion! Visitors only need to reach out and pass through the black harp, and the tone will be played. How can it play without strings? The staff revealed the secret to us - he pressed the "light" button on the piano, and 14 red laser beams shot out from the top of the piano. He said, this is a laser harp. We use our fingers to flick the laser beam, and the harp will make a sound, with each beam having a different pitch. It is said that this harp was originally placed in a science museum in Iran, mainly to arouse children's interest in music and technology. For friends who enjoy DIY, this is a good creative mini production. Power supply voltage: DC4.5V-5.5V. LED lights: 8. Power socket: DC-005 socket. Power cord: USB to DC-005 cable. Main board circuit board size: 8.9cm x 6.0cm. The principle of a string less qin (photoelectric qin): Photoelectric pianos do not have strings, but are replaced by bright beams of light. Users only need to pluck the beam, just like plucking the strings, and can still play a melody. This production consists of two parts: a photosensitive circuit and a microcontroller. When the light beam of the light-emitting diode is blocked, the corresponding photosensitive resistor senses and produces a change in resistan