Features:
1.This photoelectric piano has a total of 7 strings, and the buzzer emits the corresponding sound level when cutting the strings.
2. Equipped with LED lights, the corresponding LED lights up when cutting the strings, totaling 7 LEDs.
3. 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.
4. This production consists of two parts: a photosensitive circuit and a microcontroller.
5. It can arouse interest in music and technology, and for friends who enjoy DIY, this is a good creative small production.

Product Introduction:
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.

Parameter:
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 * 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 resistance value. The system composed of 7 photosensitive resistors produces a change in high and low potentials, and the microcontroller reads the changes in the high and low potentials of the photosensitive resistor to complete the input of operation instructions. The microcontroller controls the data to be transmitted through the serial port based on the instruction information, which assigns values to the control port of the speaker and the control port of the water flow lamp to generate corresponding reactions. When there is light shining, the microcontroller reads the voltage of the photoresistor, and it is at a low level. When there is no light irradiation, the microcontroller reads the voltage of the photoresistor, and it is at a high level. In this way, when blocking the light of the laser, a switch effect can be generated in the circuit.
The frequency of sound that can be heard by the human ear is between 20Hz and 20kHz, and the frequency of harp notes should also be within this range. However, different notes have their own fixed frequencies. The above-mentioned audio can be generated through the built-in 16 bit timer of the microcontroller. For example, the standard tone la of the harp is 440Hz. According to calculations, its half cycle is 1136 μ s. In this way, as long as the pin level is changed during half a cycle, a 440Hz square wave can be generated. After passing through the electroacoustic conversion element (speaker), the standard sound la can be produced, and other notes are also produced in this way.

Package include:
Set 1:
PCB board * 1
1K resistor * 7
4.7K resistor * 6
10K resistor * 2
1W 100 ohm resistor * 1
22P ceramic capacitor * 2
10UF25V electrolytic capacitor * 2
12M crystal oscillator * 1
8550 transistor * 1
Passive buzzer * 1
8 * 8 self-locking switch * 1
DC005 seat * 1
USB to DC005 cable * 1
3MM LED white hair * 8
3MM LED white hair blue fog light * 8
5516 photoresistor * 7
4mm heat shrink tube 15CM * 1
40P IC socket * 1
STC89C51/STC89C52/STC89C54 Microcontroller Burning Program * 1 (Microcontroller randomly shipped)

Set 2:
1X finished product
1X shell (including screws)
1X power cord