Feature: High switch for Play the stored two songs by pressing the button When cutting the string corresponding to the LED string lit,a total of 7 LED A total of seven strings,the string when the buzzer cut the corresponding sound level Specifications: Power supply:5V The harp is a harp without strings, and instead of a bright beam of light, the user can just pluck the beam and for play a melody. The photosensitive resistor and the single chip microcomputer STC89C52 are composed of two parts. The for launch of the beam tube is blocked, the corresponding photosensitive resistance induction and generate resistance changes, eight photosensitive resistance of the change of the system to produce high and low voltage, and low potential changes by microcontroller reads the photosensitive resistance, complete instructions input, single chip microcomputer control data according to the instruction information through the serial port to transmit data, both docking speaker p0 ^ 2 mouth and running water light p1 mouth to carry on the assignment, make its produce the corresponding reaction. When there is a beam, the microcomputer reads the voltage of the photosensitive resistor, which is low level. When there is no irradiation, the microcomputer reads the voltage of the photosensitive resistor, then it is high level. Thus, when shielding the light, can produce the effect of the switch in the circuit. The audible frequency of the human ear is 20Hz to 20kHz, and the frequency of harp notes should be in this range. It's just that different notes have their own fixed frequencies. The audio can be generated by the 16-bit timer that comes with the 52 single chip. For example, the standard pronunciation of the harp is 440Hz. By calculation, its half period is 1136 mu s. In this for case, the square wave of 440Hz can be generated as long as the jump pin level in the half cycle. After the electroacoustic conversion component (speaker), you can produce the standard sound la, and the other notes are created as well. Size:10*5cm/3.94*1.97inch Note: Please allow 1-3mm error due to manual measurement. pls make sure you do not mind before you bid Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you! Package Contents: 1 x harp