51 MCU Self-study Notes (V) - Buzzer

buzzer

The structure principle of the buzzer

(1) Piezoelectric buzzer: Piezoelectric buzzer is mainly composed of a multivibrator, a piezoelectric buzzer sheet, an impedance matcher, a resonance box, a shell, etc. Some piezoelectric buzzers are also equipped with a light-emitting diode on the shell.

The multivibrator is composed of transistors or integrated circuits. When the power is turned on (1.5~15V DC working voltage), the multivibrator starts to oscillate and outputs an audio signal of 100-500HZ. The impedance matcher drives the piezoelectric buzzer to sound.

The piezoelectric buzzer is made of lead zirconate titanate or lead magnesium niobate piezoelectric ceramic material. Silver electrodes are plated on both sides of the ceramic sheet, and after polarization and aging treatment, it is bonded to a brass sheet or a stainless steel sheet.

(2) Electromagnetic buzzer: The electromagnetic buzzer consists of an oscillator, an electromagnetic coil, a magnet, a vibrating diaphragm and a casing.

After the power is turned on, the audio signal current generated by the oscillator passes through the electromagnetic coil, causing the electromagnetic coil to generate a magnetic field. Under the interaction between the electromagnetic coil and the magnet, the vibrating diaphragm vibrates periodically and produces sound.

Buzzer sound principle

The sound-generating principle of a buzzer consists of a vibration device and a resonance device, and the buzzer is divided into passive external excitation type and active self-excitation type.

The working principle of the passive external excitation buzzer is: the square wave signal input into the resonant device is converted into a sound signal output.

The working principle of the self-excitation buzzer is: the DC power input passes through the amplification sampling circuit of the oscillation system

A sound signal is generated under the action of the resonance device.

Buzzer in microcontroller

Schematic diagram:

usage:

By changing the frequency of the waveform output by the microcontroller pin, the tone of the buzzer can be adjusted to produce sounds with different timbres and tones.

By changing the duty cycle of the high and low levels of the output level, the volume of the buzzer can be controlled.

Microcontroller controls the buzzer sound code

#include

typedef unsigned char u8;

typedef unsigned int u16;

sbit beep = P1^5;

void delay(u16 i)

{

  while(i--);

}

void main()

{

  while(1)

  {

    beep = ~beep;

    delay(100);

  }

}