The Sounding Principle And Solution Of Buzzer Hardware Circuit Design

The sounding principle and solution of buzzer hardware circuit design

Buzzer hardware circuit design

1 Introduction

The buzzer is an electronic sounder with an integrated structure. It is powered by DC voltage and is widely used as a sounding device in electronic products such as computers, printers, copiers, alarms, electronic toys, automotive electronic equipment, telephones, and timers. .

Classification of buzzers: two types of piezoelectric buzzers and electromagnetic buzzers.

Buzzer type description

piezoelectric buzzer

The piezoelectric buzzer uses the piezoelectric effect of the piezoelectric ceramic to drive the vibration of the metal sheet to make a sound.

Electromagnetic buzzer

The electromagnetic buzzer is a component that uses the action of the electromagnetic coil on the buzzer to produce sound.

According to the driving mode, the buzzer is mainly divided into active buzzer and passive buzzer. The active buzzer can make a sound when it is connected to DC, and the passive buzzer needs a control signal to realize the sound generation. The main difference is whether there is an oscillation source inside the buzzer.

The working principle of the active buzzer is: the DC power input passes through the amplified sampling circuit of the oscillation system to generate a sound signal under the action of the resonant device

The sounding principle of the passive buzzer is: the square wave signal is input into the resonance device and converted into the sound signal output:

In particular, the passive buzzer inputs PWM with different frequencies and duty cycles, and the sound produced by the square wave is different, in which the frequency has an impact on the tone, and the duty cycle has an impact on the volume.

Tone 1(Do)2(Re)3(Mi)4(Fa)5(So)6(La)7(Si)

Frequency (Hz)

262

294

330

349

392

440

494

2 Buzzer circuit design

Passive Buzzer Circuit Design

Passive buzzer, it needs pulses of a certain frequency (high and low levels) to sound. The TP1 PNP transistor in the figure acts as a current amplifier to drive the buzzer. When the J7 terminal has a high level coming in, DCCircuit board design , the PNP transistor TP1 is cut off, and the buzzer cannot be powered. DC circuit board design , when a low level comes in from the J7 terminal, the PNP transistor TP1 is turned on, and the buzzer is powered on. If there is a certain frequency at the J7 terminal When the pulse signal (high and low level flipping continuously), the passive buzzer will make a sound.

Active Buzzer Circuit Design

The current is amplified through resistor R2 and PNP transistor TP1 to drive the buzzer. Resistor R1 is a pull-up resistor used to prevent the buzzer from sounding by mistake. When the BEEP pin outputs a low level, the PNP transistor is turned on, and the buzzer sounds; when the BEEP pin outputs a high level, the PNP transistor is turned off, and the buzzer stops sounding.