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Mechanism of piezoelectric buzzer sound

Views: 112     Author: Site Editor     Publish Time: 2019-09-05      Origin: Site

Piezoelectric buzzers are widely used in various electronic devices such as alarms, timers, and electronic toys. They are a popular choice due to their compact size, low power consumption, and high reliability. In this article, we will explore the mechanism behind the generation of sound in piezoelectric buzzers.


Introduction


Piezoelectric buzzers are devices that convert electrical energy into mechanical vibrations, which in turn generate sound waves. The buzzers consist of a piezoelectric ceramic disc that is sandwiched between two metal electrodes. When an AC voltage is applied to the electrodes, the disc vibrates, generating sound waves.


Piezoelectric Effect


The piezoelectric effect is the ability of certain materials to generate an electric charge in response to mechanical stress, and vice versa. Piezoelectric materials have a crystalline structure that is highly ordered and symmetrical. When the material is subjected to a mechanical force, the symmetry of the crystal lattice is disrupted, resulting in the generation of an electric charge.


Working Principle of Piezoelectric Buzzers


Piezoelectric buzzers consist of a piezoelectric ceramic disc that is mounted on a metal plate. The metal plate acts as a diaphragm, which amplifies the vibrations generated by the piezoelectric disc. When an AC voltage is applied to the electrodes, the piezoelectric disc expands and contracts rapidly, causing the metal plate to vibrate. This vibration generates sound waves, which are amplified by the diaphragm and radiated into the surrounding air.


Frequency and Amplitude


The frequency and amplitude of the sound generated by a piezoelectric buzzer depend on the size and shape of the ceramic disc, as well as the frequency and amplitude of the AC voltage applied to the electrodes. Generally, smaller ceramic discs produce higher frequencies, while larger discs produce lower frequencies. Similarly, higher voltages produce greater amplitudes, resulting in louder sounds.


Types of Piezoelectric Buzzers


There are two main types of piezoelectric buzzers: self-driven and externally driven. Self-driven buzzers have a built-in oscillator that generates the AC voltage required to drive the piezoelectric disc. Externally driven buzzers require an external oscillator to provide the AC voltage.


Applications of Piezoelectric Buzzers


Piezoelectric buzzers are used in a wide range of applications, including:

  • Alarms and timers

  • Electronic toys

  • Automotive warning systems

  • Medical devices

  • Home appliances


Advantages of Piezoelectric Buzzers


Piezoelectric buzzers offer several advantages over other types of sound generators, including:

  • Compact size

  • Low power consumption

  • High reliability

  • Wide operating temperature range

  • Low electromagnetic interference


Disadvantages of Piezoelectric Buzzers


Despite their many advantages, piezoelectric buzzers also have some disadvantages, including:

  • Limited frequency range

  • Limited sound pressure level

  • Poor sound quality


Conclusion


Piezoelectric buzzers are versatile devices that are used in a wide range of electronic applications. The mechanism behind their operation is based on the piezoelectric effect, which allows certain materials to convert electrical energy into mechanical vibrations. By understanding the principles behind piezoelectric buzzers, designers can choose the right type of buzzer for their application and optimize its performance.


Structure of piezoelectric diaphragm

The piezoelectric sound element must have a piezoelectric diaphragm.

This is a simple structure in which a piezoelectric ceramic adheres to brass or nickel alloy metal plate.



Mechanism of producing sound for piezo diaphragms

When a voltage is applied to the piezoelectric ceramic, it extends in its plane. When a voltage is applied to the piezoelectric diaphragm, since the metal plate is not stretched, it is bent as shown in (a). When the polarity of the applied voltage is reversed, the piezoelectric ceramic shrinks and the metal plate is bent toward the opposite side as shown in (b).

When the direction of the applied voltage alternates, the states of (a) and (b) are repeated, and as shown in (c), sound waves are generated in the air.

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