Last Updated on April 21, 2023 by You Ling
Buzzer is a common sound-generating component, widely used in various electronic products for alarms or reminders. Buzzer can be found in washing machines, microwave ovens, mixers, alarm clocks, remote-controlled cars, calculators, and more. Buzzer is also known as a sound generator, audio alarm, or audio indicator, and is a basic audio device that can generate sound based on the incoming electrical signal. The following article will introduce you to the types and characteristics of buzzers.
- What is a Piezoelectric Buzzer
- Characteristics of Piezoelectric Buzzers
- What is a Magnetic Buzzer
- Characteristics of magnetic buzzers
- Differences between piezoelectric buzzers and magnetic buzzers
- How to choose the appropriate buzzer
- Case Pictures of piezo buzzers from He-Shuai Company
There are two types of buzzers: magnetic and piezoelectric.
1、What is a Piezoelectric Buzzer?
Piezoelectric buzzers generate sound through a piezoelectric buzzer chip. The piezoelectric buzzer chip is made of piezoelectric ceramics and requires electrodes to be plated on both sides for electrical conduction. When an AC drive signal is applied to the piezoelectric buzzer chip, it will produce mechanical deformation and vibration due to the piezoelectric effect. This vibration pushes and compresses a metal plate attached to the piezoelectric ceramic, producing sound. Piezoelectric buzzers require a square wave signal to generate sound, and a higher driving voltage is needed to obtain a louder sound. NPN or PNP transistors can be used to drive the piezoelectric buzzer, and an impedance matching resistor needs to be connected in parallel to the buzzer.
2、Characteristics of Piezoelectric Buzzers
Piezoelectric buzzers generally have the following characteristics:
The working voltage of about 3 to 250V
Typical current consumption of less than 30mA
The resonant frequency of approximately 2 to 6 kHz
Due to their variability in size and reliability, piezoelectric buzzers are commonly used in home and car alarms, as well as computer equipment.
Structure of Piezoelectric Buzzer
A piezoelectric buzzer consists of a piezoelectric element, which is a piezoelectric ceramic disc attached to a metal plate. The piezoelectric element has two silver electrodes on both sides for electrical contact. The entire structure can be encapsulated in a plastic casing, with or without a driving circuit.
Piezoelectric buzzers work by utilizing the inverse piezoelectric effect, where the material undergoes deformation in the presence of an electric charge. In other words, piezoelectric buzzers work by applying an AC voltage to the piezoelectric ceramic material, which causes the ceramic to vibrate rapidly and produce sound waves.
3、What is a Magnetic Buzzer?
Magnetic buzzers use an electromagnetic coil to drive a metal diaphragm to produce sound. Therefore, magnetic buzzers have a coil and a magnet inside. When the coil is energized, it attracts the metal diaphragm, causing it to vibrate and produce sound. Magnetic buzzers are best driven with a 1/2 square wave (1/4 duty) signal to obtain better performance. Magnetic buzzers require lower driving voltage but more current compared to piezoelectric buzzers.
Similarly, NPN or PNP transistors can be used to drive magnetic buzzers. Since magnetic buzzers have a coil inside, a freewheeling diode needs to be connected in parallel to the buzzer to prevent damage to the transistor due to reverse voltage spikes.
4、Characteristics of magnetic buzzers
Magnetic buzzers have the following core characteristics:
Working voltage of approximately 1.5 to 30 V
Typical current consumption of up to approximately 100 mA or more
Resonant frequency of approximately 1 to 3 kHz
Like piezoelectric buzzers, magnetic buzzers are commonly used in household alarm clocks and clocks, watches, keyboards, and other devices.
Structure of magnetic buzzers
Magnetic buzzers contain electromagnetic components rather than piezoelectric components. Inside the buzzer, there is a coil connected to a circuit that produces a magnetic field. The buzzer also contains a flexible ferromagnetic disk. The whole thing is housed in a plastic shell.
Magnetic buzzers work on the principle of electromagnetism. When the buzzer is powered, current flows through the coil inside the buzzer, creating a magnetic field. When the magnetic field is activated, the flexible ferromagnetic disk is attracted to the coil and then returns to a static state when the magnetic field is turned off. By oscillating the signal through the coil, the buzzer produces a fluctuating magnetic field, causing the disk to vibrate. This action makes the buzzer emit sound.
5、Differences between piezoelectric buzzers and magnetic buzzers
When choosing between a magnetic buzzer or a piezoelectric buzzer, the choice typically boils down to the key specifications of each buzzer type and any driving circuit limitations on-site. As mentioned earlier, compared to piezoelectric buzzers, magnetic buzzers have lower operating voltages, higher currents, but this is not the only factor to consider. The sound specifications of each buzzer must also be considered.
Resonant frequency: Each material has a specific vibration frequency—for example, the G string on a properly tuned guitar will vibrate at the frequency of the G note when plucked. This specific frequency is known as the resonant frequency. By driving the material at its resonant frequency, it will produce the loudest sound with the least amount of input power. Piezoelectric buzzers tend to have higher resonant frequencies compared to magnetic buzzers.
Sound pressure level: The sound pressure level (SPL) is the deviation from atmospheric pressure caused by a sound wave. It is usually measured in pascals or decibels and is proportional to the input voltage. The SPL value will vary depending on the distance from the buzzer being measured.
Frequency response: Frequency response measures the efficiency of the buzzer to produce sound energy at a given frequency. This is typically represented by plotting the SPL against logarithmic frequency.
Generally, piezoelectric buzzers tend to exhibit a more linear relationship between input frequency and output audio power, while magnetic buzzers tend to have a less linear relationship. Therefore, piezoelectric buzzers tend to have a wider available frequency range compared to magnetic buzzers.
6、How to choose the appropriate buzzer
When comparing piezoelectric buzzers and magnetic buzzers for a given application, all specifications must be taken into consideration. The first thing to consider is the electrical and physical parameters of each type of buzzer. The following is a summary of the specifications for each type of buzzer:
Piezoelectric buzzer: Piezoelectric buzzers have a larger frequency range and SPL value, as well as a higher resonant frequency. Piezoelectric buzzers also have higher operating voltage and lower current requirements.
Magnetic buzzer: Compared to piezoelectric buzzers, magnetic buzzers have a smaller frequency range and SPL value, as well as a lower resonant frequency. They can also operate at lower operating voltage, but require higher current.
For extremely customized applications, another thing to consider is the audible sound transducer.
Sound transducer: Transducers are composed of a housing (usually a piezoelectric element) and electrical contacts. They do not include built-in drive circuits, which means that engineers can more flexibly modify or optimize frequencies in the application during design.
When choosing between piezoelectric buzzers and magnetic buzzers, all of these factors are important to consider. Each application is unique, so making decisions based on your specific application is crucial.
7、Case Pictures of piezo buzzers from He-Shuai Company