Piezo Buzzers vs. Magnetic Buzzers — What’s the Difference?
Communicating information from a product to its end user is a necessary task across many industries — from home appliances and security devices to automotive electronics and office automation devices, audio signals are a necessity. These audio signals can be generated using various devices. The most common device used for this purpose is the buzzer. Also known as a sounder, audio alarm or audio indicator, a buzzer is a basic audio device that generates a sound from an incoming electrical signal.
Buzzers come in two primary forms — piezo buzzers and magnetic buzzers. If you are creating a circuit with a buzzer, you’ll want to understand the differences between these two configurations. You should know how each buzzer works and how to determine which is best for your application.
What Are Piezo Buzzers?
A piezo buzzer is an electric device used to produce a tone. These lightweight and simply-constructed buzzers are inexpensive yet reliable and come in a range of sizes and frequencies to meet the needs of nearly any application.
The core characteristic that defines this type of buzzer is its piezoelectric component. Piezoelectric components are made of special materials that exhibit the piezoelectric effect (where the material can convert some energy from applied mechanical strain into an electric charge). These materials also exhibit the reverse piezoelectric effect where the material deforms when an electric charge is applied.
Piezo buzzers feature the following general properties:
–Operating voltage of ~3 to ~250 V
–Typical current consumption of < 30 mA
–Approximate resonant frequencies of 2 to 6 kHz
Piezo buzzers are often used in home and automobile alarms as well as computer devices due to their size variability and reliability.
Piezo Buzzer Structure
A piezo buzzer contains a piezo element, which is a thin disk of piezoelectric ceramic adhered to a metal plate. Both sides of the piezoelectric element have a silver electrode applied to allow for electrical contact. The whole thing can be packaged in a plastic case with or without a drive circuit.
Piezo buzzers work by leveraging the reverse piezoelectric effect — the effect where the material deforms in the presence of an electric charge. In short, a piezo buzzer works by applying an alternating voltage to the piezoelectric ceramic material. The introduction of such an input signal causes the piezoceramic to vibrate rapidly, resulting in the generation of sound waves.
What Are Magnetic Buzzers?
A magnetic buzzer is similar to a piezo buzzer in that it is used to produce a tone. However, magnetic buzzers differ from piezo buzzers in their core functionality.
Also known as electromechanical buzzers, magnetic buzzers are more traditional than piezo buzzers in that they work using a magnetic field. Instead of relying on piezo materials, magnetic buzzers use an electric charge to produce a magnetic field, which then allows another part of the buzzer to vibrate and produce sound.
Magnetic buzzers feature the following core characteristics:
–Operating voltage of ~1.5 to ~30 V
–Typical current consumption of up to ~100 mA or more
–Approximate resonant frequencies of 1 to 3 kHz
Like piezo buzzers, magnetic buzzers are often used in household alarms and devices like clocks, watches and keyboards.
Magnetic Buzzer Structure
Magnetic buzzers contain an electromagnetic element instead of a piezoelectric element. Within the buzzer is a coil of wire connected to the circuit, which produces the magnetic field. The buzzer also contains a flexible ferromagnetic disk. The whole thing is encased in a plastic casing.
Magnetic buzzers operate using electromagnetic principles. When power is applied, current runs through the coil of wire inside the buzzer, which produces a magnetic field. The flexible ferromagnetic disk is attracted to the coil when the magnetic field is activated, then returns to rest when the magnetic field is off. By oscillating the signal through the coil, the buzzer produces a fluctuating magnetic field, which vibrates the disk. This movement makes the buzzer sound.
Piezo and Magnetic Buzzer Key Specifications
When needing to decide between a magnetic buzzer or a piezo buzzer, the choice often comes down to the key specifications of each buzzer type as well as any drive circuit limitations in situ. As discussed previously, magnetic buzzers operate at lower voltages and higher currents than piezo buzzers, but this is not the only thing to consider. The sound specification for each type of buzzer must also be taken into account and are briefly discussed below-
Before diving into details, we must first define some core concepts:
Resonant frequency: Every material has a specific frequency at which it tends to vibrate — for example, the G-string on a properly tuned guitar will vibrate at the frequency of a G-note when plucked. This specific frequency is called the resonant frequency. By driving a material at its resonant frequency, the material will produce the loudest sound with the least input power. Piezo buzzers tend to have a higher resonant frequency when compared to magnetic buzzers.
Sound pressure level: The sound pressure level (SPL) is the deviation from atmospheric pressure caused by a soundwave. It is typically expressed in pascals or decibels and is proportional to the input voltage. The SPL value, will vary depending on how far away from the buzzer the measurement is taken.
Frequency response: Frequency response is a measurement of how efficiently a buzzer can produce sound energy at a given frequency. This is usually expressed by plotting the SPL vs. log frequency.
Generally speaking, piezo buzzers tend to exhibit a more linear relationship between the input frequency and output audio power, while magnetic buzzers tend to have a less linear relationship. As a result, piezo buzzers tend to have a wider range of usable frequencies than magnetic buzzers.
Choosing the Correct Buzzer Type for Application
When comparing piezo buzzers vs. magnetic buzzers for a given application, it’s essential to consider all specifications. First to consider are the electrical and physical parameters of each buzzer type. Below is a summary of the specs for each buzzer type:
Piezo buzzers: Piezo buzzers have larger frequency ranges and SPL values, as well as a high resonant frequency. Piezo buzzers also have higher operating voltages and lower current requirements.
Magnetic buzzers: Magnetic buzzers have smaller frequency ranges and SPL values and lower resonant frequencies than piezo buzzers. They also operate with lower operating voltages but high current requirements.
Another thing to consider for extremely custom applications are audible sound transducers.
Audible Sound Transducers: Transducers consist of a casing, typically a piezo element, and an electrical contact. They do not include a built-in driving circuit, which means that engineers have more flexibility in their design to modify or optimize the frequency in their application.
All of these factors are important to consider when choosing between piezo and magnetic buzzers. Each application is unique, so deciding based on your specific application is critical. If you’re considering piezo buzzers in your application, please contact APC International to discuss your needs.
At APC International, we offer a variety of piezo buzzer options to meet your needs. Our piezo buzzers come in a range of sizes and configurations for many applications, from self-oscillating buzzers to multi-tone sound generators.
Please contact APC today to learn more about our piezo buzzer products.
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