The electric buzzer, also known as a sounder or audio indicator, is a familiar device used to communicate alerts and status updates in household appliances like microwaves and clocks. Buzzers convert electrical signals into sound, making them essential in many everyday products.
There are two primary types of buzzers — piezo and magnetic. If you design a circuit that includes a buzzer, you must understand how each type works and which is better for your application.
A piezo buzzer is an electric device used to produce a tone. These lightweight, simply constructed buzzers are affordable yet reliable and come in a range of sizes and frequencies to meet nearly any application’s needs.
The piezoelectric component is the core characteristic that defines this type of buzzer. Piezoelectric components generate an electric charge when mechanically stressed — a property known as the piezoelectric effect. These same materials also respond to electrical input by changing shape, a phenomenon called the reverse piezoelectric effect.
Piezo buzzers feature the following general properties:
Piezo buzzers are available in voltage ratings from 3V to 24V or higher. Due to their size variability and reliability, you’ll often see them in alarms and computer devices.
A piezo buzzer consists of a slender disk of piezoelectric ceramic bonded to a metal plate. A silver electrode applied to both sides of the piezoelectric element allows for electrical contact. Manufacturers typically enclose the assembly in a plastic case, with or without a built-in drive circuit.
Thanks to the reverse piezoelectric effect, the ceramic deforms rapidly when you apply an alternating voltage. These vibrations produce sound waves, making the buzzer an efficient and compact audio signal generator.
Like a piezo buzzer, a traditional magnetic buzzer produces a tone. However, magnetic buzzers’ core functionality differs. Instead of relying on the piezoelectric or reverse piezoelectric effect, 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:
Magnetic buzzers typically operate at lower voltages, such as 1.5V to 12V. Like piezo buzzers, magnetic buzzers are in household alarms and devices like clocks, watches and keyboards.
Magnetic buzzers use an electromagnetic element rather than a piezoelectric element. The buzzer coil is a wire that connects to the circuit to create a magnetic field. The buzzer also contains a flexible ferromagnetic disk. A plastic casing houses the entire unit.
A wound electromagnetic coil converts electrical current into a magnetic field. As current alternates, the buzzer coil’s inductance shapes the field strength and timing, precisely pulling and releasing the diaphragm.
The alternating current creates a changing magnetic field that moves the ferromagnetic diaphragm, vibrating the disk and making the alarm buzzer sound. The buzzer coil is central to acoustic efficiency, as it improves sensitivity and loudness while reducing power loss.
Active and passive buzzers differ in how they generate tone. An active buzzer has a built-in oscillator that automatically produces a noise in response to a simple DC voltage. In contrast, passive buzzers lack an internal oscillator and therefore require an external AC signal to generate a tone.
Active buzzers output a single, fixed-frequency tone, making them a simpler option. In contrast, by controlling the input frequency, passive buzzers allow more variable tones and melodies but require more complex external circuitry or programming.
You can buy active piezo and magnetic units, each with an internal oscillator turned to a nominal frequency, usually around 2 to 4 kHz. Likewise, passive piezo and magnetic buzzers are available, which are essentially transducers that require an external signal to create motion.
When choosing between active and passive, you’ll want to consider control and simplicity. An active buzzer is plug-and-play, as it runs directly from a microcontroller pin or switchable supply, producing a fixed tone with minimal code. The trade-off is limited pitch control and sometimes a higher current draw at a single, built-in frequency.
In contrast, a passive buzzer offers full control over pitch, melody and volume by varying the external signal, but needs a proper driving circuit. For example, you might need a transistor for magnetic buzzers, or push-pull for piezo and timer/pulse-width modulated resources in firmware.
In summary, active buzzers have an internal oscillator, DC input and fixed tone, while passive buzzers require an external signal but have a flexible tone. Match the buzzer type to your available pins, power budget and needs.
When selecting a buzzer for your circuit, the decision often hinges on specs like voltage, current, drive circuit compatibility, sound quality and performance. Magnetic buzzers typically operate at lower voltages and higher currents than piezo buzzers. Let’s define core concepts before diving into the details.
Every material has a resonant frequency, or the natural frequency at which it produces maximum sound output with minimal power input. Piezo buzzers typically operate at higher resonant frequencies than magnetic buzzers, making them ideal for applications that require sharp, high-pitched tones with low energy consumption.
The sound pressure level, typically expressed in pascals or decibels, indicates how loud the buzzer is proportional to the input voltage. The SPL value will vary depending on how far away you are from the buzzer when taking the measurement.
Frequency response measures how efficiently a buzzer can produce sound energy at a given frequency, 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 typically have a less linear relationship. In other words, piezo buzzers typically offer a broader range of usable frequencies than magnetic buzzers.
Variables like frequency and SPL shape how the buzzer sounds and how well it grabs attention. Depending on your needs, the output might be a steady tone, a pulsing beep or a dynamic siren pattern.
Ultimately, selecting the appropriate combination of sound characteristics will meet technical requirements while providing effective alerts that suit your situation.
Your selection starts with understanding each type’s electrical and acoustic characteristics.
Both types are available in active and passive forms, allowing flexibility in circuit design.
Audible sound transducers are another consideration for extremely custom applications. Transducers consist of a casing, typically a piezo element, and an electrical contact. They do not include a built-in driving circuit, giving engineers more design flexibility to modify or optimize their application’s frequency.
| Feature | Piezo Buzzer | Magnetic Buzzer |
|---|---|---|
| Voltage Range | 3V – 24V+ | 1.5V – 12V |
| Current Consumption | Lower | Higher |
| Active/Passive | Both | Both |
| Sound | Wide range of tones | Basic tone |
The voltage rating determines power supply requirements while directly affecting how loudly and reliably the buzzer operates. Using a buzzer at a voltage lower than its rated value could result in a weak, inaudible sound, while exceeding the rated voltage might damage internal components or decrease the buzzer’s usable lifespan.
Common voltage ratings for buzzers include 3V, 5V, 12V, and 24V.
Always ensure the power supply and voltage rating match when choosing a buzzer. If the supply voltage is too high, you might use a series resistor or a voltage regulator to protect the buzzer. If your application requires a loud, unmistakable audible alert, choose a buzzer with a higher voltage rating and corresponding SPL. However, a lower-voltage buzzer might be more appropriate for low-power or compact devices.
Piezo and magnetic buzzers each offer distinct advantages, and the best fit depends on your voltage requirements, sound profile and design constraints. Count on APC International to help you find a solution backed by expert guidance and proven performance.
We offer various piezo buzzer options in a range of sizes and configurations for many applications, from multi-tone sound generators to self-oscillating buzzers.
Please contact APC today to learn more about our piezo buzzer products.
