8/17/2023 0 Comments A piezo buzzer![]() Because of the coil’s inductance, the diode shown in the diagram is needed to clamp the flyback voltage when the transistor is turned off quickly.įigure 4. The switch is typically a bipolar transistor or FET and is used to amplify the excitation waveform. In addition to basic continuous or pulsed sounds, you can generate sounds such as multi-tone warnings, sirens or chimes.įigure 4 shows the application circuit for a magnetic transducer. With no driving circuitry built in, a transducer gives you the flexibility to achieve a variety of sounds using various frequencies or arbitrary waveshapes. An indicator buzzer produces sound when a dc voltage is applied. This means that multi-frequency sounds such as sirens or chimes are not possible with indicator buzzers.įigure 3. While you only need to apply a dc voltage, one can only get a continuous or pulsed audio signal since the frequency is fixed internally. This simplifies circuit design (figure 3), enabling a plug-and-play approach, in exchange for reduced flexibility. The decision of whether to choose an indicator or transducer type is guided by the range of sounds required and the design of the associated circuitry to drive and control the buzzer.Īn indicator comes with driving circuitry built into the device. However, if loudness is a key requirement, piezo buzzers can typically produce a higher Sound Pressure Level (SPL) than magnetic buzzers but also tend to have a larger footprint. The characteristics of the drive signal you have available can influence whether you choose a magnetic or piezo buzzer for your application. On the other hand, while piezo buzzers exhibit a reasonably linear relationship between the input signal strength and the output audio power, the audio power of magnetic buzzers fall sharply with diminishing signal strength. The piezo buzzer is modeled as a capacitor, whereas the magnetic buzzer is modeled as a coil in series with a resistor.įor both types, the frequency of the resulting audible tone is determined by the frequency of the driving signal and can be controlled over a wide range. ![]() In contrast to the magnetic buzzer, the piezo buzzer is a voltage-driven device the operating voltage is usually higher and may be between 12V and 220V, while the current is less than 20mA. A voltage applied across these electrodes causes the piezoelectric material to deform, resulting in the movement of air that can be detected as sound. A disk of piezoelectric material is supported at the edges in an enclosure and electrical contacts are fabricated on the two sides of the disk. Magnetic buzzer construction and operating principle.įigure 2 shows the elements of a piezo buzzer. The current through the coil is determined by the applied voltage and the coil impedance.įigure 1. This deflection of the disk causes air in the vicinity to move, and this is interpreted as sound by the human ear. When the current is passed through the coil, the disk is attracted towards the coil and returns to its normal position when the current is not flowing. ![]() The applied voltage can be as low as 1.5V or up to about 12V.Īs figure 1 shows, the mechanism comprises a coil and a flexible ferromagnetic disk. ![]() Magnetic buzzers are essentially current-driven devices, typically requiring more than 20mA to operate. Let us take a look at the principles behind the different mechanisms and then consider whether the magnetic or piezo type (and the choice of indicator or actuator) could be right for your project. You can also choose between indicator and transducer types, depending on the sounds you want and the circuit-design skills available to you. Your choice can depend on the characteristics of the drive signal, or the output audio power required and physical space available. Fundamentally, a buzzer is usually either a magnetic or piezoelectric type.
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