The element is composed of a piezoelectric ceramic and a metal plate. Both the piezoelectric disc and metal plate are held together with an adhesive. The piezoceramic disc has electrodes attached to it.
The piezoelectric disc expands and contracts diametrically when an alternating current is applied to it. This produces vibrations in the piezoelectric element and generating the sound of a particular frequency or range of frequencies. The piezoelectric element is supplied alternating current from an oscillator circuit. In indicator-type piezo buzzers, the oscillator circuit is built-in to produce a fixed frequency or range of frequencies. In transducer type piezo buzzers, an external oscillator circuit is required.
This oscillator circuit is usually a square wave generator. Many piezo buzzers have a feedback line. In such buzzers, the piezoelectric element is divided into two electrically isolated parts. When the main piezo element is actuated, it squeezes the feedback component, producing a feedback voltage.
The piezo buzzers have a wide operating voltage that ranges from 3V to V. Most of the piezo buzzers used in electronic circuits have an operating voltage between 3V and 12V. These buzzers have high sound pressure levels. They have very low current consumption. The buzzers used in electronic applications have current consumption as low as 30 mA. The piezo buzzers have a large footprint and are preferred to be used in cost-sensitive electronic applications. Magnetic buzzers In a magnetic buzzer, there is a ferromagnetic disc that is attached to a pole.
There are magnets around the pole which maintains the disc in a rest position. There is a coil below the ferromagnetic disc that acts as an electromagnet.
When current is supplied to the coil, the disc is attracted to the coil. When there is no current in the coil, the disc returns to its rest position. A weight above it controls the vibrations of the disc. When an oscillating signal is applied to the coil, the electromagnetic field generated from it also fluctuates, causing vibrations in the ferromagnetic disk. This way, the sound of the frequency same as the frequency of the applied oscillating signal is produced by the magnetic buzzer.
Magnetic buzzers come in both transducer as well as indicator configurations. The magnetic buzzers have a narrow operating voltage that ranges from 1V to 16V. These buzzers produce lower-rated frequencies have low sound pressure levels. These have a slightly greater current consumption in comparison to piezo buzzers. Their current consumption can be as high as mA. When the current does not flow through the coil, the flexible ferromagnetic disk returns to the "rest" position.
The sound produced by the magnetic buzzer is produced by the movement of the ferromagnetic disk in a similar way to the way the cone in the speaker produces sound. The difference between a piezoelectric buzzer and an electromagnetic buzzer is that piezoelectric buzzers are of lower current consumption and works at higher rated frequency and wider operating voltage. The piezoelectric buzzer is modeled as a capacitor, and the electromagnetic buzzer is modeled as a coil in series with a resistor.
The reason for distinguishing the two piezo buzzers is that they have different generation principles, and the parts used to be matched are also different. If you apply a DC voltage to them and make a buzzing sound, it means it is an active piezo buzzer.
Passive piezo buzzers need external driving circuit and is complex to design in, and it runs on AC only, they usually are called 'Transducers', 'Elements' instead of 'Buzzers'. There are many specifications and varieties of piezo buzzers, such as piezoelectric buzzers and electromagnetic buzzers.
Working voltage: Electromagnetic buzzer ranges from 1. Therefore, the piezoelectric buzzer is more commonly used, and a voltage above 9V can get a relatively higher SPL. Current consumption: Depending on the voltage, it ranges from tens to hundreds of milliamperes. The piezo buzzer is so relatively power-saving that lower milliamperes can work normally, while the magnetic buzzer needs about three times more current when it starts.
Frequency ranges: 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.
Therefore, piezo buzzers tend to have a wider range of usable frequencies than magnetic buzzers. The above are some aspects that we need to consider when choosing a buzzer. The purpose of saying so much is to teach you how to choose whether the product you need is an indicator or a transducer. Look carefully at the specifications of the transducer and piezo indicator, you can find that the operating voltage unit of the transducer is Vp-p, and the voltage unit of the indicator is VDC.
From the description of the operating voltage, you can judge that a product is a buzzer or transducer. At the same time, there is a description of capacitance in the parameters of the transducer but not the piezo buzzer.
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