A buzzer is a device that converts audio signals into sound signals. They are usually powered by DC voltage and are found in products such as alarms, computers, printers, and other electronics. Buzzers are mainly divided into two categories: piezoelectric and electromagnetic, represented in a circuit by H or HA respectively. Depending on different designs and uses, buzzers can emit a broad range of sounds including music, sirens, alarms, or electric bells. In this blog, we will take a look at buzzers and discuss their functions and characteristics.
Piezoelectric buzzers use the piezoelectric effect of ceramics and the pulse current to drive the vibration of a metal plate to create sound. Buzzers of this category are usually composed of a multi-resonator, piezoelectric plate, impedance matcher, resonance box, housing, etc. Within the multi-resonator are transistors or integrated circuits and, when the power supply is switched on, the multi-resonator begins to oscillate and put out an audio signal. The impedance matcher then pushes the piezoelectric plate to create sound. The piezoelectric plate is made of either lead zirconate titanate or lead magnesium niobate piezoelectric ceramic, and silver electrodes are plated on each side of the ceramic sheet. Once polarized and aged, the silver electrodes are then bonded together with brass or stainless steel sheets
Adversely, the electromagnetic buzzer comprises an oscillator, solenoid coil, magnet, vibration diaphragm, housing, and associated parts. When the power supply is turned on, the audio signal from the oscillator passes through the solenoid coil, creating a magnetic field. The vibration diaphragm periodically vibrates and sounds under the interaction of the solenoid coil and the magnet. The frequency of a standard electromagnetic buzzer is 2-4 kHz.
Buzzers are further classified in two ways: the buzzer construction and the way the buzzer is driven. Piezoelectric buzzers use piezoelectric materials that generate an electrical charge when the material is deformed by an external force. This material also deforms when energized. Electromagnetic buzzers, on the other hand, mainly use the magnetic field generated by the energized conductor to drive the drum film on the coil. Piezoelectric buzzers are simple and durable, but only offer a single tone and color difference for alarms and other equipment. Electromagnetic buzzers, thanks to their good sound and color, can be used for voice, music, and other applications.
In regard to how the buzzer is driven, a buzzer can either be active (with drive line) or passive (external drive). Active buzzers have an oscillator inside that chimes when energized. The ideal signal is DC and usually marked as VDC, VDD, or other, which can convert direct current into pulse signals. In a passive buzzer, there is no internal oscillator, and it is not compatible with DC signals. These must be driven by a 2K-5K square wave in which the magnetic circuit is constant.
There are many different specifications of buzzers available. When selecting the appropriate buzzer, the main parameters to consider include working voltage, current consumption, drive mode, size, and sound pressure. After selecting the right buzzer, there are also precautions to consider when using it. First, it should never be used in an environment outside the marked working temperature. Second, any welding should be carried in adherence to an approved welding method: manual welding, wave soldering, and reflow soldering. Third, foreign debris should not be allowed to enter the buzzer. Fourth, non-waterproof buzzers should be kept as far away from water as possible. Finally, the buzzer should never be used outside its rated working voltage.
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