Passive buzzer buzzer related knowledge

2021-10-29


passive buzzer is an electronic sounder with integrated structure, powered by DC voltage. It is widely used as a sound generating device in computers, printers, copiers, alarms, electronic toys, automotive electronic equipment, telephones, timers and other electronic products. Passive buzzer is mainly divided into two kinds: piezoelectric buzzer and electromagnetic buzzer. The buzzer is indicated by the letters "h " or "HA " in the circuit.

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Because the working current of the passive buzzer is generally large, the I/O port of MCU cannot be directly driven, so it needs to be driven by an amplification circuit, and triode is generally used to amplify the current. The buzzer drive circuit generally includes the following parts: triode, buzzer, freewheeling diode and power filter capacitor: 1 , passive buzzer sounding element, which sounds by applying DC voltage ( active buzzer ) or square wave ( passive buzzer ) at both ends. Its main parameters include external dimensions, detection direction, working voltage, working frequency, working current, driving mode (DC/ square wave ) , etc., which can be selected according to needs. 2 . The flywheel diode buzzer is essentially an inductive element, and its current cannot be transient, so it is necessary to provide a flywheel diode to provide the flywheel. Otherwise, a spike voltage of several tens of volts will be generated across the buzzer, which may damage the drive transistor and interfere with other parts of the entire circuit system. 3 , filter capacitor filter capacitor C1 is used to filter out the influence of buzzer current on other components and improve the AC impedance of the power supply. If possible, consider connecting a 220uF electrolytic capacitor in parallel. 4 , triode transistor Q1 acts as a switch, and the high level of its base causes the triode to saturate and conduct, making the buzzer sound. The low base level turns off the triode and the buzzer stops sounding.

We should be very familiar with speakers. The commonly used headphones are two small speakers. The radio, MP3 player and TV stereo are all speakers of different power. The speaker, also known as the speaker, is an electro-acoustic conversion device that converts analog electrical signals into sound signals and is a broadband sounding device. We can often hear the buzzer, which is in our computer mainframe. When some memory sticks or video cards in the host are loose, there will be an alarm sound when the computer is turned on. This sound is emitted by the buzzer.

Passive buzzer is an integrated electronic sounder, which can emit monotonous sound under different driving waveforms, and is a narrow frequency sound device. The difference between a speaker and a passive buzzer is that the speaker can emit a variety of sounds, while a passive buzzer can only emit a few monotonous sounds. From the perspective of drive circuit and price, the buzzer is relatively simple. Simple sounds such as general alarms and prompts are issued by a buzzer, and complex sounds such as music need to be issued through a speaker.


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