passive buzzer

The passive buzzer uses the phenomenon of electromagnetic induction to attract or repel the electromagnet formed after the voice coil is connected with the permanent magnet to drive the diaphragm to produce sound. The direct current can only continuously push the diaphragm but cannot produce sound , can only produce sound when connected or disconnected.

passive buzzer

Working principle of passive electromagnetic buzzer

The AC signal generates an alternating magnetic flux on the core column of the bracket through the wire wrapped around the bracket, and the alternating magnetic flux and the constant magnetic flux of the magnetic ring are superimposed, so that the molybdenum sheet vibrates at a given frequency of the AC signal and Cooperate with the resonant cavity to produce sound. The response curve and gap value of the entire frequency and sound pressure of the product, the natural vibration frequency of the molybdenum sheet (which can be roughly refracted as the thickness of the small molybdenum sheet), the frequency of the shell (Helmholtz resonant cavity), the magnetic strength of the magnetic ring enameled wire Wire diameter is directly related.

The passive buzzer has no distinction between positive and negative. It is similar to a loudspeaker. As long as electrical signals of different frequencies are loaded on the two legs, the sound can be realized, and the sound produced according to different frequencies is also different.

When driven by a square wave signal source, a diode should be connected in antiparallel to prevent the high-voltage reverse electromotive force generated when the power is suddenly cut off from breaking down other components and shortening the service life.

Active buzzers are often more expensive than passive ones, because there are multiple oscillating circuits inside, and the sound at a specified frequency can be emitted only by connecting to a DC power of rated voltage. The frequency is determined by the internal oscillating circuit and cannot be changed.

Advantages of passive buzzer

1. Low production cost

2. Wide sound frequency range

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