Introduction to the structure and principle of piezoelectric buzzer
The piezoelectric buzzer is a piezoelectric ceramic piece that is pressed by a high pressure and adhered to a vibrating metal piece. When an AC voltage is applied, mechanical deformation stretches and contracts due to the piezoelectric effect, and this characteristic is used to vibrate the metal piece to make an audible sound.
The piezoelectric buzzer is divided into a feedback buzzer (self-excited) and a non-return buzzer (external excitation). When the feedback buzzer is matched with the positive feedback oscillation circuit, a single tone with the same frequency as the resonant cavity is generated; and the non-returned buzzer can be combined with an external oscillation circuit to select any frequency to emit sound.
The following are the two ways to fix the piezoelectric buzzer:
a. Peripheral support method – the outer edge of the buzzer is fixed in the resonant cavity, generally no feedback buzzer is used, and the buzzer must match the frequency of the resonant cavity to have a higher sound pressure output, and The push signal is generated by the external oscillating circuit to make the buzzer sound.
b. Node Support Method – The buzzer is fixed in a ring structure of the same size as the diameter of the ceramic piece. If the resonant cavity is well designed and matched with the correct frequency feedback buzzer and positive feedback circuit, it will produce a large sound pressure and the correct frequency.