The structure principle and production of buzzer

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The structure principle and production of buzzer [Copy link]

(I) Introduction to Buzzers 1. Function of Buzzer: Buzzer is an electronic sounder with an integrated structure, powered by a DC power supply. It is widely used as a sound-generating device in electronic products such as computers, printers, copiers, alarms, electronic toys, automotive electronic equipment, telephones, timers, etc. 2. Classification of Buzzers: They are mainly divided into two types: piezoelectric buzzers and electromagnetic buzzers. 3. Circuit graphic symbol of Buzzer: Buzzer is represented by the letter "H" or "HA" (the old standard uses "FM", "LB", "JD", etc.) in the circuit. Buzzer Diagram (II) Structural Principle of Buzzer 1. Piezoelectric Buzzer: Piezoelectric Buzzer is mainly composed of multivibrator, piezoelectric buzzer sheet, impedance matching device, resonance box, shell, etc. Some piezoelectric buzzer shells are also equipped with light-emitting diodes. Multivibrator is composed of transistors or integrated circuits. When the power is turned on (1.5V-15V DC working voltage), the multivibrator starts to vibrate and outputs an audio signal of 1.5-2.5kHZ. The impedance matcher drives the piezoelectric buzzer to make a sound. The piezoelectric buzzer is made of lead zirconate titanate or lead magnesium niobate piezoelectric ceramic materials. Silver electrodes are plated on both sides of the ceramic sheet, and after polarization and aging treatment, they are glued together with brass sheets or stainless steel sheets. 2. Electromagnetic buzzer: The electromagnetic buzzer consists of an oscillator, an electromagnetic coil, a magnet, a vibrating diaphragm and a shell. After the power is turned on, the audio signal current generated by the oscillator passes through the electromagnetic coil, causing the electromagnetic coil to generate a magnetic field. The vibrating diaphragm vibrates periodically and makes sound under the interaction between the electromagnetic coil and the magnet. (III) Making a buzzer (1) Preparation of electromagnet M: Wrap 100 turns of wire around an iron bolt about 6 cm long, leaving 5 cm at the end of the wire as a lead, tape the coil with transparent tape to prevent it from loosening, and then tape it to a box with tape. The electromagnet is ready. (2) Preparation of shrapnel P: Cut a long iron sheet about 2 cm wide from the tin can, bend it into a right angle, connect one lead of the electromagnet to the shrapnel, and then tape the shrapnel tightly to the wooden board. (3) Use a paper clip as contact Q, use a book to raise the paper clip, stick it with tape, lead out a wire, and connect the circuit as shown. (4) Adjust the distance between M and P (by moving the box) so that the electromagnet can attract the spring, and adjust the distance between the contact and the spring so that they can just touch. When the power is turned on, you can hear a buzzing sound. (IV) Active Buzzers and Passive Buzzers Teach you how to distinguish active buzzers from passive buzzers A small buzzer currently sold on the market is widely used in various electrical equipment, electronic production, single-chip microcomputers and other circuits that need to make sounds because of its small size (only 11mm in diameter), light weight, low price and reliable structure. The appearance of active buzzers and passive buzzers is shown in Figures a and b. a) Active b) Passive From the appearance of Figure a and Figure b, the two buzzers seem to be the same, but if you look closely, you will find that their heights are slightly different. The height of active buzzer a is 9mm, while the height of passive buzzer b is 8mm. If you place the pins of the two buzzers facing upward, you can see that the one with the green circuit board is the passive buzzer, and the one without the circuit board and sealed with black glue is the active buzzer. To further distinguish active buzzers from passive buzzers, you can also use the multimeter resistance range Rxl test: connect the black test lead to the buzzer "+" pin, and touch the other pin back and forth with the red test lead. If it triggers a click, click sound and the resistance is only 8Ω (or 16Ω), it is a passive buzzer; if it can make a continuous sound and the resistance is more than a few hundred ohms, it is an active buzzer. An active buzzer can make continuous sound by directly connecting it to the rated power supply (new buzzers are marked on the label); and a passive buzzer, like an electromagnetic speaker, needs to be connected to the audio output circuit to make sound.