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The Structure of Buzzer

May 20, 2020

1 structural principle

1. Piezoelectric Buzzer The piezoelectric Buzzer is mainly composed of a multivibrator, a piezoelectric buzzer, an impedance matching device, a resonance box, and an outer casing. Some piezoelectric buzzer housings are also equipped with light-emitting diodes.

The multivibrator is composed of a transistor or an integrated circuit. When the power is turned on (1.5~15V DC working voltage), the multivibrator starts to oscillate and outputs an audio signal of 1.5~2.5kHZ, and the impedance matching device pushes the piezoelectric buzzer to sound.

The piezoelectric buzzer is made of lead zirconate titanate or lead magnesium niobate piezoelectric ceramic material. Silver electrodes are plated on both sides of the ceramic sheet, and after polarization and aging treatment, they are adhered to the brass sheet or the stainless steel sheet.

2. Electromagnetic buzzer The electromagnetic buzzer consists of an oscillator, an electromagnetic coil, a magnet, a diaphragm, and a casing.

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 periodically vibrates the sound under the interaction of the electromagnetic coil and the magnet.

2 production process

(1) Preparation of electromagnet M: Wrap 100 turns of wire on an iron bolt of about 6 cm in length, leaving 5 cm as a lead at the end of the wire, stick the coil with a transparent tape to prevent the coil from loosening, and then glue it with tape. On a box, the electromagnet is ready.

(2) Preparation of shrapnel P: Cut a long piece of iron with a width of about 2 cm from the canned box, bend it into a right angle, attach a lead of the electromagnet to the shrapnel, and then attach the shrapnel to the wooden board with tape.

(3) Use the paper clip as the contact Q, use the book to put the paper clip high, stick it with the tape, and lead a wire, as shown in the figure.

(4) Adjust the distance between M and P (by moving the box) so that the electromagnet can attract the shrapnel, adjust the distance between the contact and the shrapnel so that they can just touch, and the buzzer can be heard after being energized.

3 classification

Teach you to distinguish between active buzzer and Passive Buzzer

a) Active b) passive

From the appearance of Figures a and b, the two buzzers look the same, but look closely, the height of the two is slightly different, the active buzzer a, the height is 9mm, and the height of the passive buzzer b is 8mm. If the pins of both buzzers are placed face up, it can be seen that one type of green circuit board is a passive buzzer, and one type which is not sealed with black glue is an active buzzer. .

To further judge the active buzzer and passive buzzer, you can also use the multimeter resistance file Rxl file test: use the black pen to connect the buzzer "-" pin, the red test pen touches the other pin back and forth. If the trigger is hum, hum, and the resistance is only 8 Ω (or 16 Ω), it is a passive buzzer; if it can emit continuous sound, and the resistance is above several hundred ohms, it is an active buzzer.

The active buzzer is connected directly to the rated power supply (the new buzzer is marked on the label) for continuous sounding; the passive buzzer is the same as the electromagnetic Speaker and needs to be connected to the audio output circuit to sound. .

The difference between active buzzer and passive buzzer:

Note: The “source” here does not refer to the power source, but to the source of the oscillation.

In other words, the active buzzer has an internal source of oscillation, so it will be called as soon as it is energized.

The passive internals do not have an oscillating source, so if you use a DC signal, you can't make it scream. Must use 2K-5K square wave to drive it

Active buzzers are often more expensive than passive ones because of the multiple oscillating circuits inside

The advantages of passive buzzers are:

Cheap

2. The sound frequency is controllable and can make the effect of “多多米索索拉西”

3. In some special cases, a control port can be multiplexed with the LED.

The advantage of the active buzzer is that the program control is convenient.

蜂鸣器的结构原理和作工艺及分类

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