What is an electromagnetic buzzer? What is the working principle?

Buzzer is an electronic sounder with integrated structure, powered by DC voltage. It is widely used in computers, printers, copiers, alarms, electronic toys, automotive electronic equipment, telephones, timers and other electronic products as a sound device.

I don't know if you know. At present, it is widely used in some electronic products, such as computers, copiers, alarms, toys, timers and other small and medium-sized electronic equipment. Used to issue an alarm or indicate content. Mainly divided into piezoelectric buzzer and electric electromagnetic buzzer two. So what is the working principle of the electromagnetic buzzer? Let's take a look.

The working principle of electromagnetic buzzer

1. Voltage buzzer Piezoelectric buzzer is mainly composed of multivibrator, piezoelectric buzzer, impedance matcher, resonant box and shell. Some piezoelectric buzzers are also equipped with light-emitting diodes on their housings.

Multivibrator is composed of transistors or integrated circuits. Turn on the power supply (1.5~15V DC working voltage), the multivibrator vibrates, outputs an audio signal of 1.5~2.5kHZ, and the impedance matcher pushes the piezoelectric buzzer to sound.

The piezoelectric buzzer is made of lead zirconate titanate or lead magnesium niobate piezoelectric ceramic material. The ceramic sheet is plated with silver electrodes on both sides, polarized and aged, and then bonded with brass sheet or stainless steel sheet.

2. Electromagnetic buzzer consists of oscillator, electromagnetic coil, magnet, diaphragm and 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. Under the interaction, the diaphragm vibrates periodically.

Manufacturing technology of electromagnetic buzzer

(1) Prepare electromagnet M: Wind 100 turns of wire on an iron bolt about 6 cm long, leaving 5 cm at the end of the wire as a lead. Stick the coil with transparent tape to prevent the coil from loosening, and then stick it on a box with tape, and the electromagnet is completed.

(2) Preparation of shrapnel P: Cut a long iron piece about 2cm wide from the tin can, bend it at a right angle, connect a lead wire of the electromagnet to the shrapnel, and then use tape to glue the shrapnel On the board.

(3) Use a paper clip to make the contact Q, the paper clip is padded with a book, and a wire is drawn out with tape, as shown in the figure to connect the circuit.

(4) Adjust the distance between M and P so that the electromagnet can attract the shrapnel, adjust the distance between the contact and the shrapnel so that they just touch, and the buzzer can be heard after power on.

Driving mode of electromagnetic buzzer

Since the self-excited buzzer is driven by DC voltage, AC signal driving is not required. Only the drive level output to the drive port, through the transistor to amplify the drive current, the buzzer can sound. It's very simple. I won't explain the self-excited buzzer here.

Single-chip microcomputer excited buzzer drive there are two ways: one is to directly drive the PWM output port, the other is the use of I/O timing flip level generated by the drive waveform to drive the buzzer.