Introduction of buzzer

1. The function of the buzzer The buzzer is an integrated structure of electronic signal buzzer, using DC voltage power supply, widely used in computers, printers, copiers, alarms, electronic toys, automotive electronic equipment, telephones, timers and other electronics Used as a sounding device in the product.

2. Classification of buzzers Buzzers are mainly divided into two types: piezoelectric buzzer and electromagnetic buzzer.

3. The circuit graphic symbols of the buzzer The buzzer is represented by the letter "H" or "HA" in the circuit (the old standard uses "FM", "LB", "JD", etc.).

The structure principle of the buzzer

1. Piezoelectric buzzer The piezoelectric buzzer is mainly composed of a multivibrator, a piezoelectric buzzer, an impedance matcher, a resonance box, and a shell. Some piezoelectric buzzers are also equipped with light-emitting diodes.

Multivibrator is composed of transistors or integrated circuits. When the power is turned on (1.5~15V DC working voltage), the multivibrator starts to vibrate and outputs 1.5~2.5kHZ audio signals, and the impedance matcher drives 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 then glued together with the brass sheet or the stainless steel sheet.

2. Electromagnetic buzzer The electromagnetic buzzer is composed of oscillator, electromagnetic coil, magnet, vibrating 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. The vibrating diaphragm periodically vibrates and produces sound under the interaction of the electromagnetic coil and the magnet.

What is the difference between an active buzzer and a passive buzzer

The "source" here does not refer to the power source. It refers to the source of the shock. In other words, the active buzzer has an internal oscillation source, so it will beep as soon as it is powered on.

The passive has no internal oscillation source, so if you use a DC signal, you can’t make it sound. A square wave of 2K~5K must be used to drive it.

Active buzzers are often more expensive than passive ones because of the multiple oscillating circuits in them.

The advantages of passive buzzer are: 1. Cheap, 2. The frequency of the sound is controllable, and it can produce the effect of "multiple mifa Solaxi". 3. In some special cases, you can reuse a control port with the LED. The advantage of the active buzzer is: convenient program control.

Does the buzzer have positive and negative poles?

Same as electrolytic capacitors, the short leg is negative. If the two legs are cut to the same length and there is no other mark, you can only apply the voltage slowly.

How to distinguish the positive and negative poles of the buzzer

If the positive and negative poles of the buzzer are connected reversely, it will not sound. One of the two wires is "black or white" and this wire is negative.

buzzer circuit schematic

Use SH69P43 as the control chip and 4MHz crystal as the main oscillator.

PORTC.3/T0 is used as I/O port to drive buzzer LS1 through transistor Q2, while PORTC.2/PWM0 is used as PWM output port to drive buzzer LS2 through transistor Q1. In addition, two buttons are connected to PORTA.3 and PORTA.2 respectively. One is the PWM button, which is used to control the PWM output port to drive the buzzer; the other is the PORT button, which is used to control the I/O port drive. The buzzer is used. The I/O port connected to the button opens an internal pull-up resistor.