Ⅰ. What is a buzzer?
Ⅱ. The structure of the buzzer
Ⅲ. The working principle of buzzer
Ⅳ. The production of the buzzer
Ⅴ. Parameters of the buzzer
Ⅵ. The typical circuit of the buzzer
Ⅶ. The advantages and disadvantages of the buzzer
Ⅷ. The component selection of the buzzer circuit
Ⅸ. The difference between active buzzer and passive buzzer
Ⅹ. Precautions for using the buzzer
Ⅰ. What is a buzzer?
The buzzer is an electronic sounder with an integrated structure. It is powered by DC voltage and is widely used as a sounding device in electronic products such as computers, printers, copiers, alarms, electronic toys, automotive electronic equipment, telephones, and timers. For example, the host computer of a desktop computer will make a "beep" sound when it is turned on, and the washing machine will make a sound when the button is pressed and the laundry is completed. These are all sent by the buzzer. The buzzer is represented by the letter "H" or "HA" in the circuit (the old standard uses "FM", "ZZG", "LB", "JD", etc.).
Ⅱ. The structure of the buzzer
1. Piezoelectric buzzer structure
(1) Leads: The piezoelectric sheet is connected to the circuit through the leads. When a voltage is applied, the leads transmit the voltage to the piezo.
(2) Diaphragm: The piezoelectric sheet is connected to a diaphragm, usually made of metal or plastic material. The vibrating membrane also vibrates when the piezoelectric sheet vibrates, thereby amplifying sound production.
(3) Piezoelectric Element: This is the core element of the buzzer, usually made of piezoelectric ceramic materials, such as piezoelectric ceramic wafers. When a voltage is applied, the piezoelectric sheet is mechanically deformed, causing vibrations.
(4) Backplate: There is a backplate under the vibrating membrane, which forms a cavity with the vibrating membrane. When the diaphragm vibrates, the air inside the cavity also vibrates, producing sound.
2. Electromagnetic buzzer structure
Electromagnetic buzzers use electromagnetic induction to generate sound. The following is the main structure of the electromagnetic buzzer.
(1) Magnet: We usually place a permanent magnet or electromagnet on the other side of the oscillator to enhance the vibration effect of the oscillator.
(2) Diaphragm: The vibrator is connected to a diaphragm, usually a film-like material. The diaphragm also produces sound when the oscillator vibrates.
(3) Leads: The buzzer is connected to the circuit through the leads. Electromagnetic effects in the coil cause vibrations when current is passed.
(4) Coil: There is a coil inside the buzzer, which is usually wound by wire. When current is passed through the coil, a magnetic field is created.
(5) Armature: We place an armature near the coil, usually a piece of metal. When the coil generates a magnetic field, it exerts force on the vibrator, causing the vibrator to vibrate.
Ⅲ. The working principle of buzzer
The principle of the conventional magnetic horn is different from the generally referred to buzzer. The buzzer generally refers to piezoelectric ceramics as the main component. Piezoelectric ceramics are a type of special ceramics capable of converting pressure and current into each other. This ability is due to its special crystal structure.
When the piezoelectric ceramic is subjected to a pressure in a certain direction to deform its crystal structure, it will generate an electric current inside, and the change of the current is closely related to the change of the pressure. vice versa. Therefore, using this characteristic, passing a certain frequency of current on the piezoelectric ceramic will cause a small deformation of the piezoelectric ceramic, and this deformation will drive the air to vibrate. If the frequency is appropriate, it can be heard by the human ear, that is, a buzzing sound is produced.
Ⅳ. The production of the buzzer
1. Prepare the electromagnet M: We wind the wire 100 times, use a 6 cm long iron bolt, and leave 5 cm at the end of the wire as a lead wire. We first secured the coil with a piece of clear tape so it wouldn't come loose, and attached it to a box, thus making an electromagnet.
2. Prepare the shrapnel P: We cut a long iron piece with a width of about 2 cm from the tin can, bent it into a right angle, connected a lead wire of the electromagnet to the shrapnel, and then glued the shrapnel to the wooden board.
3. We use a paper clip as the contact Q, use a book to put the paper clip on it, then fix it with tape, and then pull out a wire to connect the circuit.
4. We adjust the distance between M and P (by moving the box), so that the electromagnet can attract the shrapnel, and adjust the distance between the contact and the shrapnel, so that the two can just touch. After power on, we can hear the beep.
Ⅴ. Parameters of the buzzer
1. Driving Method
The drive mode of the buzzer can be direct current (DC) drive or pulse drive (PWM). Different driving methods will affect the response and sound quality of the buzzer.
2. Frequency Range
The frequency range in which the buzzer can emit sound is usually expressed in Hertz (Hz). Common frequency ranges range from a few hundred hertz to several kilohertz.
3. Sound Pressure Level
The sound output level of a buzzer is usually expressed in decibels (dB). The higher the sound pressure level, the louder the buzzer sound.
4. Operating Voltage
It refers to the voltage range in which the buzzer can work normally. Common operating voltages include 3V, 5V, 12V, etc., depending on the type and application of the buzzer.
Ⅵ. The typical circuit of the buzzer
The following is a typical circuit of a buzzer, taking an active buzzer as an example.
1. NPN type transistor
Many people on the Internet use 9013 for their circuit transistors, but there is no 9013 in proteus, so they are replaced with 2N551 similar to it. When the IO is set high, the b-end voltage of the NPN transistor is 0.7V higher than the e-end. At this time, the c terminal and the e terminal are turned on, and the buzzer starts to work. The function of the 3.3K pull-down resistor is to prevent false triggering of the buzzer by I0 in an unstable state.
2. PNP transistor
2N5401 and 2N5551 are a pair of transistors with different polarities but the same properties. When the I0 terminal is pulled low, after the e-terminal voltage is 0.7V higher than the b-terminal, the e-terminal and the c-terminal are turned on, and the buzzer starts to work. The pull-up resistor is to prevent false triggering of the buzzer when the IO is disturbed.
Ⅶ. The advantages and disadvantages of the buzzer
1. Advantages
(1) Small size
(2) Less energy consumption
(3) Simple compatibility
(4) Good frequency response
(5) Large voltage range and high sound pressure
2. Disadvantages
(1) It is difficult to control the sound and frequency of the buzzer. It requires the use of specialized controllers or circuits.
(2) The sound produced by the buzzer may be annoying, especially in the case of long-term and high-frequency use.
Ⅷ. The component selection of the buzzer circuit
The buzzer circuit has a large working current and needs to be driven by an amplifier circuit. Therefore, the buzzer circuit generally includes the following components.
1. Buzzer
When you apply a passive buzzer (square wave) or an active buzzer (DC voltage) across the sounding element, the following five points are critical. These factors include form factor, operating current, direction of sound, drive mode, and operating frequency. Also, you can select the desired parameters according to your needs.
2. Triode
The transistor saturates when the base rises. Therefore, the buzzer will sound. However, as the base voltage decreases, the transistor enters the cut-off state. This way it ends the sound.
This component helps filter the buzzer current from the rest of the circuit and improves AC power.
4. Freewheeling diode
The buzzer is a sensing element. So you can't change its current. But you can use freewheeling diodes to constantly monitor the continuous current. Otherwise, this may damage the driving transistor, causing the entire circuit system to collapse. Without the use of freewheeling diodes, the buzzer circuit can draw high currents of tens of volts.
Ⅸ. The difference between active buzzer and passive buzzer
Passive buzzer and active buzzer are two different types of sound devices, and there are some differences in their working principle, circuit connection and usage.
1. How to use: Since the frequency of the passive buzzer is fixed, generally only a single tone can be emitted. The active buzzer can produce different tones and music effects by controlling the frequency and duration of the signal.
2. Working principle: The passive buzzer uses the piezoelectric effect to generate sound and does not require an external power source. The active buzzer needs an external power supply to drive.
3. Circuit connection: Passive buzzers usually only have two pins, which are directly connected to the circuit to emit a fixed frequency sound. Active buzzers usually have three pins. One of them is a power pin, which is used to connect an external power source. The other two are signal pins, which are used to receive control signals and generate corresponding sounds.
Ⅹ. Precautions for using the buzzer
1. Do not use the buzzer in a temperature environment other than the marked working temperature (When the buzzer works outside the marked working temperature, the performance of the piezoelectric film and the shell will change, and the sound will be low).
2. Follow the marked soldering method (Commonly used soldering methods for buzzers include manual soldering, wave soldering, and reflow soldering. Wave soldering and reflow soldering are modern automated soldering technologies. Wave soldering is mainly for plug-in products, and reflow soldering is mainly for SMD products. Because the temperature of the two soldering methods is very high, the temperature resistance data must be used for the buzzer device. Of course, products suitable for wave soldering and reflow soldering can also be stopped by manual soldering.)
3. Prevent foreign matter from entering the sound hole of the buzzer (Foreign matter entering the sound hole of the buzzer may affect the vibration of the diaphragm, resulting in tiny or abnormal sounds).
4. The non-waterproof buzzer should prevent the buzzer device from being placed in a place where it may come into contact with water (Water entering the non-waterproof buzzer will cause product parts to rust, short circuit, and vibration to be blocked).
5. Do not use the buzzer outside the marked operating voltage (Due to the spontaneous polarization of ceramics, there is a residual polarization in the ceramic after these spontaneous polarizations have been processed and forced to align by the poling process. When the voltage is too high, this polarization will cause excessive discharge and charge, resulting in an arc phenomenon. The ceramic sheet breaks and the electric field decays).
