1. According to the principle of its driving mode, it can be divided into: active buzzer (including driving circuit, also known as self-excited buzzer) and passive buzzer (external driving, also known as other excited buzzer);
2. According to different construction methods, it can be divided into:magnetic buzzer and piezoelectric buzzer;
3. According to different packages, it can be divided into dip buzzer (pin buzzer) and SMD buzzer (micro buzzer);
4. According to the difference of current, it can be divided into DC buzzer and AC buzzer. Among them, DC is the most common piezoelectric buzzer, which uses piezoelectric materials, that is, when the piezoelectric materials are deformed by external forces, the piezoelectric materials will generate charges. Similarly, piezoelectric materials will deform when energized. The electromagnetic buzzer mainly uses the characteristics that the energized conductor will generate a magnetic field, and uses a fixed permanent magnet and the energized conductor to generate a magnetic force to push the tympanic membrane fixed on the coil.
The utility model is suitable for two kinds of piezoelectric alarm devices with simple tone and durable structure. The electromagnetic type is mostly used in voice, music and other equipment because of its good sound quality.
In appearance, the height of the two is slightly different. The height of active buzzer A is 9mm, while the height of passive buzzer B is 8mm. In many cases, the height of active buzzer is higher than that of passive buzzer. If the pins of the two buzzers are placed upward, it can be seen that the one with green circuit board is a passive buzzer, and the one without circuit board and closed with black glue is an active buzzer.
To judge the active buzzer and passive buzzer in one step, you can also test with the resistance gear RXL of the multimeter: connect the black lead to the "-" pin of the buzzer, and touch the red lead back and forth on the other pin. If there is a click and click sound and the resistance is only 8 Ω (or 16 Ω), it is a passive buzzer; If it can make continuous sound and the resistance is more than hundreds of ohms, it is an active buzzer.
The active buzzer can continuously sound when directly connected to the rated power supply (the new buzzer is indicated on the label); The passive buzzer, like the electromagnetic speaker, needs to be connected to the audio output circuit to make sound. Difference between active buzzer and passive buzzer:
Note: the "source" here does not refer to the power supply, but refers to the shock source. In other words, the active buzzer has a shock source inside, so it will sound as soon as it is powered on;
There is no oscillation source inside the passive, so it can't sound with DC signal. 2k-5k square wave must be used to drive it. The active buzzer is often more expensive than the passive one because there are many oscillation circuits inside.
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. After polarization and aging treatment, they are bonded with brass sheet or stainless steel sheet.
Piezoelectric ceramic sheet is an electronic pronunciation element. A piezoelectric ceramic dielectric material is placed between two copper circular electrodes. When the AC audio signal is connected on the two electrodes, the piezoelectric sheet vibrates according to the size and frequency of the signal to produce the corresponding sound. Due to its simple structure and low cost, piezoelectric ceramics are widely used in electronic and electrical appliances, such as toys, pronunciation electronic watches, electronic instruments, electronic clocks, timers and so on. Ultrasonic motor is made of related properties.
Triode BG1 and BG2 form a two-stage direct coupled low-frequency amplification circuit. A piezoelectric ceramic sheet HTD is connected between the base of BG1 tube at the input end of the amplifier and the collector of BG2 tube at the output end of the amplifier. Here, HTD is both a feedback element (using inter pole distributed capacitance) and a pronunciation element, which simplifies the circuit.
Resistor R1 is the bias resistor of BG1 tube. On the one hand, its resistance value determines the working current of the circuit, and also has a great impact on the pronunciation tone. R1 resistance increases, HTD frequency becomes lower, R1 resistance decreases, and HTD frequency becomes higher. Resistance R2 is the collector load resistance of triode BG2. Capacitor C1 is the negative feedback capacitance of BG1 tube. Changing its capacity can change the pronunciation of HTD.
Piezoelectric buzzer has the characteristics of small volume, high sensitivity, low power consumption, good reliability, low cost and good frequency characteristics. Therefore, it is widely used in the alarm of various electrical products. With the characteristics of low cost, good frequency characteristics and sensitivity, the high-voltage electric buzzer has small volume. The most common are small electronic products such as music greeting cards, electronic doorbells and electronic toys, which are used as sound generating devices, low power consumption, good reliability, electronic watches, sound generating purposes and pocket calculators.
The electromagnetic buzzer is composed of oscillator, electromagnetic coil, magnet, vibrating diaphragm and shell. After the power is connected, the audio signal current generated by the oscillator passes through the electromagnetic coil to generate a magnetic field. The vibrating diaphragm vibrates and sounds periodically under the interaction of the electromagnetic coil and magnet.
Electromagnetic buzzer is widely used in computers, printers, copiers, alarms, electronic toys, automotive electronic equipment, telephones, timers and other electronic products.
The electric buzzer uses the piezoelectric effect of piezoelectric ceramics to drive the vibration of metal sheets to make sound; The electromagnetic buzzer uses the principle of electromagnetism to suck down the metal diaphragm when it is powered on and bounce back according to the elasticity of the diaphragm when it is not powered on. Therefore, the piezoelectric buzzer is driven by square wave and the electromagnetic buzzer is driven by 1 / 2 square wave. The piezoelectric buzzer needs relatively high voltage to have enough sound voltage. Generally, it is recommended to be more than 9V or 12v dc piezo buzzer . Some specifications of piezoelectric can reach more than 120dB, and larger ones can easily reach 100dB.
Electromagnetic buzzer: with 1.5V, it can emit sound pressure of more than 85dB, but the current consumption will be much higher than that of piezoelectric buzzer. When the size is the same, the response frequency of electromagnetic buzzer can be relatively low; The sound pressure of electromagnetic buzzer is generally up to 90dB Mechanical buzzer is a small category of electromagnetic buzzer.
Piezoelectric materials have found application in a wide range of areas, such as medical instruments. control of industrial processes, semiconductor manu-facturing systems,household electrical appliances,communication control systems, various measuring instruments, and other areas.
that use piezoelectric materials - pumps, sewing machines, sensors (pressure, icing, angular velocities, etC.), optical instruments, laser printers, motors for autofocus cameras, and many others. In this case, the scope of these materials is constantly growing. Using a piezoelectric element is usually reduced to four categories: sensors, generators, power actuators, and transducers.
In generators, piezoelectric materials can generate a voltage suflcient to cause a spark between the electrodes, and thus can be used as electrodes to ignite
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