In addition, the sound decibel of piezoelectric buzzer is proportional to the voltage, and the voltage level is generally higher than that of electromagnetic buzzer. Because of the existence of the coil, the electromagnetic buzzer will produce a spike at the moment when the coil is on and off, which will affect the sound quality effect The piezoelectric buzzer has no coil, so there will be no influence of the spike pulse. The main difference between electromagnetic buzzer and piezoelectric buzzer in structure is coil and piezoelectric ceramic. Ultrasonic devices are also realized by this principle. Therefore, the buzzer can be made to sound only by applying a varying voltage to both ends of the piezoelectric ceramic. After the voltage is removed, the metal diaphragm will recover its original deformation. After the power is applied to the piezoelectric ceramic, the piezoelectric ceramic will change and drive the metal diaphragm to deform. Buzzer is mainly composed of piezoelectric ceramic and metal diaphragm. Piezoelectric buzzer works by using piezoelectric effect. (2) working principle of piezoelectric buzzer Changing the square wave frequency can change the sound. However, there is no oscillation source inside the passive buzzer, so it needs to be driven by a square wave externally. There is an oscillation source inside the active buzzer, which only needs to apply a suitable voltage to both ends of the coil. Battery buzzer can be divided into active buzzer and passive buzzer according to whether there is vibration source inside. If a varying current is supplied, the buzzer will sound. After an appropriate voltage is applied to both ends of the coil, the current flowing through the coil will generate a magnetic field, which will deform the metal diaphragm. The electromagnetic buzzer is composed of a coil and a metal diaphragm. (1) working principle of electromagnetic buzzer Its working principle is described in detail below. The biggest difference between the two is the working principle. The buzzer commonly used on the development board and the experimental board is an electromagnetic buzzer. According to different working principles, it can be divided into electromagnetic buzzer and piezoelectric buzzer. # include "pitches.Buzzer is a commonly used sounding component in the design of electronic products. The pitches library is not found in the Arduino IDE but you can download the ZIP file from Github and include the library in the Arduino IDE by clicking in the menu line: Sketch -> Include Library -> Add. If you take a look into the source code of the library you see that the library is nothing else than a lookup table for different notes to their frequency. You could now use the tone function and define the connected output pin, the frequency and the duration of the output generation, but if you do not know the frequency of different notes, we can also use the pitches library from Mike Putnam. Instead we use the Arduino tone function to generate a square wave of the specified frequency (and 50% duty cycle). Therefore we can not use the analog write function, because this function has a fixed frequency of 500Hz. To create a melody the passive buzzer needs an AC signal where we can define the frequency. Let me know in the comment section if you know the melody that we create in this example. The passive buzzer has the advantage that we can not only create a tone, but also a melody with different frequencies. The digital I/O pin of the Arduino, EPS8266 or ESP32 microcontroller is therefore connected to the gate of the MOSFET with a resistor of 220Ω in series, because the Arduino operation voltage of 5V or even the 3.3V operation voltage of the ESP8266 or ESP32 would damage the transistor. Otherwise we were not able to switch off a load that has a higher voltage than the control voltage.
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