active buzzer and passive buzzer how to distinguish?

active buzzer is an integrated electronic sounder, powered by DC voltage , It is widely used as electronic toys, alarms, computers, copiers, printers, telephones, automotive electronic equipment, The sound device of timers and other electronic products. Buzzer is mainly divided into two kinds: piezoelectric buzzer and electromagnetic buzzer. Active buzzers are represented in the circuit by the letters "H " or "HA " for . The principle of

active buzzer: 1 , piezoelectric buzzer is mainly composed of impedance matching device, piezoelectric buzzer, multivibrator, resonator box and shell. Some piezoelectric buzzer housings are also equipped with light-emitting diodes. The multivibrator consists of a transistor or an integrated circuit. When (1.5~15V DC operating voltage ) is powered on, the multivibrator starts to vibrate and outputs an audio signal of 100~500Hz . The impedance matcher drives the piezoelectric buzzer to sound. The piezoelectric buzzer is made of lead magnesium niobate or lead zirconate titanate piezoelectric ceramic material. Silver electrodes were plated on both sides of the ceramic plate, bonded with stainless steel plate or brass plate on after polarization and aging treatment. 2 , Electromagnetic buzzer The electromagnetic buzzer is composed of a magnet, an electromagnetic coil, an oscillator, a diaphragm and a housing. 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 winding of the diaphragm between the electromagnetic coil and the magnet. The fundamental difference between

active buzzer and passive buzzer is that the product has different requirements for input signals. The ideal signal of active buzzer is usually DC marked as VDC and VDD . Since there is a simple oscillation circuit inside the buzzer, is to realize the alternation of magnetic field, driving the aluminum sheet to vibrate and sound , can convert the constant direct current into a pulse signal of a certain frequency through . However, some active buzzers can work under a specific AC signal, but the voltage and frequency of the AC signal are very high, so this mode of operation is generally not used. Passive buzzer without internal drive circuit, some companies and factories called sounder, GB called sounder. Passive buzzer ideal signal square wave. If the buzzer does not respond when the DC signal is given, because the magnetic circuit is constant, the molybdenum plate cannot vibrate and sound. Simple difference between active buzzer and

passive buzzer: 1 , test with meter: test with multimeter resistance Rxl : connect buzzer ''pin with black probe, touch red probe back and forth on another pin, if it is passive buzzer with resistance only 8 ; if it can make a continuous sound and the resistance is above a few hundred ohms, it is an active buzzer . 2 , DC voltage test; The general voltage of 12M passive buzzer is 1.5V , and the general voltage of active electromagnetic buzzer is 1.5 , 3.0 , 5.0 , 9.0 , 12V . The corresponding voltage is input with DC voltage, and the frequency is about 500 Hz. Active buzzer can directly sound, passive electromagnetic buzzer can only sound if it does not directly sound.