How to understand the simple difference between active buzzer and passive buzzer? The fundamental difference between active buzzer and passive buzzer is that products have different requirements for input signals; The ideal signal of active buzzer is DC, which is usually marked as VDC, VDD, etc. Because there is a simple oscillation circuit inside the buzzer, which can convert the constant DC into a pulse signal of a certain frequency, so as to realize the alternating magnetic field and drive the vibration and pronunciation of aluminum sheet.

However, some active Buzzers can also work under specific AC signals, but they have high requirements for the voltage and frequency of AC signals, which is generally not used.
The passive buzzer has no internal drive circuit. Some companies and factories call it a buzzer, which is called a sounder in the national standard. The ideal signal square wave of passive buzzer. If a DC signal is given, the buzzer does not respond because the magnetic circuit is constant and the molybdenum sheet cannot vibrate. The following distinguishing methods:
1、 Visual inspection:
Compare ks-12c01ye and ks-12d05ya, where "C" represents passive and "d" represents active;
The shape of the former is 12 * 8.5, and the latter is 12 * 9.5. They are very similar. For example, when the pins of the two buzzers are placed upward, it can be seen that one with green circuit board is a passive buzzer, and the one without circuit board and closed with black glue is an active buzzer.
However, this is only the preliminary standard of judgment, not the only standard. If ks-1240t2pa is added, the identification is more complex. Its overall dimension is 12.5 * 6. This is a small piezoelectric passive buzzer on the market; With the needs of the continuous development of the market, the requirements for quality are becoming higher and higher. Many manufacturers need 12mm buzzers and need bottom sealing glue. In order to stabilize their performance and prevent the magnetic core from falling off, visual inspection is only a preliminary identification method.
2、 Multimeter test:
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 a click sound is triggered 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.
3、 DC voltage test;
The general voltage of 12mm passive is 1.5V. The general voltage of active electromagnetic buzzer is 1.5, 3.0, 5.0, 9.0 and 12V. Input the corresponding voltage with DC voltage (which can be adjusted from small to large). The frequency is about 500Hz. The active electromagnetic buzzer can ring directly. The passive electromagnetic buzzer can ring only when it is driven by square wave.