When the pins of the two buzzers are placed upward, you can see that one with a green circuit board is a passive buzzer, and the other with a vinyl seal without a circuit board is an active buzzer.

2. The test sound is different

Connect the "+"pin of the buzzer with a black stylus, and the red stylus touches the other pin back and forth. If clicking sound or clicking sound is triggered and the resistance is only 8 Ω, it is a passive buzzer; If it can emit continuous sound and the resistance is above several hundred ohms, it is an active buzzer.

3, the vibration frequency is different

Input the corresponding voltage (from small to large) with DC voltage, and the frequency is about 2.7KHZ. The active electromagnetic buzzer can ring directly, and the passive electromagnetic buzzer needs square wave to drive the ring directly.

Extended data:

Buzzer driving circuit usually includes triode, freewheeling diode, filter capacitor and buzzer. As a sounding element, the buzzer can sound by applying a square wave or voltage at its two ends.

The function of the free-wheeling diode is to provide free-wheeling, otherwise the tip voltage of tens of volts will be generated at both ends of the buzzer, which may damage the triode and interfere with other parts of the whole circuit.

The function of filter capacitor is to filter out the influence of buzzer current on other parts and improve the AC impedance of power supply.

References:

Baidu encyclopedia-active buzzer

References:

Baidu Encyclopedia-Passive Buzzer