As the buzzer operating current is generally larger, so that the microcontroller I / O port is not directly driven * (but AVR can drive low-power buzzer), the general use of transistors to amplify the current, the use of amplifier to drive It's okay

Buzzer drive circuit generally contains the following sections: a transistor, a buzzer, a freewheeling diode and a power supply filter capacitor.

1. buzzer

Vocal components, at both ends of the applied DC voltage (active buzzer) or square wave (passive buzzer) can sound, the main parameters of the size, sound direction, the operating voltage, operating frequency, operating current, Drive mode (DC / square wave) and so on. These can be selected according to need.

2. Freewheeling diode

The buzzer is essentially an inductive component whose current can not transient, so there must be a freewheeling diode to provide freewheeling. Otherwise, a spike voltage of tens of volts will be generated across the buzzer, which may damage the driver transistor and interfere with other parts of the entire circuit.

3. Filter capacitor

The role of the filter capacitor C1 is to filter out the effects of the buzzer current on other parts and to improve the AC impedance of the power supply. It is best to connect a 220uF electrolytic capacitor in parallel, if possible.

4. Transistor

Transistor Q1 from the switch role, the base of the high-level transistor saturation turn-on, the buzzer sound; and the base low turn the transistor off, the buzzer stops sounding.