What is the circuit of common buzzer? Because the working current of the buzzer is generally large, so that the I / O port of the single chip microcomputer cannot be directly driven * (but AVR can drive the low-power buzzer), it is necessary to use the amplification circuit to drive, and generally use the triode to amplify the current.
The buzzer driving circuit generally includes the following parts: a triode, a buzzer, a freewheeling diode and a power filter capacitor.
The sounding element can sound by applying DC voltage (active buzzer) or square wave (passive buzzer) at both ends. Its main parameters are overall dimension, sounding direction, working voltage, working frequency, working current, driving mode (DC / square wave), etc. These can be selected according to needs.
2. Freewheeling diode
The buzzer is essentially an inductive element, and its current cannot be transient, so there must be a freewheeling diode to provide freewheeling. Otherwise, a peak voltage of tens of volts will be generated at both ends of the buzzer, which may damage the driving triode and interfere with other parts of the whole circuit system.
3. Filter capacitor
The function of filter capacitor C1 is to filter, filter out the influence of buzzer current on other parts, and also improve the AC impedance of the power supply. If possible, connect another 220uF electrolytic capacitor in parallel.
Triode Q1 acts as a switch, and the high level of its base makes the triode saturate and turn on, making the buzzer sound; The base low level turns off the triode and the buzzer stops sounding.