4. How to design a driving circuit for buzzers?
Piezo buzzers as capacitive loads should be cyclically charged and discharged. Cients are reminded of discharging the buzzer in a cycle, which can normally be accomplished by placing a resistor in parallel to the buzzer.
Electromagnetic buzzers as inductive loads should be accompanied by applicable amplifiers such as transistors. Transistors must bear three times the rated current of magnetic buzzers. For instance, if the rated current of a magnetic buzzer is 100mA, then the transistor must be able to bear 300mA. Furthermore, clients are advised to place a diode in parallel to the magnetic buzzer, in attempt to avoid noise and to protect surrounding circuits. Since inductive loads have back electromotive force, it is necessary to cancel it by diodes, preferably by Schottky diodes.
In general, making buzzers generate continuous sound is simple, for clients merely have to ensure continuous operation. As for intermittent sound, indicators utilize built-in on-off circuit to produce intermittent sounds; on-off circuit can be designed for fast intermittent sound or slow intermittent sound. Transducers on the other hand, requires client to send on-off signals, which is generated by customized modules or oscillators.
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