User Manual

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Lesson 6 Buzzer
Introduction
In this lesson, w e will learn how to drive an active buzzer to beep with a PNP transistor.
Components
- 1 * Raspberry Pi
- 1 * Breadboard
- 1 * Buzzer (Active)
- 1 * PNP transistor (8550)
- 1 * Resistor (1KΩ)
- Jumper wires
Principle
Buzzer
As a type of electronic buzzer with integrated structure, buzzers, w hich are supplied by DC
power, are widely used in computers, printers, photocopiers, alarms and other electronic
products for voice dev ices. Buzzers can be categorized as active and passive ones (see the
follow ing picture). Turn the pins of two buzzers face up, and the one with a green circuit
board is a passive buzzer, while the other enclosed with a black tape is an active one.
The difference between an active buzzer and a passiv e buzzer is: An active buzzer has a
built-in oscillating source, so it will make sounds w hen electrified. But a passive buzzer does
not have such source, so it will not beep if DC signals are used; instead, you need to use
square waves whose frequency is between 2K and 5K to drive it. The activ e buzzer is often
more expensive than the passive one because of multiple built-in oscillating circuits.
The following is the electrical symbol of a buzzer. It has two pins with positiv e and negative
poles. With a + in the surface represents the anode and the other is the cathode.
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