User Manual

35
Lesson 6 Buzzer
Introduction
In this lesson, we 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
As a type of electronic buzzer with integrated structure, buzzers, which are supplied by DC
power, are widely used in computers, printers, photocopiers, alarms, electronic toys,
automotive electronic devices, telephones, timers and other electronic products for voice
devices. Buzzers can be categorized as active and passive ones (see the following 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 passive buzzer is:
An active buzzer has a built-in oscillating source, so it will make sounds when 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 active buzzer is often more expensive than the passive one because of multiple built-in
oscillating circuits.