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.

Schematic Diagram

In this experiment, an active buzzer is used. When the GPIO of Raspberry Pi output is supplied with low level (0V) by programming, the transistor will conduct because of current saturation and the buzzer will make sounds. But when high level is supplied to the IO of Raspberry Pi, the transistor will be cut off and the buzzer will not make sounds.

Experimental Procedures

Step 1: Build the circuit (Pay attention to the positive and negative poles of the buzzer)

For C Language Users:

Step 2: Change directory. 

    cd /home/pi/Sunfounder_SuperKit_C_code_for_RaspberryPi/06_Beep/

Step 3: Compile.

    gcc beep.c -o beep -lwiringPi

Step 4: Run. 

     sudo ./beep

For Python Users:

Step 2: Change directory.

    cd /home/pi/Sunfounder_SuperKit_Python_code_for_RaspberryPi/

Step 3: Run. 

     sudo python3 06_beep.py

Now, you should hear the buzzer make sounds.

Further Exploration

If you have a passive buzzer in hand, you can replace the active buzzer with it. Now you can make a buzzer sound like “do re mi fa so la si do” with just some basic knowledge of programming. Give a try!