1.2.2 Passive Buzzer

Introduction

In this project, we will learn how to make a passive buzzer play music.

Required Components

In this project, we need the following components.

../_images/list_1.2.2.png

It’s definitely convenient to buy a whole kit, here’s the link:

Name

ITEMS IN THIS KIT

LINK

Raphael Kit

337

Raphael Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION

PURCHASE LINK

GPIO Extension Board

BUY

Breadboard

BUY

Jumper Wires

BUY

Resistor

BUY

Buzzer

BUY

Transistor

BUY

Schematic Diagram

In this experiment, a passive buzzer, a PNP transistor and a 1k resistor are used between the base of the transistor and GPIO to protect the transistor.

When GPIO17 is given different frequencies, the passive buzzer will emit different sounds; in this way, the buzzer plays music.

../_images/image333.png

Experimental Procedures

Step 1: Build the circuit. (The Passive buzzer with green circuit board on the back.)

../_images/image106.png

Step 2: Change directory.

cd ~/raphael-kit/c/1.2.2/

Step 3: Compile.

gcc 1.2.2_PassiveBuzzer.c -lwiringPi

Step 4: Run.

sudo ./a.out

The code run, the buzzer plays a piece of music.

Note

If it does not work after running, or there is an error prompt: "wiringPi.h: No such file or directory", please refer to Install and Check the WiringPi.

Code

#include <wiringPi.h>
#include <softTone.h>
#include <stdio.h>

#define BuzPin    0

#define  CL1  131
#define  CL2  147
#define  CL3  165
#define  CL4  175
#define  CL5  196
#define  CL6  221
#define  CL7  248

#define  CM1  262
#define  CM2  294
#define  CM3  330
#define  CM4  350
#define  CM5  393
#define  CM6  441
#define  CM7  495

#define  CH1  525
#define  CH2  589
#define  CH3  661
#define  CH4  700
#define  CH5  786
#define  CH6  882
#define  CH7  990

int song_1[] = {CM3,CM5,CM6,CM3,CM2,CM3,CM5,CM6,CH1,CM6,CM5,CM1,CM3,CM2,
                CM2,CM3,CM5,CM2,CM3,CM3,CL6,CL6,CL6,CM1,CM2,CM3,CM2,CL7,
                CL6,CM1,CL5};

int beat_1[] = {1,1,3,1,1,3,1,1,1,1,1,1,1,1,3,1,1,3,1,1,1,1,1,1,1,2,1,1,
                1,1,1,1,1,1,3};


int song_2[] = {CM1,CM1,CM1,CL5,CM3,CM3,CM3,CM1,CM1,CM3,CM5,CM5,CM4,CM3,CM2,
                CM2,CM3,CM4,CM4,CM3,CM2,CM3,CM1,CM1,CM3,CM2,CL5,CL7,CM2,CM1
                };

int beat_2[] = {1,1,1,3,1,1,1,3,1,1,1,1,1,1,3,1,1,1,2,1,1,1,3,1,1,1,3,3,2,3};

int main(void)
{
    int i, j;
    if(wiringPiSetup() == -1){ //when initialize wiring failed,print message to screen
        printf("setup wiringPi failed !");
        return 1;
    }

    if(softToneCreate(BuzPin) == -1){
        printf("setup softTone failed !");
        return 1;
    }

    while(1){
        printf("music is being played...\n");

        for(i=0;i<sizeof(song_1)/4;i++){
            softToneWrite(BuzPin, song_1[i]);
            delay(beat_1[i] * 500);
        }

        for(i=0;i<sizeof(song_2)/4;i++){
            softToneWrite(BuzPin, song_2[i]);
            delay(beat_2[i] * 500);
        }
    }

    return 0;
}

Code Explanation

#define  CL1  131
#define  CL2  147
#define  CL3  165
#define  CL4  175
#define  CL5  196
#define  CL6  221
#define  CL7  248

#define  CM1  262
#define  CM2  294

These frequencies of each note are as shown. CL refers to low note, CM middle note, CH high note, 1-7 correspond to the notes C, D, E, F, G, A, B.

int song_1[] = {CM3,CM5,CM6,CM3,CM2,CM3,CM5,CM6,CH1,CM6,CM5,CM1,CM3,CM2,
                CM2,CM3,CM5,CM2,CM3,CM3,CL6,CL6,CL6,CM1,CM2,CM3,CM2,CL7,
                CL6,CM1,CL5};
int beat_1[] = {1,1,3,1,1,3,1,1,1,1,1,1,1,1,3,1,1,3,1,1,1,1,1,1,1,2,1,1,
                1,1,1,1,1,1,3};

The array, song_1[] stores a musical score of a song in which beat_1[] refers to the beat of each note in the song (0.5s for each beat).

if(softToneCreate(BuzPin) == -1){
        printf("setup softTone failed !");
        return 1;
}

This creates a software controlled tone pin. You can use any GPIO pin and the pin numbering will be that of the wiringPiSetup() function you used. The return value is 0 for success. Anything else and you should check the global errnovariable to see what went wrong.

for(i=0;i<sizeof(song_1)/4;i++){
    softToneWrite(BuzPin, song_1[i]);
    delay(beat_1[i] * 500);
}

Employ a for statement to play song_1.

In the judgment condition, i<sizeof(song_1)/4,“devide by 4” is used because the array song_1[] is an array of the data type of integer, and each element takes up four bytes.

The number of elements in song_1 (the number of musical notes) is gotten by deviding sizeof(song_1) by 4.

To enable each note to play for beat * 500ms, the function delay(beat_1[i] \* 500) is called.

The prototype of softToneWrite(BuzPin, song_1[i]) is:

void softToneWrite (int pin, int freq);

This updates the tone frequency value on the given pin. The tone does not stop playing until you set the frequency to 0.

Phenomenon Picture

../_images/image107.jpeg