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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.

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.

Experimental Procedures¶

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

Step 2: Change directory.

cd ~/raphael-kit/python/

Step 3: Run.

sudo python3 1.2.2_PassiveBuzzer.py

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

Code

Note

You can Modify/Reset/Copy/Run/Stop the code below. But before that, you need to go to source code path like raphael-kit/python. After modifying the code, you can run it directly to see the effect.

import RPi.GPIO as GPIO
import time

Buzzer = 11

CL = [0, 131, 147, 165, 175, 196, 211, 248]     # Frequency of Bass tone in C major
CM = [0, 262, 294, 330, 350, 393, 441, 495]     # Frequency of Midrange tone in C major
CH = [0, 525, 589, 661, 700, 786, 882, 990]     # Frequency of Treble tone in C major

song_1 = [  CM[3], CM[5], CM[6], CM[3], CM[2], CM[3], CM[5], CM[6], # Notes of song1
            CH[1], CM[6], CM[5], CM[1], CM[3], CM[2], CM[2], CM[3],
            CM[5], CM[2], CM[3], CM[3], CL[6], CL[6], CL[6], CM[1],
            CM[2], CM[3], CM[2], CL[7], CL[6], CM[1], CL[5] ]

beat_1 = [  1, 1, 3, 1, 1, 3, 1, 1,             # Beats of song 1, 1 means 1/8 beat
            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 ]

song_2 = [  CM[1], CM[1], CM[1], CL[5], CM[3], CM[3], CM[3], CM[1], # Notes of song2
            CM[1], CM[3], CM[5], CM[5], CM[4], CM[3], CM[2], CM[2],
            CM[3], CM[4], CM[4], CM[3], CM[2], CM[3], CM[1], CM[1],
            CM[3], CM[2], CL[5], CL[7], CM[2], CM[1]    ]

beat_2 = [  1, 1, 2, 2, 1, 1, 2, 2,             # Beats of song 2, 1 means 1/8 beat
            1, 1, 2, 2, 1, 1, 3, 1,
            1, 2, 2, 1, 1, 2, 2, 1,
            1, 2, 2, 1, 1, 3 ]

def setup():
    GPIO.setmode(GPIO.BOARD)        # Numbers GPIOs by physical location
    GPIO.setup(Buzzer, GPIO.OUT)    # Set pins' mode is output
    global Buzz                     # Assign a global variable to replace GPIO.PWM
    Buzz = GPIO.PWM(Buzzer, 440)    # 440 is initial frequency.
    Buzz.start(50)                  # Start Buzzer pin with 50% duty cycle

def loop():
    while True:
        print ('\n    Playing song 1...')
        for i in range(1, len(song_1)):     # Play song 1
            Buzz.ChangeFrequency(song_1[i]) # Change the frequency along the song note
            time.sleep(beat_1[i] * 0.5)     # delay a note for beat * 0.5s
        time.sleep(1)                       # Wait a second for next song.

        print ('\n\n    Playing song 2...')
        for i in range(1, len(song_2)):     # Play song 1
            Buzz.ChangeFrequency(song_2[i]) # Change the frequency along the song note
            time.sleep(beat_2[i] * 0.5)     # delay a note for beat * 0.5s

def destory():
    Buzz.stop()                 # Stop the buzzer
    GPIO.output(Buzzer, 1)      # Set Buzzer pin to High
    GPIO.cleanup()              # Release resource

if __name__ == '__main__':      # Program start from here
    setup()
    try:
        loop()
    except KeyboardInterrupt:   # When 'Ctrl+C' is pressed, the program destroy() will be  executed.
        destory()

Code Explanation

CL = [0, 131, 147, 165, 175, 196, 211, 248]     # Frequency of Bass tone in C major
CM = [0, 262, 294, 330, 350, 393, 441, 495]     # Frequency of Midrange tone in C major
CH = [0, 525, 589, 661, 700, 786, 882, 990]     # Frequency of Treble tone in C major

These are the frequencies of each note. The first 0 is to skip CL[0] so that the number 1-7 corresponds to the CDEFGAB of the tone.

song_1 = [  CM[3], CM[5], CM[6], CM[3], CM[2], CM[3], CM[5], CM[6],
            CH[1], CM[6], CM[5], CM[1], CM[3], CM[2], CM[2], CM[3],
            CM[5], CM[2], CM[3], CM[3], CL[6], CL[6], CL[6], CM[1],
            CM[2], CM[3], CM[2], CL[7], CL[6], CM[1], CL[5] ]

These arrays are the notes of a song.

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 ]

Every sound beat (each number) represents the ⅛ beat, or 0.5s

Buzz = GPIO.PWM(Buzzer, 440)
Buzz.start(50)

Define pin Buzzer as PWM pin, then set its frequency to 440 and Buzz.start(50) is used to run PWM. What’s more, set the duty cycle to 50%.

for i in range(1, len(song_1)):
            Buzz.ChangeFrequency(song_1[i])
            time.sleep(beat_1[i] * 0.5)

Run a for loop, then the buzzer will play the notes in the array song_1[] with the beats in the beat_1[] array, .

Now you can hear the passive buzzer playing music.

1.2.2 Passive Buzzer¶

Introduction¶

Required Components¶

Schematic Diagram¶

Experimental Procedures¶

Phenomenon Picture¶