1.2.1 Active Buzzer¶

Introduction¶

In this project, we will learn how to drive an active buzzer to beep with a PNP transistor.

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	-
Transistor	BUY

Schematic Diagram¶

In this experiment, an active buzzer, a PNP transistor and a 1k resistor are used between the base of the transistor and GPIO to protect the transistor. When the GPIO17 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. (The active buzzer has a white table sticker on the surface and a black back.)

Step 2: Open the code file.

cd ~/raphael-kit/python

Step 3: Run.

sudo python3 1.2.1_ActiveBuzzer.py

The code run, the buzzer beeps.

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

# Set GPIO17 as buzzer pin
BeepPin = 17

def setup():
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(BeepPin, GPIO.OUT, initial=GPIO.HIGH)

def main():
    while True:
        # Buzzer on (Beep)
        print ('Buzzer On')
        GPIO.output(BeepPin, GPIO.LOW)
        time.sleep(0.1)
        # Buzzer off
        print ('Buzzer Off')
        GPIO.output(BeepPin, GPIO.HIGH)
        time.sleep(0.1)

def destroy():
    # Turn off buzzer
    GPIO.output(BeepPin, GPIO.HIGH)
    # Release resource
    GPIO.cleanup()

# If run this script directly, do:
if __name__ == '__main__':
    setup()
    try:
        main()
    # When 'Ctrl+C' is pressed, the program
    # destroy() will be  executed.
    except KeyboardInterrupt:
        destroy()

Code Explanation

GPIO.output(BeepPin, GPIO.LOW)

Set the buzzer pin as low level to make the buzzer beep.

time.sleep(0.1)

Wait for 0.1 second. Change the switching frequency by changing this parameter.

Note

Not the sound frequency. Active Buzzer cannot change sound frequency.

GPIO.output(BeepPin, GPIO.HIGH)

Close the buzzer.