Case 09: Buzzer
11. Case 09: Buzzer#
The buzzer is an integrated structure of electronic sounders, widely used as sounding devices in computers, printers, photocopiers, alarms, electronic toys, automotive electronics, telephones, timers and other electronic products. In this lesson, we use Pico:ed to drive the buzzer and make it sound different syllables as an alarm.
11.2. Components List#
1 × Pico:ed
1 × USB Cable
1 × Breadboard Adapter
1 × 83×55mm Breadboard
1X NPN Transistor
1× 100Ω Resistors
N* Dupont Cables
11.3. Main Components#
The buzzer is a sound producing device, which consists of a vibrating and resonating device. The buzzer can be subdivided into active and passive types according to the type of control.
The active type buzzer works on the principle of sound generation: the buzzer has an integrated internal oscillation system and an amplification sampling circuit, which causes the resonant device to generate a sound signal when a DC power supply passes through the buzzer.
A passive type buzzer works on the principle of sound generation: a square wave signal is input to the resonant device and converted into an acoustic signal output, the working sound generation principle of a passive type buzzer is as follows.
Note: For this project, we are using a passive buzzer.
A transistor is a semiconductor device that controls current and serves to amplify weak signals into electrical signals with a large amplitude value.
If the PWM signal generated by the Pico:ed is fed directly into the buzzer, the buzzer will only emit a weak sound because the drive current of the IO port is usually too weak to drive a device like the buzzer. This is where we need to use a transistor to amplify the current from the PWM signal so that the buzzer can make a normal sound. A typical application circuit for driving a buzzer with a transistor is as follows.
Connect the components as the pictures suggest:
1.Connect the buzzer in series with the 100Ω resistor and the transistor to the P0 port
This is the picture after finishing the connections:
Program Preparation: Prpgramming environment
# Import the modules that we need: import board import pwmio import time # Set the pins used for buzzer and the play tones of the buzzer piezo = pwmio.PWMOut(board.P0_A0, duty_cycle=0,frequency=440, variable_frequency=True) def play_note(note): piezo.frequency = note piezo.duty_cycle = 65535 // 2 time.sleep(0.25) piezo.duty_cycle = 0 time.sleep(0.05) # While true, play the tones while True: play_note(494) time.sleep(0.2) play_note(262) time.sleep(0.2) play_note(294) time.sleep(0.2)
Details of the Code:#
Import the modules that we need.
boardis the common container, and you can connect the pins you’d like to use through it. The
pwmiomodule contains classes that provide access to the basic pulse IO and the
pwmiomodule contains classes that provide access to the basic pulse IO.
import board import pwmio import time
Set the pins used for buzzer and the play tones of the buzzer
piezo = pwmio.PWMOut(board.P0_A0, duty_cycle=0,frequency=440, variable_frequency=True) def play_note(note): piezo.frequency = note piezo.duty_cycle = 65535 // 2 time.sleep(0.25) piezo.duty_cycle = 0 time.sleep(0.05)
If the pins you are using are not P0_A0, the other pin numbers can be viewed by entering the following code in the shell window below the Thonny editor.
>>> import board >>> help(board) object <module 'board'> is of type module __name__ -- board board_id -- elecfreaks_picoed BUZZER_GP0 -- board.BUZZER_GP0 I2C0_SDA -- board.BUZZER_GP0 I2C0_SCL -- board.I2C0_SCL BUZZER -- board.BUZZER BUZZER_GP3 -- board.BUZZER P4 -- board.P4 P5 -- board.P5 P6 -- board.P6 P7 -- board.P7 P8 -- board.P8 P9 -- board.P9 P10 -- board.P10 P11 -- board.P11 P12 -- board.P12 P13 -- board.P13 P14 -- board.P14 P15 -- board.P15 P16 -- board.P16 SDA -- board.SDA P20 -- board.SDA SCL -- board.SCL P19 -- board.SCL BUTTON_A -- board.BUTTON_A BUTTON_B -- board.BUTTON_B SMPS_MODE -- board.SMPS_MODE VBUS_SENSE -- board.VBUS_SENSE LED -- board.LED P0_A0 -- board.P0_A0 P0 -- board.P0_A0 A0 -- board.P0_A0 P1_A1 -- board.P1_A1 P1 -- board.P1_A1 A1 -- board.P1_A1 P2_A2 -- board.P2_A2 P2 -- board.P2_A2 A2 -- board.P2_A2 P3_A3 -- board.P3_A3 P3 -- board.P3_A3 A3 -- board.P3_A3
While true, play the tones
while True: play_note(494) time.sleep(0.2) play_note(262) time.sleep(0.2) play_note(294) time.sleep(0.2)
The buzzer alarms and repeats in the specific tones.
How to program if we want to alarm for high temperature with the TMP36 sensor and the buzzer?