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.. _py_pi5_bell:
3.1.10 Alarm Bell
===================
Introduction
-----------------
In this project, we will make a manual alarm device. You can replace the
toggle switch with a thermistor or a photosensitive sensor to make a
temperature alarm or a light alarm.
Required Components
------------------------------
In this project, we need the following components.
.. image:: ../python_pi5/img/4.1.15_alarm_bell_list.png
:width: 800
:align: center
.. It's definitely convenient to buy a whole kit, here's the link:
.. .. list-table::
.. :widths: 20 20 20
.. :header-rows: 1
.. * - Name
.. - ITEMS IN THIS KIT
.. - LINK
.. * - Raphael Kit
.. - 337
.. - |link_Raphael_kit|
.. You can also buy them separately from the links below.
.. .. list-table::
.. :widths: 30 20
.. :header-rows: 1
.. * - COMPONENT INTRODUCTION
.. - PURCHASE LINK
.. * - :ref:`gpio_extension_board`
.. - |link_gpio_board_buy|
.. * - :ref:`breadboard`
.. - |link_breadboard_buy|
.. * - :ref:`wires`
.. - |link_wires_buy|
.. * - :ref:`resistor`
.. - |link_resistor_buy|
.. * - :ref:`led`
.. - |link_led_buy|
.. * - :ref:`Buzzer`
.. - |link_passive_buzzer_buy|
.. * - :ref:`slide_switch`
.. - |link_slide_switch_buy|
.. * - :ref:`transistor`
.. - |link_transistor_buy|
.. * - :ref:`capacitor`
.. - |link_capacitor_buy|
Schematic Diagram
-------------------------
============ ======== ======== ===
T-Board Name physical wiringPi BCM
GPIO17 Pin 11 0 17
GPIO18 Pin 12 1 18
GPIO27 Pin 13 2 27
GPIO22 Pin 15 3 22
============ ======== ======== ===
.. image:: ../python_pi5/img/4.1.15_alarm_bell_schematic.png
:width: 600
:align: center
Experimental Procedures
-----------------------------
**Step 1**: Build the circuit.
.. image:: ../python_pi5/img/4.1.15_alarm_bell_circuit.png
**Step 2:** Change directory.
.. raw:: html
.. code-block::
cd ~/davinci-kit-for-raspberry-pi/python-pi5
**Step 3:** Run.
.. raw:: html
.. code-block::
sudo python3 3.1.10_AlarmBell.py
After the program starts, the toggle switch will be toggled to the
right, and the buzzer will give out alarm sounds. At the same time, the
red and green LEDs will flash at a certain frequency.
.. warning::
If there is an error prompt ``RuntimeError: Cannot determine SOC peripheral base address``, please refer to :ref:`faq_soc`
**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-pi5``.
.. raw:: html
.. code-block:: python
#!/usr/bin/env python3
from gpiozero import LED, Button, TonalBuzzer
import time
import threading
# Initialize TonalBuzzer on GPIO pin 22
BeepPin = TonalBuzzer(22)
# Initialize LEDs on GPIO pins 17 and 27
ALedPin = LED(17)
BLedPin = LED(27)
# Initialize Button on GPIO pin 18
switchPin = Button(18)
# Global flag to control the buzzer and LED states
flag = 0
def ledWork():
"""
Control LED blinking pattern based on the flag state.
When flag is set, alternately blink ALedPin and BLedPin.
"""
while True:
if flag:
# Alternate blinking of LEDs
ALedPin.on()
time.sleep(0.5)
ALedPin.off()
BLedPin.on()
time.sleep(0.5)
BLedPin.off()
else:
# Turn off both LEDs if flag is not set
ALedPin.off()
BLedPin.off()
# Define the musical tune as a list of notes and their durations
tune = [
('C4', 0.1), ('E4', 0.1), ('G4', 0.1),
(None, 0.1),
('E4', 0.1), ('G4', 0.1), ('C5', 0.1),
(None, 0.1),
('C5', 0.1), ('G4', 0.1), ('E4', 0.1),
(None, 0.1),
('G4', 0.1), ('E4', 0.1), ('C4', 0.1),
(None, 0.1)
]
def buzzerWork():
"""
Play a tune using the buzzer based on the flag state.
The tune is played only when the flag is set.
"""
while True:
for note, duration in tune:
if flag == 0:
break
print(note) # Output the current note to the console
BeepPin.play(note) # Play the current note
time.sleep(duration) # Pause for the duration of the note
BeepPin.stop() # Stop the buzzer after playing the tune
def main():
"""
Monitor button press to update the flag state.
Sets the flag when the button is pressed.
"""
global flag
while True:
flag = 1 if switchPin.is_pressed else 0
try:
# Initialize and start threads for buzzer and LED control
tBuzz = threading.Thread(target=buzzerWork)
tBuzz.start()
tLed = threading.Thread(target=ledWork)
tLed.start()
main()
except KeyboardInterrupt:
# Stop the buzzer and turn off LEDs on program interruption
BeepPin.stop()
ALedPin.off()
BLedPin.off()
**Code Explanation**
#. This segment includes the import of essential libraries for implementing delays and threading. It also imports the LED, Button, and TonalBuzzer classes from the gpiozero library, crucial for controlling GPIO devices on a Raspberry Pi.
.. code-block:: python
#!/usr/bin/env python3
from gpiozero import LED, Button, TonalBuzzer
import time
import threading
#. Sets up a buzzer on GPIO pin 22, two LEDs on GPIO pins 17 and 27, and initializes a button on GPIO pin 18. A global flag is also defined to manage the state of the buzzer and LEDs.
.. code-block:: python
# Initialize TonalBuzzer on GPIO pin 22
BeepPin = TonalBuzzer(22)
# Initialize LEDs on GPIO pins 17 and 27
ALedPin = LED(17)
BLedPin = LED(27)
# Initialize Button on GPIO pin 18
switchPin = Button(18)
# Global flag to control the buzzer and LED states
flag = 0
#. This function controls the blinking of the LEDs based on the flag's state. If the flag is set (1), it alternates between turning on and off each LED. If not set (0), both LEDs are turned off.
.. code-block:: python
def ledWork():
"""
Control LED blinking pattern based on the flag state.
When flag is set, alternately blink ALedPin and BLedPin.
"""
while True:
if flag:
# Alternate blinking of LEDs
ALedPin.on()
time.sleep(0.5)
ALedPin.off()
BLedPin.on()
time.sleep(0.5)
BLedPin.off()
else:
# Turn off both LEDs if flag is not set
ALedPin.off()
BLedPin.off()
#. The tune is defined as a sequence of notes (frequency) and durations (seconds).
.. code-block:: python
# Define the musical tune as a list of notes and their durations
tune = [
('C4', 0.1), ('E4', 0.1), ('G4', 0.1),
(None, 0.1),
('E4', 0.1), ('G4', 0.1), ('C5', 0.1),
(None, 0.1),
('C5', 0.1), ('G4', 0.1), ('E4', 0.1),
(None, 0.1),
('G4', 0.1), ('E4', 0.1), ('C4', 0.1),
(None, 0.1)
]
#. Plays a predefined tune when the flag is set. The tune stops if the flag is unset during its play.
.. code-block:: python
def buzzerWork():
"""
Play a tune using the buzzer based on the flag state.
The tune is played only when the flag is set.
"""
while True:
for note, duration in tune:
if flag == 0:
break
print(note) # Output the current note to the console
BeepPin.play(note) # Play the current note
time.sleep(duration) # Pause for the duration of the note
BeepPin.stop() # Stop the buzzer after playing the tune
#. Continuously checks the state of the button to set or unset the flag.
.. code-block:: python
def main():
"""
Monitor button press to update the flag state.
Sets the flag when the button is pressed.
"""
global flag
while True:
flag = 1 if switchPin.is_pressed else 0
#. Threads for ``buzzerWork`` and ``ledWork`` are started, allowing them to run concurrently with the main function.
.. code-block:: python
try:
# Initialize and start threads for buzzer and LED control
tBuzz = threading.Thread(target=buzzerWork)
tBuzz.start()
tLed = threading.Thread(target=ledWork)
tLed.start()
main()
#. Stops the buzzer and turns off LEDs when the program is interrupted, ensuring a clean exit.
.. code-block:: python
except KeyboardInterrupt:
# Stop the buzzer and turn off LEDs on program interruption
BeepPin.stop()
ALedPin.off()
BLedPin.off()