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2.2.3 Reed Switch Module

Introduction

In this project, we will learn about the reed switch, which is an electrical switch that operates by means of an applied magnetic field.

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
LED	BUY
Reed Switch Module	BUY

Schematic Diagram

T-Board Name	physical	wiringPi	BCM
GPIO17	Pin 11	0	17
GPIO27	Pin 13	2	27
GPIO22	Pin 15	3	22

Experimental Procedures

Step 1: Build the circuit.

Step 2: Change directory.

cd ~/raphael-kit/python-pi5

Step 3: Run.

sudo python3 2.2.4_ReedSwitch_zero.py

The green LED will light up when the code is run. If a magnet is placed close to the reed switch module, the red LED lights up; take away the magnet and the green LED lights up again.

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. After modifying the code, you can run it directly to see the effect.

#!/usr/bin/env python3
from gpiozero import LED, Button

# Initialize the reed switch and LEDs using GPIO Zero
reed_switch = Button(17, pull_up=True)  # Reed switch on GPIO 17, using an internal pull-up resistor
green_led = LED(27)                     # Green LED connected to GPIO pin 27
red_led = LED(22)                       # Red LED connected to GPIO pin 22

def update_leds():
    """
    Update the state of the LEDs based on the reed switch.
    Turns the red LED on and green LED off when the reed switch is pressed, and vice versa.
    """
    if reed_switch.is_pressed:
        green_led.off()          # Turn off the green LED
        red_led.on()             # Turn on the red LED
    else:
        green_led.on()           # Turn on the green LED
        red_led.off()            # Turn off the red LED

try:
    green_led.on()               # Turn on the green LED at the start
    while True:
        # Set the callback functions for reed switch state changes
        reed_switch.when_pressed = update_leds   # Callback when the switch is pressed
        reed_switch.when_released = update_leds  # Callback when the switch is released

except KeyboardInterrupt:
    # Clean up resources and exit on Ctrl+C
    green_led.off()
    red_led.off()
    pass

Code Explanation

1. This line specifies that the script is to be run using Python 3. It imports LED and Button (used for the reed switch) from the gpiozero library.

   #!/usr/bin/env python3
   from gpiozero import LED, Button
   

2. Initializes the reed switch on GPIO pin 17 with an internal pull-up resistor. Also initializes two LEDs connected to GPIO pins 27 and 22.

   # Initialize the reed switch and LEDs using GPIO Zero
   reed_switch = Button(17, pull_up=True)  # Reed switch on GPIO 17, using an internal pull-up resistor
   green_led = LED(27)                     # Green LED connected to GPIO pin 27
   red_led = LED(22)                       # Red LED connected to GPIO pin 22
   

3. Defines the update_leds function, which updates the LED states based on the reed switch’s state. The red LED is turned on and the green LED is turned off when the switch is pressed, and the opposite when released.

   def update_leds():
       if reed_switch.is_pressed:
           green_led.off()          # Turn off the green LED
           red_led.on()             # Turn on the red LED
       else:
           green_led.on()           # Turn on the green LED
           red_led.off()            # Turn off the red LED
   

4. Sets the initial state of the green LED to on. The main loop assigns the update_leds function as callbacks for the when_pressed and when_released events of the reed switch. Includes exception handling for KeyboardInterrupt to clean up and exit the program gracefully.

   try:
       green_led.on()               # Turn on the green LED at the start
       while True:
           # Set the callback functions for reed switch state changes
           reed_switch.when_pressed = update_leds   # Callback when the switch is pressed
           reed_switch.when_released = update_leds  # Callback when the switch is released
   
   except KeyboardInterrupt:
       # Clean up resources and exit on Ctrl+C
       green_led.off()
       red_led.off()
       pass