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2.1.2 Micro Switch

Introduction

In this project, we will learn how to use Micro Switch. A Micro Switch is a small, very sensitive switch which requires minimum compression to activate. Because they are reliable and sensitive, micro switches are often used as a safety device.

They are used to prevent doors from closing if something or someone is in the way and other applications similar.

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
Micro Switch	-
Capacitor	BUY

Schematic Diagram

Connect the left pin of the Micro Switch to GPIO17, and two LEDs to pin GPIO22 and GPIO27 respectively. Then when you press and release the move arm of the Micro Switch, you can see the two LEDs light up alternately.

Experimental Procedures

Step 1: Build the circuit.

Step 2: Get into the folder of the code.

cd ~/raphael-kit/python-pi5

Step 3: Run.

sudo python3 2.1.2_MicroSwitch_zero.py

While the code is running, press the moving arm, then the yellow LED lights up; release the moving arm, the red LED turns on.

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  # Import LED and Button classes from gpiozero
from time import sleep  # Import sleep function for delays

# Initialize micro switch on GPIO pin 17 with the pull-up resistor disabled
micro_switch = Button(17, pull_up=False)
# Initialize LED1 connected to GPIO pin 22
led1 = LED(22)
# Initialize LED2 connected to GPIO pin 27
led2 = LED(27)

try:
    # Continuously check the state of the micro switch and control LEDs accordingly
    while True:
        if micro_switch.is_pressed:  # If the micro switch is pressed
            print('LED1 ON')  # Print a message to the console
            led1.on()       # Turn on LED1
            led2.off()      # Turn off LED2
        else:  # If the micro switch is not pressed
            print('    LED2 ON')  # Print a message to the console
            led1.off()      # Turn off LED1
            led2.on()       # Turn on LED2

        sleep(0.5)  # Pause for 0.5 seconds before checking the switch again

except KeyboardInterrupt:
    # Handle KeyboardInterrupt (Ctrl+C) to exit the loop gracefully
    pass

Code Explanation

1. This line sets the script to run with Python 3. It imports LED and Button from gpiozero for controlling GPIO devices, and sleep from time for delays.

   #!/usr/bin/env python3
   from gpiozero import LED, Button  # Import LED and Button classes from gpiozero
   from time import sleep  # Import sleep function for delays
   

2. Initializes a micro switch connected to GPIO pin 17 with the pull-up resistor disabled, and two LEDs connected to GPIO pins 22 and 27.

   # Initialize micro switch on GPIO pin 17 with the pull-up resistor disabled
   micro_switch = Button(17, pull_up=False)
   # Initialize LED1 connected to GPIO pin 22
   led1 = LED(22)
   # Initialize LED2 connected to GPIO pin 27
   led2 = LED(27)
   

3. In the main loop, it checks the state of the micro switch. If pressed, LED1 turns on and LED2 off. If not pressed, LED1 turns off and LED2 on. The loop repeats every 0.5 seconds. Catches a KeyboardInterrupt (like Ctrl+C) to allow for graceful script termination.

   try:
       # Continuously check the state of the micro switch and control LEDs accordingly
       while True:
           if micro_switch.is_pressed:  # If the micro switch is pressed
               print('LED1 ON')  # Print a message to the console
               led1.on()       # Turn on LED1
               led2.off()      # Turn off LED2
           else:  # If the micro switch is not pressed
               print('    LED2 ON')  # Print a message to the console
               led1.off()      # Turn off LED1
               led2.on()       # Turn on LED2
   
           sleep(0.5)  # Pause for 0.5 seconds before checking the switch again
   
   except KeyboardInterrupt:
       # Handle KeyboardInterrupt (Ctrl+C) to exit the loop gracefully
       pass