2.1.2 Slide Switch

Introduction

In this project, we will learn how to use a slide switch. Usually,the slide switch is soldered on PCB as a power switch, but here we need to insert it into the breadboard, thus it may not be tightened. And we use it on the breadboard to show its function.

Required Components

In this project, we need the following components.

Schematic Diagram

Connect the middle pin of the Slide Switch to GPIO17, and two LEDs to pin GPIO22 and GPIO27 respectively. Then when you pull the slide, 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 ~/davinci-kit-for-raspberry-pi/python-pi5

Step 3: Run.

sudo python3 2.1.2_Slider_zero.py

While the code is running, get the switch connected to the left, then the yellow LED lights up; to the right, the red light 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 davinci-kit-for-raspberry-pi/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 for GPIO control
from time import sleep  # Import sleep function for adding delays

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

try:
    # Main loop to control LED states based on the micro switch's state
    while True:
        if micro_switch.is_pressed:  # Check if the micro switch is pressed
            print('    LED1 ON    ')  # Print status message
            led1.on()   # Turn on LED1
            led2.off()  # Turn off LED2
        else:  # If the micro switch is not pressed
            print('    LED2 ON    ')  # Print status message
            led1.off()  # Turn off LED1
            led2.on()   # Turn on LED2

        sleep(0.5)  # Wait for 0.5 seconds before rechecking the switch state

except KeyboardInterrupt:
    # Handle a keyboard interrupt (Ctrl+C) for a clean exit from the loop
    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 for GPIO control
   from time import sleep  # Import sleep function for adding 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 the micro switch on GPIO pin 17 with the pull-up resistor disabled
   micro_switch = Button(17, pull_up=False)
   # Initialize LED1 on GPIO pin 22
   led1 = LED(22)
   # Initialize LED2 on GPIO pin 27
   led2 = LED(27)
   

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

   try:
   # Main loop to control LED states based on the micro switch's state
   while True:
       if micro_switch.is_pressed:  # Check if the micro switch is pressed
           print('    LED1 ON    ')  # Print status message
           led1.on()   # Turn on LED1
           led2.off()  # Turn off LED2
       else:  # If the micro switch is not pressed
           print('    LED2 ON    ')  # Print status message
           led1.off()  # Turn off LED1
           led2.on()   # Turn on LED2
   
       sleep(0.5)  # Wait for 0.5 seconds before rechecking the switch state
   
   except KeyboardInterrupt:
       # Handle a keyboard interrupt (Ctrl+C) for a clean exit from the loop
       pass