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1.1 Blinking LED

Introduction

Welcome to your first project! In this tutorial, we will learn how to make an LED blink using Python programming and the GPIO pins. This project is an excellent introduction to hardware and software integration, demonstrating how simple code can interact with real-world components.

Before we start, let’s briefly explain the basics:

What is an LED?

An LED (Light Emitting Diode) is a small electronic component that lights up when an electrical current flows through it. LEDs are widely used in electronics because they are efficient and long-lasting.
What is a GPIO Pin?

GPIO stands for General Purpose Input/Output. These pins allow the Raspberry Pi to communicate with external devices, such as LEDs, sensors, or buttons. Each pin can be programmed to send signals (output) or read signals (input).

In this tutorial, we’ll connect an LED to a GPIO pin and write a Python program to make it blink. Let’s get started!

What You’ll Need

Here’s the list of components and their purposes:

COMPONENT	PURCHASE LINK
Breadboard	BUY
Jumper Wires	BUY
Resistor	BUY
LED	BUY
Fusion HAT+	-
Raspberry Pi	-

Circuit Diagram

The resistor limits the current flowing through the LED, preventing it from burning out. Without a resistor, the LED may draw too much current, which can damage both the LED and the Raspberry Pi.

Wiring Diagram

Follow the wiring diagram below to connect your components:

Run the Code

Let’s write the Python code to control the LED. You’ll create a script that turns the LED on and off at regular intervals.

Navigate to the Code Directory:

Open your terminal and type:
```
cd ~/ai-lab-kit/python
```
Run the Program:

Use the following command to execute the script:
```
sudo python3 1.1_LED.py
```
You should see the LED blinking on and off at regular intervals.
Edit the Code (Optional):

To modify the program, open the code file in a text editor:
```
nano 1.1_LED.py
```
Make your changes, then press Ctrl+X to exit. Save your modifications by typing Y when prompted. Run the script again to see your changes.

Code

Here’s the complete Python script for this project:

#!/usr/bin/env python3
from fusion_hat.pin import Pin, Mode
from time import sleep

# Initialize an LED connected to GPIO pin 17 as an output pin.
led = Pin(17,mode=Mode.OUT)

try:
   # Start an infinite loop to toggle the LED state.
   while True:
      # Turn on the LED and print a message to the console.
      led.high()
      print('...LED ON')

      # Wait for 0.5 seconds with the LED on.
      sleep(0.5)

      # Turn off the LED and print a message to the console.
      led.low()
      print('LED OFF...')

      # Wait for 0.5 seconds with the LED off.
      sleep(1)

except KeyboardInterrupt:
   # Gracefully handle a keyboard interrupt (Ctrl+C) by breaking the loop.
   pass

This Python script controls an LED connected to GPIO pin 17 of a Raspberry Pi. When executed, the LED alternates between turning on and off in half-second intervals. Simultaneously, the console prints “LED is ON” and “LED is OFF” to indicate the LED’s current state. The program runs indefinitely until interrupted by a user pressing Ctrl+C.

Understanding the Code

Imports:

The fusion_hat library simplifies controlling GPIO devices. The Pin class allows you to control an LED with basic methods like on() and off(). The sleep function introduces delays between commands.

Note

For the usage of fusion-hat, please refer to the fusion-hat documentation .
Initialization:

The line led = Pin(17,mode=Mode.OUT) tells the Raspberry Pi that an LED is connected to GPIO pin 17.
Main Loop:

Inside the while True loop: The LED turns on (led.on()) and off (led.off()) with a 0.5-second pause (sleep(0.5)) in between.
Graceful Exit:

The try...except block ensures the program stops cleanly when interrupted (e.g., by pressing Ctrl+C).

Troubleshooting

LED Does Not Light Up
- Cause: Incorrect GPIO pin or faulty wiring.
- Solution: Double-check the LED’s connection to GPIO pin 17 and ensure the resistor is correctly placed to prevent damage to the LED.
KeyboardInterrupt Not Working
- Cause: The program does not exit gracefully.
- Solution: Ensure the script is running in a terminal where Ctrl+C is captured, not as a background process.
Incorrect GPIO Setup
- Cause: fusion_hat library is not installed.
- Solution: See Install fusion-hat module.
LED Flickers or Behaves Erratically
- Cause: Unstable power supply or poor connections.
- Solution: Ensure a stable power source and secure wiring.

Extendable Ideas

Variable Blink Speed: Add user input to control the LED’s blinking speed dynamically:

interval = float(input("Enter blink interval in seconds: "))

while True:
    led.on()
    sleep(interval)
    led.off()
    sleep(interval)

Multi-LED Control: Connect multiple LEDs to different GPIO pins and control them in patterns (e.g., sequential lighting or simultaneous blinking).

Conclusion

Congratulations! You’ve completed your first Raspberry Pi project. By controlling an LED, you’ve learned how to use GPIO pins and write Python scripts to interact with hardware. This foundational knowledge will serve as a stepping stone for more complex projects. Keep experimenting and exploring!