How to Blink Two LED's with Raspberry Pi 4 (Double LED Blink)

After mastering the single LED blink, the next step is to control multiple outputs. In this project, we will connect a Red LED and a Green LED to your Raspberry Pi 4 and make them blink alternately.

1. Components Required

• Raspberry Pi 4 (with Raspberry Pi OS)
• 2x LEDs (Red and Green)
• 220Ω Resistors
• Breadboard and Jumper Wires

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2. The Circuit and Connections

Since we are using two LEDs, we need two separate GPIO pins. We will use GPIO 18 (Pin 12) and GPIO 24 (Pin 18).

Connection Table:

Component	Color	GPIO Pin	Physical Pin
LED 1	Red	18	12
LED 2	Green	24	18
Ground	—	GND	6

Note: Both LEDs can share the same Ground (GND) pin by using the "negative rail" on your breadboard.

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3. The Python Code

Open Thonny IDE and paste the following code:

from gpiozero import LED
from time import sleep

# Define the two LEDs
red_led = LED(18)
green_led = LED(24)

print("Double LED Blink is running... Press Ctrl+C to stop.")

try:
    while True:
        red_led.on()
        green_led.off()
        print("Red is ON")
        sleep(0.5)

        red_led.off()
        green_led.on()
        print("Green is ON")
        sleep(0.5)

except KeyboardInterrupt:
    red_led.off()
    green_led.off()
    print("\nProgram stopped safely.")

4. Conclusion

You have now learned how to control multiple outputs! This is the foundation for building traffic lights or complex robotics.