By Doug Lowe

In this simple electronics project, you get to build a simple breadboard circuit that connects an LED to a Raspberry Pi via the GPIO port on pin 3 of the header. The figure shows the completed project.

electronics-flasher
The Raspberry Pi LED Flasher (Project 55).

In this project, you connect an external LED to a Raspberry Pi, and then use a simple sketch to turn the LED on and off at 0.5-second intervals.

electronics-sketch-a

Parts needed to build an LED flasher

  • One Raspberry Pi 2 or 3 with Raspbian installed, connected to a monitor, keyboard, and power
  • One small solderless breadboard (RadioShack 2760003)
  • One 5mm red LED (RadioShack 2760209)
  • One resistor (orange-orange-brown)
  • Two jumper wires (M/F)

electronics-sketch-b

Steps for building an LED flasher

  1. Insert resistor R1. 

    R1 – 330 Ω: A3 to ground bus

  2. Insert LED1.
    Cathode (short lead): D5
    Anode (long lead): D3
    electronics-cathode
  3. Connect the ground bus to the Raspberry Pi header pin 2.
    Use a jumper to connect any hole in the ground bus on the breadboard.
  4. Connect pin 3 on the Raspberry Pi A5 on the breadboard.
  5. Open the Python 2 IDLE Editor with root privileges.
  6. Create and save the sketch shown here, using the filename LedBlink.
    import RPi.GPIO as GPIO
    import timeGPIO.setmode(GPIO.BOARD)
    GPIO.setup(3, GPIO.OUT)

    while True:
    GPIO.output(3, GPIO.HIGH)
    time.sleep(0.5)
    GPIO.output(3, GPIO.LOW)
    time.sleep(0.5)
  7. Run the LedBlink program by choosing Run →  Run Module (or press F5).
    The LED on the breadboard will flash on and off at half-second intervals.