Blink an LED

Parts in this circuit

Wiring, pin by pin

Red = 5 V, orange = 3.3 V, black = GND, other colours = signals. “Pin” is the position on the 40-pin header; the GPIO number is what the code uses. Power the Pi from a 5.1 V supply and wire with the power off.

Python code (gpiozero)

from gpiozero import LED
from time import sleep

led = LED(17)          # an LED on GPIO17

while True:
    led.on()
    print("LED on")
    sleep(1)
    led.off()
    print("LED off")
    sleep(1)

The same program with RPi.GPIO

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)      # use GPIO numbers, not pin positions
GPIO.setup(17, GPIO.OUT)    # GPIO17 is an output

try:
    while True:
        GPIO.output(17, GPIO.HIGH)
        print("LED on")
        time.sleep(1)
        GPIO.output(17, GPIO.LOW)
        print("LED off")
        time.sleep(1)
finally:
    GPIO.cleanup()          # always release the pins at the end

How the code works

• LED(17) tells Python that an LED is wired to GPIO17. Python sets that pin high (3.3 V) or low (0 V).
• sleep(1) waits one second without freezing the Pi.
• while True repeats forever, so the LED blinks until you press Stop.

Parts to buy

The links open a search on each store, so you see what is in stock today. Check the model, voltage and price before you order.