GPIO Basics: Blinking an LED

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Blinking an LED is the classic first physical-computing project, and it's the perfect way to prove your Zero W's GPIO header, your wiring, and your code all work together before moving on to anything more complex.

What You'll Need

Item	Why
An LED	The thing you're actually lighting up
A current-limiting resistor (330 ohm is a safe, common value)	Without it, an LED will draw too much current from the GPIO pin, which can damage the LED and potentially the pin driving it - the resistor limits current to a safe level
A breadboard	Makes wiring temporary connections easy without soldering
Jumper wires	To connect the breadboard to the GPIO header

Remember from the GPIO Pinout Reference lesson: GPIO pins are 3.3V only and are not 5V tolerant. Never wire the LED circuit to one of the board's 5V pins - use a 3.3V-driven GPIO pin as shown below, and always route current through the resistor.

Wiring It Up

LEDs have two legs of different lengths: the longer leg is the anode (positive) and the shorter leg is the cathode (negative). Wire the circuit like this:

The LED's longer leg (anode) connects through the resistor to physical pin 11, which is GPIO17 in code.
The LED's shorter leg (cathode) connects to a ground pin - physical pin 9 is a convenient one nearby.

The resistor can sit on either side of the LED in the circuit (between the pin and the anode, or between the cathode and ground) - what matters is that it's somewhere in that single loop limiting the current.

The Code

For a first GPIO project like this, the currently-recommended library is gpiozero - it ships with Raspberry Pi OS and has a simple, readable, high-level API. The older, lower-level RPi.GPIO library still exists and still works, and you'll see it in plenty of older tutorials, but it requires more manual setup code (configuring pin modes, cleanup, etc.) for the same result - gpiozero is simpler and is the one to actually use for this.

from gpiozero import LED
from time import sleep

led = LED(17)

while True:
    led.on()
    sleep(1)
    led.off()
    sleep(1)

This page's code and terminal commands are a preview, not something you can run right on this website - this server runs PHP, not the Zero W's own operating system. Save this as a .py file on your Zero W (over the SSH connection from the previous lesson) and run it with python3 blink.py.

How the Code Works

from gpiozero import LED - imports the LED class, which wraps up the details of driving a GPIO pin high and low.
from time import sleep - imports Python's built-in sleep function so we can pause between blinks.
led = LED(17) - creates an LED object attached to GPIO17 (the BCM number, corresponding to physical pin 11, exactly as wired above).
led.on() and led.off() - set that GPIO pin high (3.3V) or low (0V), turning the LED on or off.
sleep(1) - pauses execution for 1 second so you can actually see each state.
The while True: loop repeats the on/off/sleep sequence forever, producing a steady blink. (You could also replace the loop body with led.blink(), which does the same on/off/sleep cycle for you.)

Next steps: With your first GPIO project working, move on to Using the Camera Module to add vision to your projects.

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