6: PWM Fade

This project makes one LED fade up and down instead of only being fully on or fully off.

This is your first “not just ON/OFF” output. The LED is still switching on and off, but PWM switches it so fast that your eyes see it as different brightness levels.

Coding ideas you will use:

Learn more (optional):

Goal

Make an LED slowly brighten and dim.

Parts you need

Important: choose the right resistor

Your kit has 150Ω and 100Ω resistors.

  • For a red or yellow LED, use 150Ω
  • For a green, blue, or white LED, use 100Ω

Using the wrong resistor can damage an LED.

Wiring idea

Build it first, then compare your setup to the picture. Did you connect each part to the pin you meant to use?

Use one GPIO pin to control the LED through a resistor.

Hint

The circuit is the same as what you built in 5: Blink with Code.

Example path:

GPIO -> resistor -> LED -> GND

Wiring diagram showing GP7 (GPIO 7) connected through a resistor to an LED, with the LED returning to GND for a PWM fading project

What PWM means

PWM stands for Pulse Width Modulation.

That sounds more complicated than it is. The board turns the pin on and off very quickly. By changing how long it stays on during each tiny cycle, the LED can look brighter or dimmer to your eyes.

You are not changing the LED into a different kind of part. You are changing how much power it seems to get over time.

Code

Pin reminder

Wired your LED to a different GPIO pin? Update LED_GPIO in the code below to match your wiring.

from machine import Pin, PWM
import time

LED_GPIO = 7

# Set up PWM on the chosen GPIO pin
pwm_led = PWM(Pin(LED_GPIO))
# Set the frequency (1000Hz is standard for LEDs)
pwm_led.freq(1000)

print("Starting PWM fade on GPIO", LED_GPIO, "...")
# Duty cycle ranges from 0 to 65535 (16-bit)
duty_step = 500

while True:
    # Fade Up
    for duty in range(0, 65536, duty_step):
        pwm_led.duty_u16(duty)
        time.sleep(0.01)

    # Fade Down
    for duty in range(65535, -1, -duty_step):
        pwm_led.duty_u16(duty)
        time.sleep(0.01)

Arduino Code Coming Soon

What to notice

Try this