How to Create a Fading LED with PWM

Steps to Create a Fading LED Project

1

Open OmniBoard Studio and create a new project.

2

Build the block diagram to fade an LED in and out using a PWM block and a variable for brightness.

Try to build the diagram yourself, or click here to see one solution. ▼

• ● Place a Start block, then connect it to a While True block.
• ● Inside the loop, use a For Loop block counting from 0 to 1023 (fade in). Connect a Set PWM Duty block inside the For Loop and set the duty cycle to the loop variable.
• ● Add a short Timer block (e.g. 2 ms) inside the For Loop so the fade is visible.
• ● After the fade-in loop, add a second For Loop counting from 1023 down to 0 (fade out) with the same Set PWM Duty and Timer blocks.

3

Build the circuit — it is the same as the Blinking LED circuit.

• ● Make sure the GPIO pin you choose supports PWM output (check your microcontroller's datasheet).
• ● Connect the LED anode (long leg) through a resistor to the PWM-capable GPIO pin, and the cathode (short leg) to ground.

4

Compile the code and upload it to your microcontroller.

5

Watch your LED smoothly fade in and out in a continuous breathing pattern!

Bonus Information

• Here is an example of simplified MicroPython code for a fading LED:

import machine  # Needed for controlling the GPIO pins
import time     # Needed for creating delays

pwm = machine.PWM(machine.Pin(2))  # Set GPIO pin 2 as a PWM output
pwm.freq(1000)                     # Set PWM frequency to 1000 Hz

while True:
    for duty in range(0, 1024):    # Fade in: 0 → full brightness
        pwm.duty(duty)
        time.sleep_ms(2)

    for duty in range(1023, -1, -1): # Fade out: full brightness → 0
        pwm.duty(duty)
        time.sleep_ms(2)
                

• And here is simplified code for Python (Raspberry Pi):

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
GPIO.setup(2, GPIO.OUT)
pwm = GPIO.PWM(2, 1000)  # Pin 2, 1000 Hz
pwm.start(0)             # Start with 0% duty cycle

while True:
    for dc in range(0, 101):    # Fade in
        pwm.ChangeDutyCycle(dc)
        time.sleep(0.02)

    for dc in range(100, -1, -1): # Fade out
        pwm.ChangeDutyCycle(dc)
        time.sleep(0.02)
                

• What is PWM?
• PWM stands for Pulse Width Modulation. It is a technique where a digital signal is rapidly switched on and off. By changing the ratio of time the signal is on versus off (called the duty cycle), we can control the average power delivered to a device — like dimming an LED or controlling motor speed.
• What is a duty cycle?
• The duty cycle is the percentage of time the PWM signal is HIGH (on) within one period. A 0% duty cycle means the output is always off, 50% means it is on half the time, and 100% means it is always on. In MicroPython, duty values range from 0 to 1023 instead of percentages.