How to Fade LED in Arduino: Simple PWM Example

To fade an LED in Arduino, connect the LED to a PWM-capable pin and use analogWrite(pin, value) where value ranges from 0 (off) to 255 (fully on). Gradually change this value in a loop to create a smooth fading effect.

Syntax

The main function to control LED brightness is analogWrite(pin, value).

• pin: The Arduino pin connected to the LED (must support PWM).
• value: Brightness level from 0 (off) to 255 (full brightness).

Use a loop to change value gradually for fading.

arduino

analogWrite(pin, value);

Example

This example fades an LED connected to pin 9 smoothly from off to fully on and back repeatedly.

arduino

const int ledPin = 9;  // PWM pin connected to LED

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // Fade in from 0 to 255
  for (int brightness = 0; brightness <= 255; brightness++) {
    analogWrite(ledPin, brightness);
    delay(10);  // Wait 10ms for visible fade
  }
  // Fade out from 255 to 0
  for (int brightness = 255; brightness >= 0; brightness--) {
    analogWrite(ledPin, brightness);
    delay(10);
  }
}

Output

LED brightness smoothly increases from off to fully on, then decreases back to off repeatedly.

Common Pitfalls

Common mistakes when fading an LED include:

• Using a pin that does not support PWM (LED will only turn fully on or off).
• Not setting the pin mode to OUTPUT in setup().
• Using digitalWrite() instead of analogWrite() for fading.
• Changing brightness too fast or too slow, making the fade look abrupt or too slow.

arduino

/* Wrong: Using digitalWrite for fading (LED will not fade smoothly) */
const int ledPin = 9;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  for (int brightness = 0; brightness <= 255; brightness++) {
    digitalWrite(ledPin, brightness > 127 ? HIGH : LOW); // Incorrect usage fixed
    delay(10);
  }
}

/* Right: Use analogWrite for smooth fading */
// See example section for correct code.

Quick Reference

Tips for fading LED on Arduino:

• Use PWM pins (marked with ~ on Arduino boards).
• Use analogWrite() to set brightness.
• Brightness values range from 0 to 255.
• Use delays between brightness changes for smooth fading.
• Always set pin mode to OUTPUT in setup().

Key Takeaways

Use PWM pins and analogWrite() to control LED brightness smoothly.

Brightness values range from 0 (off) to 255 (full brightness).

Gradually change brightness in a loop with small delays for fading effect.

Set pin mode to OUTPUT before using analogWrite().

Avoid using digitalWrite() for fading as it only turns LED fully on or off.