This tutorial intends to demonstrate how to fade light on and off with arduino. To accomplish this, we shall use analogWrite function which uses pulse Width Modulation(PWM) to vary the light state.

Components Required

  • Arduino Board
  • LED
  • 220 ohm Resistor
  • Wires
  • Breadboard

Connection Preview

Simple Fade

Procedure

  • Connect the anode (the longer, positive leg) of your LED to digital output pin 9 on your board through a 220 ohm resistor
  • Connect the cathode (the shorter, negative leg) directly to ground.
  • Open the Editor(if you haven’t)
  • Before Setup function declare the following variables
int led = 9;           // the PWM pin the LED is attached to
int brightness = 0;    // how bright the LED is
int fadeAmount = 5;    // how many points to fade the LED by
  • In the setup function declare pin 9 to be an output
 pinMode(led, OUTPUT);
  • in the loop function, set the brightness of pin 9
 analogWrite(led, brightness);
  • Then change the brightness, using fadeAmount
  brightness = brightness + fadeAmount;
  • Reverse the direction of the fading at the ends of the fade
  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount;
  }
  • wait for 30 milliseconds to see the dimming effect
delay(30);

Full Source Code

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int led = 9;           // the PWM pin the LED is attached to
int brightness = 0;    // how bright the LED is
int fadeAmount = 5;    // how many points to fade the LED by

// the setup routine runs once when you press reset:
void setup() {
  // declare pin 9 to be an output:
  pinMode(led, OUTPUT);
}

// the loop routine runs over and over again forever:
void loop() {
  // set the brightness of pin 9:
  analogWrite(led, brightness);

  // change the brightness for next time through the loop:
  brightness = brightness + fadeAmount;

  // reverse the direction of the fading at the ends of the fade:
  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount;
  }
  // wait for 30 milliseconds to see the dimming effect
  delay(30);
}