Tag Archives: pulse width modulation

Arduino Basics Lesson 1-4: “These Peoples Try To Fade Me!”

For the “Arduino For Kooks” course, I recommend you get the Arduino Starter Kit available here.

So far, in this series, we have learned to read and write digital information with an Arduino. We have also learned to read analog information with the Arduino and a potentiometer. In this video, we will learn how to send pseudo-analog signals from the Arduino to a device by fading the light on an LED.

The Circuit:

Connect a jumper wire from pin 9 on the Arduino (9 is an analog out pin as denoted by the tilde [~] sign) to a 220R resistor. Connect the other end of the resistor to the anode of an LED. Connect the cathode of the LED to the ground pin of the Arduino using another jumper wire.

The Sketch:

/*
  Fade

  This example shows how to fade an LED on pin 9 using the analogWrite()
  function.

  The analogWrite() function uses PWM, so if you want to change the pin you're
  using, be sure to use another PWM capable pin. On most Arduino, the PWM pins
  are identified with a "~" sign, like ~3, ~5, ~6, ~9, ~10 and ~11.

  This example code is in the public domain.
*/

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);
}

What happens if we change the delay attribute?

What happens if we change the value of the fadeAmountvariable?

As a challenge, see if you can figure out how to use a potentiometer to control the fade effect–either through the rate of the fade or the brightness.