Fade In and Out

Part of the Outputs section of Coddy's Arduino journey. Lesson 4 of 24.

To fade back down, the step has to change direction. Keep the step in its own variable, fadeAmount. Adding a negative number makes the brightness go down:

int brightness = 0;
int fadeAmount = 5;

void loop() {
  analogWrite(9, brightness);
  brightness = brightness + fadeAmount;
  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount;
  }
  delay(30);
}

A minus sign in front of a variable flips its sign: -fadeAmount turns 5 into -5, and -5 back into 5.

The if checks both ends. At the top the step becomes -5 and the LED dims; at the bottom it becomes 5 again and the LED brightens. The LED breathes, and never jumps from bright to dark.

Challenge

Easy

Make the LED on pin 9 fade in and then out, again and again:

a fadeAmount variable of 5 beside brightness
add fadeAmount to the brightness each time loop() runs, then wait 30 ms
flip its sign when the brightness reaches 0 or 255

Press Run, then Check.

Try it yourself

const int ledPin = 9;
int brightness = 0;
// make fadeAmount here

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

void loop() {
  analogWrite(ledPin, brightness);
  brightness = brightness + 5;
  if (brightness > 255) {
    brightness = 0;
  }
  delay(30);
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Outputs

Practice on your own: Arduino playground