Arduino Playground

Understanding Blink without Delay Demo Code

This is the sample code from Dan Hoover's article Understanding Blink Without Delay

It shows how to use the millis() function to blink 3 LEDs, each with a different interval:

Click on "Run Code" to see it in action. Can you achieve the same effect with less code and still without using delay() ?

For more information, check out Dan's YouTube tutorial:

Have questions? Feedback? Please share with us below:

sketch.ino

// Code from https://github.com/mudmin/AnotherMaker/tree/master/blink-without-delay

int red = 2;
int intervalRed = 1000; //how long to delay in millis
unsigned long previousRed = 0;
int redState = LOW;

int blue = 3;
int intervalBlue = 2500; //how long to delay in millis
unsigned long previousBlue = 0;
int blueState = LOW;

int green = 4;
int intervalGreen = 5000; //how long to delay in millis
unsigned long previousGreen = 0;
int greenState = LOW;

void setup() {
  Serial.begin(9600);
  pinMode(red, OUTPUT);
  pinMode(blue, OUTPUT);
  pinMode(green, OUTPUT);
}

void checkRed() {
  unsigned long currentMillis = millis();

  if (currentMillis - previousRed >= intervalRed) {
    //save this reading!
    previousRed = currentMillis;

    //figure out if you should turn the LED on or off
    if (redState == LOW) {
      redState = HIGH;
    } else {
      redState = LOW;
    }
    digitalWrite(red, redState);
  }
}

void checkGreen() {
  unsigned long currentMillis = millis();

  if (currentMillis - previousGreen >= intervalGreen) {
    //save this reading!
    previousGreen = currentMillis;

    //figure out if you should turn the LED on or off
    if (greenState == LOW) {
      greenState = HIGH;
    } else {
      greenState = LOW;
    }
    digitalWrite(green, greenState);
  }
}

void checkBlue() {
  unsigned long currentMillis = millis();

  if (currentMillis - previousBlue >= intervalBlue) {
    //save this reading!
    previousBlue = currentMillis;

    //figure out if you should turn the LED on or off
    if (blueState == LOW) {
      blueState = HIGH;
    } else {
      blueState = LOW;
    }
    digitalWrite(blue, blueState);
  }
}


void loop() {
  checkRed();
  checkGreen();
  checkBlue();
}