Blink without Delay more logical without redundancy

  Blink without Delay

  Turns on and off a light emitting diode (LED) connected to a digital pin,
  without using the delay() function. This means that other code can run at the
  same time without being interrupted by the LED code.

  The circuit:
  - Use the onboard LED.
  - Note: Most Arduinos have an on-board LED you can control. On the UNO, MEGA
    and ZERO it is attached to digital pin 13, on MKR1000 on pin 6. LED_BUILTIN
    is set to the correct LED pin independent of which board is used.
    If you want to know what pin the on-board LED is connected to on your
    Arduino model, check the Technical Specs of your board at:

  created 2005
  by David A. Mellis
  modified 8 Feb 2010
  by Paul Stoffregen
  modified 11 Nov 2013
  by Scott Fitzgerald
  modified 9 Jan 2017
  by Arturo Guadalupi
  modified 16 Jun 2020

  This example code is in the public domain.

// constants won't change. Used here to set a pin number:
const int ledPin =  LED_BUILTIN;// the number of the LED pin

// Variables will change:
int ledState = LOW;             // ledState used to set the LED

// Generally, you should use "unsigned long" for variables that hold time
// The value will quickly become too large for an int to store
unsigned long previousMillis = 0;        // will store last time LED was updated

// constants won't change:
const long interval = 2000;           // interval at which to blink (milliseconds)

void setup() {
  // set the digital pin as output:
  pinMode(ledPin, OUTPUT);

void loop() {
  // here is where you'd put code that needs to be running all the time.

  // check to see if it's time to blink the LED; that is, if the difference
  // between the current time and last time you blinked the LED is bigger than
  // the interval at which you want to blink the LED.

  if (millis() - previousMillis >= interval) {
    // save the last time you blinked the LED
    previousMillis = millis();

    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;

    // set the LED with the ledState of the variable:
    digitalWrite(ledPin, ledState);

Do you have a question?

Perhaps something like the following.

const byte RedLED = 2;  // reference digital pin 2 as RedLED

void setup() {
   pinMode(RedLED, OUTPUT);  // set RedLED (2) pin as an output


void loop() {
   static unsigned long previousTime = millis();   // capture initial previous time
   unsigned long currentTime = millis();           // capture current time
   if (currentTime - previousTime >= 500) {        // run every 500 milliseconds
      previousTime = currentTime;                  // save the previous time
      digitalWrite(RedLED, !digitalRead(RedLED));  // toggle on/off LED

Do you have a question?

Why are you making it so difficult for beginners in particular? Just a positive first experience, determines whether someone is still committed. Blinking wihthout delay with an unnecessary variable, make it especially difficult for beginners to understand the solution. The forum is full of blinking questions.

Maybe if you’d described the “redundancy”…?

Maybe if you'd described the "redundancy"..?


Why is it “redundant”?

Did you mean “currentMillis”?
It provides consistency.

Someone who really wanted to torture beginners unnecessarily inserted previousTime in this example.
It is like chess, the beginner is forced to think one turn further. Beginners need a sense of achievement.

Where is “previousTime”?
Which code are you looking at?

You want to kid me. Just stay with millis ()

I have no idea what you’re banging on about.