Arduino Blink Without Delay() Explained

In this arduino tutorial, we shall discuss how to blink an LED without using the delay() function. Arduino program uses the delay() function to freeze the condition of a sketch running in an arduino at any moment it is evoked. If an arduino project contains a code that blinks an LED, say we have:

This means that the variable ledPin will go to a high state and remain on that state for 2 seconds, then go to a LOW state and remain on that LOW state for 2 seconds. For these periods that ledPin stay on a HIGH state and LOW state, the activities that are happening in the arduino during these times freeze to whatever they are doing and no other code in the sketch will be executed during those times. So, let’s say that a part of the sketch in question is a code that can receive a button pressed anytime and do something in response. If this button is coincidentally pressed when any of the delays is in action, because the delay has frozen all new code execution, the arduino will not take note of the pressed button.

Blink Without Delay Using Millis() Function

To solve this problem, we have to find a way to blink the LED without using the delay() function. To this we will utilize the “millis()” function.

millis() is a function that keeps track of how long arduino has been ON, or from the moment the reset button of the arduino is pressed, and produce the result in milliseconds.  With this function and some other conditional functions, we can keep track of a certain time frame and blink the LED with this time frame. For example, we can choose to say, if the time from when the arduino has been ON is 1 second i.e. 1000 milliseconds ledPin should come ON, etc. if we are able to realize this blink without delay, we can include button press code in our sketch without fear of design malfunction. To implement this design, we utilize the circuit below. The circuit is a simple arduino circuit with one LED connected to pin 2 of the arduino using a resistor.

Design Components

1. Arduino Uno  (1)
2. 330Ω                (1)
3. LED                  (1)

const int ledPin =  2;
  int ledState = LOW;           
    unsigned long previousMillis = 0;       
      const long interval = 1000; 
        void setup()
          {pinMode(ledPin, OUTPUT);}
           void loop() 
           {
             unsigned long currentMillis = millis();
              if (currentMillis - previousMillis >= interval) {
             previousMillis = currentMillis;
           if (ledState == LOW) {
        ledState = HIGH; }
      else {
    ledState = LOW;}
digitalWrite(ledPin, ledState);}
    }

Table 1: Explanation of the codes in the sketch above

With the loop function, the process keeps repeating with the LED blinking after every one second.

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