5 LEDs Program in IoT: Complete Code and Circuit

Q. Write a program to blink 5 LEDs in serial mode with a delay of 2 seconds.

This is the important program in O Level Module 4 — IOT Practical — that blinks 5 LEDs in serial mode, meaning they will all turn on and off together in sequence with a 2-second delay.

Variable Declaration

int led1 = 12;
int led2 = 11;
int led3 = 10;
int led4 = 9;
int led5 = 8;

• These lines define 5 integer variables named⁣ led1 to⁣ led5.
• Each variable holds the number of the Arduino pin to which a corresponding LED is connected.
• led1 is connected to digital pin 12.
• led2 to pin 11, and so on down to led5 on pin 8.

Setup Function

void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  pinMode(led4, OUTPUT);
  pinMode(led5, OUTPUT);
}

• The setup()function runs once when the Arduino starts.
• pinMode(pin, OUTPUT) tells the Arduino to treat the given pin as an output pin—meaning it will send voltage to control things like LEDs.
• Each of your 5 LED pins is set as an output.

Loop Function

void loop() {
  digitalWrite(led1, HIGH);
  delay(2000);
  digitalWrite(led1, LOW);

  digitalWrite(led2, HIGH);
  delay(2000);
  digitalWrite(led2, LOW);

  digitalWrite(led3, HIGH);
  delay(2000);
  digitalWrite(led3, LOW);

  digitalWrite(led4, HIGH);
  delay(2000);
  digitalWrite(led4, LOW);

  digitalWrite(led5, HIGH);
  delay(2000);
  digitalWrite(led5, LOW);
}

What It Does:

This function runs over and over in a loop forever.

Each LED’s sequence explained:

• digitalWrite(ledX, HIGH); turns ON the LED connected to that pin.
• delay(2000); keeps it ON for 2000 milliseconds (2 seconds).
• digitalWrite(ledX, LOW); turns OFF that LED.
• Then the next LED in line is turned on in the same way.

CODE

// Program for Blink 5 LEDs in Serial Mode
//
int led1 = 12;
int led2 = 11;
int led3 = 10;
int led4 = 9;
int led5 = 8;
void setup()
{
pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);
pinMode(led3, OUTPUT);
pinMode(led4, OUTPUT);
pinMode(led5, OUTPUT);
}
void loop()
{
digitalWrite(led1, HIGH);
digitalWrite(led2, HIGH);
digitalWrite(led3, HIGH);
digitalWrite(led4, HIGH);
digitalWrite(led5, HIGH);
delay(2000); // Wait for 2000 millisecond(s)
digitalWrite(led1, LOW);
digitalWrite(led2, LOW);
digitalWrite(led3, LOW);
digitalWrite(led4, LOW);
digitalWrite(led5, LOW);
delay(2000); // Wait for 2000 millisecond(s)
}