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📡 NIELIT O Level Practical • M4-R5.1

IoT Practical Programs

Explore complete IoT practical source codes, Arduino projects, sensor interfacing programs, viva questions, and step-by-step video explanations from DEEPAKRAJTech live classes.

📡 100+ Arduino Programs 💻 Source Code 🔌 Sensor Interfacing 🎥 Video Explanation
M4-R5.1 O Level Practical 📅 Jul 2026

Write a program for detection of the light using photo resistor with output as light detected and LED state.

Arduino LDR LED Circuit Diagram 

              
  int ldr = A0;
  int led = 13;
  int value = 0;
  
  void setup()
  {
    pinMode(led, OUTPUT);
    Serial.begin(9600);
  }
  
  void loop()
  {
    value = analogRead(ldr);
  
    if (value < 500)
    {
      digitalWrite(led, HIGH);
      Serial.println(value);
    }
    else
    {
      digitalWrite(led, LOW);
      Serial.println(value);
    }
  
    delay(500);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to read analog data out of the sensor (LM35 Temperature sensor) and convert it to temperature data.

Arduino LM35 Temp Circuit Diagram 

              
  int sensor = A0;
  int value = 0;
  float temp;
  
  void setup()
  {
    Serial.begin(9600);
  }
  
  void loop()
  {
    value = analogRead(sensor);
  
    temp = ((value * 5.0) / 1023.0 - 0.5) * 100;
  
    Serial.print("Temperature = ");
    Serial.print(temp);
    Serial.println(" C");
  
    delay(1000);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to blink tricolor LED and use pushbutton to control this blinking.

Arduino Circuit Diagram 

              
  int red = 13;
  int green = 12;
  int blue = 11;
  int button = 2;
  
  void setup()
  {
    pinMode(red, OUTPUT);
    pinMode(green, OUTPUT);
    pinMode(blue, OUTPUT);
    pinMode(button, INPUT);
  }
  
  void loop()
  {
    if (digitalRead(button) == HIGH)
    {
      digitalWrite(red, HIGH);
      delay(500);
      digitalWrite(red, LOW);
  
      digitalWrite(green, HIGH);
      delay(500);
      digitalWrite(green, LOW);
  
      digitalWrite(blue, HIGH);
      delay(500);
      digitalWrite(blue, LOW);
    }
    else
    {
      digitalWrite(red, LOW);
      digitalWrite(green, LOW);
      digitalWrite(blue, LOW);
    }
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to buzz when water is detected by a water sensor.

Arduino Water Sensor Circuit Diagram 

              
  int sensor = A0;
  int buzzer = 13;
  int value;
  
  void setup()
  {
    Serial.begin(9600);
    pinMode(buzzer, OUTPUT);
  }
  
  void loop()
  {
    value = analogRead(sensor);
  
    Serial.println(value);
  
    if (value < 300)
    {
      tone(buzzer, 750);
    }
    else
    {
      noTone(buzzer);
    }
  
    delay(200);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to control three LEDs with three separate buttons.

Arduino 3 LED Button Circuit Diagram 

              
  int btn1 = 2;
  int btn2 = 3;
  int btn3 = 4;
  
  void setup()
  {
    pinMode(btn1, INPUT);
    pinMode(btn2, INPUT);
    pinMode(btn3, INPUT);
  
    pinMode(13, OUTPUT);
    pinMode(12, OUTPUT);
    pinMode(11, OUTPUT);
  }
  
  void loop()
  {
    if (digitalRead(btn1) == HIGH)
      digitalWrite(13, HIGH);
    else
      digitalWrite(13, LOW);
  
    if (digitalRead(btn2) == HIGH)
      digitalWrite(12, HIGH);
    else
      digitalWrite(12, LOW);
  
    if (digitalRead(btn3) == HIGH)
      digitalWrite(11, HIGH);
    else
      digitalWrite(11, LOW);
  
    delay(100);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program for controlling the Light Emitting Diode (LED) with a push button state and LED state.

Arduino LED Button Circuit Diagram 

              
  int button = 2;
  int led = 13;
  
  int ledState = LOW;
  int lastButtonState = LOW;
  
  void setup()
  {
    pinMode(button, INPUT);
    pinMode(led, OUTPUT);
  }
  
  void loop()
  {
    int currentButtonState = digitalRead(button);
  
    if (currentButtonState == HIGH && lastButtonState == LOW)
    {
      ledState = !ledState;
      digitalWrite(led, ledState);
      delay(100);
    }
  
    lastButtonState = currentButtonState;
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program for Emergency Ambulance Siren using Buzzer.

arduino ambulance siren Circuit Diagram 

              
  int buzzer = 8;

  void setup()
  {
    pinMode(buzzer, OUTPUT);
  }
  
  void loop()
  {
    for (int i = 500; i <= 1000; i += 10)
    {
      tone(buzzer, i);
      delay(10);
    }
  
    for (int i = 1000; i >= 500; i -= 10)
    {
      tone(buzzer, i);
      delay(10);
    }
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to develop automatic street light enabling and disabling system using Light Dependent Resistor (LDR).

Street Light LDR Circuit Diagram 

              
  int ldr = A0;
  int bulb = 2;
  
  void setup()
  {
    pinMode(bulb, OUTPUT);
    pinMode(ldr, INPUT);
  }
  
  void loop()
  {
    if (analogRead(ldr) > 500)
      digitalWrite(bulb, LOW);
    else
      digitalWrite(bulb, HIGH);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to control an LED using an IoT development board.

Arduino LED Circuit Diagram 

              
  void setup()
  {
    pinMode(13, OUTPUT);
  }
  
  void loop()
  {
    digitalWrite(13, HIGH);
    delay(500);
  
    digitalWrite(13, LOW);
    delay(500);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to use Seven Segment display.

Arduino Seven Segment Display Circuit Diagram 

              
  // 7-Segment Display ke Segments ka Arduino Pins se Connection

  int a = 7;
  int b = 8;
  int c = 9;
  int d = 10;
  int e = 11;
  int f = 13;
  int g = 12;
  
  // 0 se 9 tak ke Numbers ki Binary Table (1 = ON, 0 = OFF)
  
  int n[10][7] = {
    {1, 1, 1, 1, 1, 1, 0}, // 0
    {0, 1, 1, 0, 0, 0, 0}, // 1
    {1, 1, 0, 1, 1, 0, 1}, // 2
    {1, 1, 1, 1, 0, 0, 1}, // 3
    {0, 1, 1, 0, 0, 1, 1}, // 4
    {1, 0, 1, 1, 0, 1, 1}, // 5
    {1, 0, 1, 1, 1, 1, 1}, // 6
    {1, 1, 1, 0, 0, 0, 0}, // 7
    {1, 1, 1, 1, 1, 1, 1}, // 8
    {1, 1, 1, 1, 0, 1, 1}  // 9
  };
  
  void setup()
  {
    // Sabhi Pins ko Output Set Karna
  
    pinMode(a, OUTPUT);
    pinMode(b, OUTPUT);
    pinMode(c, OUTPUT);
    pinMode(d, OUTPUT);
    pinMode(e, OUTPUT);
    pinMode(f, OUTPUT);
    pinMode(g, OUTPUT);
  }
  
  void loop()
  {
    // 0 se 9 tak Counting
  
    for (int i = 0; i < 10; i++) {
      displayNumber(i);
      delay(1000);
    }
  }
  
  // Display par Number Dikhane ka Function
  
  void displayNumber(int i)
  {
    digitalWrite(a, n[i][0]);
    digitalWrite(b, n[i][1]);
    digitalWrite(c, n[i][2]);
    digitalWrite(d, n[i][3]);
    digitalWrite(e, n[i][4]);
    digitalWrite(f, n[i][5]);
    digitalWrite(g, n[i][6]);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to read humidity from a DHT11 sensor and display it.

Arduino DHT11 Sensor Display Circuit Diagram 

              
  #include <Adafruit_LiquidCrystal.h>

  Adafruit_LiquidCrystal lcd(0);
  
  const int sensorPin = A0;
  
  void setup()
  {
    lcd.begin(16, 2);
    lcd.print("Temp Monitor");
  }
  
  void loop()
  {
    int reading = analogRead(sensorPin);
  
    float voltage = reading * (5.0 / 1024.0);
  
    float temp = (voltage - 0.5) * 100;
  
    lcd.setCursor(0, 1);
    lcd.print("Temp: ");
    lcd.print(temp);
    lcd.print("  C   ");
  
    delay(1000);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to use a button as a toggle switch for a buzzer.

Toggle Switch for Buzzer Circuit Diagram 

              
  int state = 1;

  void setup()
  {
    pinMode(2, INPUT_PULLUP);
  }
  
  void loop()
  {
    if (digitalRead(2) == LOW) {
  
      state = !state;
  
      if (state)
        tone(4, 700);
      else
        noTone(4);
  
      while (digitalRead(2) == LOW);
  
      delay(100);
    }
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to turn on an LED when LDR value drops below a threshold.

LDR and LED Circuit Diagram 

              
  void setup()
  {
    pinMode(13, OUTPUT);
  
    Serial.begin(9600);
  }
  
  void loop()
  {
    if (analogRead(A0) < 550) {
      digitalWrite(13, HIGH);
    }
    else {
      digitalWrite(13, LOW);
    }
  
    Serial.println(analogRead(A0));
  
    delay(100);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to Interfacing the RGB (Red Green Blue) LED (Light Emitting Diode) with output in Time (ms) and Color of LED.

RGB Lights Circuit Diagram 

              
  void setup()
  {
    pinMode(13, OUTPUT);
    pinMode(12, OUTPUT);
    pinMode(11, OUTPUT);
  
    Serial.begin(9600);
  }
  
  void loop()
  {
    digitalWrite(13, HIGH);
    Serial.println("Red LED ON");
    delay(2000);
    digitalWrite(13, LOW);
  
    digitalWrite(12, HIGH);
    Serial.println("Blue LED ON");
    delay(2000);
    digitalWrite(12, LOW);
  
    digitalWrite(11, HIGH);
    Serial.println("Green LED ON");
    delay(2000);
    digitalWrite(11, LOW);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Use the Serial Monitor in the Arduino IDE to display a message (“Hello, Arduino!”) upon successfully uploading a sketch. How does the Serial Monitor help in debugging?

Arduino Serial Monitor Circuit Diagram 

              
  void setup()
  {
    Serial.begin(9600);
  }
  
  void loop()
  {
    Serial.println("Hello, Arduino!");
  
    delay(1000);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program using any one development board (Eg., Arduino or Raspberry Pi) to read data from a sensor. Experiment with both analog and digital sensors.

Arduino Circuit Diagram analog and digital sensors 

              
  void setup()
  {
    pinMode(2, INPUT_PULLUP);
    Serial.begin(9600);
  }
  
  void loop()
  {
    int analogValue = analogRead(A0);
    int buttonState = !digitalRead(2);
  
    Serial.print("analog = ");
    Serial.print(analogValue);
  
    Serial.print("    Button = ");
    Serial.println(buttonState);
  
    delay(1000);
  }

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M4-R5.1 O Level Practical 📅 Jul 2026

Write a program to print “Hello World!” to the LCD (Liquid Crystal Display) and shows the time in seconds since the Arduino was reset.

Arduino Liquid Crystal Display Circuit Diagram 

              
  #include <Adafruit_LiquidCrystal.h>

  Adafruit_LiquidCrystal lcd(0);
  
  void setup()
  {
    lcd.begin(16, 2);
    lcd.setBacklight(1);
  
    lcd.setCursor(0, 0);
    lcd.print("Hello World!");
  }
  
  void loop()
  {
    lcd.setCursor(0, 1);
    lcd.print("Time: ");
    lcd.print(millis() / 1000);
    lcd.print("  Sec  ");
  
    delay(1000);
  }

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M4-R5.1 O Level Practical 📅 Jan 2026

Write a program to interface Light Dependent Resistor (LDR) and LED with Arduino board. Whenever there is sufficient light falls on LDR the LED is off and when there is dark around LDR the LED is put on.

LED is off and when there is dark around 

              
  int ldrPin = A0;
  int ledPin = 9;
  int ldrValue = 0;
  int threshold = 500;
  
  void setup() {
      pinMode(ledPin, OUTPUT);
      Serial.begin(9600);
  }
  
  void loop() {
      ldrValue = analogRead(ldrPin);
      Serial.println(ldrValue);
    
    if (ldrValue < threshold) {
          digitalWrite(ledPin, HIGH);
    } else {
          digitalWrite(ledPin, LOW);
    }
    
      delay(100);
  }

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M4-R5.1 O Level Practical 📅 Jan 2026

Write a program to interface Light Dependent Resistor (LDR) and display the values read on the Serial monitor after delay of 2 seconds each.

interface Light Dependent Resistor 

              
  // Reads LDR values and prints them to Serial Monitor

  int ldrPin = A0;   // LDR connected to analog pin A0
  int ldrValue = 0;  // Variable to store LDR value

  void setup() {
      Serial.begin(9600);  // Start Serial communication
  }

  void loop() {
      ldrValue = analogRead(ldrPin);  
      Serial.print("LDR Value: ");
      Serial.println(ldrValue);

      delay(1000); // Wait for 1 seconds
  }

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M4-R5.1 O Level Practical 📅 Jan 2026

Write a program to interface LEDs at pins 10,11,12,13 and button at pins 7. The press of button changes the pattern of LED glow. (considering four patterns of LED glow)

changes the pattern of LED glow 

              
  // The press of button changes the pattern of LED glow

  const int ledPins[] = {10, 11, 12, 13};
  const int buttonPin = 7;

  int currentPattern = 0;
  int lastButtonState = 0; // For button state check

  void setup() {
    for (int i = 0; i < 4; i++) {
          pinMode(ledPins[i], OUTPUT);
    }
      pinMode(buttonPin, INPUT);
  }

  void loop() {
      int buttonState = digitalRead(buttonPin);

    if (buttonState == HIGH && lastButtonState == LOW) {
          currentPattern = (currentPattern + 1) % 4;
          delay(300); // debounce
    }
      lastButtonState = buttonState;

      runPattern(currentPattern);
  }

  void runPattern(int p) {
    switch (p) {
          case 0:
            // Pattern 1: Forward running light
      for (int i = 0; i < 4; i++) {
                clearLEDs();
                digitalWrite(ledPins[i], HIGH);
                delay(150);
      }
            break;

          case 1:
            // Pattern 2: Forward + Backward running light
      for (int i = 0; i < 4; i++) {
                clearLEDs();
                digitalWrite(ledPins[i], HIGH);
                delay(150);
      }
      for (int i = 2; i >= 1; i--) {
                clearLEDs();
                digitalWrite(ledPins[i], HIGH);
                delay(150);
      }
            break;

          case 2:
            // Pattern 3: Outside to Inside
            clearLEDs();
            digitalWrite(ledPins[0], HIGH);
            digitalWrite(ledPins[3], HIGH);
            delay(200);
            clearLEDs();
            digitalWrite(ledPins[1], HIGH);
            digitalWrite(ledPins[2], HIGH);
            delay(200);
            break;

          case 3:
            // Pattern 4: Quick strobe effect
      for (int j = 0; j < 10; j++) { // blink 10 times
                setAllLEDs(HIGH);
                delay(600);
                setAllLEDs(LOW);
                delay(600);
      }
            break;
    }
  }

  void clearLEDs() {
    for (int i = 0; i < 4; i++) {
          digitalWrite(ledPins[i], LOW);
    }
  }

  void setAllLEDs(int state) {
    for (int i = 0; i < 4; i++) {
          digitalWrite(ledPins[i], state);
    }
  }

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M4-R5.1 O Level Practical 📅 Jan 2026

Write a program to interface LEDs at pins 10,11,12,13 and buttons at pins 7,8. When first time button at pin 7(increment button) is pressed first LED at pin 10 is switched on, when second time button is pressed the next LED at 11 is switched on. Similarly, when the button at pin 8 (decrement button) is pressed the LEDs are switched off sequentially.

LEDs are switched on and off sequentially 

              
  // LED Control using Increment and Decrement Buttons
  const int ledPins[] = {10, 11, 12, 13};
  const int plushBtn = 7;
  const int minusBtn = 8;

  int ledIndex = 0;
  bool plushBtnState = HIGH;
  bool minusBtnState = HIGH;

  void setup() {
    for (int i = 0; i < 4; i++) {
          pinMode(ledPins[i], OUTPUT);
          digitalWrite(ledPins[i], LOW);
    }
      pinMode(plushBtn, INPUT);
      pinMode(minusBtn, INPUT);
  }

  void loop() {
      bool currentInc = digitalRead(plushBtn);
      bool currentDec = digitalRead(minusBtn);

      // Increment button pressed
    if (plushBtnState == HIGH && currentInc == LOW) {
      if (ledIndex < 4) {
              digitalWrite(ledPins[ledIndex], HIGH);
              ledIndex++;
      }
          delay(200);
    }

      // Decrement button pressed
    if (minusBtnState == HIGH && currentDec == LOW) {
      if (ledIndex > 0) {
              ledIndex--;
              digitalWrite(ledPins[ledIndex], LOW);
      }
          delay(200);
    }

      plushBtnState = currentInc;
      minusBtnState = currentDec;
  }

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M4-R5.1 O Level Practical 📅 Jan 2026

Write a program to interface Button, buzzer and LED, whenever the button is pressed the buzzer gives beep for 100ms and LED status is toggled.

interface Button, buzzer and LED 

              
  // Buzzer gives beep for 100ms and LED status is toggled

  int ledState = LOW;
  int buttonState = 0;
  int lastButtonState = LOW;

  void setup() {
      pinMode(2, INPUT);
      pinMode(12, OUTPUT);
      pinMode(13, OUTPUT);
  }

  void loop() {
      buttonState = digitalRead(2);

    if (buttonState == HIGH && lastButtonState == LOW) {
          ledState = !ledState;
          digitalWrite(13, ledState);
          digitalWrite(12, HIGH);
          delay(100);
          digitalWrite(12, LOW);
    }
      lastButtonState = buttonState;
      delay(100); 
  }

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M4-R5.1 O Level Practical 📅 Jan 2026

Write a program to interface Button and LED, so that LED blinks/glow when button is pressed.

interface Button and LED 

              
  // LED blinks/glow when button is pressed

  int buttonState = 0;

  void setup() {
      pinMode(2, INPUT);
      pinMode(13, OUTPUT);
  }

  void loop() {
      buttonState = digitalRead(2);
    if (buttonState == HIGH) {
          digitalWrite(13, HIGH);
    } else {
          digitalWrite(13, LOW);
    }
      delay(100);
  }

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M4-R5.1 O Level Practical 📅 Jan 2026

Write a program to interface LED and Buzzer with Arduino board, so that buzzer is put on whenever LED is on and Buzzer is put off when LED is off.

interface LED and Buzzer with Arduino board 

              
  // LED and Buzzer is on and off delay of 1 sec

  void setup() {
      pinMode(13, OUTPUT);
      pinMode(12, OUTPUT);
  }

  void loop() {
      digitalWrite(13, HIGH);  
      digitalWrite(12, HIGH); 
      delay(1000);             

      digitalWrite(13, LOW);      
      digitalWrite(12, LOW);   
      delay(1000);                   
  }

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M4-R5.1 O Level Practical 📅 Jan 2026

Write a program to interface buzzer with Arduino board to buzz on/off with the delay of 1sec.

interface buzzer with Arduino board 

              
  // Buzz on/off with the delay of 1sec
  
  void setup()
  {
      pinMode(13, OUTPUT);
  }

  void loop()
  {
      digitalWrite(13, HIGH);
      delay(1000);
      digitalWrite(13, LOW);
      delay(1000); 
  }

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M4-R5.1 O Level Practical 📅 Jan 2026

Write a program to run pattern(s) on LEDs connect at pins 10,11,12,13. Pattern example:

program to run pattern 

              
  int leds[] = {10, 11, 12, 13};

  // Each row represents a step in the pattern
  int pattern[][4] = {
    {1, 0, 0, 0},
    {0, 1, 0, 0},
    {0, 0, 1, 0},
    {0, 0, 0, 1},
    {1, 1, 0, 0},
    {0, 1, 1, 0},
    {0, 0, 1, 1}
  };

  int steps = sizeof(pattern) / sizeof(pattern[0]);

  void setup() {
    for (int i = 0; i < 4; i++) {
          pinMode(leds[i], OUTPUT);
    }
  }

  void loop() {
    for (int i = 0; i < steps; i++) {
      for (int j = 0; j < 4; j++) {
              digitalWrite(leds[j], pattern[i][j]);
      }
          delay(3000);
    }
  }

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M4-R5.1 O Level Practical 📅 Jan 2026

Write a program to interface LEDs on pin no. 10,11,12,13 and blink alternatively at the delay of 1 sec.

LEDs on pin no. 10,11,12,13 and blink alternatively 

              
  // Blinks 4 LEDs one-by-one

  void setup() {
    for (int i = 10; i <= 13; i++) {
          pinMode(i, OUTPUT);
    }
  }
  
  void loop() {
    for (int i = 10; i <= 13; i++) {
          // Turn OFF all LEDs
      for (int j = 10; j <= 13; j++) {
              digitalWrite(j, LOW);
      }
          // Turn ON current LED
          digitalWrite(i, HIGH);
          delay(1000);
    }
  }

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M4-R5.1 O Level Practical 📅 Jan 2026

Write a program to Blink default Light Emitting Diode(LED) on Arduino board with the delay of 2 sec.

Blink default Light Emitting Diode 

              
  // LED Blink with 2 Second Delay

  void setup() {
    // Pin 13 ko output mode me set karna
    pinMode(13, OUTPUT);
  }
  
  void loop() {
    // LED ON karna
    digitalWrite(13, HIGH);
    delay(2000); // 2 second delay
  
    // LED OFF karna
    digitalWrite(13, LOW);
    delay(2000); // 2 second delay
  }

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