View source for IPDL - 4: IoT Sensor Interface with Arduino

== IPDL - 4: IoT Sensors Interface with Arduino (Temperature/Light Sensors) ==

=== Objective ===
To interface an '''LDR''' and '''DHT11 temperature sensor''' with Arduino Uno and read light intensity and temperature values through the Serial Monitor.

=== Required Components ===

* Arduino Uno
* LDR (Light Dependent Resistor) sensor/module
* DHT11 temperature sensor
* Breadboard
* Jumper wires
* 10 kΩ resistor (if using a bare LDR)
* USB cable

=== Circuit Diagram ===

<!-- IMAGE PLACEHOLDER:
Suggested image: Circuit diagram showing Arduino Uno connected to an LDR sensor on A0 and DHT11 data pin on digital pin 2, with both sensors connected to 5V and GND.
Suggested filename: Arduino-LDR-DHT11-circuit.png
-->

=== Board Connections ===

<!-- IMAGE PLACEHOLDER:
Suggested image: Actual board connection photo showing Arduino Uno, LDR, DHT11, breadboard and jumper wires.
Suggested filename: Arduino-LDR-DHT11-board-connection.png
-->

=== Pin Connections ===

{| class="wikitable" style="text-align:center; width:100%;"
! Component
! Connection
|-
| LDR VCC
| Arduino 5V
|-
| LDR GND
| Arduino GND
|-
| LDR Analog Output
| Arduino A0
|-
| DHT11 VCC
| Arduino 5V
|-
| DHT11 GND
| Arduino GND
|-
| DHT11 DATA
| Arduino Digital Pin 2
|}


=== Working Principle ===

The '''LDR (Light Dependent Resistor)''' changes its resistance according to the amount of light falling on it. Its analog output is connected to Arduino analog pin '''A0'''. The Arduino reads this value using '''analogRead()'''.

The '''DHT11''' is a digital temperature and humidity sensor. It sends temperature and humidity readings to the Arduino through its data pin. In this experiment, the DHT11 data pin is connected to digital pin '''2'''.

The Arduino reads both sensors and displays their values on the '''Serial Monitor'''.

=== Arduino Code ===

<pre>
// © 2025, Cognifront. Member of The IoT Kits Family.

// Experiment: IoT Sensors Interface with Arduino
// Sensors: LDR and DHT11

#include <DHT.h>

#define DHTPIN 2
#define DHTTYPE DHT11

int ldrPin = A0;

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);

  dht.begin();

  Serial.println("LDR and DHT11 Sensor Monitoring Started...");
}

void loop() {
  // Read LDR value
  int ldrValue = analogRead(ldrPin);

  // Read temperature and humidity
  float temperature = dht.readTemperature();
  float humidity = dht.readHumidity();

  Serial.print("LDR Value: ");
  Serial.println(ldrValue);

  if (isnan(temperature) || isnan(humidity)) {
    Serial.println("DHT11 reading failed!");
  }
  else {
    Serial.print("Temperature: ");
    Serial.print(temperature);
    Serial.println(" °C");

    Serial.print("Humidity: ");
    Serial.print(humidity);
    Serial.println(" %");
  }

  Serial.println("-------------------------");

  delay(2000);
}
</pre>

=== Required Arduino Library ===

The code uses the '''DHT sensor library'''.

Install it from:

GitHub Repository, visit [https://github.com/adafruit/DHT-sensor-library].

=== Observation ===

* The LDR value changes when the amount of light falling on the sensor changes.
* The DHT11 displays the surrounding temperature in °C.
* The DHT11 also provides the surrounding humidity value.
* Sensor readings are displayed on the Serial Monitor at '''9600 baud'''.
* DHT11 readings are taken every 2 seconds.

=== Result ===

The LDR and DHT11 sensors were successfully interfaced with Arduino Uno, and their readings were displayed on the Serial Monitor.

=== Conclusion ===

This experiment demonstrates how Arduino Uno can interface with different types of IoT sensors. The LDR provides an analog light-level reading, while the DHT11 provides digital temperature and humidity data.