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✅ ESP32 + DHT11 Serial Monitor Code (Copy–Paste)

#include "DHT.h"

// -------------------- DHT Pin & Type --------------------



#define DHTPIN 4

      // ESP32 GPIO4 (D4 pin)

#define DHTTYPE DHT11

 // DHT11 sensor type

// Create DHT object

DHT dht(DHTPIN, DHTTYPE);

void setup()

//

Start Serial Communication

  Serial.begin(115200);

  // Print a message once when ESP32 starts

Serial.println("DHT11 Sensor Reading...");

  // Start DHT sensor

  dht.begin();

void loop()

  // DHT11 sensor needs minimum 2 seconds delay between readings

  delay(2000);

  // Read Humidity (%)

  float humidity = dht.readHumidity();

  // Read Temperature (°C)

  float temperature = dht.readTemperature();

// If sensor reading fails,

humidity/temperature becomes NAN

if (isnan(humidity) || isnan(temperature))

    Serial.println("Failed to read from DHT sensor!");

    return;

//

Print Temperature

  Serial.print("Temperature: ");

  Serial.print(temperature);

  Serial.print(" °C  |  ");

  // Print Humidity

  Serial.print("Humidity: ");

  Serial.print(humidity);

  Serial.println(" %");

}

📌 Wiring (DHT11 3-pin module → ESP32)

DHT11 Pin	ESP32
VCC	3.3V
GND	GND
DATA	GPIO4 (D4)

🧠 Detailed Code Explanation (Line by Line)

✅ 1) Library Include

This line adds the DHT sensor library.

Without this library, ESP32 cannot understand:

readHumidity()
readTemperature()
begin()

✅ 2) Define Pin and Sensor Type

🔹 DHTPIN 4

This means the DHT11 data pin is connected to GPIO 4 of ESP32.

🔹 DHTTYPE DHT11

This tells the library which sensor you are using:

DHT11 (low cost, low accuracy)
DHT22 (better accuracy)

✅ 3) Create DHT Sensor Object

This creates an object named dht.

Now you can use:

dht.begin()
dht.readHumidity()
dht.readTemperature()

✅ 4) Setup Function

This runs only one time when ESP32 starts.

🔹 Start Serial Communication

This starts serial communication between:

ESP32 ↔ Laptop/PC

Speed = 115200 baud.

🔹 Print message

This prints a message once, to confirm code started.

🔹 Start DHT sensor

This initializes the sensor.

If you don’t call this, DHT11 will not work.

✅ 5) Loop Function

This runs again and again forever.

🔹 Delay 2 seconds

⚠️ DHT11 needs minimum 2 seconds between readings.

If you read too fast:

sensor gives wrong values
or returns NAN

🔹 Read humidity

This reads humidity and stores it in a float variable.

Example:

60.00 %

🔹 Read temperature

This reads temperature in Celsius.

Example:

28.00 °C

✅ 6) Check for Error

If sensor is not connected properly, or sensor fails, the library returns:

❌ NAN = Not A Number

So we check it.

🔹 Print error

This prints the error and stops this loop cycle.

✅ 7) Print Output on Serial Monitor

This prints values like:

🖥 Serial Monitor Settings

In Arduino IDE:

✅ Tools → Serial Monitor

Baud rate: 115200