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DHT22 Digital Temperature & Humidity Sensor Module

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Ekostra Electronics

On April 5, 2025

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DHT22 Digital Temperature & Humidity Sensor

High-Precision Environmental Sensing for Arduino Projects

Introduction

The DHT22 (AM2302) is a calibrated digital sensor that provides high-accuracy temperature and humidity measurements. With its single-wire serial interface, it’s perfect for weather stations, greenhouse monitoring, and HVAC systems.

DHT22 Digital Temperature & Humidity Sensor

Key Features

🌡️ High Accuracy

±0.5°C temperature, ±2% humidity

🔌 Simple Interface

Single-wire digital communication

📶 Long Range

Up to 20m signal transmission

🔄 Fast Updates

2-second sampling rate

Technical Specifications

Temperature Range	-40°C to 80°C
Humidity Range	0-100% RH
Operating Voltage	3.3V – 5.5V DC
Current Consumption	1.5mA (measuring), 50μA (standby)
Resolution	0.1°C / 0.1% RH
Dimensions	27mm × 59mm × 13.5mm

Pin Configuration

Pin	Function	Arduino Connection
1	VCC (3.3V-5V)	5V
2	DATA	Digital Pin (D2)
3	NC	Not Connected
4	GND	GND

Note: Requires 4.7KΩ-10KΩ pull-up resistor between DATA and VCC

Wiring with Arduino

// Basic Connections:
// VCC  → 5V
// DATA → D2 (with pull-up resistor)
// GND  → GND

// Basic Connections:

// VCC → 5V

// DATA → D2 (with pull-up resistor)

// GND → GND

Important: Avoid long wires (>20cm) without proper shielding to prevent signal issues

Library Setup

Install the DHT sensor library by Adafruit
Include the required libraries:

Arduino

#include <DHT.h> #include <Adafruit_Sensor.h>

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#include <DHT.h>
#include <Adafruit_Sensor.h>
Initialize the sensor:

Arduino

#define DHTPIN 2 // Digital pin connected #define DHTTYPE DHT22 // DHT 22 (AM2302) DHT dht(DHTPIN, DHTTYPE); void setup() { dht.begin(); }

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#define DHTPIN 2 // Digital pin connected
#define DHTTYPE DHT22 // DHT 22 (AM2302)

DHT dht(DHTPIN, DHTTYPE);

void setup() {
dht.begin();
}

Basic Sensor Example

#include <DHT.h>

#define DHTPIN 2
#define DHTTYPE DHT22

DHT dht(DHTPIN, DHTTYPE);

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

void loop() {
  delay(2000); // Wait between measurements
  
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  
  if (isnan(h) || isnan(t)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }
  
  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print("%\tTemperature: ");
  Serial.print(t);
  Serial.println("°C");
}

#include <DHT.h>

#define DHTPIN 2

#define DHTTYPE DHT22

DHT dht(DHTPIN, DHTTYPE);

void setup() {

Serial.begin(9600);

dht.begin();

}

void loop() {

delay(2000); // Wait between measurements

float h = dht.readHumidity();

float t = dht.readTemperature();

if (isnan(h) || isnan(t)) {

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

return;

}

Serial.print("Humidity: ");

Serial.print(h);

Serial.print("%\tTemperature: ");

Serial.print(t);

Serial.println("°C");

}

Advanced Features

Heat Index Calculation

// Calculate heat index (feels-like temp)
float hic = dht.computeHeatIndex(t, h, false);
Serial.print("Heat index: ");
Serial.print(hic);
Serial.println("°C");

// Calculate heat index (feels-like temp)

float hic = dht.computeHeatIndex(t, h, false);

Serial.print("Heat index: ");

Serial.print(hic);

Serial.println("°C");

Fahrenheit Conversion

// Read temperature in Fahrenheit
float f = dht.readTemperature(true);
Serial.print("Temperature: ");
Serial.print(f);
Serial.println("°F");

// Read temperature in Fahrenheit

float f = dht.readTemperature(true);

Serial.print("Temperature: ");

Serial.print(f);

Serial.println("°F");

Sensor Diagnostics

// Check sensor status
if (dht.read() == DHTLIB_OK) {
  Serial.println("Sensor working properly");
} else {
  Serial.println("Sensor error detected");
}

// Check sensor status

if (dht.read() == DHTLIB_OK) {

Serial.println("Sensor working properly");

} else {

Serial.println("Sensor error detected");

}

Power Saving

// Put sensor to sleep between readings
digitalWrite(DHTPIN, LOW);
delay(60000); // Sleep for 1 minute
digitalWrite(DHTPIN, HIGH);
delay(2000); // Allow sensor to stabilize

// Put sensor to sleep between readings

digitalWrite(DHTPIN, LOW);

delay(60000); // Sleep for 1 minute

digitalWrite(DHTPIN, HIGH);

delay(2000); // Allow sensor to stabilize