DHT11 vs DHT22 | Difference between DHT11 and DHT22

Introduction

DHT11 and DHT22 are two of the most commonly used temperature and humidity sensors in electronics and IoT applications. They are widely used in weather stations, home automation, and agricultural monitoring due to their ease of use, low cost, and compatibility with microcontrollers like Arduino and Raspberry Pi.

While both sensors serve the same purpose, they differ in terms of accuracy, response time, operating range, and cost. This article provides a detailed comparison to help you choose the right sensor for your project.

Overview of DHT11 and DHT22

DHT11

• Measures temperature and humidity.
• Lower cost and less accurate than DHT22.
• Limited operating range.
• Suitable for hobby projects and basic applications.

DHT22 (AM2302)

• More precise and has a wider measurement range.
• Slightly more expensive than DHT11.
• Better suited for applications requiring higher accuracy.

Technical Specifications Comparison

Feature	DHT11	DHT22 (AM2302)
Temperature Range	0°C to 50°C	-40°C to 80°C
Temperature Accuracy	±2°C	±0.5°C
Humidity Range	20% – 90% RH	0% – 100% RH
Humidity Accuracy	±5% RH	±2% RH
Resolution	8-bit	16-bit
Sampling Rate	1 reading per second	0.5 readings per second
Operating Voltage	3.3V – 5V	3.3V – 6V
Power Consumption	Low	Low
Response Time	1 second	2 seconds
Cost	Lower	Slightly higher

Key Differences Between DHT11 and DHT22

1. Measurement Range

• DHT11: Works only between 0°C and 50°C, making it unsuitable for extreme temperature conditions.
• DHT22: Can measure temperatures from -40°C to 80°C, making it better for industrial and outdoor use.

2. Accuracy

• DHT11: Has a temperature accuracy of ±2°C and humidity accuracy of ±5% RH.
• DHT22: More accurate with ±0.5°C temperature accuracy and ±2% RH humidity accuracy.

3. Resolution

• DHT11: Provides 8-bit data resolution.
• DHT22: Provides 16-bit data resolution, which results in more precise readings.

4. Sampling Rate

• DHT11: 1 reading per second (1Hz sampling rate).
• DHT22: 0.5 readings per second (takes a reading every 2 seconds).

5. Cost

• DHT11 is cheaper than DHT22, making it ideal for cost-sensitive projects.
• DHT22 is slightly more expensive, but the improved accuracy and range justify the price.

6. Physical Appearance

• DHT11 is typically blue and smaller in size.
• DHT22 is white and slightly larger.

Which Sensor Should You Choose?

Requirement	Best Choice
Budget-friendly projects	DHT11
High accuracy needed	DHT22
Extreme temperature monitoring	DHT22
Indoor basic weather station	DHT11
Industrial or outdoor monitoring	DHT22

When to Use DHT11

• If you need basic temperature and humidity readings.
• For applications within 0°C to 50°C.
• When you need low-cost sensors.
• Best for beginner electronics projects.

When to Use DHT22

• If you need precise measurements.
• When working with extreme temperatures (-40°C to 80°C).
• If high humidity accuracy is important.
• Suitable for industrial, agricultural, and scientific applications.

Interfacing DHT11 and DHT22 with Microcontrollers

Both sensors use a single-wire digital communication protocol and can be connected to microcontrollers like Arduino, ESP8266, Raspberry Pi, etc.

Example: Connecting DHT11/DHT22 to Arduino

Wiring:

DHT Pin	Arduino Pin
VCC	5V
Data	Digital Pin 2
GND	GND

Arduino Code for Reading Data

#include <DHT.h>
#define DHTPIN 2       // Pin connected to the sensor
#define DHTTYPE DHT22  // Use DHT11 or DHT22 accordingly

DHT dht(DHTPIN, DHTTYPE);

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

void loop() {
  float temperature = dht.readTemperature();
  float humidity = dht.readHumidity();
  
  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.print(" °C   Humidity: ");
  Serial.print(humidity);
  Serial.println(" %");
  delay(2000);  // Delay for stable readings
}

Explanation:

• The DHT.h library is used to communicate with the sensor.
• The temperature and humidity values are read and displayed on the serial monitor.

DHT22 & DHT11 Pinout

DHTxx Data Format

When Humidity and Temperature sensor sends data, it sends the MSB first. The 40bits of data is divided into 5 bytes. For DHT11 sensor 2nd and 4th byte is always Zero. The significance of these bytes is as follows:

• 1st Byte: Relative Humidity Integral Data in % (Integer Part)
• 2nd Byte: Relative Humidity Decimal Data in % (Fractional Part) – Zero for DHT11
• 3rd Byte: Temperature Integral in Degree Celsius (Integer Part)
• 4th Byte: Temperature in Decimal Data in % (Fractional Part) – Zero for DHT11
• 5th Byte: Checksum (Last 8 bits of {1st Byte + 2nd Byte + 3rd Byte+ 4th Byte})

 

Conclusion

Both DHT11 and DHT22 are excellent choices for temperature and humidity sensing. The choice depends on the accuracy, range, and budget of your project:

• DHT11 is more affordable and works well for simple projects.
• DHT22 offers better accuracy and a wider range, making it ideal for advanced applications.

By understanding the differences, you can select the best sensor based on your specific requirements.

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