1B27 DHT11 Temperature and Relative Humidity Sensor Module

The DHT11 Module sensor is designed to detect temperature and humidity, This smart sensor provides you with digital output that accurately reflects the temperature and humidity in your surroundings. You don't need to worry about calibration which is already taken care of! With its high dependability and long-term stability, you can trust this sensor to deliver reliable and precise measurements every time. The secret behind its accuracy lies in its clever design: a special capacitive sensor element monitors humidity, while a temperature-sensitive thermistor measures temperature with impressive precision. Say hello to a user-friendly and reliable companion that will take your environmental sensing to the next level.

Datasheet

Package Includes:

• 1x DHT11 Humidity and Temperature Module
• 3 x Female-to-female jumper wire

Features:

• Accurate Relative Humidity and Temperature Measurement: The sensor excels at providing precise measurements of both relative humidity and temperature. You can rely on its readings to gain a comprehensive understanding of your environment's conditions.
• Full Range Temperature Compensation: The module comes with full range temperature compensation, ensuring that temperature variations do not compromise the accuracy of the humidity readings. This feature guarantees reliable and consistent measurements across various temperature ranges.
• Calibrated for Convenience: The DHT11 Module sensor is pre-calibrated, saving you the hassle of manual calibration. It is ready to use right out of the box, allowing for quick and effortless integration into your projects.
• Digital Signal Output: The sensor produces a digital output, making it easy to interface with microcontrollers and other digital devices. You can effortlessly read the sensor data and integrate it into your systems or applications.
• Long-Term Stability: Built with an emphasis on stability, this sensor maintains its accuracy and performance over extended periods. You can rely on its dependable operation over time without worrying about frequent recalibration or fluctuations in readings.
• Low Power Consumption: Designed with efficiency in mind, the DHT11 Module sensor boasts low power consumption. It minimizes energy usage, making it ideal for battery-operated or energy-conscious applications.
• Ready-to-Go Module: The module is readily available in a convenient, plug-and-play form. It can be directly connected to a microcontroller unit (MCU) without requiring additional components or complicated setup processes. This streamlined integration saves you time and effort during implementation.
• Screw Hole for Secure Fixation: To provide ease of installation, the module is equipped with a screw hole. This feature allows you to securely fasten the sensor in place, ensuring it remains stable and steady during operation.

Description:

The DHT11 sensor is a highly popular and reliable digital sensor used for temperature and humidity monitoring. It incorporates a capacitive humidity sensor and a thermistor-based temperature sensor to accurately measure environmental conditions. The humidity sensing capability spans from 20% to 90%, with a remarkable accuracy of 5%. Similarly, the temperature sensing range extends from 0 to 50 degrees Celsius, providing readings with an impressive accuracy of 2 degrees Celsius. With a quick sampling time of approximately 2 seconds, this sensor ensures near real-time updates of temperature and humidity data. Communication with a microcontroller unit is achieved through a digital pin using a straightforward one-wire interface protocol. It's important to note that the DHT11 lacks analog inputs, simplifying the integration process. The sensor boasts the convenience of pre-calibration, delivering a digital output that is ready for immediate use. Its unique design incorporates a capacitive sensor element for precise relative humidity monitoring and utilizes a negative temperature coefficient (NTC) thermistor to accurately measure temperature. This combination guarantees high dependability and long-term stability, ensuring consistent and reliable performance over extended periods. To further enhance usability, the module includes a pull-up resistor and an additional filter capacitor, providing optimal support for the DHT11 sensor. As a result, the module is readily deployable, requiring no additional components or complex setup procedures. It can be easily connected directly to a microcontroller unit (MCU) for seamless integration into your projects.

Principle of Work:

The DHT11 sensor internally utilizes a combination of capacitive humidity sensing and thermistor-based temperature sensing to measure environmental conditions. Let's dive into the detailed workings of the sensor and how it sends information to the microcontroller unit (MCU):

1. Sensing the Environment: The DHT11 sensor consists of a capacitive humidity sensor and a thermistor-based temperature sensor. The capacitive humidity sensor measures the moisture content in the air by detecting changes in the capacitance caused by humidity variations. Simultaneously, the thermistor-based temperature sensor measures the ambient temperature using the electrical resistance changes of a thermistor with temperature fluctuations.
2. Signal Conversion: Once the humidity and temperature values are detected, the DHT11 sensor converts these analog signals into digital signals for easy processing by the MCU. This conversion ensures that the sensor's output is in a format that the MCU can understand and utilize.
3. Triggering and Data Transmission: To initiate the data transmission process, the MCU sends a trigger signal to the DHT11 sensor. Upon receiving the trigger signal, the sensor switches from a low power consumption state to an active mode.
4. Data Collection and Feedback: After being triggered, the sensor proceeds to collect and organize 40 bits of data that represent both the humidity and temperature readings. It's important to note that this data collection process occurs independently within the sensor.
5. Feedback Signal: Once the data collection is complete, the sensor sends a feedback signal back to the MCU to indicate that it is ready to transmit the collected data.
6. One-Wire Communication: For communication between the MCU and the DHT11 sensor, a one-wire interface protocol is utilized. This protocol allows data transmission using a single communication line, simplifying the connection requirements and reducing the number of pins needed.
7. Data Transmission: With the feedback signal received, the DHT11 sensor starts transmitting 40 bits of data to the MCU. The data is transmitted bit by bit, with each bit being represented by a specific duration of high or low signal on the communication line.
8. Data Interpretation: The MCU receives the transmitted data and interprets it accordingly. By decoding the received bits, the MCU extracts the humidity and temperature values to use them in further calculations or to display the information to the user.
9. Further Communication: Once the data transmission is complete, the MCU can trigger another round of data collection by sending a new trigger signal to the DHT11 sensor. This allows for continuous monitoring and retrieval of updated temperature and humidity readings.

Pinout of the Board:

Connect 3.3-5.5V in the VCC (+) pin and ground on the GND(-) pin. Connect the middle pin which is a digital output of the sensor module with a microcontroller digital I/O pin. 

Applications:

1. Consumer Products: The DHT11 module is often incorporated into consumer products such as thermostats, hygrometers, and indoor climate monitors. It enables users to monitor and control temperature and humidity levels in their homes, offices, or other living spaces.
2. Weather Stations: Weather enthusiasts and hobbyists use the DHT11 module in DIY weather station projects. By combining the DHT11 module with other sensors and components, they can create weather monitoring systems to measure and display real-time temperature and humidity data.
3. Humidity Regulation Systems: The DHT11 module plays a crucial role in humidity regulation systems. It is utilized in humidifiers and dehumidifiers to measure and control the humidity levels in environments such as greenhouses, storage facilities, and server rooms.
4. Air Conditioning Systems: The DHT11 module is integrated into air conditioning systems to provide accurate temperature and humidity measurements. It helps regulate and maintain optimal comfort levels by enabling the system to adjust cooling or dehumidification settings based on the sensed data.
5. Agricultural Applications: The DHT11 module is employed in agricultural settings for monitoring temperature and humidity conditions in greenhouses, crop storage areas, and livestock enclosures. It assists in creating optimal growth environments for plants and ensuring the well-being of animals.
6. Industrial Automation: The module is utilized in industrial automation systems where precise temperature and humidity monitoring is necessary. It enables the monitoring of environmental conditions in manufacturing facilities, cleanrooms, and storage areas to ensure product quality and process control.
7. Data Logging: The DHT11 module can be integrated into data logging systems to record temperature and humidity data over time. This is useful in research, environmental studies, and building performance analysis.

Circuit:

To utilize the DHT11 sensor with an Arduino board and display the temperature readings on the serial monitor, follow these connection steps:

1. Connect the VCC pin of the DHT11 module to the 5V pin on the Arduino board. This provides power to the module.
2. Connect the GND pin of the DHT11 module to the GND (ground) pin on the Arduino board. This establishes the common ground reference.
3. Connect the OUT pin of the DHT11 module to the A0 (analog input) pin on the Arduino board. This allows the Arduino to receive the temperature data from the sensor.

Library: 

You need to install the below DHT11 library:

1. Download the DHT11 library by clicking on the following link: DHT Library.
2. Once the library is downloaded, open the Arduino IDE (Integrated Development Environment) on your computer.
3. In the Arduino IDE, navigate to "Sketch" in the menu bar, then select "Include Library" and click on "Add .ZIP Library".
4. Locate the downloaded DHT11 library ZIP file on your computer and select it. The IDE will automatically install the library.

Code:

This code sets up the communication with the DHT11 sensor, reads the humidity and temperature values, and displays them in the serial monitor with appropriate labels. It repeats this process in a loop with a delay of 5 seconds between each reading.

#include "dht.h"

#define DHT_PIN A0 // Analog Pin A0 of Arduino is connected to DHT11 OUT pin

dht DHT;

void setup()
{
  Serial.begin(9600);
  delay(500);
  Serial.println("DHT11 Humidity & Temperature Sensor");
  Serial.println();
  delay(1000);
}

void loop()
{
  DHT.read11(DHT_PIN);

  Serial.print("Humidity: ");
  Serial.print(DHT.humidity);
  Serial.print("%\t\t");
  Serial.print("Temperature: ");
  Serial.print(DHT.temperature);
  Serial.println("°C");

  delay(5000); // Reduce Time for Quick Reply
}  

1. #define DHT_PIN A0: This line defines a constant named DHT_PIN and assigns it the value A0, which corresponds to the analog input pin A0 of the Arduino board. This pin is connected to the OUT pin of the DHT11 sensor.

2. dht DHT;: This line declares an object named DHT of type dht. The dht is the class provided by the DHT library and allows you to access various functions and properties related to the DHT11 sensor.

3. void setup(): This is the setup function which is called once when the Arduino board starts running. It performs the following tasks:

   • Serial.begin(9600): Initializes the serial communication at a baud rate of 9600. This allows you to send and receive data between the Arduino board and the computer via the serial monitor.
   • delay(500): Pauses the execution for 500 milliseconds to ensure stable communication.
   • Serial.println("DHT11 Humidity & Temperature Sensor"): Prints the text "DHT11 Humidity & Temperature Sensor" on the serial monitor. This serves as a message to indicate the purpose of the code.
   • Serial.println(): Prints an empty line for better readability.
   • delay(1000): Adds a delay of 1000 milliseconds before entering the loop function to provide some time for setup.

4. void loop(): This is the loop function, which runs repeatedly after the setup function. It performs the following tasks:

   • DHT.read11(DHT_PIN): Invokes the read11 function of the DHT object to read temperature and humidity data from the DHT11 sensor connected to the DHT_PIN (A0) of the Arduino board.
   • Serial.print("Humidity: "): Prints the text "Humidity: " on the serial monitor.
   • Serial.print(DHT.humidity): Prints the humidity value read from the sensor using the humidity property of the DHT object.
   • Serial.print("%\t\t"): Prints the percentage symbol and two tabs for formatting purposes.
   • Serial.print("Temperature: "): Prints the text "Temperature: " on the serial monitor.
   • Serial.print(DHT.temperature): Prints the temperature value read from the sensor using the temperature property of the DHT object.
   • Serial.println("°C"): Prints the degree Celsius symbol and moves the cursor to the next line.
   • delay(5000): Pauses the execution for 5000 milliseconds (5 seconds) before the next iteration to provide a delay between readings.

Technical Details:

• Operating Voltage: 3.3V to 5.5V
• Supply current (running) 0.5mA typ. (2.5mA max.)
• Supply current (stand-by) 100uA typ. (150uA max.)
• Temperature range 0 / +50°C ±2°C
• Humidity range 20-90%RH ±5%RH
• Interface Digital
• 5 Hz sampling rate (Once every 2 Seconds)
• Low power consumption
• Accuracy: ±2°C and ±5%
• Dimension: 3.5 x 2 x 6.5 cm

Resources:

Tutorial1

Comparisons:

The DHT11 and DHT22 modules are both popular temperature and humidity sensors, but they have some differences in terms of performance and specifications:

1. Accuracy: The DHT22 module generally provides higher accuracy compared to the DHT11 module. The DHT22 has a temperature accuracy of ±0.5°C and a humidity accuracy of ±2%RH, while the DHT11 has a temperature accuracy of ±2°C and a humidity accuracy of ±5%RH. Therefore, the DHT22 offers more precise measurements.
2. Sensing Range: The DHT22 module has a wider sensing range compared to the DHT11 module. The DHT22 can measure temperatures between -40°C to 125°C and humidity between 0%RH to 100%RH. In contrast, the DHT11 has a temperature range of 0°C to 50°C and humidity range of 20%RH to 80%RH. The extended sensing range of the DHT22 makes it suitable for applications in extreme temperature conditions.
3. Response Time: The DHT22 module generally has a faster response time compared to the DHT11 module. The DHT22 typically takes around 2 seconds to provide a reading, while the DHT11 may require around 2 to 5 seconds for accurate readings. The faster response time of the DHT22 allows for more frequent and real-time data acquisition.
4. Pin Compatibility: The pinout and wiring for both modules are generally similar, with VCC (power), GND (ground), and DATA pins. However, the DHT22 module may require an external pull-up resistor on the DATA pin, while the DHT11 module typically incorporates it internally.
5. Availability: Both the DHT11 and DHT22 modules are widely available and compatible with Arduino and other microcontroller platforms. You can easily find libraries and example codes for both modules to facilitate their integration into your projects.