The DHT11 sensor is an advanced solution that translates temperature and humidity into proportional digital outputs. This sensor, meticulously pre-calibrated, employs a distinctive capacitive sensor element to monitor relative humidity. The addition of a negative temperature coefficient (NTC) thermistor enhances its capabilities, enabling accurate temperature measurement. The board is known for its exceptional dependability and long-term stability, setting it apart as a reliable choice for precise environmental monitoring.

 

Package Includes:

• 1 x DHT11 Temperature And Humidity Sensor 

 

Features:

• Dual Sensing Technology: This sensor employs a combination of a capacitive humidity sensor and a thermistor-based temperature sensor for accurate environmental monitoring.
• Humidity Sensing: The DHT11 accurately senses humidity levels ranging from 20% to 90% with a precision of 5%.
• Temperature Sensing: It measures temperature variations within a range of 0 to 50 degrees Celsius, providing readings with an accuracy of 2°C.
• Rapid Sampling: With a sample time of approximately 2 seconds, the sensor promptly captures temperature and humidity changes, ensuring up-to-date data.
• Digital Communication: Utilizing a one-wire interface protocol, the Temperature and Humidity Sensor conveniently communicates with a microcontroller unit via a digital pin. It does not rely on analog inputs.
• Pre-Calibrated Output: The sensor provides a pre-calibrated digital output, ensuring consistent and accurate readings.
• Unique Capacitive Humidity Sensor: Featuring a distinctive capacitive sensor element, the sensor precisely monitors relative humidity levels in the environment.
• Temperature Compensation: The inclusion of a negative temperature coefficient (NTC) thermistor enhances temperature measurement accuracy.
• Dependability and Stability: Known for its high dependability and long-term stability, this sensor consistently delivers reliable data.

 

Description:

temperature and humidity measurement. This versatile instrument employs a sophisticated amalgamation of cutting-edge technologies, including a capacitive humidity sensor and a thermistor-based temperature sensor. In its quest to unveil environmental intricacies, this sensor adeptly discerns humidity levels across a spectrum spanning from 20% to 90%, offering results with an impressive accuracy of 5%. Simultaneously, its temperature-sensing prowess spans the comprehensive range of 0 to 50 degrees Celsius, relaying findings with an exceptional precision of 2°C. The sensor's rapid response is a testament to its efficiency, with a sample time that clocks in at nearly 2 seconds. This ensures that fluctuations in temperature and humidity are promptly captured, making the DHT11 a dynamic tool for real-time environmental monitoring. Enabling seamless integration into projects, the Temperature and Humidity Sensor establishes communication with a microcontroller unit through a digital pin using the one-wire interface protocol. Notably, this design omits the need for analog inputs, simplifying the interaction process.

At the core of the DHT11's remarkable capabilities lies its digitally pre-calibrated output, a feature that guarantees consistently accurate readings. The distinctive capacitive sensor element takes center stage, diligently overseeing relative humidity with precision. This function is further fortified by the ingenious inclusion of a negative temperature coefficient (NTC) thermistor, a true stalwart in temperature measurement. This sensor is a paragon of reliability and stability, traits that underscore its dependability over extended periods of use. From its inception, the DHT11 was engineered to withstand the test of time, becoming an indispensable asset for those seeking enduring accuracy and insight in temperature and humidity monitoring.

 

Principle of Work:

Internally, the DHT11 sensor employs advanced technology to accurately measure temperature and humidity. It consists of two main sensing elements: a capacitive humidity sensor and an NTC thermistor for temperature sensing:

1. Capacitive Humidity Sensor: The capacitive humidity sensor measures relative humidity by taking advantage of the moisture-absorbing characteristics of certain materials. It comprises a moisture-absorbing substrate sandwiched between two conductive electrodes. As the surrounding air's humidity changes, the substrate absorbs or releases moisture, altering its dielectric constant. This, in turn, modifies the capacitance between the electrodes. By measuring the changes in capacitance, the sensor can accurately determine the relative humidity of the environment.
2. NTC Thermistor: The NTC thermistor, also known as a negative temperature coefficient thermistor, is a temperature-sensitive resistor. Its resistance decreases as the temperature increases. The NTC thermistor is integrated into the DHT11 sensor and is used to measure the ambient temperature. By monitoring the changes in the thermistor's resistance, the sensor can deduce the temperature of the surroundings.

Interaction with MCU: The DHT11 sensor communicates with a microcontroller unit (MCU) to provide real-time temperature and humidity data. This interaction occurs through a digital pin using a one-wire interface protocol:

1. The MCU sends a start signal to the DHT11 sensor by pulling the data line low for a specified period.
2. After receiving the start signal, the sensor responds with a low signal to acknowledge the request.
3. The sensor then transmits data in a 40-bit binary format. This data includes the relative humidity and temperature readings.
4. The MCU reads the data by measuring the duration of high and low signals sent by the sensor.
5. The MCU decodes the binary data to extract humidity and temperature values.
6. The MCU performs any necessary calculations or conversions to obtain human-readable temperature and humidity readings.
7. Finally, the MCU can process and utilize the acquired data for various applications, such as displaying the readings on a screen, logging data, or controlling other devices based on environmental conditions.

 

Pinout of the Board:

• VCC (Pin 1): The red wire should be connected to a power source ranging from 3.3V to 5V. In instances where 3.3V power might be insufficient, attempting 5V power could yield better results.
• Data Output (Pin 2): This wire carries the data output from the DHT11 sensor, providing temperature and humidity information.
• Unused Pin (Pin 3): Pin 3 does not have any specific function and can be left unconnected.
• Ground (GND): The black wire should be connected to the ground to complete the circuit.

1. For enhanced data transmission, you can employ a 10K ohm resistor between the VCC and the data pin. This setup acts as a medium-strength pull-up on the data line, optimizing signal stability.
2. A crucial point to note is the proper wiring configuration, as incorrectly connecting the VCC and GND pins can result in damage to the sensor. This cautionary measure is imperative to prevent the sensor from burning out due to incorrect wiring.

 

Applications:

1. Home Automation: The DHT11 sensor is commonly used in home automation systems to regulate heating, cooling, and ventilation based on real-time temperature and humidity conditions. It helps maintain a comfortable and energy-efficient environment.
2. Weather Stations: Weather enthusiasts and hobbyists often employ the DHT11 sensor to create DIY weather stations, providing local temperature and humidity data for personal use or sharing with online weather communities.
3. Greenhouses and Gardening: In agriculture and horticulture, the sensor ensures optimal conditions for plant growth by monitoring temperature and humidity levels. It aids in maintaining greenhouse environments and promoting healthy plant development.
4. Indoor Climate Control: HVAC systems benefit from the DHT11's data to adjust temperature and humidity settings in indoor spaces, ensuring occupant comfort and energy efficiency.
5. Food Storage: The sensor's ability to monitor humidity aids in controlling food storage conditions. It helps prevent spoilage and mold growth by maintaining suitable humidity levels.
6. Data Logging: The DHT11 can be integrated into data logging systems to track temperature and humidity changes over time. This is useful for analyzing trends and making informed decisions.
7. Laboratories and Research: Scientific research facilities employ the sensor to monitor controlled environments, ensuring accurate experimental conditions in areas like pharmaceutical research and material testing.
8. IoT Devices: The DHT11 is a popular choice in Internet of Things (IoT) projects, where it provides essential environmental data for various smart devices and applications.
9. Energy Efficiency: Building management systems use the sensor to optimize energy consumption by adjusting temperature and humidity settings based on occupancy and external conditions.
10. Healthcare: The DHT11 sensor can be used in medical applications to monitor conditions like humidity in storage areas for medications and sensitive equipment.
11. Server Rooms: Critical infrastructure like server rooms and data centers require precise environmental monitoring to prevent equipment overheating and ensure stable operations.
12. Education: The DHT11 is an accessible tool for educational purposes, teaching students about sensors, data acquisition, and environmental science.

 

Circuit:

Let's establish a connection between the DHT11 sensor and the Arduino for temperature monitoring and display. By linking the DHT11 sensor to the A0 analog input on the Arduino, we can seamlessly capture temperature data. This data will then be relayed to the serial monitor, providing real-time insights into the temperature conditions.

• VCC of the Module connected to the 5V Arduino Pin 
• GND of the Module connected to the GND Arduino Pin 
• OUT of the Module connected to the A0 Arduino Pin with a pull-up 10K ohm resistor connected to VCC.

 

Library: 

1. Begin by downloading the DHT11 library package. This can be done by accessing the DHT Library 
2. Once the download is complete, launch your Arduino IDE (Integrated Development Environment).
3. Navigate to the "Sketch" tab in the menu bar and choose "Include Library."
4. From the dropdown options, select "Add .ZIP Library."
5. Locate and select the previously downloaded DHT11 library package.

By following these steps, you will seamlessly integrate the DHT11 library into your Arduino IDE environment, unleashing its full potential for your projects.

 

Code:

The next code is for reading and displaying humidity and temperature data from a DHT11 sensor using an Arduino:

#include "dht.h"  // Include the DHT library
dht DHT;

#define DHT_PIN A0  // Define the analog pin A0 for DHT11

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

void loop() {
  int readResult = DHT.read11(DHT_PIN);  // Read data from DHT11 sensor
  
  if (readResult == 0) {  // Check if data read was successful
    Serial.print("Humidity: ");
    Serial.print(DHT.humidity);
    Serial.print("% ");
    
    Serial.print("Temperature: ");
    Serial.print(DHT.temperature);
    Serial.println(" °C");
  } else {
    Serial.println("Error reading data from DHT11 sensor.");
  }
  
  delay(5000);  // Delay for 5 seconds before the next reading
}

1. Include Library: The code includes the "dht.h" library, which provides functions for interacting with DHT series sensors.
2. Library Initialization: An instance of the dht class called DHT is created. This instance will be used to interact with the DHT11 sensor.
3. Pin Definition: The analog pin A0 is assigned to the variable DHT_PIN. This pin will be used to read data from the DHT11 sensor.

4. Setup Function:

   • Serial communication is initiated at a baud rate of 9600.
   • A delay of 500 milliseconds is added to allow time for the Serial communication to stabilize.
   • A message indicating the sensor's purpose is printed to the Serial monitor.
   • Another delay of 1000 milliseconds is added for readability.

5. Loop Function:

   • The read11 function from the DHT instance is called, passing the DHT_PIN as an argument to read data from the DHT11 sensor. The result of this operation is stored in the readResult variable.
   • If the readResult is 0 (indicating successful data read), the code:
     • Prints the humidity value obtained from DHT.humidity followed by a percentage sign.
     • Prints the temperature value obtained from DHT.temperature followed by the unit "°C".
   • If the readResult is not 0 (indicating an error in data reading), an error message is printed.

6. Delay: After each reading, the code waits for 5 seconds using the delay function before taking the next reading. This delay prevents rapid and unnecessary data collection.

 

Technical Details:

• 3 to 5V power and I/O
• 2.5mA max current use during conversion (while requesting data)
• Good for 20-80% humidity readings with 5% accuracy
• 0-50°C temperature readings ±2°C accuracy
• 1 Hz sampling rate (once every second)
• Body size 15.5mm x 12mm x 5.5mm
• 4 pins with 0.1" spacing

Resources:

• Tutorial1

 

Comparisons:

the DHT11 is a budget-friendly option suitable for simple projects with moderate accuracy requirements. On the other hand, the DHT22 offers better accuracy and a wider range, making it a better choice for projects demanding more precise measurements and reliable performance. Your choice between the two sensors should depend on the specific requirements of your application and the level of accuracy you need:

. Accuracy:

• DHT11: The DHT11 is generally less accurate compared to the DHT22. It provides ±5% accuracy for humidity and ±2°C accuracy for temperature readings.
• DHT22: The DHT22 offers higher accuracy, with ±2% accuracy for humidity and ±0.5°C accuracy for temperature readings.

2. Sensing Range:

• DHT11: The humidity sensing range of the DHT11 is 20% to 90%, and the temperature sensing range is 0°C to 50°C.
• DHT22: The DHT22 has a wider humidity sensing range of 0% to 100%, and a temperature sensing range of -40°C to 80°C.

3. Response Time:

• DHT11: The DHT11 has a slower response time compared to the DHT22. It takes around 2 seconds to provide a reading.
• DHT22: The DHT22 has a faster response time, taking about 0.5 seconds to generate a reading.

4. Build Quality:

• DHT11: The DHT11 is generally considered to have a lower build quality and may be more prone to failure over time.
• DHT22: The DHT22 is built with better quality components and is more reliable in the long run.

5. Price:

• DHT11: The DHT11 is usually more affordable compared to the DHT22, making it a cost-effective choice for basic applications.
• DHT22: The DHT22 is slightly more expensive but offers improved accuracy and performance.

6. Applications:

• DHT11: Due to its lower accuracy and limited sensing range, the DHT11 is well-suited for less critical applications where a general sense of temperature and humidity is sufficient.
• DHT22: The DHT22's higher accuracy and wider sensing range make it suitable for applications requiring more precise measurements, such as research, data logging, and industrial monitoring.