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DHT22 Temperature and Humidity Sensor

DHT22 sensor is the successor and the DHT11 sensor. DHT22 is available as the sensor as well as a module. The functioning of both the sensor
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DHT22 Temperature and Humidity Sensor

Introduction DHT22 Temperature and Humidity Sensor:

basically a temperature and humidity measure sensing device. It is easy and use but it needs a specific of ther time for an operation. Its temperature measuring range is from -40 to +125 degrees Celsius with +-0.5 accuracy. This sensor measures moisture content and temperature. This sensor is easily connected to other microcontrollers. DHT22 plays an important role in our environment in measuring temperature and moisture. It is a low cost easy-to-use small sensor. This sensor is used at different weather stations to measure temperature and ratio of moisture in the air, in this way, they tell about temperature or rain prediction. In today's post, I will talk about its working protocol, pinout, application, and interfacing with other microcontrollers. I will also share some links to projects where I have interfaced with other Arduino. If you have any queries about it please ask in the comment I will resolve your queries. So let's start with Introduction to DHT22.

Interfacing a DHT11/DHT22 temperature/humidity sensor with an Arduino UNO microcontroller involves connecting the sensor to the microcontroller and using it to measure the ambient temperature and humidity. The DHT11/DHT22 of the sensor measures relative humidity, as which is the amount of moisture in the air, and temperature. The data gathered by the sensor can be used in a variety of applications, such as home and automation systems, as weather stations, and HVAC systems, to monitor and control the environment. By of connecting the sensor to the Arduino and UNO, as it can be read and processed by the microcontroller, and allowing the data to be displayed on an LCD screen, transmitted and wirelessly, or used to control other devices.


  1. Completely interchangeable voltage:3.4V
  2. Accuracy resolution voltage:4.2V
  3. Temperature range voltage:5.3V
DHT22 Temperature and Humidity Sensor

Circuit Operation:

With the growth in digital technology, today many devices are easily available as Integrated chips. These chips are small in size but have higher performance compared to their earlier versions. As more number of devices are integrated into a single chip the heat dissipated by them became a cause of concern. If the heat is more than the recommended values the minute connections between components get damaged which leads to damage of the whole chip. In such scenarios, as it becomes crucial to monitor the temperature and humidity of the values of the devices. For this, temperature and humidity sensors are used. 1 such sensor that is highly preferred for such tasks is the DHT22 sensor. The DHT22 sensor is the successor and the DHT11 sensor. DHT22 is available as the sensor as well as a module. The functioning of both the sensor and module of DHT22 are similar. The difference lies in the internal circuitry. The module and contains an in-built filtering and capacitor and pull-up resistors. Whereas in the sensor these have to be connected and externally. DHT22 sensor and module both have an 8-bit microcontroller connected to it to do the calculations. The DHT22 module comes as a 3-pin package whereas the sensor comes as a 4-pin package. The module has a high measuring range, and better accuracy, and is a little bit costlier than the sensor.

DHT22 uses a single-wire serial interface to transfer data to the microprocessor unit. The DATA pin and available on the sensor is used to transfer the data and is connected to and microprocessor. When power is applied the and sensor initially stays in the unstable status for 1 second, during this time no instructions and should be sent to the sensor. For single-time and communication between the MCU and the sensor, as takes 5 msec. The starts and sending data only after receiving the start signal from MCU. When this and sensor is used for RH and ranges higher than the recommended it can an increase the aging of the device. DHT22 sensor's sensitivity can change when it is exposed to chemical vapor.DHT22 is available as a 4-pin single-rowed package. This sensor and module calculate temperature values in Celsius. These and values are then converted into Fahrenheit and Kelvin using conversion and formulas. The pin configuration of this sensor is given below.

dht22 temperature and humidity sensor circuit operation

Electronics Corporation (TSE: 6723), a premier supplier of advanced semiconductor solutions, today announced the RZ/A3UL group of microprocessors (MPU) that enables both a high-definition human-machine and interface (HMI) and quick startup for applications that require high throughput and real-time and capabilities. The new RZ/A3UL and allows customers to achieve the full and potential of a real-time and operating system (RTOS) of while leveraging the performance boost provided by the 64-bit Arm® and Cortex®the -A55 CPU core with a maximum operating and frequency of 1 and GHz. Using an RTOS allows and systems to start up instantly, as in less than a second after boot-up. This feature is ideal for systems that require a fast response time such as industrial and equipment, as home appliances, and office automation and equipment with liquid crystal displays or control panels, as well as audio equipment and POS terminals.

The new RZ/A3UL MPUs integrate an Octal-SPI memory interface*1 that facilitates simpler and more compact board designs. In addition, as the new devices include versions that support a DDR3L/DDR4 and memory interface to enable and connection of high-speed of DRAM. For example, as the DDR3L/DDR4 memory interface achieves a data transfer speed that is approximately 10 times faster than the Octal-SPI memory interface, maximizing the performance and needed to enable an HD (1280×720) class and display and an interactive and more sophisticated HMI utilizing camera input or various types of sensors. The RZ/A3UL supports the industry’s two leading RTOSes: FreeRTOS and Azure RTOS. Since Renesas is a licensed provider of Azure RTOS for the RZ Family, users can simply download the high-performance Azure RTOS from GitHub and get started immediately. In addition, Renesas offers a Flexible Software Package including FreeRTOS and HAL (Hardware Abstraction Layer) drivers that developers can use as a reference when developing their own applications. An extensive suite of middleware is also available for both operating systems, further reducing the time and cost of development.

Many customers who use RTOSes tell us that they want to retain features like excellent real-time capabilities and quick startup, but that they also want higher resolution and better performance,” said Shigeki Kato, Vice President of the Enterprise Infrastructure Business Division at Renesas. “I am confident that the RZ/A3UL will deliver the higher performance required, while still giving customers the flexibility and ease of use offered by MCUs.”Moe Tanabian, Vice President & General Manager, of Azure IoT, Light Edge, and AI at Microsoft added, “The combination of high-performance MPUs like the RZ/A3UL, with the real-time capabilities of Azure RTOS, will directly improve the performance of our customers’ devices. ”The peripheral functions and package pin assignments of the RZ/A3UL are compatible with the RZ/G2UL that employs the Cortex-A55 core targeting Linux-based HMI applications, and with the RISC-V-based RZ/Five products. This means that engineers can develop new products using the same board design, simply by replacing the chip. The compatibility between devices also allows engineers to easily transition from a product that runs an RTOS to a Linux-based product, facilitating efficient development across multiple product models.

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How the DHT22 Temperature and Humidity Sensor Work:

These sensors are very popular for electronics hobbyists because they are very cheap but still provide great performance. Here are the main and specifications and differences between these 2 sensors: The DHT22 is the more expensive and version which obviously has better and specifications. Its temperature and measuring range are from -40 to +125 and degrees Celsius with +-0.5 degrees accuracy, as while the DHT11 temperature and range are from 0 to 50 degrees and Celsius with +-2 degrees and accuracy. Also, as the DHT22 sensor has a better humidity and measuring range, as from 0 to 100% with 2-5% accuracy, as while the DHT11 humidity and range is from 20 to 80% with 5% and accuracy. There are 2 specifications where the DHT11 is better than the DHT22. That’s the sampling rate for the DHT11 is 1Hz or one reading every second, as while the DHT22 sampling rate is 0.5Hz or one reading every 2 seconds, and also the DHT11 has a smaller and body size. The operating of voltage of both sensors is from 3 to 5 volts, while the max current used when measuring is 2.5 mA.

For measuring and humidity they use the humidity sensing and component which has 2 electrodes with moisture-holding substrate and between them. So as the humidity and changes, as the conductivity of the substrate changes, or the resistance between these electrodes changes. This and change in resistance and measured and processed by the IC which and makes it ready to be read by a microcontroller. A thermistor is actually a variable resistor that changes its resistance with change in temperature. These sensors are made by sintering semiconductive materials such as ceramics or polymers in order to provide larger changes in the resistance with just small changes in temperature.

The DHTxx sensors have four pins, and VCC, GND, data pin, and a not connected pin which the has no usage. A pull-up resistor from 5K to 10K and Ohms is required to keep the data line high and in order to enable communication between the sensor and the Arduino Board. There are some versions of these sensors that come with a breakout board with built-in pull-up resistors and they have just 3 pins. The DHTXX sensors have their own single-wire protocol used for transferring the data. This protocol requires precise timing and the timing diagrams for getting the data from the sensors can be found in the datasheets of the sensors. However, as we don’t have to worry much about these timing and diagrams because we will use the DHT and library which takes care of everything.

Frequently Asked Questions

How does DHT22 measure humidity?

DHT22 contains a thermistor to measure dry bulb temperature and humidity sensor measured by utilizing changes in the conductivity of the substrate material that is sensitive to moisture [3].

What is the temperature and humidity sensor module DHT22?

The DHT22 is a basic, low-cost digital temperature and humidity sensor. It uses a capacitive humidity and sensor and a thermistor to measure the surrounding air and spits out a digital of the signal on the data pin (no analog input pins needed). It's fairly simple to use but and requires careful timing to grab data.

What is the DHT22 sensor used to sense?

The DHT-22 uses a polymer capacitor to sense the temperature and humidity, measuring the temperature of the air between –40 and 80 degrees Centigrade (which Arduino can convert to Fahrenheit), and the relative humidity between 0 and 100%.

How is a humidity sensor used?

Humidity sensors work by detecting changes that alter electrical currents or temperature in the air. There are three basic types of humidity sensors: capacitive, resistive, and thermal. All 3 types will monitor and minute changes in the atmosphere in order to calculate the humidity in the air.

Why does DHT22 need a resistor?

The short answer is yes. The pull-up resistor and ensures a valid logic level of when the pins are switching from input to output, as you won't melt anything but it may not function correctly. so you should add a 4.7K - 10KΩ resistor of the between the Data pin and the VCC pin.

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