This sensor is also used in our weather stations to measure atmospheric temperature and humidity. On the basis of this information, experts can make rain predictions etc. for coming days. In this tutorial, I will explain its working, pinout, protocol and interfacing with other microcontrollers in detail. I will also post some tutorial links where I have interfaced it with other microcontrollers. If you have any query about it, ask in comments and I will resolve it. So, let’s start with the Introduction to DHT11:
Introduction to DHT11
- DHT11 is a low cost embedded sensor, which is used to measure temperature (in a range from 0 to 50 degree Celsius with an accuracy of +-2 C) and moisture (in a range from 20% to 80% with an accuracy of +-5%).
- It consists of a capacitive humidity sensor which measures humidity in the air.
- For temperature measurement, it has a thermistor embedded in it, which is a resistive and wet NTC temperature measuring device.
- It works with both 3.3V and 5V microcontroller systems.
- This sensor has excellent quality, fast response time and anti interference ability.
- In DHT11, calibration coefficients are already stored in OTP program Memory, we just have to call these calibration coefficients while the internal sensors detect signal in the process.
- It uses low power in transmitting simple signals up to 20 meters.
- It comes in a single package comprising of 4 pins with 0.1″ spacing between them and special package can be provided according to user demand.
- It is quite accurate & precise in its readings as compared to other expensive sensors i.e. SHT10, DS18B20 etc.
DHT11 Pinout & Description
- DHT11 Pinout consists of 4 Pins in total, which are shown in below table:
|Pin#1||Vcc||This pin is used for input purpose at this pin we apply 3.3 v to 5v input supply.|
|Pin#2||Data||By this pin we get output of temperature and humidity values, by serial transmission protocol.|
|Pin#4||Ground||This pin is used for Ground ( Connected to 0V or GND ).|
For Better understanding lets see its picture, which given below.
Now, we discuss DHT11 working principle with detail.
Working of DHT11
- Lets start its working, it has two main part one is used for temperature measurement and other is used for humidity measurement. It also contain on IC which is used to send data to other Microcontroller. Now we discuss its working with details. First we discuss its Temperature Measurement Part.
DHT11 Temperature Measurement Part
- For temperature measurement it consists of NTC sensor or thermistor which measure temperature.
- Thermistor is basically a variable resistor which changes its resistance with change in temperature. Thermistors are made by sintering of semiconductors materials, such as ceramic or polymers in orders to large change in resistor with small change in temperature. when temperature changes there is a change in resistance of thermistor by this change we find temperature of our environment.
- For better understanding lets see its picture.
Now, discuss its Humidity Measurement part.
DHT11 Humidity Measurement Part
- For Humidity Measurement it uses humidity measurement component, which has two electrodes with humidity holding substrate between them.
- As moisture content changes in our environment, the conductivity of substrate changes or resistance between electrode changes. By this change in resistance we can find our outside environment humidity.
- For further information lets see its picture.
Now lets discuss its specification.
Specifications of DHT11
- These are some specification of DHT11, we discuss them with detailed.
- Its operating voltage are 3.5 v to 5.5 v.
- Its operating current are 0.3 to 5.5 mA.
- It send and receive data by serial transmission.
- Its operating temperature is -40°C to 80°C.
- Humidity range is 0% to 100%.
- It humidity and temperature resolution are 16-bit.
- Its accuracy is ±0.5°C and ±1%.
- Its sampling rate is 0.5 Hz.
- Its dimensions are 27mm x 59mm x 13.5mm (1.05″ x 2.32″ x 0.53″).
- It has four pins with 0.1″ spacing.
- Its weight is 2.4g.
- It is low cost sensor. Its price is just $1 to $5.
- It has long term stability ±0.5% per year.
Applications of DHT11
These are some application of DHT11.
- It can be used for Humidity and Temperature measurement.
- It is also used at weather station for temperature measurement.
- It is an automatic climate control sensor.
- It is also use as environment monitoring device.
So, that was all about DHT11, If you have any question about it please ask in comment box. I will resolve your queries. Take care.