Raspberry Pi: DHT11/DHT22 Temperature and Humidity (Python)

Learn how to interface the DHT11 and DHT22 digital temperature sensors with the Raspberry Pi to get temperature and humidity readings. You’ll learn how to connect the sensors to the Raspberry Pi, include the required libraries, and write a Python script that displays the current temperature and humidity on the shell/terminal.

Raspberry Pi with DHT11 DHT22 Getting Temperature and Humidity Python

Table of Contents

Throughout this tutorial, we’ll cover the following main topics:

Prerequisites

Before continuing with this tutorial, check the following prerequisites.

  1. Get familiar with the Raspberry Pi board—if you’re not familiar with the Raspberry Pi, you can read our Raspberry Pi Getting Started Guide here.
  2. You must know how to run and create Python files on your Raspberry Pi. We like to program our Raspberry Pi via SSH using an extension on VS Code. We have a detailed tutorial about that subject: Programming Raspberry Pi Remotely using VS Code (Remote-SSH).
  3. Know how to use the Raspberry Pi GPIOs so that you know how to wire the circuit properly. Read the following tutorial: Raspberry Pi Pinout Guide: How to use the Raspberry Pi GPIOs?

Introducing DHT11/DHT22 Sensors

The DHT11 and DHT22 sensors are used to measure temperature and relative humidity. These are very popular among makers and electronics hobbyists.

DHT11/DHT22 Temperature and Humidity Sensors

These sensors contain a chip that does analog to digital conversion and spit out a digital signal with the temperature and humidity. This makes them very easy to use with any microcontroller.

DHT11 vs DHT22

The DHT11 and DHT22 are very similar but differ in their specifications. The following table compares some of the most important specifications of the DHT11 and DHT22 temperature and humidity sensors. For a more in-depth analysis of these sensors, please check the sensors’ datasheet.

DHT11
DHT22
Temperature range0 to 50 ºC +/-2 ºC-40 to 80 ºC +/-0.5ºC
Humidity range20 to 90% +/-5%0 to 100% +/-2%
ResolutionHumidity: 1%
Temperature: 1ºC
Humidity: 0.1%
Temperature: 0.1ºC
Operating voltage3 – 5.5 V DC3 – 6 V DC
Current supply0.5 – 2.5 mA1 – 1.5 mA
Sampling period1 second2 seconds
Price$1 to $5$4 to $10
Where to buyCheck pricesCheck prices

The DHT22 sensor has a better resolution and a wider temperature and humidity measurement range. However, it is a bit more expensive, and you can only request readings with 2 seconds interval.

The DHT11 has a smaller range and it’s less accurate. However, you can request sensor readings every second. It’s also a bit cheaper.

Despite their differences, they work in a similar way, and you can use the same code to read temperature and humidity. You just need to select in the code the sensor type you’re using.

DHT Pinout

DHT sensors have four pins as shown in the following figure. However, if you get your DHT sensor in a breakout board, it comes with only three pins and with an internal pull-up resistor on pin 2.

DHT22 Temperature and Humidity Sensor using Arduino IDE

The following table shows the DHT22 and DHT11 pinout. When the sensor is facing you, pin numbering starts at 1 from left to right

DHT pinConnect to
13.3V
2Any digital GPIO; also connect a 4.7k Ohm pull-up resistor
3Don’t connect
4GND

DHT Sensor Breakout Board

If you got a DHT11 or DHT22 sensor on a breakout board, they only come with three pins and have an internal pull-up resistor on the data pin.

DHT22 sensor

In this case, wiring is even simpler and you don’t need to wire an external resistor. The DHT breakout boards usually have labels on the pins: GND, VCC, and DATA.

DHT pinConnect to
GNDGND
VCC3V3 (OUT)
DATGPIO 4 (or any other digital pin)

Parts Required

Raspberry Pi with DHT22 Circuit

Here’s a list of parts you need to build the circuit (if you don’t have a DHT breakout board, you need a 4.7kOhm resistor):

You can use the preceding links or go directly to MakerAdvisor.com/tools to find all the parts for your projects at the best price!

Wiring the DHT11/DHT22 Sensor to the Raspberry Pi

Wire the DHT22 or DHT11 sensor to the Raspberry Pi as shown in the following schematic diagram. If you have a DHT breakout board, ignore the resistor.

Raspberry Pi DHT Sensor Wiring

In this example, we’re connecting the DHT data pin to GPIO 4. However, you can use any other suitable digital GPIO. Learn more about the Raspberry Pi GPIOs here.

Getting DHT11/22 Temperature and Humidity

There are different ways to get temperature and humidity readings from the DHT11 or DHT22 sensors using the Raspberry Pi with Python. We’ll use the Adafruit_CircuitPython_DHT Python library.

Update your Raspberry Pi

First, update and upgrade your Raspberry Pi, if any updates are available. Run the following command:

sudo apt update && sudo apt upgrade

If there’s a need to update, it will ask you if you want to continue. Click Y and Enter to proceed. You may need to wait a few minutes if it needs to update.

Create a Virtual Environment

We’ll install the DHT library in a virtual environment. Creating a virtual environment will isolate the Python libraries we’re using, in this case, the DHT library, from the rest of the system.

We’ll create our virtual environment on a directory on our Desktop. Enter the following command on a Terminal window to move to the Desktop:

cd ~/Desktop

Create a folder for your project. This is where we’ll create the virtual environment and install the library. We’ll create a folder called dht_test.

mkdir dht_test

Move to the newly created folder:

cd ~/Desktop/dht_test

Create a virtual environment for this directory called myenv. This must be the same directory where we’ll install the DHT library. Replace myenv with the desired name for your virtual environment.

python3 -m venv myenv

Then, you can run the following command to check that the virtual environment is there.

ls -l
Create a Virtual Environment Raspberry Pi Python

Activate the virtual environment:

source myenv/bin/activate

Your prompt should change to indicate that you are now in the virtual environment.

Activate Python Virtual Environment

Installing the Adafruit_CircuitPython_DHT Library

Now that we are in our virtual environment, we can install the library. Run the following command:

python3 -m pip install adafruit-circuitpython-dht

After a few seconds, the library will be installed (ignore any yellow warnings about deprecated packages).

Installing the Adafruit_CircuitPython_DHT Library

Python Code for Raspberry Pi DHT11/DHT22

The following script gets temperature and humidity from the DHT sensors and prints the readings on the Python shell. Create a new Python file with a name of your choice, for example, dht_basic.py, and copy the following code.

# Complete Project Details: https://RandomNerdTutorials.com/raspberry-pi-dht11-dht22-python/
# Based on Adafruit_CircuitPython_DHT Library Example

import time
import board
import adafruit_dht

# Sensor data pin is connected to GPIO 4
sensor = adafruit_dht.DHT22(board.D4)
# Uncomment for DHT11
#sensor = adafruit_dht.DHT11(board.D4)

while True:
    try:
        # Print the values to the serial port
        temperature_c = sensor.temperature
        temperature_f = temperature_c * (9 / 5) + 32
        humidity = sensor.humidity
        print("Temp={0:0.1f}ºC, Temp={1:0.1f}ºF, Humidity={2:0.1f}%".format(temperature_c, temperature_f, humidity))

    except RuntimeError as error:
        # Errors happen fairly often, DHT's are hard to read, just keep going
        print(error.args[0])
        time.sleep(2.0)
        continue
    except Exception as error:
        sensor.exit()
        raise error

    time.sleep(3.0)

View raw code

To create and run Python scripts on the Raspberry Pi, we like to use VS Code with an SSH extension: Programming Raspberry Pi Remotely using VS Code (Remote-SSH).

How the Code Works

Continue reading to learn how the code works, or skip to the Demonstration section.

Importing libraries

Start by importing the required libraries: the time module to add delays to our code, the board module to interact with the Raspberry Pi GPIOs and the adafruit_dht to read from the DHT sensor.

import time
import board
import adafruit_dht

DHT Sensor

On the following line, we initialize our DHT sensor. We are using a DHT22 connected to GPIO 4 (you can use any other suitable GPIO as long as you change the code on the following line):

sensor = adafruit_dht.DHT22(board.D4)

If you’re using a DHT11, it should be like this:

sensor = adafruit_dht.DHT11(board.D4)

From now on, we’ll refer to our DHT sensor as sensor in our code.

While loop

Then, we have a loop that keeps the program running indefinitely, until you stop the program. Inside the loop we’ll try to read the sensor and display the readings.

while True:
    try:

Reading Temperature and Humidity

Getting temperature in Celsius degrees and humidity is as easy as using the temperature and humidity properties of the sensor object. So, you can get temperature like this:

temperature_c = sensor.temperature

By default, it will get the temperature in Celsius degrees. We add a line to convert it to Fahrenheit degrees.

temperature_f = temperature_c * (9 / 5) + 32

We save the humidity value on the humidity variable:

humidity = sensor.humidity

After getting sensor readings, we’ll display them on the shell using the print() function.

print("Temp={0:0.1f}ºC, Temp={1:0.1f}ºF, Humidity={2:0.1f}%".format(temperature_c, temperature_f, humidity))

Formatting the printing output

Temp={0:0.1f}ºC, Temp={1:0.1f}ºF, Humidity={2:0.1f}%: This is the format string that defines how the output will be displayed. The format string contains placeholders indicated by curly braces {} that will be filled in with actual values using the .format() method.

Temp={0:0.1f}ºC indicates the placeholder for the first value (temperature). It specifies how the value will be formatted:

  • {0}: This specifies the index of the value to be inserted (0 refers to the first value provided to the .format() method).
  • :0.1f: This is a formatting specification that specifies how the value should be displayed. The 0 represents the minimum number of digits, and the .1f means that it will display the value as a floating-point number with one digit after the decimal point.

Temp={1:0.1f}ºF: This part of the format string follows the same structure as above but refers to the second value (temperature_f).

Humidity={2:0.1f}%: This part of the format string refers to the third value (humidity).

Finally, .format(temperature_c, temperature_f, humidity) inserts the actual values into the placeholders within the format string. The values provided in the parentheses are inserted into the placeholders according to their respective indexes (0, 1, 2).

If we can’t get valid temperature and humidity readings, we handle the exceptions on the except blocks:

except RuntimeError as error:
    # Errors happen fairly often, DHT's are hard to read, just keep going
    print(error.args[0])
    time.sleep(2.0)
    continue
except Exception as error:
    sensor.exit()
    raise error

We get new temperature readings every three seconds. You can adjust the delay time by changing the argument of the sleep() method.

time.sleep(3)

Demonstration

Save your Python file on the same folder of your virtual environment (in our case Desktop/dht_test). Then run it on your Raspberry Pi. Run the following command (make sure you are on the correct path—the same folder of the virtual environment):

python dht-basic.py

The virtual environment must be active to run the script. If the virtual environment is not active, you can rerun the following command to activate myenv.

source myenv/bin/activate

You should get new temperature and humidity readings on the Python Shell or on the Raspberry Pi Terminal every three seconds.

Raspberry Pi Print Temperature and Humidity DHT22 DHT11 Sensor

You can stop the execution of the program by pressing CTRL+C.

You may also like reading: Raspberry Pi: BME280 Temperature, Humidity and Pressure Sensor (Python).

Wrapping Up

In this tutorial, you learned how to interface the DHT11 and DHT22 digital temperature and humidity sensors with the Raspberry Pi and how to write a Python program to get and display readings. This is one of the most basic projects to get you started with the DHT11 or DHT22 sensor.

We hope you found this tutorial useful. If you’re a beginner to the Raspberry Pi, you can get started with the following tutorials:

You can check all our Raspberry Pi projects on the following link:

Finally, if you would like to interface the DHT11/22 sensor with other microcontrollers, we have tutorials for ESP32, ESP8266, and Arduino:

Thanks for reading.



Learn how to build a home automation system and we’ll cover the following main subjects: Node-RED, Node-RED Dashboard, Raspberry Pi, ESP32, ESP8266, MQTT, and InfluxDB database DOWNLOAD »
Learn how to build a home automation system and we’ll cover the following main subjects: Node-RED, Node-RED Dashboard, Raspberry Pi, ESP32, ESP8266, MQTT, and InfluxDB database DOWNLOAD »

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22 thoughts on “Raspberry Pi: DHT11/DHT22 Temperature and Humidity (Python)”

  1. Hi Sara, can you develop tutorials on how to interface a force Sensor FSR402 or better sensor on esp32 or esp8266. For the measurement of power on a bike crank. Mahen.

    Reply
  2. Hi Sara,
    I am getting error external-managed-environment when executing
    sudo pip3 install Adafruit_DHT
    It seems the latest versions of Python do not allow global package installations using pip
    Any idea
    Best regards
    Roger

    Reply
  3. Hi Sara,

    Thanks for the tutorial.
    I am having issues running this script with a DHT11 connected to my Raspberry pi 5.

    When I run the script I get the following output:

    “Unable to set line 4 to input”
    I then have to Ctrl+C to end the program.

    I’ve double checked the wiring, all looks good.

    Any ideas please?

    Thanks

    Reply
    • Hi.
      How are you running the code?
      Are you running on your virtual environment? Did you install the library we recommend?
      Regards,
      Sara

      Reply
      • Hi,

        Code is being run via virtual environment, the Adafruit_CircuitPython_DHT Library is installed.

        Full error (post Ctrl+C):

        (iot_env) pi@raspberrypi:~/iot_env $ /home/pi/iot_env/bin/python /home/pi/iot_env/DHT11.py
        Unable to set line 4 to input
        ^CTraceback (most recent call last):
        File “/home/pi/iot_env/DHT11.py”, line 16, in
        temperature_c = sensor.temperature
        ^^^^^^^^^^^^^^^^^^
        File “/home/pi/iot_env/lib/python3.11/site-packages/adafruit_dht.py”, line 273, in temperature
        self.measure()
        File “/home/pi/iot_env/lib/python3.11/site-packages/adafruit_dht.py”, line 218, in measure
        pulses = self._get_pulses_pulseio()
        ^^^^^^^^^^^^^^^^^^^^^^^^^^
        File “/home/pi/iot_env/lib/python3.11/site-packages/adafruit_dht.py”, line 147, in _get_pulses_pulseio
        while self.pulse_in:
        File “/home/pi/iot_env/lib/python3.11/site-packages/adafruit_blinka/microcontroller/bcm283x/pulseio/PulseIn.py”, line 174, in len
        message = self._wait_receive_msg()
        ^^^^^^^^^^^^^^^^^^^^^^^^
        File “/home/pi/iot_env/lib/python3.11/site-packages/adafruit_blinka/microcontroller/bcm283x/pulseio/PulseIn.py”, line 110, in _wait_receive_msg
        message = self._mq.receive(block=True, type=type)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        sysv_ipc.Error: Signaled while waiting

        During handling of the above exception, another exception occurred:

        Traceback (most recent call last):
        File “/home/pi/iot_env/DHT11.py”, line 27, in
        sensor.exit()
        File “/home/pi/iot_env/lib/python3.11/site-packages/adafruit_dht.py”, line 89, in exit
        def exit(self) -> None:

        KeyboardInterrupt

        Not sure if the output is relevant/helpful.

        Thanks
        Matt

        Reply
        • This did help in my case:
          sensor = adafruit_dht.DHT22(board.D4, use_pulseio=False)
          BTW. I moved away from the DHT sensors due to the instability when reading.
          Best regards,
          Roger

          Reply
          • Thanks – I did see that suggestion yesterday whilst researching the issue.
            Unfortunately, didn’t work for me:

            Traceback (most recent call last):
            File “/home/pi/iot_env/DHT11.py”, line 28, in
            raise error
            File “/home/pi/iot_env/DHT11.py”, line 16, in
            temperature_c = sensor.temperature
            ^^^^^^^^^^^^^^^^^^
            File “/home/pi/iot_env/lib/python3.11/site-packages/adafruit_dht.py”, line 273, in temperature
            self.measure()
            File “/home/pi/iot_env/lib/python3.11/site-packages/adafruit_dht.py”, line 220, in measure
            pulses = self._get_pulses_bitbang()
            ^^^^^^^^^^^^^^^^^^^^^^^^^^
            File “/home/pi/iot_env/lib/python3.11/site-packages/adafruit_dht.py”, line 162, in _get_pulses_bitbang
            with DigitalInOut(self._pin) as dhtpin:
            ^^^^^^^^^^^^^^^^^^^^^^^
            File “/home/pi/iot_env/lib/python3.11/site-packages/digitalio.py”, line 185, in init
            self.direction = Direction.INPUT
            ^^^^^^^^^^^^^^
            File “/home/pi/iot_env/lib/python3.11/site-packages/digitalio.py”, line 215, in direction
            self._pin.init(mode=Pin.IN)
            File “/home/pi/iot_env/lib/python3.11/site-packages/adafruit_blinka/microcontroller/generic_linux/libgpiod/libgpiod_pin_2_x.py”, line 51, in init
            self._line_request = self._chip.request_lines(
            ^^^^^^^^^^^^^^^^^^^^^^^^^
            File “/home/pi/iot_env/lib/python3.11/site-packages/gpiod/chip.py”, line 315, in request_lines
            req_internal = self._chip.request_lines(line_cfg, consumer, event_buffer_size)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            OSError: [Errno 16] Device or resource busy

          • Thanks – I did see that suggestion yesterday whilst researching the issue.
            Unfortunately, didn’t work for me:

            OSError: [Errno 16] Device or resource busy

  4. Hi Sara, the sketch doesn’t work on my Pi 3b+, latest 64-bit OS. Here the error log:
    myenv) kdbeer@raspberrypi:~/mu_code/DHT11 $ python DHT11_basic.py

    /home/kdbeer/mu_code/DHT11/myenv/lib/python3.9/site-packages/adafruit_blinka/microcontroller/bcm283x/pulseio/libgpiod_pulsein64: error while loading shared libraries: libgpiod.so.2: cannot open shared object file: No such file or directory

    Traceback (most recent call last):
    File “/home/kdbeer/mu_code/DHT11/DHT11_basic.py”, line 11, in
    sensor = adafruit_dht.DHT11(board.D4)
    File “/home/kdbeer/mu_code/DHT11/myenv/lib/python3.9/site-packages/adafruit_dht.py”, line 294, in init
    super().init(True, pin, 18000, use_pulseio)
    File “/home/kdbeer/mu_code/DHT11/myenv/lib/python3.9/site-packages/adafruit_dht.py”, line 86, in init
    self.pulse_in = PulseIn(self._pin, maxlen=self._max_pulses, idle_state=True)
    File “/home/kdbeer/mu_code/DHT11/myenv/lib/python3.9/site-packages/adafruit_blinka/microcontroller/bcm283x/pulseio/PulseIn.py”, line 89, in init
    message = self._wait_receive_msg(timeout=0.25)
    File “/home/kdbeer/mu_code/DHT11/myenv/lib/python3.9/site-packages/adafruit_blinka/microcontroller/bcm283x/pulseio/PulseIn.py”, line 107, in _wait_receive_msg
    raise RuntimeError(
    RuntimeError: Timed out waiting for PulseIn message. Make sure libgpiod is installed.
    can you give me hint how to solve it ?

    Thanks for helping !

    Reply
  5. it additionally needed:
    (myenv) pi@raspberrypi:~/Desktop/dht_test $ python3 -m pip install RPi.GPIO

    else showing error:
    ModuleNotFoundError: No module named ‘RPi’

    Reply
  6. Hi Sara,
    I went through all your steps but always fail at running the skript. All errors returned are about failed imports because no such modul exsist. I am a complete beginner and don´t know how to solve the problem.

    I would be happy with some help

    Best Regards
    Faris

    Reply

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