SENSORS/ACTUATORS

INTERNET OF THING (IoT)

ESP32 - Temperature Humidity Sensor

This tutorial instructs you how to use ESP32 to read temperature and humidity value from DHT11 or DHT22 sensors, and print it to Serial Monitor.

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-C
1	×	DHT11 Temperature Humidity Sensor Module
1	×	(Optional) Temperature and Humidity Sensor DHT22
1	×	10 kΩ resistor
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) DC Power Jack
1	×	(Recommended) Screw Terminal Expansion Board for ESP32

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Disclosure: some of these links are affiliate links. We may earn a commission on your purchase at no extra cost to you. We appreciate it.

Introduction to DHT11 and DHT22 Temperature and Humidity Sensor

In short, the DHT22 sensor is a more accurate, larger range but more expensive than DHT11. Let's see the common and differences between them

The commons

The same pinout
The same wiring to ESP32
The similar ESP32 code

The differences

The below table show the detaied differences between DHT11 and DHT22:

	DHT22	DHT11
The price	low cost	ultra low cost
The humidity range	0% to 100%	20% to 80%
The humidity accuracy	± 2% to 5%	5%
The temperature range	-40°C to 80°C	0°C to 50°C
The temperature accuracy	± 0.5°C	± 2°C
The reading rate	0.5Hz (one time per 2 seconds)	1Hz (one time per second)
Dimension	15.1mm x 25mm x 7.7mm	15.5mm x 12mm x 5.5mm
Operating Voltage	3 to 5V	3 to 5V

DHT11 and DHT22 Pinout

DHT11 and DHT22 sensor includes 4 pins:

GND pin: connect this pin to GND (0V)
VCC pin: connect this pin to VCC (3.3V or 5V)
DATA pin: the pin is used to communicate between the sensor and ESP32
NC pin: Not connected

DHT11 and DHT22 temperature and humidity sensor Pinout

We highily recommend you using DHT11 and DHT22 sensor modules. The modules have a built-in resistor and have only three pin: VCC, GND, and DATA pins (or alternatively: +, -, and OUT pins).

DHT11 and DHT22 temperature and humidity module Pinout

image source: diyables.io

The pins order on the module's can be different between manufacturers. Please check the pin labels printed on the module carefully.

Wiring Diagram between DHT11/DHT22 and ESP32

Wiring to ESP32 is the same for both sensors. In orginal form, A resistor from 5K to 10K Ohms is required to keep the data line high and in order to enable the communication between the sensor and the ESP32

ESP32 - DHT11 Sensor Wiring

ESP32 DHT11 Temperature and humidity Sensor Wiring Diagram

This image is created using Fritzing. Click to enlarge image

ESP32 - DHT22 Sensor Wiring

ESP32 DHT22 Temperature and humidity Sensor Wiring Diagram

This image is created using Fritzing. Click to enlarge image

ESP32 - DHT11 Module Wiring

Most of DHT22 sensor modules have a built-in resistor, so you don't need to add it. it saves us some wiring or soldering works.

ESP32 DHT11 Temperature and humidity Module Wiring Diagram

This image is created using Fritzing. Click to enlarge image

ESP32 - DHT22 Module Wiring

Most of DHT22 sensor modules have a built-in resistor, so you don't need to add it. it saves us some wiring or soldering works.

ESP32 DHT22 Temperature and humidity Module Wiring Diagram

This image is created using Fritzing. Click to enlarge image

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

ESP32 Code - DHT11

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-temperature-humidity-sensor */ #include <DHT.h> #define DHT_SENSOR_PIN 21 // ESP32 pin GPIO21 connected to DHT11 sensor #define DHT_SENSOR_TYPE DHT11 DHT dht_sensor(DHT_SENSOR_PIN, DHT_SENSOR_TYPE); void setup() { Serial.begin(9600); dht_sensor.begin(); // initialize the DHT sensor } void loop() { // read humidity float humi = dht_sensor.readHumidity(); // read temperature in Celsius float tempC = dht_sensor.readTemperature(); // read temperature in Fahrenheit float tempF = dht_sensor.readTemperature(true); // check whether the reading is successful or not if ( isnan(tempC) || isnan(tempF) || isnan(humi)) { Serial.println("Failed to read from DHT sensor!"); } else { Serial.print("Humidity: "); Serial.print(humi); Serial.print("%"); Serial.print(" | "); Serial.print("Temperature: "); Serial.print(tempC); Serial.print("°C ~ "); Serial.print(tempF); Serial.println("°F"); } // wait a 2 seconds between readings delay(2000); }

ESP32 Code - DHT22

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-temperature-humidity-sensor */ #include <DHT.h> #define DHT_SENSOR_PIN 21 // ESP32 pin GPIO21 connected to DHT22 sensor #define DHT_SENSOR_TYPE DHT22 DHT dht_sensor(DHT_SENSOR_PIN, DHT_SENSOR_TYPE); void setup() { Serial.begin(9600); dht_sensor.begin(); // initialize the DHT sensor } void loop() { // read humidity float humi = dht_sensor.readHumidity(); // read temperature in Celsius float tempC = dht_sensor.readTemperature(); // read temperature in Fahrenheit float tempF = dht_sensor.readTemperature(true); // check whether the reading is successful or not if ( isnan(tempC) || isnan(tempF) || isnan(humi)) { Serial.println("Failed to read from DHT sensor!"); } else { Serial.print("Humidity: "); Serial.print(humi); Serial.print("%"); Serial.print(" | "); Serial.print("Temperature: "); Serial.print(tempC); Serial.print("°C ~ "); Serial.print(tempF); Serial.println("°F"); } // wait a 2 seconds between readings delay(2000); }

Two above codes have only one line different.

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Do the wiring as above image.
Connect the ESP32 board to your PC via a micro USB cable
Open Arduino IDE on your PC.
Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
Click to the Libraries icon on the left bar of the Arduino IDE.
Type “DHT” on the search box, then look for the DHT sensor library by Adafruit
Install the library by clicking on Install button.

A windows appears to ask you to install dependencies for the library
Install all dependencies for the library by clicking on Install All button.

Copy one of the above code and open with Arduino IDE
Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
Make the sensor colder or hotter. For example, putting the sensor near a hot cup of coffee
See the result on Serial Monitor. It looks like the below:.

COM6

Send

Humidity: 31.00% | Temperature: 27.00°C ~ 80.60°F Humidity: 31.00% | Temperature: 27.00°C ~ 80.60°F Humidity: 31.00% | Temperature: 27.00°C ~ 80.60°F Humidity: 31.00% | Temperature: 27.00°C ~ 80.60°F Humidity: 31.00% | Temperature: 28.00°C ~ 82.40°F Humidity: 31.00% | Temperature: 28.00°C ~ 82.40°F Humidity: 31.00% | Temperature: 28.00°C ~ 82.40°F Humidity: 31.00% | Temperature: 28.00°C ~ 82.40°F Humidity: 32.00% | Temperature: 28.00°C ~ 82.40°F Humidity: 31.00% | Temperature: 29.00°C ~ 84.20°F Humidity: 32.00% | Temperature: 29.00°C ~ 84.20°F Humidity: 31.00% | Temperature: 29.00°C ~ 84.20°F

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