SENSORS/ACTUATORS

ESP8266 - DHT11

This tutorial instructs you how to use ESP8266 to read the temperature and humidity from DHT11 sensor. In detail, we will learn:

How to connect ESP8266 to the DHT11 sensor
How to program ESP8266 to read temperature and humidity values from a DHT11

We suggest:

Utilizing a waterproof DS18B20 temperature sensor if you are only looking to measure temperature. This is an affordable and tidy sensor that can be placed in either hot or cold water.
Utilizing a DHT22 temperature and humidity sensor if you are only looking to measure temperature and humidity with a higher accuracy.

Hardware Preparation

1	×	ESP8266 NodeMCU
1	×	Micro USB Cable
1	×	Temperature and Humidity Sensor DHT11
1	×	10 kΩ resistor
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) 5V Power Adapter for ESP8266
1	×	(Optional) ESP8266 Screw Terminal Adapter

Or you can buy the following sensor kit:

DIYables Sensor Kit 30 types, 69 units

Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you. We appreciate your support.

Overview of DHT11 Temperature and Humidity Sensor

The Temperature and Humidity Sensor Pinout

The DHT11 on the market comes with two forms: sensor and module.

The DHT11 sensors has four pins:

GND pin: must be connected to GND (0V)
VCC pin: must be connected to VCC (5V)
DATA pin: used for communication between the sensor and ESP8266
NC pin: Not connected, this pin can be disregarded

DHT11 temperature and humidity sensor pinout

The DHT11 module has three pins:

GND pin (-): must be connected to GND (0V)
VCC pin (+): must be connected to VCC (5V)
OUT pin: used for communication between the sensor and ESP8266

※ NOTE THAT:

The arrangement of the pins on a module may be different depending on the manufacturer. It is IMPERATIVE to use the labels printed on the module for reference. Be sure to take a close look!

Wiring Diagram

ESP8266 - DHT11 Sensor Wiring

A resistor with a value between 5K and 10K Ohms is necessary to maintain the data line at a high level, thus enabling communication between the sensor and the ESP8266.

ESP8266 NodeMCU DHT11 Temperature and humidity Sensor wiring diagram

This image is created using Fritzing. Click to enlarge image

ESP8266 - DHT11 Module Wiring

Most DHT11 sensor modules have an integrated resistor, thus eliminating the need for additional wiring or soldering.

ESP8266 NodeMCU DHT11 Temperature and humidity Module wiring diagram

This image is created using Fritzing. Click to enlarge image

How To Program For DHT11 Temperature Sensor

To begin, the library must be included:

#include "DHT.h"

Specify the ESP8266 pin that is connected to the DHT11 sensor.

#define DHTPIN 2

Specify the type of sensor: DHT11

#define DHTTYPE DHT11

Create a DHT object.

DHT dht11(DHTPIN, DHTTYPE);

Begin the setup of the sensor:

dht11.begin();

Read the humidity value.

float humi = dht11.readHumidity();

Read the temperature in Celsius.

float tempC = dht11.readTemperature();

Read the temperature in Fahrenheit.

float tempF = dht11.readTemperature(true);

ESP8266 Code for DHT11

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-dht11 */ #include <DHT.h> #define DHT_SENSOR_PIN D7 // ESP8266 pin D7 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); }

Detailed Instructions

To get started with ESP8266 on Arduino IDE, follow these steps:

Check out the how to setup environment for ESP8266 on Arduino IDE tutorial if this is your first time using ESP8266.
Wire the components as shown in the diagram.
Connect the ESP8266 board to your computer using a USB cable.
Open Arduino IDE on your computer.
Choose the correct ESP8266 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
Connect a USB cable to the ESP8266 and the PC.
Open the Arduino IDE, select the correct board and port.
In the Arduino IDE, navigate to the Tools menu, then select Manage Libraries.

Search for “DHT”, and then locate the DHT sensor library by Adafruit.
Press the Install button to complete the installation.

You will be prompted to install some other library dependencies.
To install all of these libraries, click the Install All button.

ESP8266 NodeMCU Adafruit Unified sensor library

Copy the code that corresponds to the sensor you have and open it with the Arduino IDE.
Click the Upload button in the Arduino IDE to compile and upload the code to the ESP8266.
Change the temperature of the environment around the sensor.
Check the result on the Serial Monitor.

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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9600 baud

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Additional Knowledge

Let's compare DHT11 and DHT22 sensors.

The commons between DHT11 and DHT22

Pinouts remain the same.
The wiring to ESP8266 is unaltered.
Programming, with the use of a library, is comparable, only requiring one line of code to be altered.

The differences between DHT11 and DHT22

	DHT11	DHT22
Price	ultra low cost	low cost
Temperature Range	0°C to 50°C	-40°C to 80°C
Temperature Accuracy	± 2°C	± 0.5°C
Humidity Range	20% to 80%	0% to 100%
Humidity Accuracy	5%	± 2 to 5%
Reading Rate	1Hz (once every second)	0.5Hz (once every 2 seconds)
Body size	15.5mm x 12mm x 5.5mm	15.1mm x 25mm x 7.7mm

Evidently, the DHT22 is more precise than the DHT11, has a wider range of measurements, yet costs more.