2.2.3 DHT-11

Introduction

The digital temperature and humidity sensor DHT11 is a composite sensor that contains a calibrated digital signal output of temperature and humidity. The technology of a dedicated digital modules collection and the technology of the temperature and humidity sensing are applied to ensure that the product has high reliability and excellent stability.

The sensors include a wet element resistive sensor and a NTC temperature sensor and they are connected to a high performance 8-bit microcontroller.

Components

../_images/list_2.2.3_dht-11.png

Schematic Diagram

../_images/image326.png

Experimental Procedures

Step 1: Build the circuit.

../_images/image207.png

Step 2: Go to the folder of the code.

cd /home/pi/davinci-kit-for-raspberry-pi/nodejs/

Step 3: Install dependencies.

sudo npm install node-dht-sensor

Step 4: Run the code.

sudo node dht11.js

After the code runs, the program will print the temperature and humidity detected by DHT11 on the computer screen.

Code

var sensor = require("node-dht-sensor");

setInterval(function(){
  sensor.read(11, 17, function(err, temperature, humidity) {
    if (!err) {
      console.log(`temp: ${temperature}\`C, humidity: ${humidity}%`);
    }
  });
},1000);

Code Explanation

var sensor = require("node-dht-sensor");

Import the module node-dht-sensor module, which provides functions for us to read the value of DHT-11.

Note

For more details, please refer to: https://www.npmjs.com/package/node-dht-sensor

sensor.read(11, 17, function(err, temperature, humidity){...})

The node-dht-sensor module provides the read() function for us to read the measured temperature and humidity, where 11 means DHT-11, 17 means and its connected to GPIO17.

if (!err) {
  console.log(`temp: ${temperature}\`C, humidity: ${humidity}%`);
}

When there is no error in the reading, the temperature and humidity values are printed on the terminal.

Phenomenon Picture

../_images/image209.jpeg