NodeMcu DHT11 & MQTT

• Introduction
• Preparation
• Connection
• Upload Sketch
• MQTT Client Settings
• Running Result

Introduction

We will use MQTT protocol to send and get data from NodeMCU ，Browser or Mobile APP will send control signal to DHT11 sensor and monitor humidity and temperature through Internet.When the MQTT Dashboard sends a D command, the monitor window shows the temperature and humidity.

Hardware:

• NodeMCU board  x 1
• DHT11 temperature/humidity sensor x 1
• Breadboard x 1
• jumper wires

Software:

• Arduino IDE(version 1.6.4+)
• ESP8266 Board Package and the Serial Port Driver
• MQTT Clirnt (MQTTBox here)
• Arduino library: PubSubClient
• Arduino library:DHT
• Arduino library:ESP8266WiFi

Upload Sketch

Upload Sketch

Connect the NodeMCU to computer via USB cable,open Node_mcu_dht11by using Arduino IDE(Version1.6.4+):

Edit the code to fit your own WiFi and MQTT settings as following operations:

1)Hotspot Configration:

const char* ssid = “your_hotspot_ssid”;

const char* password = “your_hotspot_password”;

Find above code line,put your own ssid and password on there.

2)MQTT  Server  Address Setting

const char* mqtt_server = “broker.mqtt-dashboard.com”;

You can use your own MQTT broker URL or IP address to set above mqtt_server value. You can also use some famous free MQTT server to test the project such as  “broker.mqtt-dashboard.com”,  “iot.eclipse.org” etc.

3)MQTT Client Settings

If your MQTT broker require clientID,username and password authentication,you need to change

if (client.connect(clientId.c_str()))

to

if (client.connect(clientId,userName,passWord)) //put your clientId/userName/passWord here

If not,just keep them as default.

After do that,choose the coresponding board type and port type as below,then upload the sketch to the NodeMCU.

• Board:”NodeMCU 1.0(ESP-12 Module)”
• CPU Frequency:”80MHz”
• Flash Size:”4M (3M SPIFFS)”
• Upload Speed:”115200″
• Port: Choose your own Serial Port for your NodeMCU

MQTT Client Settings

About how to config the MQTT client,check this link.

Topics Settings:

• Topic to publish: dht11
• Topic to subscribe: dht11

Sketch Running Result

Once the upload is successful, open monitor window and you will see the result

DHT11 sensor shows temperature and humidity

Remote MQTT Client Settings

If you send a D command on the MQTT Dashboard, the serial port will show temperature and humidity. Sending 0 or other characters will prompt you to enter D.

• Step 1) Install iot mqtt dashboard app
  You can search “iot mqtt dashboard app” from google play store as following:
  

or directly Download the app from IOT MQTT Dashboard Android APP

• Step 2) Add a mqtt broker by   click “+” button as following:

• Step 3)config clientid, mqtt server and port as following:

Client Id should be anything which is not blank,
Server must be same as mqtt_server variable value in code
port must be 1883
After completes the required fields, click “CREATE” button

• Step 4)click PUBLISH  TAB, then click “+” button to define some graphic widgets which can help us to publish messages to mqtt server。

• Step 5)define “Text” widget as per following graph:

firendly name should be anything which is not blank,

Topic fills in the dht11 already defined in the code

After completes the required fields, click “CREATE” button

• Step 6)Finally came to this interface we can start sending instructions
  

Running Result

When the D command is entered on the PUBLISH interface of the mobile phone’s MQTT Dashboard

In monitor window, you will see the following result

When you enter characters other than D on the MQTT Dashboard.

The following results are displayed in the monitor window.