Use NodeMCU to send tilt sensor value to remote MQTT client

About NodeMCU

NodeMCU is a very popular Micro controller with wifi access. It is based on ESP8266 – a cheap but powerful chip and fully support Arduino IDE. If you familiar with Arduino IDE, you can program NodeMCU in no time.

Objective

Objective

In this project, we will connect a tilt sensor with NodeMCU. Tilt voltage value is sent to A0 pin of NodeMCU and then published to MQTT broker with topic “OsoyooCommand”. A MQTT client which subscribed topic “OsoyooCommand” will get tilt value in real time.

Parts and Devices

NodeMCU board  x 1 pc

Tilt sensor x 1 pc

10K Resistors x 1 pc

Breadboard x 1 pc

jumper wires

Connection Graph

Programming Prerequisite:

Before running the project, we need set up the  Arduino IDE as per following procedures:

• If you don’t have Arduino IDE, please go to https://www.arduino.cc/en/Main/Software download the IDE.
• Add ESP8266 support in Arduino IDE, read this https://osoyoo.com/2016/10/25/how-to-use-arduino-ide-to-program-esp8266-wifi-module/
• In Arduino IDE->Tools->Board Manager menu, select NodeMCU (0.9 or higher)  and corresponding COM port (showed in your device manager)

Library Installation:

In Arduino IDE, we need install MQTT client library to communicate with MQTT broker and  IRremoteESP8266 library to access DHT11 sensor, please download these two library from following two links:

• https://osoyoo.com/wp-content/uploads/samplecode/pubsubclient.zip

Unzip above two files, move the unzipped folder to Arduino IDE library folder (you can also import these two zip files to Arduino library from IDE).

Download sample code from following link

https://osoyoo.com/wp-content/uploads/2016/12/esp8266_iot_tiltseensor.txt , copy the code into Arduino IDE. Before running the code, please do following changes to fit your wifi and MQTT setting:

1)Line 19 and 20:

const char* ssid = “your_hotspot_ssid”;

const char* password = “your_hotspot_password”;

You need change these 2 lines to match your wifi SSID and password

2)Line 21

const char* mqtt_server = “broker.emqx.io”;

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.mqttdashboard.com”,  “iot.eclipse.org” etc

If you want to install your own MQTT broker in Ubuntu Linux, please read this article https://osoyoo.com/2016/09/07/how-to-install-mosquitto-mqtt-server-on-linux

3)if your MQTT server require username and password authentication,  you need change line 86

Running the code

After you running the code, please open the serial terminal window in upright corner of Arduino IDE.

If wifi hotspot name and password setting is ok and MQTT broker is connected, you will see following result:

After the NodeMCU connected to wifi and MQTT broker,  it will collect tilt sensor value and publish it to a MQTT broker with topic “OsoyooCommand”.

You can select any MQTT client tool to subscribe  the topic ” OsoyooCommand” from the same MQTT broker of NodeMCU. simply use google to search MQTT client in internet, or search MQTT in Apple store or Google Play, you can find many free MQTT client software. In  my case, I uses MQTTBox for Windows, you can learn MQTTBox configuration in following article: https://osoyoo.com/2016/12/02/nodemcu-potentiometer-mqtt/

After click Save button, Click Add Subscriber button and create a new subscriber screen. You will see tilt voltage value in the subscriber screen s as per following picture.