Introduction: UCL-Embedded -Relay Communication Box

About: Obayda Haj Hamoud Student at UCL Odense

The main idea about this project is to control a set of two relays and a DHT11 sensor with a Blynk app using WiFi communication and a Nodmcu esp8266 micro controller.

Step 1: Parts List

  • 1x NodeMcu Lua ESP8266 ESP-12E WIFI Development Board.
  • 1x DHT11 Temperature Humidity Sensor Module
  • 1x Mini Bread Board
  • 2x 5V 1 Channe Relay Module
  • 2x LEDs
  • 1x Double Side Prototype PCB
  • some breadboard cables
  • some wire jumbers
  • Additional : Box to protect the module

Step 2: Building the Module

This Fritzing Diagram was made for another board "Wemos D1" . The board functioned perfectly. Though the need to minimize the total size of the whole circuit , set the board replacement in consideration.
Wiring with Node Mcu is the same.( An edition to be added soon with the used board Node Mcu. )

Step 3: IO List

The virtual pins will be explained in the next step.

Step 4: Blynk App

The following steps explain how to use the app I built.

  1. Download blynk app to your phone or tablet. IOS devices and Android devices are supported.
  2. Press on Scan QR on the top right corner.
  3. Scan the QR code attached. That is all.

Blynk app can be used with many different kind of boards. It is very easy to be used with many control possibilities.

The app can:

· Track the humidity and the temperature of the room

· Control 2 relays separately through WI-FI


· When disconnected, the app sends a notification to the phone screen.

· The app can be scheduled with some events to control e.g. relays depending on temperature or time and date.

Step 5: The Code

The Blynk app need some special libraries to be installed. The WiFi credentials and the Auth token need to be set in the code.