In this article, I will walk you through the steps to build your own DIY WiFi thermostat using an Arduino microcontroller board in around 15 minutes. This is a great low-cost project that allows you to control your home heating and cooling system remotely using your smartphone or computer.

A WiFi thermostat connects your existing heating and cooling system to your home WiFi network. This allows you to adjust the target temperature and monitor your home's climate from anywhere using a web browser or mobile app. Commercial WiFi thermostats can cost $200 or more, but with an Arduino and a few other common components you can build one yourself for under $50.

Benefits of a DIY WiFi Thermostat

Here are some of the main benefits of building your own DIY WiFi thermostat:

Parts and Tools Needed

You only need a few parts to build your own WiFi thermostat with Arduino:

For tools you will need:

Circuit Diagram

Here is the circuit diagram showing how all the components are connected:

How to Build a Low-Cost DIY WiFi Thermostat With Arduino in 15 Minutes

The temperature sensor, relay module, and ESP8266 WiFi module are all connected to the Arduino Uno which controls the system.

Step-by-Step Building Instructions

Follow these step-by-step instructions to assemble your DIY WiFi thermostat prototype on a breadboard:

1. Connect the temperature sensor

The DHT22 sensor detects the ambient air temperature and humidity. Connect the signal pin to Arduino digital pin 2.

2. Connect the relay module

The relay switches the HVAC system on and off. Connect it to Arduino pin 6.

3. Connect the ESP8266 WiFi module

This allows the Arduino to communicate over WiFi. Connect it to Arduino pins 0 and 1 for serial communication.

4. Install required libraries

In the Arduino IDE install the DHT and ESP8266WiFi libraries to handle the sensors.

5. Upload the Arduino sketch

Upload the DIY thermostat Arduino sketch to the board to control the system.

6. Configure your WiFi settings

Modify the sketch to include your WiFi SSID and password for internet access.

7. Power on and test

Use a microUSB cable to power on the Arduino. Test it works by checking the temperature reading.

Now your hardware is set up! Next you just need to program the thermostat logic.

Programming the Thermostat Software

Here are the main steps I followed to program my Arduino thermostat:

The full Arduino code for the thermostat is available on GitHub. Once loaded on the Arduino it provides the brains of the thermostat.

Constructing the Thermostat Enclosure

To complete the thermostat you need to install it in an enclosure. Here are some options:

I used a basic plastic junction box. The Arduino, breadboard and wiring fit nicely inside.

Use hot glue to secure the components in place. The temperature sensor should be outside the box to accurately measure ambient air temperature.

Installing Your DIY WiFi Thermostat

The final step is to install your thermostat and connect it to your HVAC heating/cooling system:

And that's it! Your DIY WiFi thermostat using Arduino should now be up and running.

The whole process takes around 15 minutes once you have all the components ready. Now you can control your home's temperature from anywhere and save money!


Building your own WiFi thermostat with Arduino is an easy and fun DIY IoT project. In 15 minutes you can construct a low-cost smart thermostat using common components.

The key steps are:

This inexpensive DIY thermostat allows you to monitor and control your home temperature remotely using your smartphone. It's a great way to save money and add smart automation to your home.

I hope you enjoyed this guide on how to build your own WiFi thermostat in 15 minutes with Arduino! Let me know if you have any other questions.