Home Automation with Google Assistant and Alexa under $10 (PART 1)

This is going to be one of the most interesting guides I have ever created. It’s about Home Automation and Internet-of-things (IoT). Today in this guide, we are going build a Home Automation device under $10 USD or INR 700. The best part is that this Home Automation device that we are going to build, works well with Google Assistant and Alexa.

I can also control my devices and monitor my room temperature as well as humidity level via a highly intuitive Android app. I am currently controlling 6 devices in my room. What’s more is that you can perform actions based on certain conditions while using sensors. For instance, turn on the Air Conditioner when the temperature reaches 30 C—more on that in the next post.

For now, let’s start building our first IoT home automation device.

Steps to build a Home Automation device that works with Google Assistant & Alexa

Things You Need

Total value: $9.51 or INR 694 (with free shipping worldwide)

For faster delivery, buy from Amazon.com ( US & other countries) or Amazon.in (India)

Step 1. Setting up The PC and the Arduino IDE for ESP8266

In Mac, go to Arduino>Preferences and add the above URL


Add URL JSON ESP8266 Arduino IDE

  • Click ‘OK‘ and then go to Tools> Board>Boards Manager

Board Manager

  • Search and install ESP8266 by ESP8266 Community package

Install ESP8266 Board

  • After installation, close the Window and go to Tools>Boards>select ‘NodeMCU 1.0 (ESP 12E-Module)’

Select NodemCU

  • And for now, we are done. Let’s connect the ESP8266 to the system
  • If it isn’t detected, install the driver package
  • Now go to File>New. Press CTRL+S and choose a location where you want to save your project
  • Give your project a name such as Home Automation with Google Assistant & Alexa. Save it

Step 2: Add Libraries

  • In Arduino IDE, go to Sketch>Include Library>Manage Libraries

Manage Libraries

  • In the search bar, type Adafruit MQTT and install Adafruit MQTT Library by Adafruit

Adding Library MQTT

  • Then type DHT and install DHT sensor library by Adafruit

DHT Sensor Library

Step 3: Setup Adafruit Account

  • Visit Adafruit.com and signup for an account. It’s completely free. No strings attached

Create Adafruit Account

  • Then, go to io.adafruit.com and sign in with Adafruit credentials
  • Click ‘Dashboards‘ in the left panel
  • Click Actions drop-down and click ‘Create a New Dashboard
  • Enter a Name such as ‘HomeAutomation‘ and add a description such as, ‘Controlling home devices and appliances with Google Assistant and Alexa.’

Create Dashboard

  • Click ‘Create
  • Now under Dashboards, you will see HomeAutomation. Click on it to open the HomeAutomation Dashboard
  • Click ‘+’ icon at the top

Create New Block

  • Choose a block. For instance, select ‘Toggle’ block for controlling light

Select Toggle Switch

  • Enter Feed Name as Relay1 (you can name it anything you want) and click ‘Create block

Choose feed and click Next Step

  • Then select the feed Relay1 and click ‘Next Step
  • Enter the Block Title such as Light and Enter Button On Text and Button Off Text as 0 and 1 or ON and OFF respectively

Finish Creating Block feed

  • Repeat the Step and add more block for your Lamp and Ceiling Fan or any other device you wish to control. Name the feeds as Relay2 and Relay3
  • Also, enter them appropriate Block Title

Repeat and Create 3 Block Feeds

NOTE: With NodeMCU, you can control up to 13 devices as it has 13 General Purpose Input/Output (GPIO) pins.

Also, to sense temperature, we need to add a block for Temperature and Humidity.

  • Click ‘+’ icon at the top and choose Line Chart

Select Line Graph

  • Create two feeds with name Temperature and Humidity

Create Temp and Humidity and Select both

  • Select both and click ‘Next Step
  • In the Block Settings, enter ‘Block Title‘ and put 0 in Y-axis minimum and 100 in Y-axis maximum and click ‘Create Block

Finish Create Temp and Humid Block

  • Now click ‘key‘ icon at the top right and copy the AIO key. This is the password to connect apps to the Adafruit IO. So keep it safe

Get AIO Secret key

  • Now go back to Arduino Sketch and follow the next step

Step 4: Create a New Project in Arduino IDE

  • Go to File>New
  • Copy the following code and paste it into your project
//Google Assistant Home Automation
#include <ESP8266WiFi.h>π
#include "Adafruit_MQTT.h"
#include "Adafruit_MQTT_Client.h"
#include <Adafruit_Sensor.h>
#include <DHT.h>
#include <DHT_U.h>

// pin connected to DH22 data line

#define Relay1 D0
#define Relay2 D1
#define Relay3 D2
//#define DHTTYPE DHT22
#define DHTPIN D4
#define DHTTYPE DHT11 // DHT 11

//WLAN Details
#define WLAN_PASS "PASSWORD" // Your password

/************************* Adafruit.io Setup *********************************/

#define AIO_SERVER "io.adafruit.com" //Adafruit Server
#define AIO_SERVERPORT 1883 
#define AIO_USERNAME "Replace with Adafruit Username" // Username
#define AIO_KEY "PasteAiokeyHere" // Auth Key

// DHT sensor

WiFiClient client;


Adafruit_MQTT_Publish temperature = Adafruit_MQTT_Publish(&mqtt, AIO_USERNAME "/feeds/Temperature");
Adafruit_MQTT_Publish humidity = Adafruit_MQTT_Publish(&mqtt, AIO_USERNAME "/feeds/Humidity");
Adafruit_MQTT_Subscribe Light = Adafruit_MQTT_Subscribe(&mqtt, AIO_USERNAME"/feeds/Relay1"); // Feeds name should be same everywhere
Adafruit_MQTT_Subscribe Lamp = Adafruit_MQTT_Subscribe(&mqtt, AIO_USERNAME "/feeds/Relay2");
Adafruit_MQTT_Subscribe Fan = Adafruit_MQTT_Subscribe(&mqtt, AIO_USERNAME "/feeds/Relay3");

void MQTT_connect();

void setup() {
// initialize dht22

pinMode(Relay1, OUTPUT);
pinMode(Relay2, OUTPUT);
pinMode(Relay3, OUTPUT);

// Connect to WiFi access point.
Serial.println(); Serial.println();
Serial.print("Connecting to ");

while (WiFi.status() != WL_CONNECTED) {

Serial.println("WiFi connected");
Serial.println("IP address: "); 

void temperatureAndHumidity()

float humidity_data = (float)dht.readHumidity();
float temperature_data = (float)dht.readTemperature();

// By default, the temperature report is in Celsius, for Fahrenheit uncomment
// following line.
// temperature_data = temperature_data*(9.0/5.0) + 32.0;

// Publish data
if (! temperature.publish(temperature_data))
Serial.println(F("Failed to publish temperature"));
Serial.println(F("Temperature published!"));
Serial.print("celsius: ");

if (! humidity.publish(humidity_data))
Serial.println(F("Failed to publish humidity"));
Serial.println(F("Humidity published!"));
Serial.print("Humidity: ");

// Repeat every 10 seconds
void loop() {

Adafruit_MQTT_Subscribe *subscription;
while ((subscription = mqtt.readSubscription(20000))) {
if (subscription == &Light) {
Serial.print(F("Got: "));
Serial.println((char *)Light.lastread);
int Light_State = atoi((char *)Light.lastread);
digitalWrite(Relay1, Light_State);
if (subscription == &Lamp) {
Serial.print(F("Got: "));
Serial.println((char *)Lamp.lastread);
int Lamp_State = atoi((char *)Lamp.lastread);
digitalWrite(Relay2, Lamp_State);
if (subscription == &Fan) {
Serial.print(F("Got: "));
Serial.println((char *)Fan.lastread);
int Fan_State = atoi((char *)Fan.lastread);
digitalWrite(Relay3, Fan_State);

void MQTT_connect() {
int8_t ret;

if (mqtt.connected()) {

Serial.print("Connecting to MQTT... ");

uint8_t retries = 3;
while ((ret = mqtt.connect()) != 0) {
Serial.println("Retrying MQTT connection in 2 seconds...");
if (retries == 0) {
while (1);
Serial.println("MQTT Connected!");
  • Press CTRL+S, enter the project name and choose a save location
  • Click ‘Save
  • After saving the sketch code, enter the Wi-Fi SSID & Password. The SSID is case sensitive so keep it accurate. You can get the help of your Android Wi-Fi scanner. Simply Tap on the Wi-Fi network and the SSID will be displayed
  • Then enter the Adafruit username and AIO key you copied earlier. Our sketch is now ready to flash

Paste Username and AIO key in the code

Step 5: Flashing the Custom Firmware to ESP8266 (NodeMCU)

  • To flash the firmware to the ESP8266, connect the ESP8266 based Nodemcu to the PC using the Micro USB cable and go to ‘Tools>Boards’.
  • Select ‘NodeMCU 1.0 (ESP-12E Module)’ from the Boards and ensure the following options are selected.Select Port and Config
  • Select the Port and then click Upload
  • Wait for a while until the firmware is being flashed.

Step 6: Connecting the Wires

Now that the firmware is flashed, time to wire the hardware. So, we will first connect the relay and then the DHT22 Sensor as per the following schematic

Home Automation Fritzing

Explanation: So basically we have connected the Relay input to D0, which we named Relay1 in the code. We defined D4 as the DHT22 data input pin and connected it to Data pin of DHT22

Similarly, D1 and D2 to Relay2, and Relay3. Adding Relay2 and Reay3 is optional.

We also connected the power to DHT22 taken from the 3V output and GND of Nodemcu. There are two 3v and GND terminals in NodeMCU and you need to connect them as shown in the diagram

Once done, turn on the power and make sure Wi-Fi is working

Open the com/serial port and check if the NodeMCU is able to connect to the configured Wi-Fi and able to communicate with our Adafruit MQTT server

Testing and it works

Then we connected the relay outputs to our Electric appliances existing switched as shown in the below illustration. We haven’t modified anything in our existing switch controls, just connected the relay switch terminals to them.

Relay Connections

Now we can turn off mechanical switch and power on our the HomeAutomation device to control the appliances.

The good thing about the setup is that your existing mechanical switches will work as intended.

Click Here to continue with PART 2 of DIY Home Automation With Alexa and Google Assistant

It covers setting up Google Assistant, Alexa, and Android app.

DISCLAIMER: *The post contains affiliate links and when you buy using those links, we may get some commission. This will help us pay for our servers and maintenance cost.


  1. massimo December 26, 2018
    • Henry Kane January 11, 2019
  2. Daniel Serban January 25, 2019
    • Ravi Singh January 27, 2019
  3. nishant February 11, 2019
    • Ravi Singh February 12, 2019
  4. nishant February 12, 2019
    • Ravi Singh February 15, 2019
    • Ravi Singh February 15, 2019
  5. priti February 13, 2019
    • Ravi Singh February 15, 2019
  6. yon mudi August 7, 2019
  7. yon mudi August 7, 2019

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Ad Blocker Detected!

We notice you're using an adblocker. We pay $25/month to keep this site running and serve 1 lakh readers a month – but we can't do that for free. We've made a point of never allowing auto-playing video ads or ads that obscure content and pop-ups. Please support us by whitelisting this domain.

How to disable? Refresh

%d bloggers like this: