To start with this project, You need the following components:

esp8266(NodeMcu v3 Lua)
google account (firebase)

You can buy a esp8266 from here:

Step 1: Setting Up Arduino IDE, Install Esp8266 Board:

Install esp8266 Board:

Open Arduino IDE > File > Preferences > additional Boards Manager URLs > "http://arduino.esp8266.com/stable/package_esp8266c...> OK

Tools > Board: > Boards Manager > esp8266 > install

Step 2: Setting Up Arduino IDE, Install Arduino Json Library:

Install Arduino json library:

Install version 5.13.1

Watch install video HERE

Step 3: Setting Up Arduino IDE, Install Firebase Library:

Install Firebase library:

Download latest stable build HERE > unzip in "Documents\Arduino\libraries"

NOTE, There is a bug in "v0.3 Bi-directional streaming support" > update fingerprint CLICK HERE FOR INFO

Step 4: Firebase, Create Project:

Create Firebase Project:

Go To "https://console.firebase.google.com"

Step 5: Firebase, Project Rules:

Project rules:

Database(Realtime Database) > rules

{
  /* Visit https://firebase.google.com/docs/database/security to learn more about security rules. */
  "rules": {
    ".read": true,
    ".write": true
  }
}

Step 6: Firebase, Realtime Database Data:

Realtime Database data:

Database(Realtime Database) > Data

Add: "LED1" > " "0" "

Step 7: Code:

#include <ESP8266WiFi.h>
#include <FirebaseArduino.h>
#define WIFI_SSID "SSID"
#define WIFI_PASSWORD "WIFI PASSWORD"
#define FIREBASE_HOST "?????????????.firebaseio.com"
#define FIREBASE_AUTH "AUTH KEY"
int LED1 = 4;
void setup()
{
Serial.begin(115200);
pinMode(LED1, OUTPUT);
  delay(2000);
  Serial.println('\n');
  
  wifiConnect();
  Firebase.begin(FIREBASE_HOST, FIREBASE_AUTH);
  delay(10);
}
void loop()
{  
  
Serial.print(Firebase.getString("LED1") + "\n");
analogWrite(LED1, Firebase.getString("LED1").toInt());
delay(10);
if(WiFi.status() != WL_CONNECTED)
{
  wifiConnect();
}
delay(10);
}
void wifiConnect()
{
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);             // Connect to the network
  Serial.print("Connecting to ");
  Serial.print(WIFI_SSID); Serial.println(" ...");
  int teller = 0;
  while (WiFi.status() != WL_CONNECTED)
  {                                       // Wait for the Wi-Fi to connect
    delay(1000);
    Serial.print(++teller); Serial.print(' ');
  }
  Serial.println('\n');
  Serial.println("Connection established!");  
  Serial.print("IP address:\t");
  Serial.println(WiFi.localIP());         // Send the IP address of the ESP8266 to the computer
}

Step 8: Code, Personal Info:

personal info:

SSID > name of your wifi network

WIFI PASSWORD > password of your wifi network

FIREBASE HOST > something like "?????????????.firebaseio.com". You can find it in the "Data" tab of your Realtime Database.

AUTH KEY > Project settings > Service accounts > Database secrets

Step 9: Esp8266 Drivers:

Download:

Click HERE > unzip and install

Step 10: Test the Code:

Upload code:

use esp8266 module in board manager > click "ESP-12E module".

Open serial monitor and set it to "115200".

And you should get the same data as in your database.

Esp8266 Firebase Connection