GSM Based Home Automation System using Arduino

Below mentioned simple GSM arduino project where you can control any thing through GSM module . 
Here SIM900A used , need 3.7 , 2 Amps power supply must for SIM module , ground must common .

Simple AT commands use to get output from the module , Pin 7 & 8 of Arduino used as TX & TX for GSM module .  for controlling any appliance any pin can be used  

Codes are below

#include <SoftwareSerial.h> // Library for using serial communication

SoftwareSerial SIM900(8, 7); // Pins 7, 8 are used as used as software serial pins

String incomingData;   // for storing incoming serial data

String message = "";   // A String for storing the message

int relay_pin = 9 ;    // Initialized a pin for relay module

void setup()

{

  Serial.begin(115200); // baudrate for serial monitor

  SIM900.begin(9600); // baudrate for GSM shield

  pinMode(relay_pin, OUTPUT);   // Setting erlay pin as output pin

  digitalWrite(relay_pin, HIGH);  // Making relay pin initailly low

  // set SMS mode to text mode

  SIM900.print("AT+CMGF=1\r");  

  delay(100);

  

  // set gsm module to tp show the output on serial out

  SIM900.print("AT+CNMI=2,2,0,0,0\r"); 

  delay(100);

}

void loop()

{

  //Function for receiving sms

  receive_message();

  // if received command is to turn on relay

  if(incomingData.indexOf("Led_on")>=0)

  {

    digitalWrite(relay_pin, LOW);

    message = "Led is turned ON";

    // Send a sms back to confirm that the relay is turned on

    send_message(message);

  }

  

  // if received command is to turn off relay

  if(incomingData.indexOf("Led_off")>=0)

  {

    digitalWrite(relay_pin, HIGH);

    message = "Led is turned OFF";

    // Send a sms back to confirm that the relay is turned off

    send_message(message);

  }        

}

void receive_message()

{

  if (SIM900.available() > 0)

  {

    incomingData = SIM900.readString(); // Get the data from the serial port.

    Serial.print(incomingData); 

    delay(10); 

  }

}

void send_message(String message)

{

  SIM900.println("AT+CMGF=1");    //Set the GSM Module in Text Mode

  delay(100);  

  SIM900.println("AT+CMGS=\"+92xxxxxxxxxx\""); // Replace it with your mobile number

  delay(100);

  SIM900.println(message);   // The SMS text you want to send

  delay(100);

  SIM900.println((char)26);  // ASCII code of CTRL+Z

  delay(100);

  SIM900.println();

  delay(1000);  

}