Home Automation part 2: Control household lights using a text message !

Hello and very happy new year guys! This is the very first techmagister tutorial in 2017. In this tutorial we are going to make a step forward along our journey in home automation. If you missed the first tutorial:

Home Automation Tutorial 1

Today we are going to make a home automation system to control your domestic switches using a simple sms. You just type “ON” and send it to the system from anywhere in the world. Then the switch will turn itself ON, simple as that. To do the project we need some stuffs:

• SIM 900 GSM module.

 

This is the main module for the project. SIM 900 is also one of the most popular module for IOT based products. .Now there are lots of models available in the market for cheaper price tags.SIM 900 module is a GSM device which can be operated through GSM signals. We can input a SIM to the module and using simple text message commands we can make some outputs. SIM 900 module can configure using “AT” commands easily. Its schematic can be shown as follows.

• Arduino module

This device is used to communicate with SIM 900 module and print its outputs in terminal. You can use any kind of arduino device for this.(UNO R3., MEGA, MINI etc.).

Download Arduino Software

• Wires ,1 LED,relay DC 5V relay module, Wall adapter, bulb and a holder.

Project Procedure.

1. Take the SIM 900 module and Arduino device as follows

When connecting GSM module with the Arduino it is necessary to use an external DC power supply for the Arduino because when GSM module is at its top performance the current supply from the USB (500 mA) is not enough to powerup the modules. When only using the USB power, module was tend to misbehave.

2. Connect the arduino to the PC and configure connected port in arduino App (com port).

3. Insert a working SIM to SIM 900 module.

4. Now go back to the arduino software and paste following code in a new project and deploy it into      the arduino.

#include <SoftwareSerial.h>
char incoming_char=0;
String data;
char pos = 0;
SoftwareSerial gsm (10, 11); // RX, TX
void setup()
{
delay(3000);
pinMode(13, OUTPUT);
pinMode(8, OUTPUT);
digitalWrite(8, LOW);
digitalWrite(8, HIGH);
// turn the LED on (HIGH is the voltage level)
delay(1000);
// wait for a second
digitalWrite(8, LOW);
// turn the LED off by making the voltage LOW
delay(5000);
// wait for 10 seconds
Serial.begin(9600);
gsm.begin(9600);
delay(10000);
Serial.println();
gsm.println("ATE0");
gsm.write((byte)34);
//ASCII equivalent of "ENTER"
gsm.println("AT"); // set SMS mode to text
gsm.write((byte)34);
gsm.println("AT+CMGF=1");
// set SMS mode to text
gsm.write((byte)34);
gsm.print("AT+CNMI=2,2,0,0,0");
/* blurt out contents of
new SMS upon receipt to
the GSM shield's serial out*/
gsm.write((byte)34);
while(gsm.available())
Serial.write((char)gsm.read());
delay(500);
while(gsm.available())
Serial.write((char)gsm.read());
delay(500);
gsm.println();
while(gsm.available())
delay(500);
Serial.println();
delay(1000);
// The GSM module needs to return to an OK status
}
void loop() {
while(gsm.available() >0){
while(gsm.available() >0)
{
incoming_char=gsm.read();
//Get the character from the cellular serial port.
delay(20);
data = data + incoming_char;
//store all data to an array
} delay(12);
Serial.println("printing data");
Serial.println(data);
pos = data.indexOf('O');
// searching for letter "o"
if (data.charAt(pos + 1) == 'N') {
//search for the letter "N" after the letter "O"
Serial.println("ON recieved switching ON");
digitalWrite(13, HIGH);
gsm.println("AT+CMGD=1,4"); // delete all SMS
gsm.write((byte)34);
delay(2000);
Serial.println("memory cleared");}
if (data.charAt(pos + 1) == 'F') {
//search for the letter "F" after the letter "O"
Serial.println("OFF recieved switching OFF");
digitalWrite(13, LOW);
gsm.println("AT+CMGD=1,4"); // delete all SMS
gsm.write((byte)34);
delay(2000);
Serial.println("memory cleared");
}
delay(1000);}}

About the code: 

This code has been made using AT commands . What the code does is if it receives an sms saying “ON” it checks the character after “O” & if the next character is “N”, it simply put the output pin to “HIGH”(5V) state. If the next character is “F” it makes the output “LOW”(0V).

5. Now send an SMS to the SIM which has inserted into the SIM900 module with “ON”. The    connected LED should turn on.

Now you can extend this project to operate household lights as follows.

6. Connect your relay module with an AC adapter and an AC bulb holder as follows

7. Then connect your output signal pin to DC 5V input in your relay module.

8. Then plug the adapter to an AC 240V outlet .

Make sure both arduino and SIM900 i=has powered up correctly and then send a SMS with “ON” message. Bulb should be turned “ON”.

If not, refresh the Arduino using reset button and try again. Make a comment below with your results. Like our Facebook Page to stay up to date with techmagister's awesome tutorials. See you again in another tutorial.