Wireless notice board using Arduino and GSM module

Wireless notice board is very selective term for this project, as it has a very wide scope rather than just being a simple notice board. First we should understand the purpose of this project, in this system we can display a message or notice to some display device like LCD, and this message can be easily set or changed from anywhere in the world, just by using the SMS facility of your mobile handset. Whatever notice we want to display, just send the SMS of that text, with some prefix and suffix.

This is very useful in Hotels, Malls, college, offices and can be used anywhere, even at home. Like you can set the message like “Do not disturb” at your hotel’s room gate, can set message at your home’s door step when you are away, and of course it is used as notice board in schools, colleges, cinema halls etc. And yes, it’s just not a simple Message board, the usefulness of this project is that you can set or change the message or notice from anywhere, just sending SMS from your phone.

We have previously used the SMS facility of mobile phone for home security and control the home appliances remotely: PIR Sensor and GSM Based Security System and GSM Based Home Automation using Arduino
 

Working Explanation:

In this project, Arduino UNO is used for controlling the whole process, GSM module (SIM900A) to receive the SMS/message sent from mobile phone and LCD to display the message.

We can send some message or notice like “#Circuit Digest*”, “#We Welcomes You*” through the SMS. Here we have used a prefix in the message string that is ‘#’. This prefix is used to identify the starting of the message or notice. And ‘*’ is used as suffix to indicate the end of the message or notice.

When we send SMS from mobile phone to GSM module then GSM receives that SMS and sends it to Arduino. Now Arduino read this SMS and extract main notice message from the received string and stores in another string.  And then sends the extracted message to 16x2 LCD by using appropriate commands.

Further working of this system is explained in the ‘Code Description’ section below. Before we get into programming details we should know about GSM module.

GSM Module:

GSM module is used in many communication devices which are based on GSM (Global System for Mobile Communications) technology. It is used to interact with GSM network using a computer. GSM module only understands AT commands, and can respond accordingly. The most basic command is “AT”, if GSM respond OK then it is working good otherwise it respond with “ERROR”. There are various AT commands like ATA for answer a call, ATD to dial a call, AT+CMGR to read the message, AT+CMGS to send the sms etc. AT commands should be followed by Carriage return i.e. \r (0D in hex), like “AT+CMGS\r”. We can use GSM module using these commands:

ATE0 For echo off

AT+CNMI=2,2,0,0,0  <ENTER>           Auto opened message Receiving.  (No need to open message)

ATD<Mobile Number>; <ENTER>      making a call (ATD+919610126059;\r\n)

AT+CMGF=1 <ENTER>                        Selecting Text mode

AT+CMGS=”Mobile Number” <ENTER>  Assigning recipient’s mobile number

>>Now we can write our message

>>After writing message

Ctrl+Z  send message command (26 in decimal).

ENTER=0x0d in HEX

Circuit Description:

Connections of Wireless Notice Board using GSM and Arduino are simple and shown in the figure below. Here a liquid crystal display (LCD) is used for display the “Notice” or message, which is sent though the mobile phone as SMS. Data pins of LCD namely RS, EN, D4, D5, D6, D7 are connected to arduino digital pin number 7, 6, 5, 4, 3, 2. And Rx and Tx pin of GSM module is directly connected at Tx and Rx pin of Arduino respectively. And GSM module is powered by using a 12 volt adaptor.

Code Description:

The code of the program is easily understandable; the new thing here is GSN initialization function gsm_init(), which is explained in the end.

In the program, first of all we include library for liquid crystal display (LCD) and then we defines data and control pins for LCD and some variables.