DIY – GSM Relay Control Using Smart Switch Board

The main objective of this project is to control the ON/OFF status of electrical appliances at home or company remotely using a cell phone and relay switch. The appliances may include lights, fans, pump, and air conditioners and so on. Though all the household items can be automated to change their ON/OFF status, our prototype model GSM remote control circuit uses 8 electrical appliances. The project includes multiple users to control the appliances and uses unique SMS formats for each application. The switch board can be operated by SMS feature of the mobile phones to ON/OFF the electrical appliances in home or office etc.., only by the registered users. The system validates the users and also the message sent by the user. The list of options served by the system is given below. Get ON/OFF status of the Loads Get Users List Add an User Remove an User Get Account Balance of the SIM Reset Message Counter GSM Relay Control Board – Circuit Diagram Features of the Smart Switch Board  What happens if an unregistered user operates? If an unregistered user tries to operate, the system replies a template “Unregistered User. Please contact admin.” The system also sends an SMS to the first user in the users list or the programmed user (if no user is added) a template “Tried to operate the switch board.” and the contact number of that user. Below is the real-time simulation output.     How to add a user to the system? To add or register a new user to the system, any of the previously registered users or the programmed user should send number ‘3’ as a message to the system. Then the user will receive a message template having the user name and the contact number. By editing and sending the received template with the details of the user to be added, the system will add the user. Below is the code snippet for adding a user. The above code adds the user details in the EEPROM as well as the user’s list. Edit the user name up to 10 characters and the 10-digit contact number within the same lines of the received message and send the same to the system. The user will be added to the system. Below is the simulation output for adding a user. Now, let’s add the previously shown unregistered user.     How to know the ON/OFF status of the loads? The user can request to send the ON/OFF status of the loads through option 1. The relay states are read from the output port which is dedicated to operate the relays. This data is used to frame the template and an SMS is sent to the requested user. The logic in framing the message is to use the ‘for loop’ to each load and then if the array index reaches the ON/OFF state, the state of that load is placed.   The message that contains the ON/OFF status of the loads is framed such that, the symbol ‘=’ is used as an identifier and the character after this ‘=’ symbol is read/written as the state of the load. The ON state is represented by numeric ‘1’ and the OFF state is represented by numeric ‘0’. In order to ON or OFF the load, this numeric character needs to be edited and the edited message is sent to the system.  The number of ‘=’ symbols and the character after this symbol are verified whenever this template is received by the system. If the number of ‘=’ symbols and the number of loads are not equal, or...
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