Relay and SIM808 GSM/GPRS/GPS Modem based SMS Controlled Wireless Home Automation System with ATmega32
In this project, we will learn how to make a Relay and SIM808 GSM/GPRS/GPS Modem based SMS Controlled Wireless Home Automation System with AVR ATmega32 Microcontroller. Here, we will control home appliances i.e 2 bulbs and 2 fans wirelessly using SIM808 GSM/GPRS/GPS modem and ATmega32 microcontroller. The home appliances are controlled by sending SMS to the SIM808 GSM/GPRS/GPS modem of the Home Automation System and the change in status of the home appliances are displayed in a 16X2 alphanumeric LCD.
When the SIM808 GSM/GPRS/GPS modem power is turned on, the ATmega32 microcontroller reads the initial status data sent by the SIM808 GSM/GPRS/GPS modem through USART protocol. After reading the status data, the ATmega32 microcontroller processes the SIM808 GSM/GPRS/GPS modem status data and displays the status of the modem and SIM in the alphanumeric LCD. If SIM card is not present, then "Plz Insert SIM" is displayed, if SIM card is present and modem is ready, then "SIM808 is Ready" is displayed and for other conditions, "SIM808 Error" is displayed in the alphanumeric LCD.
Now, when the SIM808 GSM/GPRS/GPS modem is ready, the LCD displays "Send Ctrl SMS:" in 1st row and "All APPli. OFF " in the 2nd row(As all the appliances are in off state initially). The Home Automation System waits for the control SMS to turn On/Off the home appliances. The control SMS are predefined sets of strings(Message of SMS). The predefined set of strings(Message of SMS) to control the home appliances are shown below:-
|Control SMS||Home Appliance Status|
|A1 ON||Bulb 1 On|
|A1 OFF||Bulb 1 Off|
|A12ON||Bulb 2 On|
|A2 OFF||Bulb 2 Off|
|A3 ON||Fan 1 On|
|A3 OFF||Fan 1 Off|
|A4 ON||Fan 2 On|
|A4 OFF||Fan 2 Off|
|ALL ON||All Appliances On|
|ALL OFF||All Appliances Off|
When the SIM808 GSM/GPRS/GPS modem receives any SMS, it sends new SMS notification to the ATmega32 microcontroller. The ATmega32 microcontroller reads the new SMS notification and displays "New Ctrl SMS" in the alphanumeric LCD. But if the ATmega32 microcontroller receives some other notification(other then SMS like Call and others), then "Unknown Error" is displayed in the alphanumeric LCD. After receiving new SMS notification, the ATmega32 microcontroller will read the SMS from the SIM808 GSM/GPRS/GPS modem memory. If it reads the SMS successfully, then it will compare the content of the SMS with the predefined set of strings else it will display "Empty location" when the read memory location is empty and "Error" when there is error in reading the SMS. When the control SMS is read successfully, the ATmega32 microcontroller compares the message of the received control SMS with the predefined ones, if received control SMS matches with any of the predefined strings, then the microcontroller sends the required control signal to the Relay driver to turn On/Off the home appliance and it displays the new status of the home appliance in the alphanumeric LCD. But if the received control SMS does not matches with any of the predefined strings, then "Invalid SMS" is displayed in the alphanumeric LCD.
Now, send different SMS to the SIM808 GSM/GPRS/GPS modem of the Home Automation System and check the change in state of home appliances.