Home automation using GSM Abstract: Home automation is very popular these days and it is common to read in magazines about itsmarvels.Withstateofthearttechnologyitispossibletoachievehomeautomationwith remote control andmonitoring via GSM phones.Imagine being able to control all the electrical appliancesofyourhomefromvirtuallyanyplaceyourareintheworld!Forexample,sayone cold winter day, you are stuck in traffic on the motorway after a long day at work. By pressing a fewkeystrokesonyourmobilephone,youactivateamacrowhichturnsontheheating,,and switches on your electrical fireplace and lava-lamps at your premises.In today's times the GSM mobile terminal has become one of the items that are constantly with us. Justlike our wallet/purse, keys or watch, the GSMmobile terminal provides us witha communication channel that enables us to communicate with the world. The want for a person to be reachable or to call anyone at any time is very appealing.Thisprojectmainlyfocusesonthecontrollingofhomeappliancesremotelyand providingsecuritywhentheuserisawayfromtheplace.ThesystemisSMSbasedanduses wireless technology to revolutionize the standards of living. This system provides ideal solution totheproblemsfacedbyhomeownersindailylife.Thesystemiswirelessthereforemore adaptable and cost-effective. The system provides security against intrusion as well as automates varioushomeappliancesusingSMS.ThesystemusesGSMtechnologythusproviding ubiquitous access to the system for security and automated appliance control. Introduction: Theaimofthepaperistoinvestigateacosteffectivesolutionthatwillprovide controlling of home appliances remotely and willalso enable home security against intrusion in theabsenceofhomeowner.Themotivationistofacilitatetheuserstoautomatetheirhomes havingubiquitousaccess.Thesystemprovidesavailabilityduetodevelopmentofalowcost system. The home appliances control system with an affordable cost was thought to be built that should be mobile providing remote access to the appliances and allowing home security. Home security has been a major issue where crime is increasing and everybody wants to take proper measures to prevent intrusion. In addition there was a need to automate home so that user can take advantage of the technological advancement in such a way that a person getting off the office doesnot get melted with the hot climate. Therefore this paper proposes a system that allows user to be control home appliances ubiquitously and also provide security on detection of intrusion via SMS using GSM technology. Home appliance control system is based on GSM network technology for transmission of SMSfromsendertoreceiver.SMSsendingandreceivingisusedforubiquitousaccessof appliancesandallowingbreachcontrolathome.Thesystemproposestwosub-systems. Appliancecontrolsubsystemenablestheuserto controlhomeappliancesremotelywhereasthe security alert subsystem provides the remote securitymonitoring. The systemis capable enough toinstructuserviaSMSfromaspecificcellnumbertochangetheconditionofthehome applianceaccordingto theusersneedsandrequirements.Thesecondaspectisthat ofsecurity alertwhichisachievedinawaythaton thedetectionofintrusionthesystemallowsautomatic generation of SMS thus alerting the user against security risk. Working principle: GSMModemisahardwarecomponentthatallowsthecapabilitytosendandreceive SMS to and from the system. The communication with the system takes placevia RS232 serial port.CellphonecanbeattachedattheplaceofGSMhardwarebutitlimitsthehardware functionality such as sending or receiving of SMS. GSM modem is a plug and play device and is attachedtothemicrocontrollerwhichthencommunicateswiththemicrocontrollerviaRS232 port. GSM modem is a bridge responsible for enabling/ disabling of SMS capability. Cellular phone containing SIM card has a specific number through which communication takes place. The device communicates with the GSM Modemvia radiofrequency.Mobile user transmits SMS using GSM technology. Mobile device communicates with the GSM Modem via radiowaves.ThemodeofcommunicationiswirelessandmechanismworksontheGSM technology.CellphonehasaSIMcardandaGSMsubscription.Thiscellphonenumberis configuredonthemicrocontroller.UsertransmitsinstructionsviaSMSandthesystemtakes action against those instructions. GSM hardware tests are run in order to check the hardware support. The system will call GSMmodemanditwillgetactivated.AfteractivationtheModemwillcheckforhardware support. If the hardware is missing or some other hardware problem there will be error, resulting incommunicationfailureandtheapplicationwillbeterminated.Ifhardwarerespondsthenthe serialportwillbeopenedforcommunicationandGSMhardwarewillallowtransmissionof SMS. The controller will then connect and after connection establishment the system will be able to detect intrusion and will alert user about the breach and similarly the system will update status of appliances by receiving SMS from the pre-defined cell number. SMS will be silently ignored if cell number is unauthorized. Components used: Micro controller GSM Modem Max232 Power Supply Software used:Embedded C Keil IDE APPLICATIONS: Home automation Office automation. In Industrial automation. Advantages: It is very safe and secure to use. Fast, effective and flawless service. We can control any appliances remotely.Highly-reliable and efficient to use. Disadvantage: If network busy the delivery of SMS may fail, so its difficult to control the appliances.It is some what complex to design. Block Diagram: MicrocontrollerGSMMODEMMOTORCOOLERDOORCONVEYERControlCircuitsON/OFFTRANSFORMERREGULATORRECTFIERFILTERPOWER SUPPLYHEATERRS232