Microcontroller Based On/Off Electrical Appliances Via Serial Port

AIM:This project describes to control the appliances of home through PC using Micro

controller.

BLOCK DIAGRAM:

DESCRIPTION:

Here the purpose of micro controller to control the devices corresponding to the input coming from PC. The micro controller check the status of devices like switched ON/OFF and inform this to PC. Then the PC informs the controller the operation to be performed. Here RS 232 is used for communication between PC and controller. Max 232 is a driver for RS-232 communication. Relay is a switch to operate the devices. Advantages are power saving, easy to operate. Applications are industrial automation, hotel environments, Office environments etc.

PC RS-232 MAX232 AT89S52

Relay

Transistor

Device

Device

COMPONENTS:

AT89S52 MAX232 RS232 RELAYS DEVICES

SKILL SET:

Functionality of all above components Embedded C programming C programming

Abstract— With advancement of technology things are becomingsimpler and easier for us. Automatic systems are being preferredover manual system. This unit talks about the basic definitionsneeded to understand the Project better and further defines thetechnical criteria to be implemented as a part of this project.The development of simple and sophisticated automation/control systems is part of the job for a practicingElectrical Engineer. This paper discusses the designand implementation of a prototype system foron/off switching of electrical appliances through anmicrocontroller . Through the use of a programmablemicrocontroller, the potential exists to developfar more sophisticated automation/control scenarios.

Microcontroller is a microprocessor designed specifically for control applications, and is equipped with ROM, RAM and facilities I / O on a single chip.AT89S52 is one of the family MCS-51/52 equipped with an internal 8 Kbyte Flash EPROM (Erasable and Programmable Read Only Memory), which allows memory to be reprogrammed

The MAX232 is an integrated circuit that converts signals from an RS-232 serial port to signals

suitable for use in TTL compatible digital logic circuits. The MAX232 is a dual driver/receiver and

typically converts the RX, TX, CTS and RTS signals.

The drivers provide RS-232 voltage level outputs (approx. ± 7.5 V) from a single + 5 V supply via

on-chip charge pumps and external capacitors. This makes it useful for implementing RS-232 in

devices that otherwise do not need any voltages outside the 0 V to + 5 V range, as power

supply design does not need to be made more complicated just for driving the RS-232 in this

case.

The receivers reduce RS-232 inputs (which may be as high as ± 25 V), to standard

5 V TTL levels. These receivers have a typical threshold of 1.3 V, and a typical hysteresis of

0.5 V.

RS-232 is defined as the“Interface between data terminalequipment and datacommunications equipment usingserial binary data exchange.” Thisdefinition defines data terminalequipment (DTE) as the computer,while data communicationsequipment (DCE)RS-232 SpecificationsTRANSMITTED SIGNALVOLTAGE LEVELS:Binary 0: +5 to +15 Vdc(called a “space” or “on”)Binary 1: -5 to -15 Vdc(called a “mark” or “off”)RECEIVED SIGNALVOLTAGE LEVELS:Binary 0: +3 to +13 VdcBinary 1: -3 to -13 VdcIV. SUPPY UNIT

Initial stage of every electronic circuit is power supplysystem which provides required power to drive the wholesystem. The specification of power supply depends on thepower requirement and this requirement is determined by itsrating. The main components used in supply system are:transformerrectifierinput filter

regulatoroutput filteroutput indicationAT89S52 is an ATMEL controller with the core of IntelMCS-51. It has same pin configuration as give above. TheAT89S52 is a low-power, high-performance CMOS 8-bitmicrocomputer with 8K bytes of Downloadable Flashprogrammable and erasable read only memory and 2K bytes ofEEPROM. The device is manufactured using Atmel’s highdensity nonvolatile memory technology and is compatible withthe industry standard 80C51 instruction set and pin out.The on-chip Downloadable Flash allows the programmemory to be reprogrammed in-system through an SPI serialinterface or by a conventional nonvolatile memoryprogrammer. By combining a versatile 8-bit CPU withDownloadable Flash on a monolithic chip, the Atmel AT89S52is a powerful microcomputer which provides a highly flexibleand cost effective solution to many embedded controlapplications.The AT89S52 provides the following standard features: 8Kbytes of Downloadable Flash, 2K bytes of EEPROM, 256bytes of RAM, 32 I/O lines, programmable watchdog timer,two Data Pointers, three 16-bit timer/counters, a six-vectortwo-level interrupt, a full duplex serial port, on-chip oscillator,and clock circuitry.FeaturesCompatible with MCS-51™Products8K bytes of In-System ReprogrammableDownloadable Flash MemorySPI Serial Interface for Program DownloadingEndurance: 1,000 Write/Erase Cycles4.0V to 5.5V Operating RangeFully Static Operation: 0 Hz to 33 MHz

256 x 8 bit Internal RAM32 Programmable I/O LinesThree 16 bit Timer/CountersEight Interrupt SourcesFull Duplex UART Serial ChannelLow Power Idle and Power Down ModesV. WHAT CAN BE AUTOMATED

Virtually anything in the home/office that is powered byelectricity can be automated and/or controlled. We can controlour electrical devices. We can turn our porch lights on automatically(Fig 4) at darkVII. CONCLUSION

An automated home can be a very simple grouping ofcontrols, or it can be heavily automated where any appliancethat is plugged into electrical power is remotely controlled.Costs mainly include equipment, components, furniture, andcustom installation.Ongoing costs include electricity to run the control systems,maintenance costs for the control and networking systems,including troubleshooting, and eventual cost of upgrading asstandards change. Increased complexity may also increasemaintenance costs for networked devices.Learning to use a complex system effectively may takesignificant time and training.Control system security may be difficult and costly tomaintain, especially if the control system extends beyond thehome, for instance by wireless or by connection to the internetor other networks.VI. FEATURES

A. Password Based Locking SystemIn this system we have ensured a safe locking system. Onseeing from outside the lock would not be visible but thisinbuilt locking system ensures security. This lock can beopened and closed with the help of a password which we will

give using a keypad. The door will only open or close only ifthe password is correct else it will remain in its original state.The lock cannot be broken because to the person standing outside can just see the closed door and not the lock as it isinbuilt. The password is given with the help of controller andcan be changed by simply making a small change in theprogram and then burning the program in the controller.B. Counter dependent automatic switching system ofroomAfter opening the lock when the person enters the room thecounter gets incremented. Now if it is a day then the lightswould not be switched on but if it is dark then the lights willautomatically switch on. Now whatever may be the number ofpeople entering the room the counter will automatically getincremented by itself and on leaving the room the counter willget decremented but the system will keep on working .Once thecounter is zero in other words once everyone leaves the roomthe switching system will automatically stop working.C. Temperature controlled cooling systemOnce the person has entered the room he would not requireto switch on anything everything will just happenautomatically. Like if the temperature is high then the fan willswitch on, on its own. Else it will remain in off state. Thistemperature is predefined by us in the controller. But thissystem will only work if there is a person in the room in otherwords if the counter is not zero.D. Light saving systemThis light saving system is used in two places for internalsection and external section. If a person is not at home orsitting inside the room and it is dark outside then the lights willautomatically get switched on and when its day the light willget switched off. This ensures power saving.E. Fire and Smoke sensor

This part detects any fire or smoke from a fire and set analarm or an indication.