OBJECTIVE The objective of the project is to

design a home security system which detects presence of intruders, occurrence of fire as well as power failure and alerts the user through the use of short messaging service (SMS) of mobile phones.

BLOCK DIAGRAM

Microcontroller

LCD 16*2

Xbee Tx

FireSensor

SmokeSensor

LPG Detector

Line Detector

Leval Sensor

ADC

0808

Microcontroller

LCD 16*2

Xbee Rx

Alarm System

The Zigbee based security system utilizes different modules which act concurrently in order to monitor the domestic situation and alert the resident in case of emergency. A number of different sensor modules are utilized to monitor intruders, fire as well as power failure. The micro-controller module processes the information that it receives from the sensor modules and decides the action to be taken. The LCD, buzzer and Zigbee modules alert the user regarding the emergency situation. The output of these three modules depends on the micro-controller module.

MODULES

SENSOR MODULEThe sensor module consists of a group of

sensor for monitoring different parameters. FIRE SENSOR UNIT ELECTRIC FAILURE

DETECTOR UNIT INTRUDER UNIT

DISPLAY MODULE The display module is used to display

the electrical information so that it can be easily understood by the user. A 16*2 Liquid Crystal Display is used as the display module in the system. It provides status updates to the user so that the user is aware whether the system is in “monitoring” state or it has detected some emergency situation

Zigbee MODULEZigbee MODEM- it transmit the signal on

receiving a microcontroller command to the specified zigbee Reciever.

LINE DRIVER- it converts the TTL logic into RS 232 logic. The PC connectors are used to get and send the information through PCs’ ports.

CONTROLLER MODULEMicrocontroller is used to monitor all the

operations in the system.It is a 40 pin IC. It takes the information and

performs operation according to present information.

In 40 pin AT89C51, there are four ports designated as P1, P2, P3 and P0. All these ports are 8-bit bi-directional ports, i.e., they can be used as both input and output ports. These ports are also bit addressable and so their bits can also be accessed individually.

OPERATIONThe system is connected to a power supply sytemAs soon as the connection are completed, the

Zigbee modem sends a Signal to the user stating “System On”.

At the same time, the LCD displays a welcome screen stating” xbee based Security System”

After that, the LCD displays a status message "Monitoring”. During this time, the system is monitoring the status of all the sensors but has not yet encountered an emergency condition

When any sensor detects an emergency state, for example, if there is an occurrence of fire, the thermistor sends a signal to the MCU

POWER SUPPLYA power supply can by broken down into a series of blocks, each of which performs a particular function. In this project, we are generating a 5V power supply .

SENSOR MODULEFIRE ALARM In this fire alarm circuit, a thermistor works as

the heat sensor. When temperature increases, its resistance decreases, and vice versa. At normal temperature, the resistance of the thermistor is approximately 10 kilo-ohms, which reduces to a few ohms as the temperature increases beyond 100°C. When thermistor becomes hot, it provides a low-resistance path to extend positive voltage to the base of transistor via diode and resistor.

Diode provides a high-resistance (10-kilo-ohm) path when the thermistor connected to the positive supply cools down. It also stops the conduction of transistor. The circuit works off a 6V-12V regulated power supply. LED is used to indicate that power to the circuit is switched on.

POWER FAILURE DETECTION The power failure alarm circuit that produces

an alarm whenever the mains supply fails . In this circuit, when power failure occurs, a pulse is sent to the P2.0 of the microcontroller unit which in turn perform the task of turning on the buzzer and at the same time displaying message on LCD. In Addition to this, a signal is sent to GSM modem to send a message to a remote mobile that power failure has occurred.

LCDThe 44780 standard requires 3 control lines as

well as either 4 or 8 I/O lines for the data bus. The user may select whether the LCD is to operate with a 4-bit data bus or an 8-bit data bus. If a 4-bit data bus is used the LCD will require a total of 7 data lines (3 control lines plus the 4 lines for the data bus). If an 8-bit data bus is used the LCD will require a total of 11 data lines (3 control lines plus the 8 lines for the data bus).

The three control lines are referred to as EN, RS, and RW

LCD and MICROCONTROLLER INTERFACINGWe have used an 8-bit data bus and is using 11of the 8051's I/O pins to interface with the LCD.

Zigbee MODULEThe Zigbee modem is a highly flexible plug and

play quad band Zigbee modem for direct and easy integration to RS232. Supports features like Voice, Data/Fax, SMS, GPRS and integrated TCP/IP stack. Here sms feature of Zigbee modem is used.

INTERFACES:-RS-232 through D-TYPE 9 pin connector, Serial

port baud rate adjustable 1200 to115200 bps (9600 default)

Power supply through DC socket SMA antenna connector Push switch type SIM holder LED status of Zigbee / GPRS module

CONNECTING Zigbee MODEMInsert SIM card: Press the yellow pin to remove

the tray from the SIM cardholder. After properly fixing the SIM card in the tray, insert the tray in the slot provided.

Connect Antenna: Screw the RF antenna on the RF cable output provided.

Connect RS232 Cable: (Cable provided for RS232 communication) Default baud rate is 9600 with 8-N-1, no hardware handshaking. Cable provided has pins 7 and 8 shorted that will set to no hardware handshaking. In you need hardware handshaking the pins 7-8 can be taken for signaling.

MAX232 INTERFACE

8051 ARCHITECTURE

FUTURE SCOPEThe idea can be implemented to monitor all

the devices inside the house .Using network interface all the houses in a

city can be linked to a common database of the local authorities and any breach can be detected and appropriate action taken accordingly.

The project can be extended to monitor the power efficiency of each device and calculate the energy requirement in a house.