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Home Security System Using Cell Phone The project is about a home security system in which a cell phone is used as a device that will alert the owner

of the house when an intruder enters the house.The owner just have to turn on the system before leaving his

house.When an intruder enters the house in the absence of the owner the owner receives a call from a

registered number which is the phone number of the haced mobile phone at his!her house.Cell phones haveswitches which when pressed short the terminals "gold plated# hence a number is seen on the screen

so what i have done is put my cell phone number on speed dial on the phone i haced and when this number i

 pressed for a while i get a call.so basically what we r doing is a circuit that will short the phone terminals. when a intruder enters the house.

$C %&'() is a dual op amp.

The output of an op amp is difference of the input times the gain of the op amp. ie. it compares the * inputs. +,T- refer datasheet for more details about the $C.

 pin * of $C '() is threshold a potentiometer is connected to it so it forms a voltage divider and a particular

voltage is set up at pin * which the op amp compares with voltage at pin '.

to pin ' an %/0 is connected it behaves in following way.1# when light shines on %/0 its resistance decreases hence a more positive voltage is set up at pin ' which

forces the output to be high.hence there is a potential difference at the terminals of the number on the cell

 phone.

*#when the light is cut off by the door which is opened by the intruder the %/0 resistance increases hence amore negative voltage is set up at pin ' which forces output to be low "2v#.

in the e3uivalent op amp circuit shown 4vid is appro5imately 2v when output is low and resistance 0o is verysmall hence the output is shorted to the ground thus shorting the * terminals of the cell phone.

 aterials (electronic components) required

1# 4 Cellphone having press buttons "i used an old one which i had#.

*# 4 126 ohm resistor.

'# 4 126 ohm potentiometer.7# 4n %/0 "%ight /ependent 0esistor# 126 ohm or 4 * legged $0 sensor "$0 sensors are better bco8

they are not affected by surrounding light#.

(# 4n %&'() "/ual op94mp# $C.

:# 4n ,ptical %4S-0 "$ used a red %4S-0#. $n case you are using $0 sensors use an $0 %4S-0.;# wires.

The cell phone i used is an old noia phone.0emove the battery then remove the front cover then the eypad an then the transparent cover over the eys.

<ou will see a thin white film on the ey terminals dont worry just remove this film using forceps but

remember only cut the film on a single ey from 2 to =. $ just pulled it out in e5citement and now i have problems starting the device i have to manually start it by shorting the terminals using any metallic object.

$nsert the battery bac into the cell phone and turn it on.

$ wanted to use ey ' for the speed dial so i was checing the terminals on ey '.

Put a multimeter on dc voltage measurement then touch the probes to the * terminals on the ey then reversethe probes on the ey terminals either way the multimeter will show a reading but it will show >ve /C voltag

when the probes are on correct 9ve ?>ve terminals.$n my case the inner one was positive and the outer one negative.Solder a red wire to the >ve terminal and a blac wire to the 9ve terminal.

4ccording to the circuit diagram solder the circuit.a small dotted board is enough as there are hardly any

components. +,T- the circuit remains same if a * legged $0 sensor is used.

Solder the red wire from the cell phone ey to the output of the op9amp $C ie. at pin 1 and the blac wire to th

ground.

Solder the %/0 to a small piece of board and solder wires to it "%/0 does not have polarity so it can beconnected any way to the main board#.

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Place the sensor and %4S-0 on opposite sides of a door.focus the %4S-0 on the Sensor such that %4S-0 falls on the sensor when door is closed and it is cut off from

the sensor when door is open.

$nsert any active sim card into the cell phone and register its number on your cell phone as @security@ or

anything you lie.insert the battery and turn the cell phone on.turn on the power supply to the circuit.

Extending the circuit

4ny intruder will never come through a given door so every door in the house needs this circuit.

the main boards will increase the times you have doors and the output of each and every op amp should be 4+/@ed "connected to inputs of 4+/ gate "/igital $C ;72)# and the final output should be connected

to the mobile >ve terminal so only 1 cell phone is re3uired.http://www.instructables.com/id/Home-Security-System-Using-Cell-Phone/?ALLS!PS

L"#$% - Single Supply 'ual (perational Ampli)iers

Utili8ing the circuit designs perfected for Auad

,perational 4mplifiers? these dual operational amplifiersfeature low power drain? a common mode input voltage

range e5tending to ground!B--? and single supply or split

supply operation. The %&'() series is e3uivalent to

onehalf of an %&'*7.These amplifiers have several distinct advantages over

standard operational amplifier types in single supply

applications. They can operate at supply voltages as low

as '.2 B or as high as '* B? with 3uiescent currents about

onefifth of those associated with the &C1;71 "on a per 

amplifier basis#. The common mode input range includes

the negative supply? thereby eliminating the necessity for 

e5ternal biasing components in many applications. The

output voltage range also includes the negative power 

supply voltage.

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