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Abstract
The door security alarm circuit gives an audio visual alarm when somebody enters from
a door. This project can also be used in locker and almirah door. This circuit is based on
operational amplifier LM741 and L!. "n op#amp produces an output voltage that is
hundreds of thousands times larger than the voltage difference between its input
terminals.
LM741 is a $ pin %& that works as a single operational amplifier circuit' it(s pin diagram is
shown below)
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&ontents *age +o.
List of ,igures -
1.1 %ntroduction
1./ *roject escription 7
1.0 &ircuit esign $
1.4 chematic esign 2
1.- 3orking 1
1. 5ardware escription 1/
/.1 %ntroduction 12
/./ *roject escription 12
/.0 &ircuit esign /
/.4 chematic esign /1
/.- 3orking //
/. 5ardware escription /4!eferences /$
"ppendices /2
4
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L%T 6, ,%8!9
,%8!9 *"9 +6)
&5"*T9! :%
1.1 *ower upply 7
1./ &ircuit iagram $
1.0 chematic iagram of project 2
1.4 %nput "& ;oltage 1
1.- & 6utput ;oltage 1
1. ,iltered ;oltage 11
1.7 6utput ;oltage 11
1.$ Transformer 10
1.2 iodes 14
1.1 &apacitor 1-
1.11 ;oltage !egulator 17
&5"*T9!#%%
/.1 ecurity "larm /
/./ &ircuit iagram /
/.0 chematic iagram of project /1
/.4 Low ;oltage rop //
/.- 5igh ;oltage rop /0
/. "larm *ath /0
/.7
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&5"*T9!#%
1.1 %+T!68&T%6+
%ntroduction
"lso called a power supply unit or PSU ' the component that supplies power to a
computer. Most personal computers can be plugged into standard electrical outlets. The
power supply then pulls the re>uired amount of electricity and converts the "& current to
& current. %t also regulates the voltage to eliminate spikes and surges common in most
electrical systems. +ot all power supplies' however' do an ade>uate voltage#regulation
job' so a computer is always susceptible to large voltage fluctuations.
*ower supplies are rated in terms of the number of watts they generate. The more
powerful the computer' the more watts it can provide to components.
" power supply is a device that supplies electric power to an electrical load. The term is
most commonly applied to electric power converters that convert one form of electrical
energy to another' though it may also refer to devices that convert another form of energy
?mechanical' chemical' solar@ to electrical energy. " regulated power supply is one that
controls the output voltage or current to a specific valueA the controlled value is held
nearly constant despite variations in either load current or the voltage supplied by the
power supply(s energy source.
9very power supply must obtain the energy it supplies to its load' as well as any energy it
consumes while performing that task' from an energy source. epending on its design' a
power supply may obtain energy from)
9lectrical energy transmission systems. &ommon eBamples of this include power
supplies that convert "& line voltage to & voltage.
9nergy storage devices such as batteries and fuel cells.
9lectromechanical systems such as generators and alternators.
olar power.
" power supply may be implemented as a discrete' stand#alone device or as an integraldevice that is hardwired to its load. 9Bamples of the latter case include the low voltage
& power supplies that are part of desktop computers and consumer electronics devices.
&ommonly specified power supply attributes include)
The amount of voltage and current it can supply to its load.
5ow stable its output voltage or current is under varying line and load conditions.
5ow long it can supply energy without refuelling or recharging ?applies to power
supplies that employ portable energy sources@.
6
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1./ *!6C9&T 9&!%*T%6+
%+T!68&T%6+
" regulated power supply is an embedded circuitA it converts unregulated "& into a
constant &. 3ith the help of a rectifier it converts "& supply into &. %ts function is to
supply a stable voltage ?or less often current@' to a circuit or device that must be operated
within certain power supply limits. The output from the regulated power supply may be
alternating or unidirectional' but is nearly always & ?irect &urrent@.
The type of stabili=ation used may be restricted to ensuring that the output remains within
certain limits under various load conditions' or it may also include compensation for
variations in its own supply source. The latter is much more common today.
The door security alarm circuit gives an audio visual alarm when somebody enters froma door. This project can also be used in locker and almirah door. This circuit is based onoperational amplifier LM741 and L!. "n op#amp produces an output voltage that ishundreds of thousands times larger than the voltage difference between its input terminals
"pplications
.&. variable bench supply ?a bench power supply usually refers to a power supply
capable of supplying a variety of output voltages useful for bench testing electronic
circuits' possibly with continuous variation of the output voltage' or just some pre#set
voltagesA a laboratory ?lab@ power supply normally implies an accurate bench power
supply' while a balanced or tracking power supply refers to twin supplies for use
when a circuit re>uires both positive and negative supply rails@.
Mobile *hone power adaptors
!egulated power supplies in appliances
;arious amplifiers and oscillators
,ig 1.1 *ower upply
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1.0 &%!&8%T 9%+
,ig 1./ : &ircuit esign of *ower upply ystem
&ircuit consists of 4 parts) tep down transformer' 4 diodes' resistor' capacitor filter D
voltage regulator %&.
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1.4 &59M"T%& 9%+
,ig 1.0 chematic ;iew of *ower upply
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1.- 36!E%+
&ircuit consists of 4 parts) tep down transformer' bridge rectifier' capacitor filter
and voltage regulator %&.
The transformer step downs the high voltage "& to a low voltage "&.
,ig 1.4 %nput ;oltage
uring the positive half cycle of secondary voltage' diodes / and 0 are forward
biased and diodes 1 and 4 are reverse biased' now the current flows through
/: FLoad:F0
uring the negative half cycle of the secondary voltage' diodes 1 and 4 are
forward biased and diodes / and 0 are reverse biased +ow the current flows
through 4:FLoad:F1
%n both the cycles load current flows in same direction' hence we get a pulsating
& voltage across the points
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The pulsating content are called ripples and a filter capacitor is used to remove the
ripples from pulsating &.
3hen the instantaneous values of pulsating & voltage increases' the capacitor
gets charged up to peak value of the input.
3hen the instantaneous values of pulsating & voltage decreases' the stored
voltage in the capacitor reverse biases the diodes / and 4. 5ence it will not
conduct' now capacitor discharges through the load. Then voltage across the
capacitor decreases.
uring the neBt cycle' when the peak voltage eBceeds the capacitor voltage' diode /
or 4 forward biases accordingly' as a result capacitor again charges to the peak
value. This process continues. 5ence we get almost smooth & voltage as shown.
Fig 1.6 Brown color indicates pulsating DC and Red color is the filtered DC voltage.
Then the filtered voltage is applied to the input of 7$- voltage regulator %&' it in
turn regulates the voltage for line and load fluctuations.
,ig 1.7 6utput ;oltage
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1. 5"!3"!9 9&!%*T%6+
1..1 &6M*6+9+T !9H8%!9
1. tep down transformer ?%& @.
/. iodes B 4 ?1+41 for low power 1+47 for moderate power@
0. &apacitor ?1I,@
4. ;oltage regulator
1../ %&!%*T%6+ 6, 9"&5 &6M*6+9+T
Transformer
,ig 1.$ Transformer
" transformer is an electrical device that transfers energy between two circuits through
electromagnetic induction. " transformer may be used as a safe and efficient voltage
converter to change the "& voltage at its input to a higher or lower voltage at its output.
6ther uses include current conversion' isolation with or without changing voltage and
impedance conversion.
" transformer most commonly consists of two windings of wire that are wound around a
common core to provide tight electromagnetic coupling between the windings. The core
material is often a laminated iron core. The coil that receives the electrical input energy is
referred to as the primary winding' while the output coil is called the secondary winding.
"n alternating electric current flowing through the primary winding ?coil@ of a transformer
generates a varying electromagnetic field in its surroundings which causes a varying magnetic
fluB in the core of the transformer. The varying electromagnetic field in the vicinity of the
secondary winding induces an electromotive force in the secondary winding' which appears a
voltage across the output terminals. %f a load impedance is connected
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across the secondary winding' a current flows through the secondary winding drawing
power from the primary winding and its power source.
" transformer cannot operate with direct currentA although' when it is connected to a &
source' a transformer typically produces a short output pulse as the current rises.
Transformers perform voltage conversionA isolation protectionA and impedance matching.
%n terms of voltage conversion' transformers can step#up voltageJstep#down current from
generators to high#voltage transmission lines' and step#down voltageJstep#up current to
local distribution circuits or industrial customers. The step#up transformer is used to
increase the secondary voltage relative to the primary voltage' whereas the step#down
transformer is used to decrease the secondary voltage relative to the primary voltage.
Transformers range in si=e from thumbnail#si=ed used in microphones to units weighing
hundreds of tons interconnecting the power grid. " broad range of transformer designs are
used in electronic and electric power applications' including miniature' audio' isolation'
high#fre>uency' power conversion transformers' etc.
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%69
,ig 1.2 iode
tructure of a vacuum tube diode. The filament may be bare' or more commonly ?as
shown here@' embedded within and insulated from an enclosing cathode.
%n electronics' a diode is a two#terminal electronic component with asymmetricconductanceA it has low ?ideally =ero@ resistance to current in one direction' and high?ideally infinite@ resistance in the other. " semiconductor diode' the most common typetoday' is a crystalline piece of semiconductor material with a p:n junction connected to
two electrical terminals.K-
" vacuum tube diode has two electrodes' a plate ?anode@ and a
heated cathode. emiconductor diodes were the first semiconductor electronic devices.The discovery of crystals( rectifying abilities was made by erman physicist ,erdinand
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a forward#biased diode varies only a little with the current' and is a function of
temperatureA this effect can be used as a temperature sensor or voltage reference.
emiconductor diodes( current:voltage characteristic can be tailored by varying the
semiconductor materials and doping' introducing impurities into the materials. These are
eBploited in special#purpose diodes that perform many different functions. ,or eBample'diodes are used to regulate voltage ?Nener diodes@' to protect circuits from high voltage
surges ?avalanche diodes@' to electronically tune radio and T; receivers ?varactor diodes@'
to generate radio fre>uency oscillations ?tunnel diodes' unn diodes' %M*"TT diodes@'
and to produce light ?light emitting diodes@. Tunnel diodes eBhibit negative resistance'
which makes them useful in some types of circuits.
&apacitor
,ig 1.1 &apacitor
" capacitor ?originally known as a condenser@ is a passive two#terminal electrical
component used to store energy electrostatically in an electric field. The forms of
practical capacitors vary widely' but all contain at least two electrical conductors ?plates@
separated by a dielectric ?i.e.' insulator@. The conductors can be thin films of metal'
aluminium foil or disks' etc. The (non#conducting( dielectric acts to increase the
capacitor(s charge capacity. " dielectric can be glass' ceramic' plastic film' air' paper'
mica' etc. &apacitors are widely used as parts of electrical circuits in many common
electrical devices. 8nlike a resistor' a capacitor does not dissipate energy. %nstead' a
capacitor stores energy in the form of an electrostatic field between its plates.
3hen there is a potential difference across the conductors ?e.g.' when a capacitor is
attached across a battery@' an electric field develops across the dielectric' causing positive
charge ?OH@ to collect on one plate and negative charge ?#H@ to collect on the other plate.
%f a battery has been attached to a capacitor for a sufficient amount of time' no current can
flow through the capacitor. 5owever' if an accelerating or alternating voltage is applied
across the leads of the capacitor' a displacement current can flow.
"n ideal capacitor is characteri=ed by a single constant value for its capacitance.
&apacitance is eBpressed as the ratio of the electric charge ?H@ on each conductor to the
potential difference ?;@ between them. The % unit of capacitance is the farad ?,@' which
is e>ual to one coulomb per volt ?1 &J;@. Typical capacitance values range from about 1 p, ?1
P1/ ,@ to about 1 m, ?1
P0 ,@.
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;6LT"9 !98L"T6!
,ig 1.11 ;oltage !egulator
" voltage regulator is designed to automatically maintain a constant voltage level. " voltage
regulator may be a simple Rfeed#forwardR design or may include negative feedback control
loops. %t may use an electromechanical mechanism' or electronic components. epending on
the design' it may be used to regulate one or more "& or & voltages.
9lectronic voltage regulators are found in devices such as computer power supplies where
they stabili=e the & voltages used by the processor and other elements. %n automobile
alternators and central power station generator plants' voltage regulators control theoutput of the plant. %n an electric power distribution system' voltage regulators may be
installed at a substation or along distribution lines so that all customers receive steady
voltage independent of how much power is drawn from the line.
The output voltage can only be held roughly constantA the regulation is specified by two
measurements)
Load regulation is the change in output voltage for a given change in load current
?for eBample) Rtypically 1- m;' maBimum 1 m; for load currents between -
m" and 1.4 "' at some specified temperature and input voltageR@.
line regulation or input regulation is the degree to which output voltage changeswith input ?supply@ voltage changes # as a ratio of output to input change ?for
eBample Rtypically 10 m;J;R@' or the output voltage change over the entire
specified input voltage range ?for eBample Rplus or minus /S for input voltages
between 2 ; and / ;' -# 5=R@.
6ther important parameters are)
Temperature coefficient of the output voltage is the change with temperature
?perhaps averaged over a given temperature range@.
%nitial accuracy of a voltage regulator ?or simply Rthe voltage accuracyR@ reflects
the error in output voltage for a fiBed regulator without taking into accounttemperature or aging effects on output accuracy.
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ropout voltage is the minimum difference between input voltage and output
voltage for which the regulator can still supply the specified current. " low drop#
out ?L6@ regulator is designed to work well even with an input supply only a
volt or so above the output voltage. The input#output differential at which the
voltage regulator will no longer maintain regulation is the dropout voltage. ,urther
reduction in input voltage will result in reduced output voltage. This value isdependent on load current and junction temperature.
"bsolute maBimum ratings are defined for regulator components' specifying the
continuous and peak output currents that may be used ?sometimes internally
limited@' the maBimum input voltage' maBimum power dissipation at a given
temperature' etc.
6utput noise ?thermal white noise@ and output dynamic impedance may be
specified as graphs versus fre>uency' while output ripple noise ?mains RhumR or
switch#mode RhashR noise@ may be given as peak#to#peak or !M voltages' or in
terms of their spectra.
Huiescent current in a regulator circuit is the current drawn internally' not
available to the load' normally measured as the input current while no load isconnected ?and hence a source of inefficiencyA some linear regulators are'
surprisingly' more efficient at very low current loads than switch#mode designs
because of this@.
Transient response is the reaction of a regulator when a ?sudden@ change of the
load current ?called the load transient @ or input voltage ?called the line transient @
occurs. ome regulators will tend to oscillate or have a slow response time which
in some cases might lead to undesired results. This value is different from the
regulation parameters' as that is the stable situation definition. The transient
response shows the behaviour of the regulator on a change. This data is usually
provided in the technical documentation of a regulator and is also dependent on
output capacitance.
Mirror#image insertion protection means that a regulator is designed for use when
a voltage' usually not higher than the maBimum input voltage of the regulator' is
applied to its output pin while its input terminal is at a low voltage' volt#free or
grounded. ome regulators can continuously withstand this situationA others might
only manage it for a limited time such as seconds' as usually specified in the
datasheet. This situation can occur when a three terminal regulator is incorrectly
mounted for eBample on a *&
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&5"*T9! %% : 9&8!%T "L"!M
*!6C9&T 9&!%*T%6+
/.1 %+T!68&T%6+)
" security alarm is a system designed to detect intrusion : unauthori=ed entry : into a
building or area. ecurity alarms are used in residential' commercial' industrial' and
military properties for protection against burglary ?theft@ or property damage' as well as
personal protection against intruders. &ar alarms likewise protect vehicles and their
contents. *risons also use security systems for control of inmates.
ome alarm systems serve a single purpose of burglary protectionA combination systems
provide both fire and intrusion protection. %ntrusion alarm systems may also be combinedwith closed#circuit television surveillance systems to automatically record the activities of
intruders' and may interface to access control systems for electrically locked doors.
5ave you ever thought about implementing your own home security alarm systemsU %t(s
one of the simplest and interesting circuits for electronic beginners. 6ur new home
security e>uipment uses a L! ?Light epended !esistor@ to detect security problems.
Theft attempt and other security threats can be controlled by using this simple circuit to
improve your security systems.
To implement this alarm system for home' you have to provide an optical path ?with
L"9! beams@ around your home. The L"9! path is made possible with one L"9! torch and 0 mirror arrangements which encloses the whole area.
,ig /.1 ecurity "larm
1
1
2
LDR1
TORCH_LDRB19V
5 0 %
RV1
5k
C10.1uF
R382k
3
2
6
7
4
1
5
U1
LM741
RL14V
B212V
D1LED-GREEN
R1330!"
BU#1
BU##ER
R21k
D2LED-RED
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/./ &%!&8%T %"!"M)
,ig /./ &ircuit iagram
The circuit consists of 4 parts) L!' +*+ Transistor'
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/.0 &5M"T%& %"!"M
,ig /.0 chematic ;iew of ecurity "larm
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/.4 36!E%+)
This circuit is based on L! ?Light epended !esistor@' a variable resistor in
which the resistance varies according to the light intensity falling on it.
The L! and resistor !1 forms a potential divider network' which is the main
part of our security alarm circuit.
3e have already discussed about how transistor acts as a switch' the same
principle is used here.
The voltage drop across the L! is used to drive the transistor switch. 3hen the
voltage drop is above cut in voltage ?.;@' the transistor is turned 6+.
L! has low resistance ?mV range@ in the presence of light and high resistance
?MV range@ in the absence of light.
%n our security alarm' a L"9! light is allowed to fall on the L! continuously
.Light from other sources should not be allowed to fall on the L!' so place the
L! in a boB with a single hole to pass L"9!.
%n this situation' the resistance offered by L! is too low' since the L"9! light
is continuously allowed to fall on the L! surface.
,ig /.4
Thus the voltage drop across the L! is also low K;W%! ?6hmGs law@ which is
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insufficient to turn 6+ the transistor' so the transistor remains in 6,, state.
3hen a person ?eg) thief@ makes a block to the continuous flow of L"9! beam'
then the light falling on the L! gets blocked. Thus its resistance increases to a
high value in the order of MV range ?"ccording to 6hmGs law ;W%!@.
,ig /.-
3hile resistance increases the voltage drop also increases' when this voltage drop
eBceeds the cut in voltage of the silicon +*+ transistor ?.;A
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/.- 5"!3"!9 9&!%*T%6+
/.-.1 L%T 6, &6M*6+9+T
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/.@ !esistor)
" resistor is a passive two#terminal electrical component that implements electrical
resistance as a circuit element. The current through a resistor is in direct proportion to thevoltage across the resistor(s terminals. This relationship is represented by 6hm(s law)
3here % is the current through the conductor in units of amperes' $ is the potential
difference measured across the conductor in units of volts' and R is the resistance of the
conductor in units of ohms. The ratio of the voltage applied across a resistor(s terminals to
the intensity of current in the circuit is called its resistance' and this can be assumed to be
a constant ?independent of the voltage@ for ordinary resistors working within their ratings.
!esistors are common elements of electrical networks and electronic circuits and are
ubi>uitous in electronic e>uipment. *ractical resistors can be made of various compounds
and films' as well as resistance wire ?wire made of a high#resistivity alloy' such as nickel#
chrome@. !esistors are also implemented within integrated circuits' particularly analogue
devices' and can also be integrated into hybrid and printed circuits.
1-
,ig /.$ !esistor
25
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0.@ L!)
"n L! ?Light dependent resistor@' as its name suggests' offers resistance in response to
the ambient light. The resistance decreases as the intensity of incident light increases' and
vice versa. %n the absence of light' L! eBhibits a resistance of the order of mega#ohms
which decreases too few hundred ohms in the presence of light. %t can act as a sensor'
since a varying voltage drop can be obtained in accordance with the varying light. %t is
made up of cadmium sulphide ?&d@.
,ig /.2 L!
4.@ Transistor)
" transistor is a semiconductor device used to amplify and switch electronic signals
and electrical power. %t is composed of semiconductor material with at least three
terminals for connection to an eBternal circuit. " voltage or current applied to one pair
of the transistor(s terminals changes the current through another pair of terminals.
uitous in modern electronic
systems. ,ollowing its development in the early 12-s' the transistor revolutioni=ed the
field of electronics' and paved the way for smaller and cheaper radios' calculators'
and computers' among other things.
,igure /.1 +*+ vJs *+* Transistor
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-.@
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"bout *roteus
$ *roteus is a great electrical suite for circuit simulation purposes.
$ *roteus is a ;irtual ystem Modeling and circuit simulation application. The suite
combines miBed mode circuit simulation' animated components andmicroprocessor models to facilitate co#simulation of complete microcontroller
based designs.
$ *roteus also has the ability to simulate the interaction between software running
on a microcontroller and any analog or digital electronics connected to it.
6verview of *roteus
Future Scope:-
%t will implement in every home so that our country will secure and theft in our country
will be less.
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!9,!9+&9
www.circuitsgallery.com
oogle
www.en.wikipedia.org
www.engineersgarage.com
www.electroskan.wordpress.com
www.datasheetarchive.com
www.youtube.com
;arious other books and maga=ines
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"**9+%&9
%9L9&T!%&) " capacitor consists of two conductors separated by non#
conductive regions. The non#conductive region is called dielectric
!9&T%,%9!) %t is combination of diodes used to rectify an "& signal into a &
one.
T!"+,6!M9!) This device is used to vary the amplitude of a signal used in
almost all the home appliances.
9M%&6+8&T6!) " solid substance that has a conductivity between
that of an insulator and that of most metals, either due to the addition
of an imurity or because of temerature e!ects"
,%LT9!) " filter circuit is an electronic circuit made using capacitors and
inductors.