CHAPTER 1
INTRODUCTION
1.1 AIM OF THE PROJECT:
A alarm is a type of security equipment that can be used to safeguard homes and
property. If we love our home then buying burglar alarm should be our first priority when
moving to a new home. Burglar crimes are continually rising with each passing day. Many have
lost their homes and families through violent burglaries in many countries today. Some have lost
what they considered precious and valuable to them. Things such as jewelry, vehicles, and
clothes are huge investments to many.
During the olden days a watchman would be hired to take care of property and offer needed
security in the home. Some homes also had fierce dogs that would be let out only at night. The
two were supposed to provide security to our belongings even in the absence of the owner.
However, hiring a watchman was not an effective method since most of them would be killed in
the line of duty. Sometimes dogs would attack even visitors while some watchmen looted
property. This led to the development of alarm equipments.
1.2 ABOUT THE CICUIT:
The circuit is divided into two parts i.e. the transmitter and the receiver part
Transmitter point:
The tranmitter circuit is othing but a laser diode driven by a battery connected to the
diode through a series resistance R1. In order to ensure that the current through the diode
remains constant irrespective of drop in battery voltage, a 3-terminal voltage regulator VR-1 has
bee used. This regulator produces a constant 5V output as long as input remains equal to or more
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than 7.5V thus ensuring a constant drive current for the laser diode. The drive current in this case
would be(3500/47) mA.
The laser diode here can be the one typically used in laser pointers emitting in red. This would be
more economical than buying one. If the experiment so desires, we can use the laser pointer itself
as a complete transmitter circuit. The pointer has in-built suitable series resistance and an
ON/OFF switch and a battery. The given circuit would help when we want to go a step further
and want to use infrared laser diode so as to get an invisible laser beam, which would be a
requirement in any intruder alarm system, I recommend the use of laser pointer for the purpose
of learning and demonstration.
Receiver part:
The receiver part basically comprises of a current to voltage converter section
configured around IC1(OP AMP 356) feeding a positive edge triggered monoshot configuration
buit around IC2(555 timer). The output of the monoshot feeds a buzzer that gives an audio beep
during the time it get a high input from the timer IC 555. The receiver section operates from +5V
DC generated from another 9V battery and 3 terminal regulator VR2. The battery can be
connected to the circuit through switch SW2
The current-to-voltage converter section converts the photocurrent produced by the photodiode
PD1 as a result of laser light falling on it into an equivalent vltage across resistor R2. This
voltage gets amplified bya factor of 23 in the non-inverting amplifier provided by an OP-AMP
and resistors R3,R4. So, when the laser light is falling on the photodiode, the opamp output is
same DC voltage, The component values have been so chosen as to produce about 5V DC for a
laser power of 0.5mW, typical of a laser pointer. Otherwise the amplifier gain can be adjusted to
produce 5VDC.
1.3 ADVANTAGES OVER COMMERCIAL SECURITY SYSTEMS:
There are dozens of different security systems on the market that utilize lasers and
can effectively protect everything from small apartments and businesses to large areas of
property. Most home laser security systems consist of two parts: a basic alarm unit and an
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infrared motion detector. Laser security systems of the past used to rely on connections wired to
a keypad, requiring the customer to use special codes to arm and disarm the system. Since the
majority of laser security systems are now wireless, the units can be turned on or off with a
wireless remote or, in some models, by touch tone phone from anywhere in the world.
The basic sensing component of a modern laser security system is an infrared motion detector.
An infrared motion detector works by using beams of infrared light to detect changes in heat
which is absent in most of the commercial security systems. Laser alarm systems provides the
state of the art features and benefits of a conventional monitored alarm system. Laser alarm
systems is an advanced and effective security system that does the job right. Laser alarm systems
can be activated in seconds without programming, installation, in-home sales people and
technicians; and with no hassle, mess, or waiting. There are no hidden costs, no on-going service
calls and costs, and Rapid Response Monitoring Service provides the most technologically
advanced monitoring service available. All at a fraction of the cost of other major brands. Laser
alarm systems is perfect for homes, condos, apartments, small offices, and retail stores.
Laser security systems have many advantages. They are simple to install and can be used
effectively inside or outside a home. The systems can be used as a highly effective perimeter
alarm for property boundaries or even for pools, where customers can have the lasers set to
detect when small children come within a set number of feet from the edge of the water. Indoors,
the sensors utilize normal power outlets and telephone jacks; outdoors, the sensors can be hidden
beneath plants and bushes and will not harm lawns or other vegetation. However, laser security
systems can be prohibitively expensive. While some security system plans allow for customers to
target one room, plans that protect large amounts of land or an entire house will cost much more
and can be difficult for many customers to afford .
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CHAPTER 2
BLOCK DIAGRAM AND EXPLANATION
2.1 BLOCK DIAGRAM:
Block diagram
2.2 BLOCK DIAGRAM EXPLANATION
2.2.1 Laser Diode/Pointer:
The laser diode is a laser where the active medium is a semiconductor similar to
that found in a light-emitting diode. The most common type of laser diode is formed from a p-n
junction and powered by injected electric current. In this we are using 593 nm – Yellow-Orange
laser pointers, DPSS. The common wavelengths used are:
375 nm – excitation of Hoechst stain, Calcium Blue, and other fluorescent
dyes in fluorescence microscopy
405 nm – InGaN blue-violet laser, in Blu-ray Disc and HD DVD drives
445 nm – InGaN Deep blue laser multimode diode recently introduced (2010) for use in
mercury free high brightness data projectors
473 nm – Bright blue laser pointers, still very expensive, output of DPSS systems
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485 nm – excitation of GFP and other fluorescent dyes
510 nm - Green diodes recently (2010) developed by Nichia for laser projectors.
532 nm – AlGaAs-pumped bright green laser pointers, frequency doubled 1064 nm Nd:YAG
laser or (more commonly in laser pointers) Nd:YVO4 IR lasers (SHG)
593 nm – Yellow-Orange laser pointers, DPSS
635 nm – AlGaInP better red laser pointers, same power subjectively 5 times as bright as
670 nm one
640 nm – High brightness red DPSS laser pointers
657 nm – AlGaInP DVD drives, laser pointers
670 nm – AlGaInP cheap red laser pointers
760 nm – AlGaInP gas sensing: O2
785 nm – GaAlAs Compact Disc drives
808 nm – GaAlAs pumps in DPSS Nd:YAG lasers (e.g. in green laser pointers or as arrays
in higher-powered lasers)
848 nm – laser mice
980 nm – InGaAs pump for optical amplifiers, for Yb:YAG DPSS lasers
1064 nm – AlGaAs fiber-optic communication
1310 nm – InGaAsP, InGaAsN fiber-optic communication
1480 nm – InGaAsP pump for optical amplifiers
1512 nm – InGaAsP gas sensing: NH3
1550 nm – InGaAsP, InGaAsNSb fiber-optic communication
1625 nm – InGaAsP fiber-optic communication, service channel
1654 nm – InGaAsP gas sensing: CH4
1877 nm – GaSbAs gas sensing: H2O
2004 nm – GaSbAs gas sensing: CO2
2330 nm – GaSbAs gas sensing: CO 2680 nm – GaSbAs gas sensing: CO2
2.2.2 Photo Transistor:
A photodiode is a type of photodetector capable of converting light into
either current or voltage, depending upon the mode of operation.[1] The common, traditional solar
cell used to generate electric solar power is a large area photodiode.
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Photodiodes are similar to regular semiconductor diodes except that they may be either exposed
(to detect vacuum UV or X-rays) or packaged with a window or optical fiber connection to allow
light to reach the sensitive part of the device. Many diodes designed for use specifically as a
photodiode will also use a PIN junction rather than the typical p-n junction.
Materials commonly used to produce photodiodes
2.2.3 Op-Amp LM 356:
The LM356 is a power amplifier designed for use in low voltage consumer
applications. The gain is internally set to 20 to keep external part count low, but the addition of
an external resistor and a capacitor between 1 and 8 will increase the gain to any value up tp 200.
The inputs are grounded referenced while the output is automatically biased to one half the
supply voltage. The quiescent power drain is only 24mW when operating from a 6V supply,
making the LM356 ideal for battery operation.
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MaterialElectromagnetic spectrum
wavelength range (nm)
Silicon 190–1100
Germanium 400–1700
Indium gallium arsenide 800–2600
Lead(II) sulfide <1000 – 3500
Connection Diagram
Applications of LM 356 are Am-FM radio amplifiers, Portable tape player amplifiers,
Intercoms, TV sound system, Line drivers, Ultrasonic drivers, Small servo drivers, Power
converters.
2.2.4 Monostable 555 timer:
The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse
generation and oscillator applications. Depending on the manufacturer, the standard 555 package
includes over 20 transistors, 2 diodes and 15 resistors on a silicon chip installed in an 8-pin mini
dual-in-line package. In the monostable mode, the 555 timer acts as a “one-shot” pulse generator.
The pulse begins when the 555 timer receives a signal at the trigger input that falls below a third
of the voltage supply. The width of the output pulse is determined by the time constant of an RC
network, which consists of a capacitor (C) and a resistor (R). Applications include timers,
missing pulse detection, bouncefree switches, touch switches, frequency divider, capacitance
measurement, pulse-width modulation (PWM) and so on.
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Pin diagram
Graph
2.2.5 Piezo Buzzer:
The piezo buzzer produces sound based on reverse of the piezoelectric effect. The
generation of pressure variation or strain by the application of electric potential across a
piezoelectric material is the underlying principle. These buzzers can be used alert a user of an
event corresponding to a switching action, counter signal or sensor input. They are also used in
alarm circuits.
The buzzer produces a same noisy sound irrespective of the voltage variation applied to it. It
consists of piezo crystals between two conductors. When a potential is applied across these
crystals, they push on one conductor and pull on the other. This, push and pull action, results in a
sound wave. Most buzzers produce sound in the range of 2 to 4 kHz.
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The Red lead is connected to the Input and the Black lead is connected to Ground.
2.2.6 Capacitor:
A capacitor is a passive electronic component consisting of a pair
of conductors separated by a dielectric (insulator). When there is a potential difference (voltage)
across the conductors, a static electric field develops across the dielectric, causing positive
charge to collect on one plate and negative charge on the other plate. Energy is stored in the
electrostatic field. An ideal capacitor is characterized by a single constant value,capacitance,
measured in farads. This is the ratio of the electric charge on each conductor to the potential
difference between them.
Capacitors are widely used in electronic circuits for blocking direct current while
allowing alternating current to pass, in filter networks, for smoothing the output of power
supplies, in the resonant circuits that tune radios to particular frequencies and for many other
purposes.
2.2.7 Resistor:
A linear resistor is a two-terminal, linear, passive electronic component that
implements electrical resistance as a circuit element. The current flowing through a resistor is in
a direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage
applied across resistor's terminals to the intensity of current flowing through the resistor is called
resistance. This relation is represented with a well-known Ohm's law:
2.2.8 Diode:
A p–n junction is formed by joining P-type and N-type semiconductors together in very
close contact. The term junction refers to the boundary interface where the two regions of the
semiconductor meet. If they were constructed of two separate pieces this would introduce a grain
boundary, so p–n junctions are created in a single crystal of semiconductor by doping, for
example by ion implantation, diffusion of dopants, or by epitaxy
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2.2.9 Switch:
A switch is an electrical component that can break an electrical circuit, interrupting
the current or diverting it from one conductor to another.
2.2.10 Battery:
An electrical battery is one or more electrochemical cells that convert stored
chemical energy into electrical energy.In this we are using a 9V battery.
2.2.11 Relay:
A relay is an electrically operated switch. Many relays use an electromagnet to operate
a switching mechanism mechanically, but other operating principles are also used. Relays are
used where it is necessary to control a circuit by a low-power signal (with complete electrical
isolation between control and controlled circuits), or where several circuits must be controlled by
one signal. The first relays were used in long distance telegraph circuits, repeating the signal
coming in from one circuit and re-transmitting it to another. Relays were used extensively in
telephone exchanges and early computers to perform logical operations.
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CHAPTER 3
CIRCUIT DIAGRAM AND OPERATION OF CIRCUIT
3.1 Circuit diagram:
3.2 Operation of the circuit:
The transmitter circuit is nothing but a laser diode (LD1) driven by a 9V PP3
battery. The output of IC1 is regulated 5V as long as its input remains equal to or more than
7.5V, thus ensuring a constant drive current for the laser diode. The battery (Batt1) is connected
to the circuit through switch S1. The laser diode (LD1) can be replaced with a laser pointer
(torch) emitting red laser beam. The laser pointer itself can be used as a transmitter. The pointer
has in-built series resistance, on/off switch and battery. The receiver circuit is basically a current-
to-voltage converter built around IC LM356 (IC3). The output of IC3 is fed to the monostable
built around 555 timer (IC4). The high output of the monostable drives the piezobuzzer to sound
an audio alarm. The receiver section operates off 5V DC generated from another 9V battery and
voltage regulator IC 7805 (IC2). The battery (Batt.2) is connected to the circuit through switch
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S2. When the laser light transmitted through LD1 falls on phototransistor T1, the output of the
op-amp (IC3) at its pin 6 remains high. In this condition, the output of IC4 remains low and the
buzzer does not sound. When the laser beam falling on phototransistor T1 is interrupted by
someone, the output of op-amp IC3 goes low and IC3 produces a pulse. This pulse triggers
monostable IC4 and its output goes high to sound the alarm for a time period of about R8xC8.
Assemble the transmitter and receiver circuits on separate generalpurpose PCBs and enclose in
suitable cabinets. Mount the transmitter and receiver units on opposite pillars of the entrance,
aligning the two such that the laser beam from the transmitter directly falls on the
phototransistor. Block the laser beam with your hand and measure the op-amp output. It should
not be low. At pin 3 of IC4, we should get a positive-going pulse of one-second duration
beginning with high-to-low edge of the trigger pulse appearing at pin 2 of IC4 or collector of
transistor T2.
CHAPTER 4
CONSTRUCTION AND TESTING
4.1 Parts List:
R2, R3 1K,1/4W
R4 22K,1/4W
R5, R7 10K,1/4W
R6 47K,1/4W
R8 1M,1/4W
C3 10uF, 25V
C4, C5, C7 0.1uF
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C6 0.01uF
C8 10uF, 16V
D1 IN4007
Battery 9V
Switches ON/OFF,SPST type
IC 555 Timer
IC OPAMP LM 356
Relay 6V
Buzzer Piezo buzzer
Transistor BC548
Photodiode(PD-1) BPX-65
Laser Diode(LD-1) Laser pointer
4.2 Construction steps:
Connect a phototransistor(T1) to the resistor R2 in series and connect it to the 3rd
pin of the IC LM 356. Connect the resistor R3 to the 2nd pin of IC LM 356. Connect the 4th pin
to the ground. Connect the resistor R4 to the 6th pin in series with the resistor R2. From the 6th
pin connect the capacitor C6, resistor R5, R6, diode D1 to the base of the transistor T2. the
resistor R5 is connected in parallel to diode D1. the collector is connected to the resistor R7. the
capacitor C5 is connected to the pin 7 and 8 of the IC 356 and 555 timer. the collector of T2 is
connected to the pin 2 of 555 timer. The pins 6,7 are connected to resistor R8 and capacitor C8.
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the pin 3 is connected to the piezo buzzer. The pins 4,6,7,8 of 555 timer and pin 7 of LM356 are
connected to the collector of the T1. The pin 1 of 555 timer is connected to the ground and pin 5
is connected to C7 which in turn connected to the ground. The relay is connected to the 555
timer.
4.3 Testing:
Switch on the transistor circuit. Align the transmitter and receiver circuit so that the laser
beam falls on the photodiode. We can use a small transmitter receiver distance, even a
few feet, for the purpose.
If necessary, change the value of one or more resistors(R5,R6,R7) to get a signal peak
magnitude of 2 to 3 V at opamp output.
Block the laser radiation with our hand and again measure the opamp output. It should be
near zero volt.
If we have the services of an oscilloscope, observe the pulse waveforms appearning at
pin-8 of IC-1 and pin-6 of IC-3. At pin-8 of IC-4, we would see a HIGH-to-LOW
transition every time we block the laser beam.
We can observe change in the pitch of the audio beep by changing the frequency of the
signal on the transmitter card.
CHAPTER 5
SPECIFICATION AND APPLICATION
5.1 Specification:
PCB 4x4
593 nm – Yellow-Red laser pointers
Battery 9V
Photodiode BPX-65 or equivalent
PiezoBuzzer
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5.2 Advantages:
Simplicity of installation.
The effective ability to be used indoors and outdoors.
It could be used as an effective alarm for the house/company boundaries.
It uses the normal power outlets and telephone jacks in case it used indoors.
It could be expensive and could be difficult for many customers to afford it.
5.3 Disadvantages:
The disadvantage of laser beamsystem is that it may get activated by a cat walking on
the wall or a large bird sitting on the wall.
They are more expensive compared to simple security alarm systems.
5.4 Applications:
Can be used as home security system
Can be used in Museums, Banks, Offices for safe guard many valuable things.
CHAPTER 6
CONCLUSION
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The Laser Based Intruder Alarm was built to our satisfaction. This project is about
how to prevent theft in homes, offices, banks, museums etc, This project can be implemented by
both wired and wireless technologies. Another application of this instrument is as an "ANTI-
THEFT SYSTEM", that means to protect vehicles from kidnapping. In short I am sure that this
device is highly useful to mankind especially present scenario.
References:
http://www.ieee.org/searchresults/index.html?
cx=006539740418318249752%3Af2h38l7gvis&cof=FORID%3A11&qp=&ie=UTF-8&oe=UTF-
8&q=laser+alarm+systems&siteurl=www.ieee.org%252Findex.html
http://en.wikipedia.org/wiki/Main_Page
http://books.google.com/books?
id=Dx3Mdx_oDHsC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f
=false
http://www.scribd.com
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