This document describes the design and working of a laser security system. The system uses a laser light beam to cover a large area and trigger an alarm if the beam is interrupted. It lists the required components like an LDR, resistor, transistor, laser pointer, LED, battery, and wiring. The circuit diagram and experimental setup are provided. When the laser beam falls on the LDR, its resistance is low and the alarm is inactive. If an object interrupts the beam, the LDR resistance increases and triggers the transistor to activate the buzzer alarm. Advantages are it provides contactless security and can be used for theft detection and other applications.

1. LASER
SECURITY
SYSTEM

2. Content
Introduction
Components/Materials Required
Circuit Diagram
Experimental Setup
Working
Uses of Laser Security System
Advantages of Laser Security System
Conclusion

3. Security is the most important factor today.
Technology develops day by day in the world.
The crime gang also improves their technology
to perform their operation.
So technology of security should modern with
time to protect the crime works. We decided to
make a laser security system project as our
project. In this project we have used the laser
light to cover a large area.
We know laser light goes through long distance
with out scattering effect. It’s also visible at
source and at incident point, otherwise invisible.
INTRODUCTION:

4. These two properties helps us to build
up a modern security system, which
may name as “laser security”.
When any person or object or cross
over the laser line the security alarm
will ring and also the focus light will
“on” to focus the entrance of
unauthorised person. We can make a
security boundary of single laser light
by using mirror at every corner for
reflection.

5. Components/Materials Required :
1.Breadboard : A breadboard also known as
protoboard is a type of solder less electronic circuit
building. You can build a electronic circuit on the
breadboard without any soldering !Best of all it is
reusable
2.LDR : A photo resistor is also called light dependent
resistor or photocell is a light controlled variable
resistor. The resistance of a photo resistor decreases
with increasing incident light intensity in other words,
it exhibits photoconductivity

6. 3.Resistor: A resistor is an electrical component that
limits or regulates the flow of electrical current in an
electric circuit. Resistors can also be used to provide a
specific voltage for an active device such
as an transistor.
4.NPN Transistor : NPN is one of the two types of
bipolar transistor consisting of a layer of
P-doped semiconductor(the “base”)
between two N-doped layers. A small
current entering the base is amplified
to produce a large collector and
emitter current.

7. 5.Laser Pointer : A laser pointer or laser
pen is a small handheld device with a
power
source and a laser diode
emitting a very narrow
coherent low powered
laser beam of visible light.
6.LED : A light emitting device emits
visible light through it.

8. 7.Battery : A container consisting of
one or more cells, in which chemical
energy
is converted into electricity
and used as a source of power.
8.Wire : Metal drawn out
into the form of a thin
flexible thread or rod.

9. 9.Buzzer: An electrical device
that makes a buzzing noise
and is used for signaling.
10.Battery clip: It is used to connect the
battery terminals.
11.Capacitor: A device used to store an
electric charge, consisting of one or more
pairs of conductors separated by an
insulator.

10. Circuit Diagram:

11. Experimental setup
:
Connect a photocell to a 5K resistor.This will pick
up the laser light and enable the alarm.
Use a 2N7000 transistor to link the resistor. The
attached schematic should demonstrate how the
parts come together. Use a breadboard to hold
them in place and make sure the board is small
enough to fit into a project box. Do not connect the
battery yet.
Use tape, glue or strips to Velcro to mount the
project box on either side of the door you wish to
protect.
Connect a 9V battery to the first project box and
replace it in the exact position is was in.
Turn the laser on with the toggle switch and make
sure it lines up perfectly with the photo cell.The
alarm is now activated. If any thing breaks the
beam, the siren will go off.

13. Working:
This circuit is based on LDR(Light
Depended Resistor),variable resistor
in which the resistance varies
according to the light intensity falling
on it.
LDR and resistor R1 forms a potential
driver network which is the main part
of our security alarm circuit.
We have already discussed about
how transistor acts as a switch, the
same principle is used here.

14. The voltage drop across the LDR is used t drive the
transistor switch. When the voltage drop is above cut in
voltage(0.6v),the transistor is turn ON.
LDR has low resistance in the presence of light and high
resistance in the absence of light.
In our security alarm, a laser light is allowed to fall on the
LDR continuously using 3 mirrors.
Light from another source should not allowed to fall on
the LDR, so place the LDR in a box with a single hole to
pass laser.
In this situation the resistance offered by LDR is too low.
Since the LASER light is continuously
In this situation the resistance offered by LDR is too low
.Since the LASER light is continuously allowed to fall on
the LDR surface.

15. Thus the voltage drop across the LDR is also low
When a person makes a blocks to the
continuously
[V=IR(Ohm’s Law)] which is insufficient to turn
ON the transistor, so the transistor remains off
state.
flow of LASER beam, then the light falling on
the LDR gets blocked. This its increases to a
high value in the order of M ohm range
(according to the
Ohm’s Law V=IR)

16. While resistance increases voltage drop also
Then current from vice starts flowing to
ground via
The beep sound from the security alarm gives
the
increases when this voltage drop exceeds
cut in voltage of silicon NPN
transistor(2N7000) it will
turn ON.
the buzzer and transistor, which makes the
beep
sound.
indication of some security failures.

17. Uses
& Advantages of laser
security system :
1) Laser security system locks working:
Laser door alarm is based on the
interruption of laser beam. The laser
pointer is used as the source of light
beam.
2) Laser system:
Laser technology products
will calculate distance by
measuring the time of flight of
very short infrared light

18. 3) Theft detection by laser system:
It can be design as a simple
electronic project for demonstration in
science exhibition. It can also be made
as a mini or major project for electrical
or electronic students.

19. 4)Other uses of laser system :
The laser security system are
high tech
innovations that have gained
popularity in home and office security
system.

20. Conclusion:
1)Home security is rapidly growing field and there
are
new & improved burglar alarms popping up
every
day.
2)With rapid advancement of technology the field
is
turning out to be an area full of scope and
new
changes can be made to make it’s more
efficient.
3) It has years to come, because security is of
prime
importance to one and all.

21. Thank
You

22. ~Thank You~.......