i
SNATCH THEFT ALARM SYSTEM
AZLIZA BINTI MUKSIN
Submitted to the Faculty of Electrical Engineering
in partial fulfillment of the requirement for the degree of
Bachelor of Electrical Engineering (Electronics)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
APRIL 2010
ii
I declare that this thesis entitled “Snatch Theft Alarm System” is the result of my
own original writing except the quotation and summaries that cited clearly in the
references.
Signature
: …………………………….
Name
: AZLIZA BINTI MUKSIN
Date
: 23 APRIL 2010
iii
This thesis is dedicated to
My family for their supports
and guide me throughout my academic career
iv
ACKNOWLEDGEMENT
Praise be to Allah for His blessings and giving me the strength along the
journey of completing the project as well as the thesis writing, without it, I would
not been able to come this far. First and foremost, I would like to take this
opportunity to express my deepest gratitude to my project supervisor En Camallil bin
Omar who had presently giving me moral supports and patiently guided me
throughout the entire project. It would be have difficult to complete this project
without the guidance.
My outmost thanks also go to my family who has given me support
throughout my academic years. Not forgetting their eternally moral support and
understanding of my absent from home which is far apart from here while doing this
project.
My special thanks to these individuals, Dr Mohd Nassir (MiCE coordinator)
who has help me with the equipments to program the microcontroller, Dr. Zainul
Abidin Halim (microprocessor lab technicians) who have lending me a helping hand
when dealing with lab facilities and to all my friends who has willingly offered help
despite our tight schedule, thank you from the bottom of my heart. Finally yet
importantly, to those who have, in a way or another contributed to the pleasant
month of my final year project. Your presence and your countless effort and support
had given me strength and great confidence. My fellow friends should also be
recognized for their continual support and encouragement. Thank you.
v
ABSTRACT
The snatch theft alarm system is designed through this project to provide the
personal portable security system. This device can be used especially in personal
protection security system. This project is operated directly after been triggered and
the sound will always active unless the owner insert the mono plug to the mono jack
socket back. The device is small in size, inexpensive and the siren/alarm is active
more than 100 meters. The sound that produces from this device is directly activated
after triggered that not only can attract the public, but also easy to detect the location
of the thief and can save the property. A system is designed so that it can be used as a
personal portable security system and inhibits the bag snatching.
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ABSTRAK
Sistem Penggera Peragut telah dibangunkan melalui projek ini untuk
menyediakan sistem keselamatan peribadi mudah alih. Alat ini boleh digunakan
terutamanya sebagai sistem perlindungan peribadi. Projek ini juga boleh beroperasi
sebaik sahaja input dikesan selain mempunyai saiz yang kecil, murah dan siren atau
bunyi yang terhasil akan aktif serta sentiasa berbunyi sehingga pemiliknya
memasukkan semula „mono plug‟ ke dalam „mono jack socket‟. Bunyi kuat yang
terhasil melalui alat ini bukan sahaja mampu menarik perhatian orang sekeliling
sekiranya berlaku kejadian ragut, malah dapat mengesan lokasi peragut itu selain
dapat menyelamatkan harta benda. Sistem ini direka sebagai sistem keselamatan
peribadi mudah alih dan juga mengelakkan kejadian ragut.
vii
TABLE OF CONTENTS
CHAPTER
TITLE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
CONTENTS
vii
LIST OF TABLES
ix
LIST OF FIGURES
x
LIST OF APPENDICES
CHAPTER 1
PAGE
xii
INTRODUCTION
1
1.1 Background
1
1.2 Objective
3
1.3 Scope of Work
3
1.4 Problem Statements
3
1.5 Summary of Work
6
1.6 Outline of Thesis
7
viii
CHAPTER 2
LITERATURE REVIEW
8
2.1 Overview
8
2.2 Characteristics of Wireless Snatch Theft
Alarm System
CHAPTER 3
CHAPTER 4
8
2.3 Timer 555 (Monostable)
10
2.4 Siren/Alarm Sound
13
2.5 Multisim Software
14
METHODOLOGY
16
3.1 Introduction
16
3.2 Power Supply
20
3.3 Siren/Buzzer
21
3.4 Range Distance
22
RESULTS AND DISCUSSIONS
23
4.1 Multisim Simulation Results
23
4.1.1 Before Snatch (When Mono Plug
Is Inserted)
24
4.1.2 During Snatch (When Mono Plug
Is Detached)
25
4.1.3 When Mono Plug is Inserted After
The Siren is Activated
26
4.1.4 The Simulation Result When Power
Supply is Disconnected
4.2 Hardware Implementation
27
28
ix
CHAPTER 5
CONCLUSION AND RECOMMENDATIONS 31
5.1 Conclusions
31
5.2 Problems
32
5.3 Recommendations
33
REFERENCES
34
APPENDICES
35
x
LIST OF TABLES
TABLE NO.
TITLE
1.1
Total Robbery Cases Reported for Year
PAGE
2000-2003 (Including Mugging, Bag
Snatching, but not Pick Pocketing)
2.1
4
Characteristics of Wireless Snatch Theft
Alarm System
9
xi
LIST OF FIGURES
FIGURE NO.
TITLE
1.1
Crime Incident Rate per 10,000
PAGE
Populations
5
1.2
Project Flow Chart
6
2.1
Internal Block Diagram of Timer 555
(Monostable)
10
2.2
Schematic of Timer 555 (Monostable)
11
2.3
Waveform of Timer 555 (Monostable)
12
2.4
Time Delay of Timer 555 (Monostable)
13
2.5
Sound Level Scale
14
3.1
Basic Concept of the Project
16
3.2
Circuit of the Project
18
3.3
9V Buzzer
21
4.1
The Simulation Result When Both Switches
Are Closed
24
xii
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
4.2
The Simulation Result When S1 is Open
25
4.3
The Simulation Result When S1 is Closed
26
4.4
The Simulation Result When Power Supply
Is Disconnected
27
4.5
Snatch Theft Alarm System with Dimension
28
4.6
Inside the Casing Box of Snatch Theft
Alarm System
4.7
Closed Up Inside the Casing Box of Snatch
Theft Alarm System
4.8
29
29
Snatch Theft Alarm System after the Mono
Plug is Detached
30
xiii
LIST OF APENDICES
APPENDICES
TITLE
PAGE
A
Timer 555 Datasheet
35
B
Comparator CA3140 Datasheet
47
1
CHAPTER 1
INTRODUCTION
1.1
Background
In Malaysia and Southeast Asia in general, snatch theft is a criminal act of
forcefully stealing from a pedestrian's person while employing rob-and-run tactics. It
is typical for two thieves to work together and ride a moped to make theft and escape
easier. A person steers the vehicle while another does the act of theft itself. However,
some snatch thieves work alone or do not use a motorcycle to rob.
A growing problem in Malaysia, some instances of snatch theft have caused
fatalities, when the person holding onto the handbag has been dragged by the
motorbike, or through subsequent acts of violence. This, combined with the apparent
lack of police control over crime, has prompted outrage among its citizens enough to
take justice into their own hands in apprehending thieves.
The purpose of an alarm system is usually taken to be to alarm or inform
others of the present of the theft. In other words, the obvious presence of an alarm
system could act as a deterrent [4].
2
There are three basic types of alarm system which are hardwired, wireless
and self-contained. Wireless systems work from using radio waves instead of wires
to communicate between the control panel and detection devices. For hardwired
systems, you will have to run wires from each sensor to the control panel. A selfcontained alarm system is single units often shaped like an everyday object such as a
VCR (Video Cassette Recording) and also has the alarm, sensor and control unit in a
single unit.
A basic alarm system consists of a main control unit, a siren or sounder and at
least one detection device. The control panel is the electronic brain of the alarm
system. It receives signals from detection devices and processes this information to
decide the next course of action. Once alarm has been triggered by a detector, a
signal (circuit opening or closing) indicating an alarm condition is sent back to the
control [5]. This could be to allow the siren to sound immediately or sound after a
time delay. A siren may not even be triggered at all as the control unit quietly
contacts an alarm monitoring company. The control unit also is used for arming and
disarming the system which is achieved via a keypad or remote control.
For a hardwired burglar alarm system, the control panel is generally larger as
devices need to be wired into terminals on the panel. A control panel for a wireless
alarm system is usually smaller as minimal wiring is needed (usually only main
supply and siren cabling). However, as wireless alarms operate using radio
frequencies, other electrical goods such as televisions and radios may interfere with
the signals sent by the system‟s transmitters and create a false reading. It‟s important
therefore, to place the control box away from such items. Hardwired systems don‟t
have this pitfall.
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1.2
Objective
The objective of this project is to design a portable snatch theft alarm system
which can be operated directly after triggered. This device will also be able to inhibit
the bag snatching that will attract the public, can save the property and easy to detect
the location of the thief.
1.3
Scope of work
To fulfill the requirement of the system, the scopes of work that had been
identified to carry out this project. The scope of this project includes using Multisim
software to test the functionality of the circuit after the circuit is design and also
build the hardware for the system on the PCB Board.
1.4
Problem statements
A large percentage of women carry a purse or handbag in which they keep
money and personal effects when travelling and shopping. Since the bag often
contains money and other valuable items, it has become a frequent object of theft.
Bag snatchers will grabbed the handbag and run with it to a secluded place where the
bag will be searched for valuable and then discarded. Bag-snatching has reached
serious proportions, particularly in urban areas, and is of particular concern because
of frequent injury sustained by the victims, particularly elderly women. Some
instances of snatch theft have caused fatalities. This happened when the person
holding onto the handbag has been dragged by the motorbike, or through subsequent
4
acts of violence. For example, a 31-year-old pregnant lady was the victim of snatch
thieves and she was attacked by two men on her motorcycle. She suffered head
injuries after falling from her motorcycle because lost control and died at the
hospital.
While various types of alarm devices have been developed heretofore, these
have not been particularly suitable for inhibiting bag-snatchers because of their cost,
size and efficiency and also because of the relatively complex steps that must be
followed to set and wear the device. Accordingly, it is an object of the present
invention to provide a low-cost, efficient alarm device for use inhibiting bagsnatching. Another object of this invention is to provide a snatch theft alarm system
of simple design and construction and one which is conveniently set and worn by the
wearer but which is substantially tamper-proof and cannot be readily disabled by the
thief. Table 1.1 and Figure 1.1 below show the statistics of snatch theft taken from
Royal Malaysian Police website.
Table 1.1: Total robbery cases reported for year 2000 - 2003 (including mugging,
bag snatching, but not pick pocketing)
5
Figure 1.1: Number of Incident Reported in Malaysia
6
1.5
Summary of Work
Implementation and works of the project are summarized into the flow chart as
shown in Figure 1.2. Gantt Charts as shown in Figure 1.3 and Figure 1.4 show the
details of the works of the project that had been implemented in the first and second
semester.
Study on how to design the circuit
Design the electronic circuit and test using
Multisim software
Design the electronic circuit on Protoboard
Board & Convert to PCB Board
Study resulting effect during performance
Describe the advantages of the device
Figure 1.2: Project Flow Chart
7
1.6
Outline of Thesis
This thesis consists five chapters. In first chapter, it discuss about the
introduction, objective and scope of this project as long as summary of works.
Chapter 2 will discuss more on theory and literature reviews that have been
done. In this chapter, an overview will be given on some projects that had been done
by other researcher on snatch theft alarm system. It also brief discuss about timer
555, sounds, and Multisim Software.
Chapter 3 discusses some basic concepts and theories on the snatch theft
alarm system and how to apply it as personal portable security system.
Chapter 4 explained the method used in this project and concept of this
project. There are divided into two sections which are simulation and hardware
implemention. Multisim software was used in simulation implemention in order to
get the simulation results.
Chapter 5 concludes this project and stated about problems faced during the
project and also recommendation for the future work that can be done.
.
8
CHAPTER 2
LITERATURE REVIEW
2.1
Overview
In this chapter, an overview will be given on some projects that had been
done by other researcher on snatch theft alarm system. It also brief discuss about
timer 555, sounds, and Multisim Software.
2.2
Characteristics of Wireless Snatch Theft Alarm System
From the previous work, the snatch theft alarm system is done by Wan Mohd
Nizam Wan Omar at 2007 by using wireless network approached. To facilitate the
implementation of this project, the device separated becomes two main parts which
are remote controls part and siren part. The first part of this project is remote control
and function as a controller of the project from a long distance. Remote control
consists of two parts which are radio frequency (RF) transmitter circuit that held by
the owner and radio frequency (RF) receiver circuit that attached inside the owner‟s
9
bag. When the thief snatches the bag, the transmitter will send the signal to the
receiver and activated the siren. The transmitter will send the signal to the receiver
through radio frequency wave while the receiver will receive the signal from
transmitter to activate the siren / alarm. The loud sound made by the siren / alarm
will attract the public and much easier to detect the location of the thief. It‟s also
using radio frequency wave as a medium of operation. In addition, antenna is used in
previous project to get desired results.
Table 2.1: Characteristics of Wireless Snatch Theft Alarm System
Characteristics
Medium of Operation
•Radio frequency (wireless alarm system)
Distance Range
• 100 meter including hidden area
• Siren will stop operating (deactivated) if the range
distance is exceeds 100 meter because outside the radio
frequency wave.
Frequency
• 316kHz
Battery
• Heavy 9V battery
Siren
•ID80 siren type
•Small in size and loud sound of 115dB
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2.3
Timer 555 (Monostable)
In the monostable mode, the 555 timer acts as a “one-shot” pulse generator.
The pulse begins when the 555 timer receives a trigger signal. The width of the pulse
is determined by the time constant of an RC network, which consists of a capacitor
(C) and a resistor (R). The pulse ends when the charge on the C equals 2/3 of the
supply voltage. The pulse width can be lengthened or shortened to the need of the
specific application by adjusting the values of R and C [2].
The pulse width of time t, which is the time it takes to charge C to 2/3 of the
supply voltage, is given by
(2.1)
where t is in seconds, R is in ohms and C is in farads. See RC circuit for an
explanation of this effect [2].
Figure 2.1: Internal Block Diagram of Timer 555 (Monostable)
11
The external capacitor is initially held discharged by a transistor inside the
timer. Upon application of a negative trigger pulse of less than 1/3 VCC to pin 2, the
flip-flop is set which both releases the short circuit across the capacitor and drives
the output high [2].
Figure 2.2: Schematic of Timer 555 (Monostable)
The voltage across the capacitor then increases exponentially for a period of
t = 1.1 RA C, at the end of which time the voltage equals 2/3 VCC. The comparator
then resets the flip-flop which in turn discharges the capacitor and drives the output
to its low state. Figure 2 shows the waveforms generated in this mode of operation.
Since the charge and the threshold level of the comparator are both directly
proportional to supply voltage, the timing interval is independent of supply [2].
12
Figure 2.3: Waveform of Timer 555 (Monostable)
During the timing cycle when the output is high, the further application of a
trigger pulse will not affect the circuit so long as the trigger input is returned high at
least 10μs before the end of the timing interval. However the circuit can be reset
during this time by the application of a negative pulse to the reset terminal (pin 4).
The output will then remain in the low state until a trigger pulse is again applied.
When the reset function is not in use, it is recommended that it be connected to VCC
to avoid any possibility of false triggering. Figure 3 is a nomograph for easy
determination of R, C values for various time delays. In monostable operation, the
trigger should be driven high before the end of timing cycle [2].
13
Figure 2.4: Time Delay of Timer 555 (Monostable)
2.4
Siren/Alarm Sound
Sound is the quickly varying pressure wave travelling through a medium.
When sound travels through air, the atmospheric pressure varies periodically. The
number of pressure variations per second is called the frequency of sound, and is
measured in Hertz (Hz) which is defined as cycles per second.
The higher the frequency, the more high-pitched a sound is perceived. The
sounds produced by drums have much lower frequencies than those produced by a
whistle, as shown in the following diagrams. Please click on the demo button to hear
their sounds and the difference in pitch.
For humans, hearing is normally limited to frequencies between about 12 Hz
and 20,000 Hz (20 kHz), although these limits are not definite. The upper limit
generally decreases with age. Other species have a different range of hearing. From
14
Figure 2.2 below, it shows that the threshold of pain for normal human is 120dB
which is extremely loud and will cause hearing damage in short-term period.
Figure 2.5: Sound Level Scale
2.5
Multisim Software
National Instruments (NI) equips engineers, educators, and students with
powerful and innovative circuit design technology. Educators and students can take
advantage of easy-to-use teaching tools to overcome the traditional hurdles in
electronics education. Professional engineers can improve productivity with intuitive
capture tools, interactive simulation, board layout, and design validation.
15
NI Multisim (formerly MultiSIM) is an electronic Schematic Capture and
simulation program which is part of a suite of circuit design programs, along with NI
Ultiboard. Multisim is one of the few circuit design programs to employ the original
Berkeley SPICE based software simulation. Multisim was originally created by a
company named Electronics Workbench, which is now a division of National
Instruments. Multisim includes microcontroller simulation (formerly known as
MultiMCU), as well as integrated import and export features to the Printed Circuit
Board layout software in the suite, Ultiboard. Multisim is widely used in academia
and industry for circuit‟s education, electronic schematic design and SPICE
simulation.
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CHAPTER 3
METHODOLOGY
3.1
Introduction
From previous work, the snatch theft alarm system is done by using wireless
network approached. There are some weaknesses from previous project due to some
limitation. But in this project, the snatch theft alarm system is upgraded and
implemented by using different method. After considering some criteria, a simple,
compact circuit and using the concept of electronic circuit design can overcome the
previous project weaknesses. This chapter discusses some basic concepts and
theories on the snatch theft alarm system and how to apply it as personal portable
security system.
Figure 3.1: Block Diagram of Snatch Theft Alarm System
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Known as battery-operated anti-theft alarm systems intended for personal
use, which is attached inside the handbag for activating and inactivating the alarm
system. This type of an alarm system is suitable for taking along, for example,
during travel to protect personal property and to improve safety especially women.
The device is attaching inside the bag to complicate the thieves to throw the device
after snatch the bag.
The control section of alarm system is essentially its brain. This is the
circuitry that monitors the sensor(s) and determines from moment to moment
whether or not to sound the alarm [3]. It receives signals from detection devices and
processes this information to decide the next course of action. This could be to allow
the siren to sound immediately or sound after a time delay. A siren may not even be
triggered at all as the control unit quietly contacts an alarm monitoring company. The
control unit also is used for arming and disarming the system which is achieved via a
keypad or remote control. The control unit can be programmed to include/omit
certain zones around your property. Alarm systems are triggered by signals sent from
detection devices and these generally are capable of measuring movement, heat,
noise, smoke, shock or vibration. PIR (passive infra-red) are one of the most
common devices and are used for detecting movement. In this project, the device will
be control by mono plug and mono-jack socket. The signal is sent when the mono
plug is detached from mono jack socket after the thief snatch the bag and directly
activates the siren.
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Comparator
Timer 555
INPUT
(Mono Plug)
(Mono
Plug)
OUTPUT
OUTPUT
(Buzzer)
(Buzzer)
Figure 3.2: Circuit of the Project
The circuit kept in bag or suitcase sounds a loud alarm, if someone attempts
to snatch the bag or suitcase. This will draw the attention of other passengers and the
burglar can be caught red handed.
In the standby mode, the circuit is locked by a plug and socket arrangement (a
mono plug with shorted leads plugged into the mono-jack socket of the unit). When
the burglar tries to snatch the bag, the plug detaches from the unit‟s socket to activate
the alarm.
The circuit is designed around op-amp IC CA3140 (U1), which is configured
as a comparator. The non-inverting input (pin 3) of U1 is kept at half the supply
voltage (around 4.5V) by the potential divider comprising resistors R2 and R3 of 100
kilo-ohms each. The inverting input (pin 2) of U1 is kept low through the shorted
plug at the socket. As a result, the voltage at the non-inverting input is higher than at
the inverting input and the output of U1 is high [1].
19
The output from pin 6 of U1 is fed to trigger pin 2 of IC NE555 (U2) via
coupling capacitor C1 (0.0047 μF). U2 is configured as a monostable. Its trigger pin
2 is held high by resistor R4 (10 kilo-ohms). Normally, the output of U2 remains low
and the alarm is off. Resistor R6, along with capacitor C3 connected to reset pin 4 of
U2, prevents any false triggering. Resistor R5 (10 mega-ohms), preset VR (10
megaohms) and capacitor C2 (4.7 μF, 16V) are timing components. With these
values, the output at pin 3 of U2 is about one minute, which can be increased by
increasing either the value of capacitor C2 or preset VR.
When there is an attempt at snatching, the plug connected to the circuit
detaches. At that moment, the voltage at the inverting input of U1 exceeds the
voltage at the non-inverting input and subsequently its output goes low. This sends a
low pulse to trigger pin 2 of U2 to make its output pin 3 high. Its output is fed to the
base of single-stage transistor amplifier BD139 (T1) through resistor R7 (1 kiloohm).
The power generated from U2 is amplified by transistor T1. A buzzer is
connected to the collector of T1 to produce the alarm. The alarm can be put off if the
plug is inserted into the socket again. Transistor T1 requires a heat-sink. Resistor R7
limits the current to the base of T1.
The circuit is constructed on a PCB board and place inside a small case for
housing the circuit and 9V battery. The buzzer is small so as to make the gadget
handy. A thin plastic wire is connected along with keychain to the plug and secures it
in hand or ties up somewhere else so that when the bag is pulled, the plug detaches
from the socket easily.
20
3.2
Power Supply
9 Volt (or PP3) batteries are quite common, accounting for about 5% of all
batteries sold in the UK in 2001, according to the British Battery Manufacturers
Association. They are used in smoke detectors, telephones, microphones, and a wide
range of other devices that need a higher operating voltage than the 1.5 Volt
normally delivered by an alkaline battery.
The alkaline PP3 battery is in fact a small engineering marvel, packing six
1.5V alkaline cells into its small rectangular package, and connecting them to the
battery terminals such that the operating voltage becomes 9V.
PP3 batteries are also available using Lithium technology, or as NiMH
rechargeable batteries. The lithium PP3 battery packs more punch than the alkaline
version, and is thus ideally suited for critical applications, such as in smoke
detectors. For frequent users of 9V batteries, the rechargeable version quickly
becomes more economical than repeatedly buying new pre-charged batteries.
Alkaline 9V battery will be used in this project as a power supply rather than
three 3V lithium batteries because even though three 3V lithium batteries make the
snatch theft alarm system lighter but there are some weaknesses if three 3V lithium
batteries are being used. Three 3V lithium batteries weaknesses are the performance
period is shorter and more expensive compared with alkaline 9V battery.
21
3.3
Siren/Buzzer
A siren is the device to alert anyone nearby that a sensor(s) connected to the
alarm control panel has been triggered. There is various type of siren or alarm in the
market with respective characteristics. In this project, small size siren is be used to
reduce and minimize the space of the circuit. Choosing a suitable siren is very
important in this project to produce the loud sound that can draw attention of police
or passerby after the sirens activated. The device is also much easier to detect the
location of the thief or snatcher because of the loud sound made by the siren.
Snatcher will be frightened and the only option left for that person is to leave behind
the bag and run away. In this project, the 9V buzzer with 95dB is used to replace the
siren because of some difficulties to get the siren with loud, small in size and
inexpensive in local market.
Figure 3.3: 9V Buzzer
22
„
3.4
Range Distance
Limitation on range distance from previous project has been inspired to
overcome this problem by expanding the range distance. The circuit will be designed
so that the device will be activated directly after triggered and means there is no
limitation on range distance. Compare with previous project, the device will
deactivate after the receiver circuit is 100 meter away from the transmitter circuit.
23
CHAPTER 4
RESULTS AND DISCUSSIONS
4.1
Multisim Simulation Results
The design circuit is tested by using Multisim v7 to test the functionality of
the circuit before implement to the PCB Board. Then, the result of the simulation
will be analyzed and the correction is made if there is any error or false connection
between the component pin.
24
4.1.1
Before Snatch (When Mono Plug Is Inserted)
When there is no snatching, both switches S1 and S2 are closed which means
power supply is connected and mono plug is inserted. At this time, the output will be
0V and the siren/buzzer will be silent.
S2
S1
Figure 4.1: The Simulation Result When Both Switches Are Closed
25
4.1.2
During Snatch (When Mono Plug Is Detached)
When the bag is being snatch, only S1 is closed which means power supply is
connected but mono plug is detached. At this time, the output becomes 9.033V and
the siren/buzzer will be activated.
S2
S1
Figure 4.2: The Simulation Result When S1 Is Open
26
4.1.3
When Mono Plug is inserted After the Siren is Activated
When the siren is activating, the siren should be always sounding and cannot
deactivated until the power supply is cut off. Both switches S1 and S2 are closed
which means power supply is connected and mono plug is inserted. At this time, the
output becomes 9.033V and the siren/buzzer will be activated.
Figure 4.3: The Simulation Result When S1 Is Closed
27
4.1.4
When Power Supply is Disconnected
When the power supply is disconnected, the siren/buzzer will be
automatically deactivated and stop sounding. S2 is open and the output becomes
-4.666mV or almost 0V.
Figure 4.4: The Simulation Result When Power Supply is Disconnected
28
4.2
Hardware Implementation
The design circuit will be placed to the PCB after the design circuit is tested
by using Multisim v7. The circuit will be design by using Altium Software before
print the design circuit on PCB. Then, after the design circuit is printed on PCB using
art paper, the PCB will be etching and drill at PCB Laboratory.
After all the components are soldered, the circuit will be placed inside the
small casing box and the functionality will also be tested. The figure below shows
the picture of complete snatch theft alarm system.
Figure 4.5: Snatch Theft Alarm System with Dimensions
29
Mono Jack
Socket
Mono Plug
Figure 4.6: Inside the Casing Box of Snatch Theft Alarm System
9V Buzzer
Figure 4.7: Close Up Inside the Casing Box of Snatch Theft Alarm System
30
Figure 4.8: Snatch Theft Alarm System after the Mono Plug Is Detached
31
CHAPTER 5
CONCLUSIONS AND RECOMMENDATIONS
5.1
Conclusions
In conclusion, the objective of the project has been met and the hardware is
successfully constructed.
The snatch theft alarm system is designed through this project to provide the
personal portable security system. In illumination condition, snatch theft alarm
system has great advantages than wireless snatch theft alarm system. So, by taking
the advantages of this, it can be good affect to the better performance of a snatch
theft alarm system especially in personal protection security system.
Finally, a fully working portable snatch theft alarm system is done.
This project also can be operated directly after triggered and also small in size,
inexpensive and the siren/alarm is active more than 100 meters and directly activated
after triggered that will attract the public, easy to detect the location of the thief and
32
can save the property. A system is designed so that it can be used as a personal
portable security system and inhibits the bag snatching.
5.2
Problems
Although the device is function as expected, but the device have some
weaknesses where the device will deactivated after the mono plug is inserted. This
happen maybe because of the output is reset every time the input is detected. Also,
the output waveform is not smooth and has glitch maybe the reason is the impedance
inside the buzzer because the output waveform at the collector pin of the transistor
BD139 is smooth.
The siren with loud and small in size at the market within Malaysia is limited
and the price is much more expensive compared with other manufacturer siren
company like China and Taiwan which produce and sell the siren in cheaper price.
The time taken also will be longer and price will be expensive because including the
shipping price if the siren is ordered from oversea.
Moreover, 9V buzzer is used in order to fulfill the specification of this
project. Even though the sound level is less than 120dB, but the sound of the buzzer
is quite high which can be heard by other people around the device.
33
5.3
Recommendations
After
analyze
the
weaknesses
of
this
project,
there
are
some
recommendations that have been listed for future works to overcome the weaknesses
of this project.
For future works, the circuit of the device should be redesign to make the
device much more compact and the siren always activate after the device is triggered
(the bag is being snatched) in order to make the snatchers cannot easily disable or
deactivate the siren. The device will be only deactivated by the owner which only the
owner knows where the ON-OFF switch is located.
In addition, the siren with loud, small in size, inexpensive and easy to order
the siren is recommend in order to fulfill the specification of this project and also to
make this snatch theft alarm system is affordable.
Moreover, the device can be added with some protection device like location
tracker or the device can automatically sends SMS to the cops. If all the
recommendation is combining for future work, this snatch theft alarm system will be
more effective and inhibit the snatch theft crime.
34
REFERENCES
1. Thomas L. Floyd (2008), Electronic Devices Eight Edition. Pearson
International Edition. Pg 223-225, 658-663.
2. Johari Kasim, Abd Hamid Ahmad, and Camallil Omar (2006). Sistem
Elektronik Edisi 2. Chapter 3: 1-73.
3. Delton T. Horn (1995). Electronic alarm and security systems: a
Technician’s guide. Pg 6
4. Vivian Capel (1979), Burglar Alarm Systems. Pg 3.
5. Steven Hahn (1976). Modern Electronic Security System. Pg 15.
6. Eugene A. Sloane (1977). The Complete Book of Locks, Keys, Burglar
and Smoke Alarms, and Other security Devices.
7. Richard J. Healy (1968). Design for Security.
8. Philip Walker (1983). Electronic Security Systems.
9. Thad L. Weber (1985). Alarm Systems and Theft Prevention Second
Edition.
35
APPENDIX A
Timer 555 Datasheet
36
37
38
39
40
41
42
43
44
45
46
47
APPENDIX B
Comparator CA3140 Datasheet
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68