CHAPTER 3

DESIGN METHODOLOGY

3.1 INTRODUCTION

The design of the burglar alarm system is divided into

two major sections.

the hardware design and

The software design.

For every electronic component manufactured, there are

maximum values of operating parameters (e.g. voltage,

current, power etc), set by the manufacturers to assure

the long life of the component. Therefore it is

important that these components are not subjected to

conditions above those recommended. In fact, it is

better to operate these devices well below the rated

maximum values. This technique is called COMPONENT

DERATING. Usually, a ‘derating factor’ is used to

ensure a margin of safety between operating values and

maximum values.

Presented below are the various components (electronic)

used in the construction and their values, to achieve

stable and efficient operating conditions. The

technique of component derating was applied when

necessary.

The software design section covers the software

structure for the system to be interfaced with the

hardware development. This is presented in the form of

a flow chart, explaining the operation of the burglar

alarm system.

3.2 HARDWARE DEVELOPMENT

The hardware design consists of different blocks –

block diagrams of the different units which when

brought together form the complete electrical structure

of a burglar alarm system. These blocks are

1.The active infrared motion sensor

2.The matrix keypad.

3.The power supply unit.

4.Microcontroller circuit.

MICROCONTROLLERMOTION DETECTOR SENSOR

ALARM BUZZER

Fig 3.1 The Burglar Alarm System.

3.2.1 ACTIVE INFRARED MOTION DETECTOR

IR beam

Fig 3.2 The concept of infrared motion detector for

security system.

The sensor in fig 3.1 uses active infrared transmission

for motion detection. It consists of an infrared (IR)

transmitter and receiver. The transmitter sends

IR

IR RECIEVERMICROCONTROLLER

REFLECTING

OBJECT

KEYPAD LCD MODULE

continuous pulses of visible infrared light. The

receiver is placed directly adjacent to the transmitter

but with a light resistant material separating them.

The sensor is kept at a considerable distance from any

object. If an object comes near to the sensor, the IR

beam is reflected and picked up by the receiver. The

receiver passes on this signal to the microcontroller.

Transmitter circuit

AST5AST4-T6+T8RTRG12

RCC3

CX1

RX2M R9

Q 10

Q 11

OSC 13

CD4047

4047

R110k

C1

1nF

R25.6k

Q19014

R4680

D1IR LED

BATTERY9V

Fig 3.3 Infrared transmitter circuit.

To transmit infrared light successfully to the

receiver, the infrared light is modulated to a

frequency of 38 kHz (using a 38 kHz receiver module).

This modulation is done by switching the light on and

off at a frequency of 38 kHz. The circuit uses the

popular CD4047 IC, in the astable multivibrator mode,

to generate oscillations at 38 kHz. The only external

components required are resistor R1 and capacitor C1.

CD4047 oscillator

According to the datasheet acquired from Harris

semiconductors, the period of the oscillator is

tA = 4.40 * R1 * C1

Therefore frequency F,

F = 1/ tA = 1/ (4.40 * R1 * C1) = 38 kHz

Choosing values for R1 and C1, at C1 = 560pF.

R1 = 1/ (4.40 * 560 * 10-12 *38 * 103) = 10.6K

Using a variable resistor adjusted to 10.6K, we have R1

= 10.6K, C1 = 560pF.

The oscillator output Q voltage = 4.45V rms

Transistor – C9014

The maximum output current for the CD4047 IC is 10mA,

therefore to drive a load (i.e. IR LED) of 10mA will

damage the IC. We use the popular C9014 NPN transistor

as a switch to provide adequate current to the IR LED

without damaging the IC.

Q1 base voltage (with Q1 base connected to oscillator

output) = 4.45V

Base current IB = (4.45 – VBE)/5.6K

Where VBE = base emitter voltage drop of Q1

With VBE = 0.71 (measured value at room temperature).

Base current IB = (4.45 – 0.71)/5.6K

Therefore, IB = 667.85µA

Collector current IC = (Vcc – Vc - 2)/680

With voltage drop of LED = 2V

IC = (8.9 – 0 – 2)/680 = 10.29mA

The maximum rated current for the IR LED is 30mA.

Applying the principle of component derating and, using

a derating factor of 0.6 of the rated current, we

arrive at an operating current of not more than

0.6 * 30 * 10-3 = 18mA.

Therefore, operating the IR LED with a current of

10.3mA will be preferable for optimum working

conditions.

Receiver circuit

Fig 3.4 Infrared receiver circuit.

The receiver circuit is an IR module connected to a D

type flip flop (TC4013).

When the infrared module detects a 38 kHz IR light

source, its output produces an oscillating voltage

applied to the clock of the flip flop. The flip flop is

connected in a toggle mode – the output Q will change

state with an edge rising clock as seen in the truth

table below.

Table 3.1 Truth Table for the TC4013 flip flop.

IR module

Vcc 9V

To microcontroller

D S Q

QR

3.2.2 THE MATRIX KEYPAD

Fig 3.5 below shows the circuit schematic for the

matrix keypad. The keypad is a collection of buttons

arranged in rows and columns (a matrix).

Fig 3.5 A 4 X4 Matrix keypad

The rows and columns are connected to an input/output

(IO) port of the microcontroller. If no key has been

depressed, reading the input port will yield 1 s for

all columns since they are all connected to high (Vcc –

supply voltage). If all the rows are grounded and a key

is depressed, one of the columns will have 0 since the

key depressed provides the path to ground. It is the

function of the microcontroller to scan the keyboard

continuously to detect and identify the key that has

been depressed.

3.2.3 POWER SUPPLY UNIT

The 8051 microcontroller as well as other digital

devices operates with 5 volts to ground dc power

supply. To achieve this, we use a single 9 volts

battery which provides 9 volts dc which is regulated by

the 7805 voltage regulator IC (U1). The output of this

IC gives a stable dc voltage of 5V.

VI1 VO 3

GND

2

U17805

B19V C2

0.1uF

+5v

C14.7uF

+9V

Fig 3.6 Power supply unit for the burglar alarm

project.

Additionally, the 9V dc voltage from the battery will

be found useful in powering analog (non-digital)

components of the system, like the infrared transmitter

oscillator. The input and output capacitors are

provided for transient suppression and filtering.

3.2.4 MICROCONTROLLER CIRCUIT

The ATMEL 89C52 is a low power high performance CMOS 8-

bit microcontroller mainly designed for sequential

controlling operations. It has 8Kbytes of flash

programmable and erasable read only memory (PEROM) on

chip. This device is compatible with the industry

standard AT80C52 instruction set and pin out.

Therefore, the AT80C52 micro-controller shares a lot in

common with the AT8952, just like any other micro-

controller can be likened to a microcomputer. The on

chip flash memory allows the programs memory (code

memory) to be quickly reprogrammed using a non-volatile

memory programmer. Below is the circuit configuration

of the AT89C52 microcontroller.

XTAL218

XTAL119

ALE30EA31PSEN29

RST9

P0.0/AD0 39P0.1/AD1 38P0.2/AD2 37P0.3/AD3 36P0.4/AD4 35P0.5/AD5 34P0.6/AD6 33P0.7/AD7 32

P2.7/A15 28

P2.0/A8 21P2.1/A9 22P2.2/A10 23P2.3/A11 24P2.4/A12 25P2.5/A13 26P2.6/A14 27

P1.0/T21P1.1/T2EX2P1.23P1.34P1.45P1.56P1.67P1.78

P3.0/RXD 10P3.1/TXD 11P3.2/INT0 12P3.3/INT1 13P3.4/T0 14

P3.7/RD 17P3.6/W R 16P3.5/T1 15

AT89C52

80C52

C1

30pX1CRYSTALC2

30p

R110k

C310uF

5V Vcc

Fig 3.7 circuit configuration of the AT89C52

microcontroller.

Component list of the micro-controller section

IC1 = AT89C52 micro-controller

C1 and C2 = 30pf ceramic capacitor

X1 = 11.0592MHZ crystal oscillator

R1 = 10K

C3 = 10uF

3.2.5 OPERATION OF THE MICRO-CONTROLLER

XTAL218

XTAL119

ALE30EA31PSEN29

RST9

P0.0/AD0 39P0.1/AD1 38P0.2/AD2 37P0.3/AD3 36P0.4/AD4 35P0.5/AD5 34P0.6/AD6 33P0.7/AD7 32

P1.0/T21P1.1/T2EX2P1.23P1.34P1.45P1.56P1.67P1.78

P3.0/RXD 10P3.1/TXD 11P3.2/INT0 12P3.3/INT1 13P3.4/T0 14

P3.7/RD 17P3.6/W R 16P3.5/T1 15

P2.7/A15 28

P2.0/A8 21P2.1/A9 22P2.2/A10 23P2.3/A11 24P2.4/A12 25P2.5/A13 26P2.6/A14 27

AT89C52

AT89C52

1 2 34 5 67 8 9

0 #

1 2 3

A

B

C

D

D714

D613

D512

D411

D310

D29

D18

D07

E6

RW5

RS4

VSS

1VD

D2

VEE

3

LCDLM 016L

R210k

R110k

Q1C9014

RELAY9V

R310k

C310uF

D1DIODE

X1

CRYSTAL

C130pF

C230pF

From sensor

BATTERY9VBUZZER

BUZZER

5V

Fig 3.8 Circuit diagram of the burglar alarm system.

The AT89C52 micro-controller has a 40-pin dual inline

package feature (DIP). This micro-controller has been

configured to make use of 11.0592-megahertz (MHZ)

crystal oscillator. This crystal oscillator is

connected to pin 18 and 19 of the micro-controller

while it is connected to capacitor C1 and C2. Capacitor

C 3 and resistor R3 are provided for reset purposes.

These values are standard values. Pin 40 is connected

to the output of the voltage regulator. Pin 20 is

connected to ground. The keypad is connected to port 2,

while the LCD module (RT1012 16x2 ASCII LCD) data pins

are connected to port 1. The switch represents the

sensor connected to port 3, bit 2. Transistor Q1 drives

the 9 volts relay. Q1 is biased by R1 and R2. A buzzer

is used as the alarm bell; this can be replaced with

any other suitable alarm. Diode D1 is provided to

protect the transistor from “inductive kick” (Horowitz,

2003).

The program of operation for the microcontroller

circuit will be discussed in the next section.

3.3 SOFTWARE DEVELOPMENT

We have the alarm control panel: this consists mainly

of a small keypad, plus an additional ‘buzzer’ to

indicate that the alarm has sounded (Figure 3.8). The

alarm system is designed in such a way that the user –

having set the alarm by entering a four pass code via

the keypad – has time to open the door and leave the

room before the monitoring process starts. Similarly,

if the user opens the door when the system is armed, he

or she will have time to enter the password before the

alarm begins to sound.

Overall, the system is designed to operate as follows:

When initially activated, the system is in

‘Disarmed’ state.

In Disarmed state, the sensors are ignored. The

alarm does not sound. The

System remains in this state until the user enters

a valid password via the keypad. When a valid

password is entered, the system enters the ‘Arming’

state.

In Arming state, the system waits for 60 seconds,

to allow the user to leave the area before the

monitoring process begins. After 60 seconds, the

system enters the ‘Armed’ state.

In Armed state, the status of the various system

sensors is monitored. If the sensor is tripped, the

system enters ‘Disarming’ state. The keypad

activity is also monitored: if a correct password

is typed in, the system enters ‘Disarmed’ state.

In Disarming state, we assume that the door has

been opened by someone who may be an authorized

system user. The system remains in this state for

up to 60 seconds, after which, by default, it

enters ‘Intruder’ state. If, during the 60- second

period, the user enters the correct password, the

system enters ‘Disarmed’ state.

In Intruder state, an alarm will sound. The alarm

will keep sounding (indefinitely), until the

correct password is entered.

Overall, the burglar alarm system is somewhat

simplified, but the overall system architecture is

correct, and the code may be easily extended to add

additional features.

3.3.1 PROGRAM CODE

The program was written using M-IDE 51 compiler

following the design operation in the previous section.

Fig 3.9 is the simplified program flowchart for the

software architecture.

START

Alarm state = Disarmed

Sensors = Off

Sensor

Passcode

Alarm State = Disarmed

Pass Code

Alarm State= Arming

60secs

Alarm State = Armed

Sensor

60 secs

YES NO

YES

NO

NO

NO

YES

NO

Fig 3.9 Simplified flowchart for the software architecture

CHAPTER 4

RESULTS AND DISCUSSION

4.1 INTRODUCTION

To achieve reliable results and optimum performance

from any electronic construction project, specific

tests (static and dynamic) are carried out to determine

if the device is operating under the required standard

conditions. Also the precautions taken and safety

considerations made in achieving both the hardware and

software part of our work are considered.

4.2 MOTION DETECTOR CIRCUIT

As mentioned earlier, this consists of an infrared

transmitter and receiver

YESSound Alarm

4.2.1 INFRARED TRANSMITTER CIRCUIT

The transmitter was constructed using the CD4047

oscillator. The output of the oscillator was tested

using a multimeter in alternating current (ac) mode.

The output gave 4.45 volts.

4.2.2 INFRARED RECIEVER CIRCUIT

The three pin IR receiver used produced 7.3 volts on

its output when measured with a multimeter. If it

detects any IR beam, the output goes to 0 volts.

4.2.3 RESULTS FOR THE MOTION DETECTOR SYSTEM

Detection range for the motion sensor detector system

varies with battery strength and the reflecting object

surface. Its range is about 1.5 meters. The system was

demonstrated thus: the receiver output was connected to

a light emitting diode (LED). When an object enters the

zone, the LED starts blinking.

4.3 MICROCONTROLLER CIRCUIT

When the entire circuit is powered, the voltage drop

across each terminal of the crystal oscillator will be

between 2.3V to 2.5V to show that the crystal

oscillator is good. For the Microcontroller, regardless

of any assembled program, its entire port will be high

all through. It shows that the microcontroller is in

good order. A short blinking LED program was burnt into

the EEPROM of the microcontroller to test if the

microcontroller responded properly to the program.

4.4 STATIC TESTS

Here the various tests carried out on the components

without power supply input shall be discussed.

Capacitors

We tested the capacitors with the digital voltmeter in

the resistance mode. We observed their charging and

discharging times.

Diodes

The 1N4007 diodes gave a low resistance when forward

biased by the Digital voltmeter, and a high resistance

when reversed biased by the Digital voltmeter.

Relays

We tested the relay contacts when they were normally

closed and they were found to be continuous.

Also, the input terminals (across the relay coil) gave

a good resistance value showing that the relay coils

were good.

Resistors

The potentiometers gave resistance values varying from

0 Ω to 5.0k Ω in a fairly linear fashion. We also

confirmed the 100k Ω resistance value of the resistor

used in the MCU.

4.5 MOUNTING AND COMPONENT CONNECTIONS

All connections made between components were either

made via connecting wires or directly with solder. The

following steps were employed to achieve good

connection of components used in the project.

Soldering Iron tip was well scraped before

commencing soldering.

Good care was taken to avoid overheating of

components.

Solder sucker/extractor was used to remove improper

and unintended joints.

A digital multimeter was used for continuity,

resistance, isolation test, voltage and current

measurements.

Circuit Board preparation

We used a matrix board for mounting the most of our

circuit component. A matrix board was chosen for the

following reasons.

All connections are self isolating.

Difficulty in making unintended connections (i.e.

bridging lines)

Connection lines can be made with solder like that

of a PCB facilitating the tracing of errors during

soldering.

4.6 PROGRAMMING THE AT89C52

This was one of the most challenging parts of the whole

project. The program was written in C programming

language using the M-IDE studio application. The

program was tested using PROETUS version 7 (an advanced

microcontroller simulator). After all errors were

debugged, the program was loaded into the

microcontroller using the device below.

Fig 4.1 Program loader for the AT89C52

CHAPTER 5

CONCLUSION & RECOMMENDATION

5.1 CONCLUSION

From the circuit schematic, the write up and the tests

carried out, it can be concluded that the alarm system

is functional and can be installed were ever it is

required be it a commercial or residential asset to act

as the first line of defence before the arrival of the

police in the event that a burglary incident occurs.

5.2 RECOMMENDATION

A burglar alarm can initiate a considerable response by

police or private security personnel, who may leave

other important duties to race to the scene of the

alarm. Therefore, the following recommendations are

stated so as to avoid the problems that are most likely

to arise due to the issue of false alarms and on how to

make the system more effective:

- The active infrared detectors can be programmed to

ignore the first movement detected, as in when the

intruder moves from one detection zone to another,

and to sound the alarm only when the movement passes

through two or more detection zones within a

specified period of time.

- Another means of preventing false alarms is the dual-

technology motion detector. This is the more common

type of detector used in more sophisticated burglar

alarm systems. A dual-technology detector combines an

active infrared device and a microwave device in one

small unit. The active infrared device sees many

detection zones and measures the change in background

temperature as a target moves across them. At the

same time, the detector projects microwaves and

measures the Doppler shift when a target moves

through the protected space.

- If the alarm is to be used in commercial assets or

high security areas the following authorization

methods could be added to ensure the effectiveness of

the system e.g. addition of multiple codes, or a

fingerprint, badge, hand-geometry, retinal scan,

encrypted response generator, and other means that

are deemed secure for the asset in question.

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Dietel H.M. & Dietel P.J. (2003), “C How to Program” (4th

Edition), Prentice Hall, Pearson Education

Publishers

Horowitz P. & Winfield H., 2003, “The Art of Electronics”, 2nd

Ed., University Press, Cambridge-Great

Britain

Jorgensen D., (2009), “Literature Survey on Sensors & Actuators:

Infrared Proximity Sensor”, Department of Electrical &

Computer Engineering, Utah State University, USA

Allen, Samuel M. (2009) "Motion Sensors" Microsoft(R)

Encarta(R) [DVD]. Redmond, WA: Microsoft Corporation.

Theraja, B.L. & Theraja, A.K. (2005), “A Textbook of

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Tokhiem R. L. (1999), “Digital Electronics: Principles and

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