Report on

Simple Digital Security System

ELECTRONICS CIRCUIT DESIGN LAB (EEC 752)

Submitted bySHITANSH NIGAM (0905631091) SAURABH SINGH (0905631087)

BBDNIIT, Lucknow

(Affiliated to Gautam Buddh Technical University, Lucknow)

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ABSTRACT

Digital Security gives individuals the freedom to embrace the digital lifestyle – to

confidently engage in everyday interactions across all digital devices. Digital security

affects all aspects of the digital lifestyle, which, among others, comprises computers

and the internet, telecommunications, financial transactions, transportation, healthcare,

and secure access.

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INTRODUCTION

Here is a simple digital security system which can protect you from the burglars or the

intruders into your house/building/godown. We can use this simple and reliable security

system as a watch-dog by installing the sensing loops around a building/house, we have

to stretch the loop wires two feet above the ground. The logic in the circuit is an

enameled copper wire which has to be installed around the house, which will be then

connected to the circuit, the seven segment display, displays which part of your house

has been entered by the intruders according to the numbering given by us in the circuit.

This is a very simple and easy to build circuit, seven segment display to display the

broken loop and the buzzer to provide the alarm sound, when the loop is broken.

.

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Simple Digital Security System (SDSS)

Working of the system

The circuit is so simple to understand as it has a seven segment decoder which has 4

inputs totally. The input D is grounded and the remaining INPUTS are connected to 3

loops, so whenever a particular loop is broken for eg. loop 1 then the display will show

1 for loop and the sum of the other loops if more then 1 loop is broken. The display will

be 0 if none of the loop is broken this is controlled by the IC 1. The 3 input NOR gate is

for the purpose of the buzzer, unless the loop is broken the output of NOR gate is high

which in turn will be inverted by the inverter (NOT gate) so the input to the transistor

will be low so the buzzer will not sound. When a loop is broken the output of NOR gate

will be low, and automatically the output of NOT gate will be high which makes the

buzzer on.

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Fig. 1- The Digital Security System Circuit

Wire loops 1, 2 and 4 are connected to the A, B and C inputs of the7-segment decoder

4511(IC 1), respectively while the D input of (IC 1) is grounded permanently. The

loops are also connected to a dual 3-input NOR gate and a inverter CD4000 (IC2) to

activate the alarm. The loops are to be connected as shown in figure before using this

security system, make sure that the loops shown in fig. 2 are connected as shown in

fig.1. If you don’t want to use the buzzer, switch it off by opening switch S2. The

circuit works off a 9V regulated power supply. However battery backup is

recommended. A common cathode 7 segment display (LtS340) is used for displaying

weather the loops are intact or not.

When any loop is broken the output of NOR gate N1 goes low, while the output of gate

N2 goes high, transistor t1 conducts and buzzer sounds to alert you. You can mute the

buzzer by switching the power to circuit through switch S1.

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Fig. 2- The proposed wiring diagram of loops

Consider the following cases:

1. Secure Premises: When all the loops are closed and the premises are secure, each of the three inputs to the NOR gate of IC2 is 0. Upon applying the NOR logic, the output is 1 (HIGH) which is further applied to the inverter and hence, the final output obtained is 0 (LOW). This low signal when applied to the base of the transistor causes the transistor switch to remain OFF and the buzzer does not send off a beep, thereby indicating that no intrusion has taken place.

2. Intrusion: When a loop is broken or two or more loops are broken, the NOR gate will have non-zero inputs and hence the output will be a 0 (LOW). This when applied to the inverter becomes a 1 (HIGH) which switches the transistor to the ON state. Consequently the buzzer beeps, indicating the occurrence of an intrusion/break-in

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TRUTH TABLES

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N1- NOR gate

N2- NOT gate

L1 L2 L3 O/P0 0 0 1

0 0 1 0

0 1 0 0

0 1 1 0

1 0 0 0

1 0 1 0

1 1 0 0

1 1 1 0

I/P O/P

1 0

0 1

Parts List

Semiconductors

IC1- CD 5411

IC2- CD 4000

Q1- BC 548

Resistors

R1, R2, R3- 47KΩ

R4 - 470Ω

R5 - 1KΩ

Miscellaneous

S1, S2- ON/OFF Switch

DIS 1- LT 543(CC)

9V battery

CCB

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ADVANTAGES

1. Intruder/ Burglar detection.

2. Very low circuit cost.

3. Very less maintenance cost (only the battery needs to changed at regular intervals).

4. Everybody present nearby can be alarmed if anybody tries to steal or intrude.

5. Better than a watch dog as it doesn’t need caretaking and requires no feeding at

regular intervals.

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