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This project report is a thesis written specifically to cover the design analysis construction, test and packaging of a multipurpose security system from electric component that can be easily be obtainable from the market.

The report discusses the various unit and stages of the alarm system, thesis include:-

  1. Clock generation and frequency division unit.
  2. The control and section unit, comprising of a one shot 555 timer multiplexer, sound amplifier and the latch.
  3. The detection and switching unit made up of the fire and burgler sensors and priority encoder.
  4. The output unit comprising of the visual display and audio systems. These units have been lucidly represented with block diagrams and the calculations and the analysis of each component in the circuit of each block were done in the subsequent chapters of this part.

However, my own project is designed to serve three purposes: to detect human touch, burglar operation and to detect fire, giving the corresponding alarms and indications.

In a situation where there is a need to monitor the movement of people in a confidential building or a restricted area or to alert security-men in the case of fire outbreak, multipurpose security system is an electronic gadget which detect human shadow, human touch and fire and alert security-men through an alarm and equally display the particular room or area in which the target was hit.

The multi-purpose security system uses Light Dependent Resistor (LDR) to sense human shadow, touch switch to sense human touch and thermistor to sense fire.

The circuit is enclosed in such a way that if he sensor are installed in each various room, say room 1,2 and 3 etc. If an intruder wants to break through, say room 2 once he touches the handle of the door, the touch sensor senses his touch, then triggers an alarm and display room 2 on a big display board. If to say, there is fire outbreak in the same room 2 the fire sensor will sense it, trigger an alarm and equally display room 2. This is also application to all the room that has the sensor.

Multipurpose security system can equally be applied in banks, industries, financial institutions, schools and home to help safeguard lives and property.



  • Block diagram of multi-purpose alarm system
  • Flowchart on design and construction procedures
  • Internal circuit of 555 timer IC
  • Astable multivibrator circuit using inverters
  • Output waveform of 555 timer oscillator
  • Astable circuit configuration, using Rb = Rs + Rp
  • One short configuration using 555 timer IC unit
  • Waveform of triggered mode
  • One shot multivibrator circuit
  • Pin configuration of 74LS191
  • Functional block diagram for 74LS153
  • Circuit diagram of frequency multiplexer 74LS153
  1. Basic common-emitter circuit
  2. Load-line construction.
    • Transistor amplifier arrangement with signal symbol
    • Transistor amplifier arrangement with signal symbol
    • Amplifier configuration component values
    • Pin configuration of 74LS175
    • Functional block diagram of Quadruple D-type FF (74LS175)
    • Typical IC encoder
    • 8 line-to-line priority encoder 74LS148
    • Bimetallic heat detector
    • Time temperature curve
    • Isometric diagram of package multi-purpose alarm system.



  • Table of various frequencies of operation from the oscillator unit
  • Table of result of frequency derision
  • Table for the 74LS153 multiplexer operation
  • Functional table for D-type flip flop 74LS175
  • Functional table of 74LS148 priority encoder.



IC      Integrated Circuit

O/P    Output

I/P     Input

Vcc    +5 Volt Supply

GND Ground or Earth

NE    Segment

FF               Flip Flop

TTL            Transistor-transistor logic

CMOS        Complementary Metallic Oxide Semi Conductor Logic

CLK            Clock

CLR            Clear

F                 Frequency

C(exp)        Exponential

C/M            Count Up

C/O             Count Down

EL               Enabled Input

EO              Enabled Output

NPN           Negative-Positive-Negative

VCE              Collector Emitter Voltage

VBE              Base-Emitter Voltage

VCB              Collector Base Voltage

Sat              Saturation

IC               Collector

IB               Base Current

RB                Base Current

L/S              Loud Speaker

KΩ             Kilo ohms

KHZ           Kilo-hertz

Dip             Dual in line package

V                Volts






Title page

Approval page




List of tables

List of abbreviations

Table of contents




Objective of the project

Project layout

Background information

Block diagram



Literature Review



Detection and switching unit

Fire detector

Human shadow detector

Human touch sensor

The hatch circuit

The alarm circuit

The display board

Power supply unit




Obtaining project topic and specifications

Choosing a suitable circuit

Selecting component values

Circuit analysis

Construction and testing



Design analysis

Frequency generation

Clock generation

Amplification stage

Operation of a transistor

Switching operation of a transistor

Transistor biasing



Test, demonstration and packaging

Test analysis

Voltage test

Continuity test

Clock test




Tools and materials

IC sockets

Construction aids





Conclusion and Recommendations









The present and likely to continue state of the world economy as a whole and that of Nigeria as yet a developing country in particular has made life uncomfortable and unsatisfactory for the masses.

Every day, we hear of wars, conflicts, monumental natural disasters, fatal accidents, tribal, racial and religious clashes, to mention just a few.

All these phenomena always lead to wanton destruction of life and properties worth millions of naira.

As a result of these ugly situations today in our country in particular coupled with unemployment, which has led to decline in the standard of living, crime wave has escalated. Because the youths and the young school leavers could not secure any job, which could have kept them busy.

And since the idle mind is the devils workshop, they indulge in all sorts of  heinous and scandalous crimes in other to make ends meet. Assassination, high-way robbery, house become burglary, arson, car snatching, etc  have become the order of the day. Criminals purposefully set public markets ablaze In order to cart away peoples hard earned merchandise from the markets. Hence the incessant burning of our markets of recent.

Because of these prevailing conditions and bad condition of our economy, there is the need to safe-guard the already acquired property especially from thieves and fire disasters as the cost of replacing them is beyond the reach of average Nigerian. There is also the need to protect life or building occupant(s) form harm by burglars  or fire incidence.

Burglary can be traced back to the beginning of age and it was crudely carried out then. But today, it has advanced and become very sophisticated along side with modern technology. Hence, the crude ways used in the time past to the curtail robbery or burglary can no longer contain the present advanced techniques. Therefore, there is the need to device advance technological gadgets to march or subdue the present trend of sophistication demonstrated by burglars.

However, in the past, kitchens were built separately from the residential houses(s). These kitchens houses firewood’s, cooking utensils etc, while there is no electrical wiring and consequent electrical appliances in the residential buildings. But with development, we now have the kitchen inside the living apartments or flats where kerosene stoves, electrical cookers, boilers or heaters and cooking gas (highly inflammable) are used. there are also electrical wiring and consequent electrical appliances in our rooms. all these are potential causes of fire incidence, which could arise from the leaking of the cooking gas, electrical faults etc. Therefore, early detection of fire and burglar actions and a alarm warning are essential to prevent loss of life and property or harm to building occupant(s) so that the time needed to detect fire ignition, burglar operation and warn building occupant(s) is reduced.

Hence a corresponding vital margin of safety for evacuation of property and alerting of the police and fire men is possible.

This   function of burglar and fire detection and giving of alarm warning can be achieved from electronic alarm systems.



Alarms are frequently used for detecting the presence of an intruder. These include signaling the presence of unwanted moisture or liquids, presence or absence of light, the removal of a small object, the unwanted opening of a door, power outage, and presence of an unwanted signal in an electronic gadgets etc.

Most electronics alarms are either activated when a circuit is opened or short circuited.

However, the aim or objective of the project is to build a multi-purpose alarm system   with situation indicators from inexpensive and local electronics components that will detect burglar operations, shadow and fire incidence and give the consequent warning signal or indication in order to alert house occupants for appropriate safety actions.



The project report or thesis has been arranged and organized in such a away that as followed all the steps and procedures taken to ensure the success of this project.

Chapter one deals with the introduction of the project, where the objective of the project. The background information and what the project is all about were clearly stated.

Chapter two deals with the literature review in which the origin, concept, nature and review of the method used in designing the project were discussed.

Chapter three, however deals with the detection and the switching of the project it actually concerned about the sensor units – fire, shadow and the burglary sensors,

Chapter four contains the design analysis, component value calculations and general description of all the components and IC units used in this design are treated in details. Complete circuit realization from block diagram is discussed and treated here.

Chapter five, however deals with the methodology of the design and construction of the project. It was here that all the steps involved in realization, analysis, design, selecting component values, choosing a suitable circuit and obtaining project topic and specification are succinctly stated.

Chapter six has to do with construction proper of the designed circuits making use of the various electronic workshop tools and equally the testing analysis, packaging and assembling.

Chapter seven dealt with conclusion, recommendation and references.



The project is dominated by ICs. These include 555 timer, encoders, decoders, comparators, bitable multivibrators or flip flops IC units or chips. Hence the project can be termed a digital system.

Digital logic can be divided into combinational and sequential. Combination circuits are those in which the output state depends only on the present input states in some predetermined manner. Combinational circuits can be constructed with logic gates alone. But in sequential logic circuits, the output state depends both on the input states and on the previous history i.e. the knowledge of the past inputs or what actually took place on the previous or preceding states. Sequential circuits can be constructed from logic gates and some form of memory device, the flip flops. Sequential logic circuits may be either synchronous or asynchronous. The synchronous sequential circuits are built to operate at a clocked rate whereas asynchronous ones are without clocking.

From these facts, it can be deduced that the system (project) is a sequential logic system sense it is constructed from logic gates and a memory device, the flip flop. The units in this system are however clocked together so that they operate in synchronism with a pulse train of a certain period, regarded as the system clock. Hence the present output state of the alarm system depends both on the present input state and on the past input states. This is made possible by the memory device, flip flop.

















Fig. 1.4


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