DESIGN AND CONSTRUCTION OF AN ELECTRONIC DIGITAL SECURITY ALARM SYSTEM FOR THE BURSARY OFFICE

DESIGN AND CONSTRUCTION OF AN ELECTRONIC DIGITAL SECURITY ALARM SYSTEM FOR THE BURSARY OFFICE

ABSTRACT

The design and construction of a digital security system using Transistor-Transistor Logic (TTL) and complementary Metal Oxide Semiconductor (CMDS) is presented. The security system has five (5) sensors. The alarm will sound if sensor three is ON and any other two sensor. i.e. one lower sensor and one higher sensor are ON. Truth table gave a Boolean expression which minimized using a 5-variable karnaugh map reduction techniques. Digital logic gates were used to realize the circuit is powered by a volt d. c supply, which is reduced to a 15 volt d. c. supply using an IC regulator. A bugger and a plastic casing were also used. The system was mounted on a view board, which was tested and found to be working. 

CHAPTER ONE

1.0       INTRODUCTION 

“Electronics” is the word used in general conservation with little idea of the meaning of the term of its importance  electronics is the branch of science and technology that deals with electric circuits involving active electrical component  such as vacuum tube (almost obsolete) transistor, diodes and integrated circuit (more recent used). The nonlinear behaviour of these components and their ability to control electron flow make amplification of week signal possible, and is usually applied to information and signal processing. Electronics is distinct from electrical and electo-mechanical science and technology, which deals with the generation, distribution, switching, storage and conversion of electrical energy to and from other energy forms using wires, motors, generators, batteries, switches, relays, transformers, resistors and others passive component. Today most electronic devices uses semi-conductor component to perform electron control. The study of semi-conductor devices and related technology is considered a branch of solid-state physics, whereas the design and construction of electronic circuit to solve problems come under electronic engineering.

Electronics is an industry of great vigor and promise, and each step forward in its technology will lead to further important application. These applications in turn will result in new jobs in the design, construction and sales of new products.

An electronic component is any entity in an electronic system used to affect the electrons or their associated fields in a desired manner consistent with intended function of the electronic system. Components are generally intended to be connected together, usually by being soldered to a printed circuit board (PCB) to create an electronic circuit with a particular function (for example an amplifier, radio receiver or oscillator).

Components may be packaged singly or in more complex groups are active (e.g. diodes, translator and thyristors) or passive (e.g. resistor and capacitors).   

            Circuits and components can be divided into two groups: analog and digital, the former being gradually phased out by the letter. A particular device may consist of circuitry that has one or the other or a combination of the two types.

            The word analogue is derived from the Greek (analogous) meaning proportional. Analog describes the proportional relationship between a signal and a voltage or current that represent signal. Most analog electronic appliances are constructed from combinations of a few types of basic circuit. The number of different analog circuit so far devised a huge, especially because a “circuit” can be defined as anything from a single component to system containing thousands of components. Analog circuits are sometimes called linear circuit although many non-linear effects are used in analog circuit including vaccume tubes and transistor amplifiers, operational amplifier and oscillator.

            Digital circuits are electric circuits based on a number of discrete voltage levels. Digital circuits based on a number of discrete voltage levels. Digital circuits are the most common physical representation of Boolean algebra, and are the basis of all digital computers. To most engineers, the team “digital circuit”, “digital system” and interchangeable in the context of digital circuit. Most digital circuit uses a binary system with two voltage level labeled “0” and “1” often logic “0” will be a lower voltage and referred to as “LOW” while logic “1” is referred to as “HIGH”.

Computers, electronic clock and programmable logic controllers (used to control industrial processed) are constructed of digital circuit. Digital signal processors are another example (IEEE Dictionary of Electrical and Electronics Terms, 1986).

            Circuit design is a creative activity that requires not only experience and skill but infuction and success of achieving ones expectation at the end as well. An intimate knowledge of the circuit properties of available components as well as the ability of predicting the behaviour of circuit companies of interconnection of these components.

            Thus the design is based on: first, the electrical description of the components used in the circuit which is also called MODELING while the second which relates to the mathematical description of interconnection of the model components is called NETWORK THEORY.

            The electronic modeling and its theory to be described in this work is the security alarm system of the bursary office. The components that will be used in this work are mostly digital in nature.

1.1       REVIEW OF ALARM SYSTEM

Efforts have been made to design various systems using different electronic components.

In 1981 (Ray Marston) designed an alarm system (security), which was developed by Steve Ramasahodeo tagged “Infrared (IR) intruder alarm” system. It was a maximum useful range of about 10meters and from a basic of a domestic or commercial security alarm system. The system comprises of two units namely: an infra-red transmitter and an infra-red receiver with a relay output. The receiver unit contains facilities for operating the relays in either the latch or non-latch mode and for externally disabling the relays via concealed “by-pass” switches so that authorized persons can pass through the beam without activating alarm. The unique feature of this alarm system is the use of a dual-beam infra-red link. The two beams must be broken simultaneously to operate the alarm. The stems thus respond only to objects greater than the dual beam or setting on transmitter or receive diodes. The basic transmitter signals are generated by ICs and are wired as non-symmetrical stable multi-vibrator producing alternate periods of IC and output is buffered by another IC. Similarly the two infra-red detector diodes are connected in parallel and wired in series with a stable resistor. The installation is such that both the transmitter and the receiver should be pointing towards each other. J. spark (1997).

Designed a bulger alarm. This circuit is basically composed of L.D.R. light depended Resistor, Resistor of various transistor, buzzer, battery, thermistor.

When the bugler walks in front L.D.R., the self holding relays pulls up and the relay contacts can be used to operate a bell, buzzer or electronic siren or a bulb to give visible warning instead.

The toggle switch is used to switch the battery off, when the circuit is not being used and also to reset the circuit. The variable is used to adjust the point at which the relay pulls up. The 10 kilo ohms resistor connected to the base of transistor T1 is not used now, to make the circuit sensitive.

Rory Holmes (1981) also designed the “INFANT GUARD” alarm system to protect cabinet of cupboard which contains valuable (delicate goods) from the accessibility of young children hands. This system has as satisfactorily loud alarm sound to prevent the children from meddling in the cupboard and to warn also the parents in the house that somebody has opened the cupboard.

The circuit consist of three Section; a light threshold detector, a latching circuit and a gate antioscillator for the alarm. The light detector uses a photo transistor which has a very low dark current that is effectively negligible. When any light falls on the photo transistor , the current through it will increase and the inputs to the ICs are now taken low. The alarm oscillator uses the well known gate CMOS a stable configuration built around two ICs in which one input of each gate is driven from the output of the inverter.

In 1984, Tooley M and Whitefield designed an alarm called “ANTI – THEFT ALARM”, which provides an available and visible warning to indicate that properties and goods kept are being tampered with. The system consists of photo diodes, ICs, transistor, capacitors, and resistors all of various values. The system illustrates the uses of basic logic gate demonstrates techniques for driving light emitting diode (LED), and shows how simple square wave oscillators can be constructed 5volts supply of up to 500MA and suitable for with both anti-theft alarm and any of the subsequent project.

In 1984, Lumky G. E. desgined a “two timer alarm system” its circuit consist of three circuit boards and a warning unit, the three circuits are: -

a.         Alarm comparator, to sense the intruder

b.         Two-timers, to produce timing sequences for external warning device. It also provides a tell-tale monitor to determine whether or not the system has been activated during the owner’s absence.

c.         An automatic reset is incorporated within the design so that if the alarm is accidentally triggered, the process is not repeated, but can be absorbed simply by removing the source of alarm.

                        The system makes use of an NE 556 timer which has two 555 timers; this is to obtain two independent adjustable periods of delays. Both periods are initiated simultaneously by clamping the base of the transistor to its emitter, the intruder sensing comparators. Defects change in the external network of the sensor whether they are magnetically activated reed switches, pressure mats, micro switches or active devices such as ultrasonic Doppler movement detectors.

                        The arrangement is such that any attempt to short circuit or cut the external network wiring will result in triggering the system. The compensators are used to substitute for an open sensor; one for one all it does is to put one resistor in, when one has been taken out of the circuit.

                        Paul Horowitz and Winfield Hill, (1996) designed a synchronous (homodyne) detector. An interesting method that combines dynamic range, accuracy and speed is synchronous detection called “homodyne detection”. In this method the output is rectified by being inverted during alternative half circles. This obviously requires a clean signal at the same frequency as the signed detected, either supplied externally or regenerated internally with a phase-locked loop. Synchronous detection works well-up to frequencies of few megahertz, at least, the big disadvantages is the need for a coherent reference signal. The circuit consist of ICs, capacitors and resistors all of various values, it shows how a simple square wave can be s\constructed using logic gates (stroke 1984).

1.2       TYPES OF ALARM

An alarm gives an audible or visual warning about a problem or condition, alarms includes:     

i.          Burglar alarm, designed to warn of burglaries; this is often a silent alarm.

ii.         Alarm clocks, can produce an alarm at a given time.

iii.        Distributed control manufacturing system or DCSs, found in nuclear power plants, refineries and chemical facilities also generate alarms to direct the operators’ attention to an important event that he or she needs to address.

iv.        Alarms in an operation and maintenance (O & M) monitoring system, which informs the bad working state of (a particular part of) the system, under monitoring.

v.         Safety alarms, is a gadget system that monitors the sound or movement of a baby in his/her room enables the mother to know precisely the movement and condition of the baby.

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