DESIGN AND CONSTRUCTION OF AN AUTOMATIC SECURITY LIGHTING CONTROL SYSTEM

DESIGN AND CONSTRUCTION OF AN AUTOMATIC SECURITY LIGHTING CONTROL SYSTEM

CHAPTER ONE

1.0 GENERAL INTRODUCTION
Development in the field of electronics have contributed one of the great success stories of this country. Many years dated back, switching systems were basically on manual operations, which required an operator. The discovery of light dependent devices like photo resistors, photo cell and photo transistors which respond to light intensity can be applied to reduce the involvement of mankind in power switching operation.

As a result of these man-made error is reduced and life becomes more comfortable to live. In the past, bulky power component and hence large control current were used in switching components like switch gear, contractor, bulk control were only not found to be less reliable, occupying much space, considerable high initial cost and high cost of maintenance, but are also prone to adverse electrical hazard since they operate on high current.

Subsequent research in the field of electronic engineering has led to the invention of miniaturized components such as integrated circuit and semi conductor devices which need to operate on a low voltage to control a heavy load current with high reliability factor and at a cheaper rate.

Among thousand of control system to assist man kind independent of human intervention, security lighting system is aimed at designing and constructing electrical circuit to put ON light at night and OFF in the day time.

This design work is ideal for homes and any other places its service is required. Moreso, it can be used to eliminate crime and hazardous acts especially, when the sole occupant of a house is not around for sometimes.
Economically, the project equally assist mankind to ensure no wastage of energy even if one forgets to switch OFF the lighting system of a house in the morning before going out hence the PHCN bill will be reduced.

1.1 AIMS AND OBJECTIVES
i. This project is aimed at reducing the movement of mankind in power switching operation.

ii. To automatically control the ON and OFF of the output light when a shadow falls upon the light dependent resistor (LDR) which act as a sensor and which is placed where it is correctly and constantly illuminated.

iii. To ensure that discrete components are used in place of bulky power components to control a heavy load current.

iv. To ensure no energy wastage and hence reduction of PHCN bill.

v. To develop an inexpensive system

1.2 APPLICATION OF AN AUTOMATIC SECURITY LIGHTING SYSTEM (ASLS)
Presently the field of an automatic security lighting system is applied every corner of our society. In manufacturing industries, it appears in automatic production and process control operation, in food industries, it is used to automatically blend and package food.

It is also applied in our automobile systems contain equipments to automatically maintain a preset speed as power requirements vary due to changing conditions. Its applications in military and para-military are also numerous and extends from the armoury of gun to the control of radar system as well as automatic guidance of missile systems and air craft.

GENERAL FEATURE OF DESIGN
A great importance feature employed in this design is the application of the logic circuitry system which automatically switches ON and OFF the security light. Hence conveying the message of the presence of someone, at dusk effort and time is what has not be in existence in the time of old. It switching is performed within milliseconds.

The light dependent resistor is mounted in a tube behind lens (probably a converging lens) so as to focus the total amount of light rays coming from the constant supply illuminate on the light dependent resistor (LDR) behind the lens. Whenever the light dependent resistor (LDR) is in shadow its resistance increases, applying a negative pulse to the entire circuit. This light dependent resistor must be in a water proof container and the negative pulse throughout the entire circuit switches on the system.

1.3 BLOCK DIAGRAM OF THE AUTOMATIC SWITCH CONTROL SYSTEM FOR AN AUTOMATIC SECURITY LIGHTING SYSTEM

The sensor of the control system is a light dependant resistor (LDR) whose resistance increase as it is prevented from illumination by shadow. It should also be noted that, light dependent resistor should be kept where shadow can easily fall on it and the tube in which it is placed should be water proof.

CHAPTER TWO

2.0 INTRODUCTION
This chapter is devoted to the study of the theories of the components used in the project. These include resistors, transistors, relay, transformer, rectifier, filter and regulator.

2.1 RESISTOR
A resistor is an electrical/electronic component that offers opposition to the flow of current in a circuit. Resistors are truly ubiquitous. There are almost as many types as there are applications. Resistors are used in amplifiers as loads for active devices, in bias networks, and as feed back elements. In combination with capacitors they establish time constants and act as filters. They are used to set operating currents and signal levels. Resistors are used in power circuits to reduce voltage by dissipating power, to measure current, and to discharge capacitors after power is removed. They are used in precision circuits to establish currents, to provide accurate voltage ratios, and to set precise gain values. In logic circuits they act as bus and line terminators and as “pull-up” and “pull-down resistors. In high-voltage circuit they are used to measure voltages and to equalise leakage currents among diodes or capacitors connected in series. In radio frequency circuits they are even used as coil forms for inductors.

Resistors are available with resistances from 0.01 ohms, through 1012 ohms, standard power ratings from 1/8 watt through 250 watts, and accuracies from 0.005% through 20%. Resistors can be made from carbon composition moldings, from metal films, from wire wound on a form, or from semi conductor elements similar to field-effect transistors (FETs). But by far the most familiar resistor is the ¼ or ½ watt carbon-composition resistor. These are available in a standard set of values ranging from 1 ohm to l00rnegaohms with twice as many values available for the 5% tolerance as for the 10% types. Therejah and Therajah (2000).

We prefer the Allen – Bradley type AB (1/4 watt, 5%) resistor for general use because of its clear marking, secure lead seating, and stable properties. Resistors are so easy to use that they are often taken for granted. They are not perfect though, and it is worthwhile to look at some of their defects. The popular 5% composition type, in particular, although fine for nearly all non-critical circuit applications, is not stable enough for precision applications. You should know about its limitations so that you won’t be surprised someday. Its principal defects are variations in resistance with temperature, voltage, time and humidity. Other defects may relate to inductance (which may be serious at high frequencies), the development of thermal hotspots in power applications, or electrical noise generation in low-noise amplifiers. There are three types of resistors namely,
1. Fixed resistor
2. Variable resistor
3. Potential divider.

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