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ABSTRACT
The basic building blocks of this project (construction of a variable regulated power supply) are: The transformer which steps down the high alternating current (AC) to a lower direct current (DC). This is followed by the rectifier stage which consist of four diodes connected as a bridge rectifier, and the output is filter, at the filter stage by a capacitor and finally, regulated by integrated circuit (IC) regulator. A potentiometer connected to the IC is used to vary the output of the system. The output varies from 0v to 12v, and may be adjusted base on the required load. Almost all the electronic devices need a smooth regulated dc power supply for its operation and this project is useful to supply constant regulated variable dc power supply.
CHAPTER ONE
1.0 INTRODUCTION
Almost all basic household electronic circuits need an unregulated AC to be converted to constant DC, in order to operate the electronic device. All devices will have a certain power supply limited and the electronic circuits inside those devices must be able to supply a constant DC voltage within this limit. That is, all the active and passive electronic devices will have a certain DC operation point (Q – point) or Quiescent point), and this point must be achieved by the source of DC power the dc power supply is practically converted to each and every stage in an electronic system. Thus a common requirement for all this phases will be the DC power supply.
All low power system can be run with a battery. But for long time operating devices, batteries could prove to be costly and complicated the best method used is in the form of an unregulated power supply – a combination of a transformer, rectifiers, and a filter.
The small step down transformer is used to reduce the voltage level to the devices needs the output of the transformer is pulsating sinusoidal AC voltage, which is converted to pulsating DC with the help of a rectifier. This output is given to a filter circuit which reduces the AC ripples and passes the DC components.
An integrated circuit voltage regulator is connected to the output of a filtered rectifier and maintains a constant output voltage (or current) despite changes in the input, the load current or the temperature. The capacitor – input filter reduces the input ripple to the regulator to an acceptable level.
The combination of a large capacitor and an IC regulator is in expensive and help produce an excellent small power supply.
1.1 BACKGROUND OF THE STUDY
In recent times variable D.C power supply unit have become very useful and popular, and popular to power D.C equipment. When D.C supplies of different values are required while accumulation of different values could be used, it is cheaper and more convenient to use a variable D.C supply hence the important of variable D.C power supply.
1.2 PURPOSE OF THE PROJECT
The purpose of this work or project is to construct a variable 12v D.C power supply
1.3 SCOPE OF THE PROJECT
The project is limited to the construction and demonstration of a variable D.C power supply and the voltage rang is from 0 – 12 volts.
1.4 DEFINITION OF TERMS
Transformer: – This is an electrical device used mainly for voltage transformation to the required level.
Fuse: – This is a short piece of wire inside electrical equipment which prevent damage by melting and stopping the electricity when there is too much power.
Integrated Circuit: – This is a very small set of electronic connection printed on a single piece of semi conductor material instead of being made from separated parts.
Rectification:- This is a process of converting alternating or changing current to direct unidirectional current.
Semi-conductor:- This is a material whose conducting ability lies between that of conducting and insulators.
Complete Material Cost #3,000
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