Design And Construction Of A Digital Variable Power Supply

A variable power supply is an electronic device that supplies different level of electric energy to an electrical load. The primary function of a variable power supply is to supply different electrical energy to loads that fall at the same rating limit. The aim of this work is to build a digital power supply that has programmable output voltage and current that is displayed on an LCD.

TABLE OF CONTENTS

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRCT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• AIM/OBJECTIVE OF THE PROJECT
• PURPOSE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• ADVANTAGES OF THE PROJECT
• LIMITATION OF THE PROJECT
• APPLICATION OF THE PROJECT
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

2.0      LITERATURE REVIEW

2.1     REVIEW OF POWER SUPPLY

2.2     REVIEW OF POWER SUPPLY CHARACTERISTICS

2.3     REVIEW OF GENERAL APPLICATION OF POWER SUPPLY APPLICATIONS

2.4       REVIEW OF TYPES OF POWER SUPPLY

CHAPTER THREE

3.0      CONSTRUCTION METHODOLOGY

3.1      BLOCK DIAGRAM OF THE SYSTEM

3.2      BLOCK DIAGRAM DESCRIPTION

3.3      CIRCUIT DIAGRAM

3.4      CIRCUIT DESCRIPTION

3.5     SOFTWARE USED

3.6     HARDWARE USED

3.7      SYSTEM OPERATION

3.8     CIRCUIT DESCRIPTION

3.9     DESCRIPTION OF MAJOR COMPONENTS USED

CHAPTER FOUR

4.0       RESULT ANALYSIS

4.1      CONSTRUCTION PROCEDURE AND TESTING

4.2      ASSEMBLING OF SECTIONS

4.3      CONSRUCTION OF THE CASING

4.4     TESTING

4.5     INSTALLATION OF THE COMPLETED DESIGN

CHAPTER FIVE

• CONCLUSIONS
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

1.1                                                        INTRODUCTION

A power supply is a hardware component that supplies power to an electrical device. A power supply can be given from the battery or from a hardware circuitry which converts the AC supply into the DC supply or step-down AC to step-up AC and vice-versa. A variable power supply is one which facilitates the user to vary and adjust the desired output voltage and output current. Usually, a potentiometer is used for voltage adjustments.

Every power supply must obtain the energy it supplies to its load, as well as any energy it consumes while performing that task, from an energy source. Depending on its design, a power supply may obtain energy from various types of energy sources, including electrical energy transmission systems, energy storage devices such as a batteries and fuel cells, electromechanical systems such as generators and alternators, solar power converters, or another power supply.

All power supplies have a power input, which receives energy from the energy source, and a power output that delivers energy to the load. In most power supplies the power input and output consist of electrical connectors or hardwired circuit connections, though some power supplies employ wireless energy transfer in lieu of galvanic connections for the power input or output. Some power supplies have other types of inputs and outputs as well, for functions such as external monitoring and control.

This work is aimed at building a variable digital power supply using microcontroller and LCD. The output of this device is displayed on the LCD. To obtain a complete circuit for this work, the circuit is mainly composed of the:

• Input transformer:   The input transformer is used to transform the incoming line voltage down to the required level for the power supply. Typically the input transformer provides a step down function. It also isolates the output circuit from the line supply.
• Rectifier:   The power supply rectifier converts the incoming signal from an AC format into raw DC. Either half wave or more commonly full wave rectifiers may be used as they make use of both halves of the incoming AC signal.
• Smoothing:   The raw DC from the rectifier is far from constant falling to zero when the AC waveform crossed the zero axis, and then rising to its peak. The addition of a reservoir capacitor here fills in the troughs in the waveform, enabling the next stage of the power supply to operate. Large value capacitors are normally used within this stage.
• Voltage adjuster:   This stage of the power supply takes the smoothed voltage and uses a variable IC to provide a variable output virtually regardless of the output current and any minor fluctuations in the input level.
• DISPLAY: this power supply is unique in that it has the ability to display the actual measured values for voltage and current and also display shows the pre-set limits for voltage and current.

1.2                                                   AIM OF THE PROJECT

The aim of this work is to build a digital power supply that has programmable and variable output voltage and current.

1.3                                            OBJECTIVES OF THE PROJECT

At the end of this work student involved shall be able to:

1. Build a device provide variable power to the load using an AC supply at the input.
2. Know the working principle of a potentiometer
3. Know how to interface microcontroller with LCD

1.4                                              PURPOSE OF THE PROJECT

The main purpose of the digital variable power supply is to display adjustable output voltage on an LCD.

1.5                                           LIMITATION OF THE PROJECT

This device is limited at producing 1.25 – 30 v output using a 24 volts center tap transformer.

1.6                                         SIGNIFICANCE OF THE PROJECT

This work makes it possible for someone to use one power supply to run different devices of higher or lower voltage rating without considering buying a new or different power supply.

Using digital variable power supply, the user don’t have to assume the out voltage or current because it displaces on the LCD.

1.7                                          APPLICATION OF THE PROJECT

A variable power supply is a regulator that electricians and electrical project hobbyists use to test the capacity of voltage for any project they may have completed. The power supply is used as a gauge to make sure the piece of work the person has completed is able to withstand certain amounts of voltage and current load. Tests are generally conducted by applying different amounts of voltage to the piece of completed work a little at a time to ensure the stability of the circuit the individual has created. These types of power supplies also are used by hobbyists to power small electronics requiring variable voltage and by tattoo artists to power tattooing guns.

By using such a variable supply of power, the individual is able to spot any temperaments or inconsistencies in the circuit he’s created in a manner that allows for adjustment to be made without having to scrap the entire project. A variable power supply is a useful tool for anyone who has a background with electrical circuitry and components. It also has many uses other than just testing.

In addition to being used to test circuits, this type of power supply may be used by miniature hobbyists as well. For example, such tools are commonly used by those who work with miniature electronic train sets. The power supply can be adjusted to either speed up or slow down the train as it is pushed around the track by the power of the completed circuit.

Another common use for this type of power supply is in the tattoo industry. Variable power supplies are used every day by tattoo artists to adjust the intensity and speed of the motor on their tattoo guns in order to create the desired effect with the particular tattoo needles they are working. For instance, when a tattoo artist is outlining a new piece, the speed of the gun is increased through the power supply so the needle moves faster, creating a more consistent outline. When the artist is shading an area of the skin, the power supply is used to slow down the needle in order to create consistent color coverage within the tattoo.

A variable power supply works by restricting or increasing the voltage delivered to the circuit from the original power source. For instance, when the electronic train hobbyist starts his train on the track, he doesn’t simply flip a switch and turn the train on full blast; rather, he delivers the voltage to the circuit in small increments through the regulated variable power supply until the desired speed of the train is reached. Most common variable power supplies have voltage ranges of 1 to 3 volts up to 20 or 30, and large-scale variable power supplies can range from 6,000 to 20,000 volts, but these types of power supplies are typically only used in industrial settings.

1.8                                        PROJECT WORK ORGANISATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this work is on the introduction to this study. In this chapter, the background, significance, scope, objective, aim, purpose, application limitation and problem, advantages of this work was discussed.

Chapter two is on literature review of the study. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.