Design And Construction Of A 12V Power Supply

ABSTRACT

A 12v power supply is an electronic device that supplies 12v electric energy to an electrical load. The primary function of a power supply is to convert one form of electrical energy to another. A 12v Power supply takes in AC power from the mains supply and delivers a DC voltage to the item requiring power.

The device was completely build and coupled, the result during the test shows that the charger was able to respond to its operation by producing an output voltage of 12v when tested with a digital multimeter.

The aim of a DC power supply is to provide the required 12v of DC power from 220VAC mains.

TABLE OF CONTENTS

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

1.1 INTRODUCTION

1.2 AIM/OBJECTIVE OF THE PROJECT

1.3 SIGNIFICANCE OF THE PROJECT

1.4 ADVANTAGES OF THE PROJECT

1.5 LIMITATION OF THE PROJECT

1.6 APPLICATION OF THE PROJECT

CHAPTER TWO

LITERATURE REVIEW

2.0 LITERATURE REVIEW

2.1 REVIEW OF REGULATED 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 CIRCUIT DIAGRAM

3.3 CIRCUIT DESCRIPTION

3.4 SYSTEM OPERATION

3.6 COMPONENTS LIST

3.7 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

5.2 CONCLUSIONS

5.2 RECOMMENDATION

5.3 REFERENCES

CHAPTER ONE

1.1                                                        INTRODUCTION

A power supply is an electronic device that supplies electric energy to an electrical load. The primary function of a power supply is to convert one form of electrical energy to another and, as a result, power supplies are sometimes referred to as electric power converters. Some power supplies are discrete, stand-alone devices, whereas others are built into larger devices along with their loads. Examples of the latter include power supplies found in desktop computers and consumer electronics devices.

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.

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.

Regulator: This stage of the power supply takes the smoothed voltage and uses a regulator circuit to provide a constant output virtually regardless of the output current and any minor fluctuations in the input level.

1.2                                                      AIM OF THE PROJECT

The aim of a DC power supply is to provide the required 12v of DC power from 220VAC mains. The objectives of this study are:

1. To build a 12v electric power supply
2. To provide a constant 12v power supply

• To protect devices from over or under voltage.

1.3                                          ADVANTAGES OF THE PROJECT

Constant Power

A single–phase circuit, instantaneous power varies sinusoidally. However, a dual power supply ensures constant power supply to a device when one power source fails, which could be as a result of a lot of factors.

Pocket-Friendly

A 12v DC power supply is less expensive. Dual DC power supply is cheaper than running on a single power supply. It also comes in useful in situations where one needs more power to boost already available amps. The additional power supply doesn’t have to be of a higher wattage as not much loads need to run on it. For instance, the old power can be used to run the fan and pumps and the new DC source can power the motherboard and other components of the desktop computer.

Ease of Installation

Addition of a 12v DC power supply to an already existing direct current power supply source is easy and can be completed in less than 20 minutes. For example, once the spot is identified for the second power supply, run a cord out of the case to connect the green pin and any black pin coming from the main power supply to the auxiliary. It is as simple as that.

Convenient Temperature

Extra power supply does not change the case temperature as may logically be expected.

User-friendly

12v power connection makes it easy to switch off the air conditioning device of an ATM machine without interrupting the entire power supply during cold weather conditions and saving up energy in the process.

A 12v electric power supply is important for several reasons. Not only does it ensure stable power supply to a device, but it also helps prevent system damage. It allows for multiple usage of power by increasing power output. To put short, it ensures regular direct current power supply. The importance of a dual DC power supply cannot be overemphasized.

1.4                                           APPLICATION OF THE PROJECT

Power supplies are a fundamental component of many electronic devices and therefore used in a diverse range of applications. This list is a small sample of the many applications of power supplies.

Computer power supply

A modern computer power supply is a switch-mode power supply that converts AC power from the mains supply, to several DC voltages. Switch-mode supplies replaced linear supplies due to cost, weight, and size improvement. The diverse collection of output voltages also have widely varying current draw requirements.

Electric Vehicle power supply

Electric vehicles are those which rely on energy created through electricity generation. A power supply unit is part of the necessary design to convert high voltage vehicle battery power.

Welding power supply

Arc welding uses electricity to melt the surfaces of the metals in order to join them together through coalescence. The electricity is provided by a welding power supply, and can either be AC or DC. Arc welding typically requires high currents typically between 100 and 350 amperes. Some types of welding can use as few as 10 amperes, while some applications of spot welding employ currents as high as 60,000 amperes for an extremely short time. Older welding power supplies consisted of transformers or engines driving generators. More recent supplies use semiconductors and microprocessors reducing their size and weight.

Aircraft power supply

Both commercial and military avionic systems require either a DC-DC or AC/DC power supply to convert energy into usable voltage.

AC adapter

An AC adapter is a power supply built into an AC mains power plug. AC adapters are also known by various other names such as “plug pack” or “plug-in adapter”, or by slang terms such as “wall wart”. AC adapters typically have a single AC or DC output that is conveyed over a hardwired cable to a connector, but some adapters have multiple outputs that may be conveyed over one or more cables. “Universal” AC adapters have interchangeable input connectors to accommodate different AC mains voltages.

Adapters with AC outputs may consist only of a passive transformer (plus a few diodes in DC-output adapters), or they may employ switch-mode circuitry. AC adapters consume power (and produce electric and magnetic fields) even when not connected to a load; for this reason they are sometimes known as “electricity vampires”, and may be plugged into power strips to allow them to be conveniently turned on and off.

1.5                                                                  LIMITATION

The problem of this work is high heat loss, and lower efficiency levels when compared to a switch-mode power supply.

This device output is regulated, that means it will required heat heatsink for the regulator.

1.6                                                                  SCOPE OF THE STUDY

Scope of this work covers the building of a 12v power supply. The device was built using an IC 7812 for obtaining the required voltage. The AC mains voltage will be stepped down by the transformer, rectified by bridge rectifier and filtered by capacitor to obtain a steady 12v DC level.