Design And Construction Of A Single Channel Audio Amplifier With Audio Level Indicator Using OLED

ABSTRACT

An amplifier is an electronic device that increases the voltage, current, or power of a signal. Amplifiers are used in wireless communications and broadcasting, and in audio equipment of all kinds. They can be categorized as either weak-signal amplifiers or power amplifiers. The most frequently-used device for power amplification is the bipolar transistor. In an amplifier, audio level indicator is incorporated to display the audio signal level of an amplifier. The main aim of this work is to build a single channel audio amplifier with audio level indicator using OLED.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• AIM AND OBJECTIVE OF THE PROJECT
• APPLICATION OF THE PROJECT
• PURPOSE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• LIMITATION OF THE PROJECT
• SCOPE OF THE STUDY
• METHODOLOGY

CHAPTER TWO

LITERATURE REVIEW

• OVERVIEW OF AN AMPLIFIER
• HISTORICAL BACKGROUND OF THE STUDY
• OVERVIEW OF DIRECT-COUPLED AMPLIFIER
• IMPORTANT CHARACTERISTICS OF AN AMPLIFIER
• TYPES OF AMPLIFIERS
• TYPES OF POWER AMPLIFIERS

CHAPTER THREE

METHODOLOGY

• BLOCK DIAGRAM OF AN AUDIO POWER AMPLIFIER
• BLOCK DESCRIPTION
• SYSTEM CIRCUIT DIAGRAM
• WORKING OF AUDIO AMPLIFIER CIRCUIT
• PROGRAM CODE

CHAPTER FOUR

4.0      TEST AND RESULT ANALYSIS

• CONSTRUCTION PROCEDURE AND TESTING ANALYSIS
• CASING AND PACKAGING
• ASSEMBLING OF SECTIONS
• TESTING OF SYSTEM OPERATION

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 – 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers. It is the final electronic stage in a typical audio playback chain.

Power Amplifier (also known as a large signal amplifier), is to deliver power to the load, and as we know from above, is the product of the voltage and current applied to the load with the output signal power being greater than the input signal power. In other words, a power amplifier amplifies the power of the input signal which is why these types of amplifier circuits are used in audio amplifier output stages to drive loudspeakers.

The power amplifier works on the basic principle of converting the DC power drawn from the power supply into an AC voltage signal delivered to the load. Although the amplification is high the efficiency of the conversion from the DC power supply input to the AC voltage signal output is usually poor.

The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification (this is particularly associated with record turntable signals), equalization, tone controls, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio power amplifiers require these low-level inputs to adhere to line levels.

While the input signal to an audio power amplifier may measure only a few hundred microwatts, its output may be tens or hundreds of watts for a home system or thousands or tens of thousands of watts for a concert sound reinforcement system.

Not all amplifiers are the same and are therefore classified according to their circuit configurations and methods of operation. In “Electronics”, small signal amplifiers are commonly used devices as they have the ability to amplify a relatively small input signal, for example from a Sensor such as a photo-device, into a much larger output signal to drive a relay, lamp or loudspeaker for example.

The classification of an amplifier depends upon the size of the signal, large or small, its physical configuration and how it processes the input signal, which is the relationship between input signal and current flowing in the load.

1.2                                   AIM AND OBJECTIVE OF THE PROJECT

The main aim of this study is to build a single channel audio amplifier with audio level indicator using OLED.

1. To build a portable audio amplifying device
2. To display the audio output of the amplifier

• To build an audio VU (volume unit) meter based on an Arduino microcontroller

1.3                                         APPLICATION OF THE PROJECT

Important applications include public address systems, theatrical and concert sound reinforcement systems, and domestic systems such as a stereo or home-theatre system. Instrument amplifiers including guitar amplifiers and electric keyboard amplifiers also use audio power amplifiers. In some cases, the power amplifier for an instrument is integrated into a single amplifier “head” which contains a preamplifier, tone controls, and electronic effects. In other cases, musicians may create a setup with separate rack mount preamplifiers, equalizers, and a power amplifier in a separate chassis.

1.4                                              PURPOSE OF THE PROJECT

Amplifier’s main purpose is to take the weak signal and make it strong to drive a speaker. The power amplifiers usually get necessary amplification energy of input signals from the AC supply. Ideally without distortion an amplifier can deliver signal at the output without distortion.

1.5                                         SIGNIFICANCE OF THE PROJECT

Today there are many categories of amplifiers used for multifarious purposes. In simple terms an amplifier picks up a weak signal and converts it into a strong one. It is widely used in several devices to boost electrical signals. Radios, televisions and telephones are a few examples to point out in this regard. There are innumerable other applications of amplifiers and it is not easy to enumerate all of them. Some of the common types of amplifiers are used in electronic gadgets and audio systems. These are also used in musical instruments and guitars. This project serves to demonstrate how the knowledge of electronics can be applied to build solutions for any part of your day to day life.

1.6                                           LIMITATION OF THE PROJECT

1. Noise: This device tends to add some random noise to the signals passing through them, hence degrading the SNR (signal to noise ratio). This, in turn, limits the accuracy of any measurement.
2. Limited output voltage, current, and power levels. This amplifier cannot output signals above 1.5w.
3. A 9V DC was used for powering the circuit. A 9V PP3 battery is fine.

1.7                                                   SCOPE OF THE STUDY

The amplifier circuit of this work was built with transistors. This transistor is already biased with the help of the divider bias network. The volume unit (VU) meter uses AVR ATMega 328. For the display, the project was designed to be compatible with small (and cheap) monochrome OLED displays based on the SSD1306 or SH1106 driver.

1.7                                                        METHODOLOGY

To achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Draw a block diagram.

• Test for continuity of components and devices,

1. Design and calculation for the amplifier was carried out.
2. Studying of various component used in circuit.
3. Construct the amplifier circuit.

• Finally, the whole device was cased and final test was carried out.

1.8                                                         PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work,   chapter two presents the literature review of the study,  chapter three describes the methods applied,  chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.