Design And Construction Of An Electronics Lectern/Podium

ABSTRACT

This work is on a mobile electronic lectern/podium which is an integration of PC and audio visual equipments, which makes a classroom and presentation hall interactive. An electronic lectern consists of an Audio system which includes amplifier, speakers and microphones and ports are available for CD, DVD, USB, MP3 connection as per customer’s requirement. This aim of work is to build a reading desk which composes of public addressing system with wireless microphone which can be used to address audience.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE: INTRODUCTION    

1.0.	Background of study
1.1.	Problem statement
1.2.	General Objectives
1.3.	Specific Objectives
1.4.	Scope of study
1.5.	Significance of study
1.6.	Limitations
1.7.	Organization of Chapter
CHAPTER	TWO: LITERATURE REVIEW
2.0.	Lectern
2.1.	Applications of lecterns
2.2.	Sound Powered lecterns
2.2.1.	SL400 – Sound Powered Lectern
2.2.2.	SL370 Table Top Sound Lectern
2.2.3.	The Executive Sound Column Lectern
CHAPTER	THREE: METHODOLOGY
3.1.	Materials
3.1.1.	JRC4558
3.1.2.	Mid-Range PC Board Relays
3.1.3.	C945 NPN Transistor
3.1.4.	Cordless Microphone Module
3.2.	Designing
3.2.1.	Designing of System Device Block Diagram

 

3.2.2.	Design of System Device Circuit
3.3	Construction
3.3.1.	Construction of the Class AB Power Amplifier
3.3.2.	Split Power Supply
3.3.3.	Tone Control Circuit.
3.3.4.	Four Channel Audio Mixer
3.4.	Mode of operation of system device
3.5	System Design
3.5.1	System Device Block Diagram
3.5.2.	System device circuit
3.5.3	System Development
CHAPTER	FOUR: RESULTS AND DISCUSSION
4.0.	Characteristics of Sound
4.0.1.	Noise Level and Sound Pressure Level (SPL)
4.0.2.	Sound Pressure Level Decreases with Distance
4.0.3.	Sound Reverberation and Absorption
4.1.	Discussion
4.2.	Costs Benefits Analysis
4.2.1	Material list
4.2.2	Labour cost
CHAPTER	FIVE: CONCLUSION AND RECOMMENDATION
5.0	Conclusion
5.1	Recommendations

 

REFEREENCES

GLOSSARY

LIST OF TABLES

LIST OF FIGURES

CHAPTER ONE

INTRODUCTION

1.1                                                                Background of study

A lectern is the slanted-top high-desk that you as the speaker stand behind and use when reading your presentation notes. A lectern is also known as podium is a raised platform on which a speaker stands during a presentation. The reading lectern is wide and deep providing over 12² inches of usable surface. A mobile electronic lectern is a portable type of lectern that is used for voice reinforcement in conference and meeting rooms, auditoriums, churches, hotels, motels, schools, meeting halls, etc. This system is the combination of microphones, signal processors, amplifiers, and loudspeakers that makes live or pre-recorded sounds louder and may also distribute those sounds to a larger or more distant audience [1].

An electronic lectern system is also used to enhance the sound of the sources on a stage. A sound reinforcement system may be very complex, including hundreds of microphones, complex audio mixing and signal processing systems, tens of thousands of watts of amplifier power, and multiple loudspeaker arrays, all overseen by a team of audio engineers and technicians. On the other hand, a sound reinforcement system can be as simple as a small public address (PA) system, consisting of a single microphone connected to an amplified loudspeaker. In both cases, these systems reinforce sound to make it louder or distribute it to a wider audience.

The result is superb voice reproduction with a minimum of reverberation. Additional features include: unidirectional dynamic microphone, shock-mount holder for the microphone, input for

second microphone, output for tape or external PA system, output for external speaker, speech equalizer with switch, auxiliary input, volume and tone controls [2].

An electronic lectern would effectively cover audiences of 2500 or more indoor. Lecterns used in academia generally in seminar rooms and lecture theatres may have certain features that common lecterns lack, based on the technological sophistication of the venue. Lecterns of this sort are generally attached or integrated into a large desk, as the amount of support material tends to be larger in academic contexts than in straightforward public talks. In a church, the lectern is usually the stand on which the Bible rests and from which the “lessons” (reading from Scripture) are read during the service. The lessons may be read or chanted by a priest, deacon, minister, or layperson, depending upon the liturgical traditions of the community. The lectern is normally set in front of the pew, so that the reader or speaker faces the congregation [3].

1.2                                                                  Problem Statement

Setting up loudspeakers, amplifier and microphones with limited time whenever audience need to address causes lots of stress and complexity. One can imagine the stress that it entails, especially with the margin of error being large enough to cause misconnection that could lead to damage of the system. Lectern in these modern days in almost every auditorium has one way or the other become a necessity as it serves as a slim table besides which a group of people could be addressed from. The powered lectern combines the whole setup into one unit which makes it convenient to be fixed anywhere public address and lecterns are needed.

1.3                                                        Objectives of the study

General Objectives

The general objective of this project is to design and construct a portable electronic lectern with a wireless microphone.

• Specific Objectives

Specifically, the system device would be able to:

• Produce sound for in-and-out door

   1.4                                                                   Scope of study

Audio sources like dynamic microphones, MP3, Compact Disc players are considered based on their decibel and impedance and a 3 channel audio mixer is designed. The channels are well labeled for clarity of sources which require pre-amplification. The JRC4558 dual Operational amplifier is used to design a number class ‘A’ amplifiers which is used to balance sound levels. Active high and low filters are used as equalization of sound to improve on the frequency response of the signal from the mixing stage before further amplified by the class ‘AB’ power amplifier to the loud speakers. The input connectors would be mounted on the front panel and then connected to the three audio channel mixer. The mixer would source its power from the split power supply via a 12volts regulator. The output of the mixer would directly be amplified by an inbuilt class ‘AB’ power amplifier. The loudspeakers are arranged in a format that ensures that the total impedance is between 4-16 ohms.

1.5                                                                 Significance of study

The significance of this project are as follows:

• Accessible shelves inside a lectern allow for the convenient storage of lecturers’ pointers, papers, and laptop computers while keeping the paraphernalia out of sight until it’s ready for
• Swift set-up requiring little or no expertise in setting
• Built-in storage space gives the presenter and the presentation space a more professional look.
• It has a 50 Watt inbuilt
• It has an LED Light for
• It is designed to support an Anti-hock with gooseneck microphone holder for unidirectional Dynamic microphone.
• It has a Mic/Aux Volume, Speech Filter and Tone
• It has two 6’’ loudspeakers with connection for External Speaker

1.6                                                              Limitations of the study

Basic limitation of the construction of this project is that:

• Quality of electrical and electronics components in terms of its
• The cost of producing a single unit of this project is relatively expensive since the prices of electronics components are cheaper when bought in a high
• Inadequate time and the high outages of power also amount in many challenges in coming out with a much more refined
• The difficulties involved in getting the major components from class A source was very difficult because all the companies who manufactures these components do not sell components in small quantities and it was very hectic getting all these

1.6                                                            Organization of the Study

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.