engineering

  • DESIGN AND CONSTRUCTION OF AN AUDIO AMPLIFIER

    CHAPTER ONE

    Introduction

    This project involved design and construction of an audio amplifier .The term audio refers to sound or human hearing as the range of human hearing extends from about 20 hertz to 20,000 hertz (i.e. 20k hertz) but varies considerably with age and individuals. That is we can hear air pressure change or vibration that vary in pitch from about 20 times per second to about 20,000 times per second.

    The term pitch describes the subjective sensation of hearing an air pressure vibration or sound meaning pitch of a double bass is low, that is flute or soprano is high. The more the air pressure vibrates pre second, the higher the pitch.

    Transistor which has the ability to amplify cannot amplify the air pressure (acoustic) directly; therefore it is necessary to first convert the air pressure vibration into equivalent electrical vibration by means of a sound transducer, a microphone or similar acoustic electrical transducer. Meaning that if one sings into a microphone, a pure tone that has a pitch say 1000 vibration per second will be gotten. The microphone output will be an electrical AC signal that has lets say about frequency of 15,000 hertz after passing through the amplifier circuit.

    Amplifier circuit is the interconnection of diodes, capacitors resistors, transformers, integrated circuits, transistors, heat Zink each of which has a required function. The circuit is capable of amplifying a very weak signal to a larger signal.

    For amplifier circuit to be able to drive more load (speakers), a good number of pair of transistors has to be used. Hence, the number of pair of transistor should not be too much to avoid humming.

    Aim and Objectives

    The main aim and objective of this project work is to design an audio amplifier system which can be used to amplify a very weak signal to produce a higher output so that it drives a number of loud speakers.

    Scope of Study and Limitation

    This project work is the design and construction of audio amplifier that could be able to drive a higher number of loads i.e. speakers with good impedance matching, with good volume.

    The limitation is that, it is just an audio amplifier without any application like

    • Audio amplifier with mixer
    • Equalizers using operational amplifier
    • Photo voltaic light sensors using operational amplifier
    • Medical electronic monitoring system using operational amplifier
    • Phase detector using operational amplifier
    • Electronic thermometer using operational amplifier and so on.

    Justification

    This project work is relevant to the needs of the department, school, churches, mosques, and the society at large. It is useful in a congregation where it is used to raise the voice of the speaker so that he/she could be heard louder and clearer by the congregation. It can also be used to raise the volume of music and sound, during programme like NASTES, which as a result reduce stress and cost. This project is worthwhile, and stands to benefit many.

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  • Safety Issues Involving Workers on Building Construction Sites in Nigeria (case study Abuja)

    ABSTRACT

    Safety Issues Involving Workers on Building Construction Sites in Nigeria (case study Abuja). The term Building Worker refers to any personnel engaged in the physical construction of a building. Just like every other occupation they are faced with challenges in performing their duties. The safety of building construction workers on sites is key to achieving success in any project, when these workers are physically healthy work can go on smoothly as virtually all works on site are dependent on the workers for implementation. Numerous building projects are situated in Abuja, Nigeria with little or no attention being paid to safety issues. This research looked into the level of safety implementation of the Construction companies and the level of safety awareness of the workers in Abuja city. 80 questionnaires were issued, 69 (85%) copies were retrieved.

    The findings revealed that building site workers in Nigeria lacked the requisite trainings needed to perform their trades. The Construction company’s practice of not providing the basic safety materials and facilities was also exposed. The older workers were aware of their rights as employees on site. Lack of safety training was the major cause of accidents among the workers with minor injuries being mostly experienced. The Unqualified laborers were most frequently engaged in accidents on the sites. Accidents mainly occurred among workers less than 20 years of age. The Governmental agencies need to step up their enforcement activities in order to adequately protect these workers, the available safety regulations need updating and if possible solely Nigerian regulations should be designed.

     

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  • DESIGN AND CONSTRUCTION OF INTRUDER DETECTOR ALARM SYSTEM WITH DIRECTION/LOCATION DISPLAY

    ABSTRACT

    This research is on Design and construction of intruder detector alarm system with direction/location display. This project work deals with the use of Direction/Location Display which is capable of detecting intrusion at any location, sound and alarm and display the exact location of the intruder using seven segment displays. This project work is realized using top down methodology with active and passive components available in the local market. It is realized in different modules, all combined to form one function unit. The inputs are opto-couplers configured with laser diodes and light Dependent Resistor. (LDR) which act as the electronic eyes installed at the sensory points. The control unit is made up of one short delay circuit, audio frequency generator, priority encoder and decoder, piezo-buzzer and single digit seven segment display. The system is packaged in a well-furnished wooden material. This system does not record/display the intruder. In a case of simultaneous intrusion, the display shows the location with the highest priority. And the system is powered from a mains supply. The result being a system which can detect intrusion, sound an audible alarm and displays the exact location of the intruder. It has a wide a range of application in surveillance especially in industrial and home security.

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  • DESIGN AND BUILDING OF A SMALL SHELL AND TUBE HEAT EXCHANGER USING ALGORITHM

    ABSTRACT

    This research work is on Design and building of a small shell and tube heat exchanger using algorithm. A heat exchanger is a device which is used to transfer thermal energy between two or more fluid. This project is mainly focusing on designing one type of a heat exchanger which is shell and tube heat exchanger. In this project a fixed tube plate type shell and tube heat exchangers was chosen, exchanger of 150000 lb per hour of kerosene that will be heated from 75 to 120°F by cooling a gasoline stream from 160 to 120°F at a calculated heat load of 3240000. The specification of the Heat exchanger as well as the detailed mechanical design was calculated. It is established that the heat exchanger with gasoline at the shell side and kerosene at the tube side is adequate for the operation. The available area obtained from the calculation is 2105ft2 and also the overall heat transfer coefficient obtained is  Btu h -1 ft -2 °F-1  with a LMTD of  42.75°F. It is also seen that the heat exchanger is satisfactory and consist of 6 tube passes with tube outside diameter of 14 (BWG) and length of 24mm,the  shell outside diameter of 803.4mm and thickness of 3.72mm. The material for construction for the shell side is carbon steel.

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  • COMPARATIVE STUDY OF BIOGAS PRODUCTION FROM COW DUNG, CHICKEN DROPPINGS AND CYMBOPOGON CITRATUS AS ALTERNATIVE ENERGY SOURCES IN NIGERIA

    ABSTRACT

    This study was carried out to produce biogas from Cow dung, Chicken droppings and Cymbopogon citratus as well as the respective co-digestion of Cow dung and Chicken droppings with Cymbopogon citratus. 25 litre digesters and gas collection systems were designed and fabricated using locally available materials. The digesters were used to digest cow dung, chicken droppings and Cymbopogon citratus respectively as single substrates as well as to co-digest cow dung and chicken droppings respectively with Cymbopogon citratus. The respective feed materials were collected locally. They were pre-fermented, digested and analysed in accordance with standard methods. For the single substrates, the total volume of gas produced were 0.191m3 (0.032 m3/kg), 0.211m3 (0.035m3/kg) and 0.125 m3 (0.021 m3/kg) (before scrubbing) and 0.125m3 (0.021m3/kg), 0.130m3 (0.022 m3/kg), 0.090 m3 (0.015 m3/kg) (after scrubbing) for cow dung, chicken droppings and lemon grass respectively. For the co-digested substrates, Cow dung + Lemon grass produced 0.146m3 (0.024 m3/kg) before scrubbing and 0.100m3 (0.017m3/kg) after scrubbing while Chicken droppings + Lemon grass produced 0.193m3 (0.032 m3/kg) before scrubbing and 0.127m3 (0.0.021m3/kg) after scrubbing. The average ambient temperatures during the study were within the mesophilic range (20-40oC). The pH values were stable and always in the optimal range between 6.5-8.0. The reductions in total solid were 75.3 %, 60.1%, 98.2%, 61.9% and 35% for cow dung, chicken droppings, lemon grass, cow dung + lemon grass and chicken droppings + lemon grass respectively. The total coliform contents of the residue were 2.00 x107 CFU/100ml, 6.00 x 107 CFU/100ml, 1.00 x 107 CFU/100ml and 1.00 x 107 CFU/100ml for cow dung, chicken droppings, cow dung + Lemon grass,  and chicken droppings + Lemon grass respectively with 95%, 70%, 95% and 99% reduction in each case. Pathogens such as Salmonella spp and Klebsiella sp. were still present in the residue although E.Coli and Shigella sp. were removed. The estimated methane contents of the gas from cow dung, chicken droppings, Lemon grass, Cow dung + Lemon grass and Chicken droppings + Lemon grass were 65.59%, 61.71%, 71.95%, 68.53% and 66% respectively. The cooking rates for water were 0.079L/min, 0.070L/min, 0.067L/min, 0.064L/min and 0.060L/min for unscrubbed lemon grass, cow dung + lemon grass, chicken droppings + lemon grass, cow dung and chicken droppings respectively while those for scrubbed lemon grass, cow dung + lemongrass, chicken droppings + lemon grass, cow dung and chicken droppings were 0.12L/min, 0.10L/min, 0.091L/min, 0.085L/min and 0.079L/min respectively. The rice cooking rates were 0.0038kg/min, 0.0034kg/min, 0.0033kg/min, 0.0031kg/min, and 0.0030kg/min for unscrubbed lemon grass, cow dung+ lemongrass, chicken droppings + lemon grass, cow dung and chicken droppings respectively while those for scrubbed lemon grass, cow dung+ lemongrass, chicken droppings + lemon grass, cow dung and chicken droppings were 0.0055kg/min, 0.0048kg/min,      0.0045kg/min,      0.0041kg/min      and      0.0039kg/min       respectively.

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