Last Updated 18 Jan 2017

Public Addressing System

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Table of Contents Acknowledgment…………………………… Abstract…………………………………………… Introduction…………………… * Background of the Study…………… * Statement of the Problem……………………… * Objective of the Study……………………………… * Scope and Limitations……………………………. * Significance of the Study…………………………… * Conceptual Framework……………………………. Discussion……………………………………………… * Schematic Diagrams………………………… * Parts List……………………………………… Conclusion……………………………………… Glossary……………………………………………… References……………………………………… Appendices…………………………………………… Recommendations………………………………… Acknowledgment

The proponents would like to express their sincerest and deepest gratitude to the following for their contribution and involvement in the project: to God Almighty, for His unfathomable grace and overwhelming blessings, to their parents, for providing the place to stay throughout the project. If it weren’t for their financial, emotional, mental, and spiritual support, the proponents wouldn’t have completed the project, to the librarians of the Don Honorio Ventura Technological State University for their assistance, to their supportive Electronics Engineering Department Instructor, Engr.

May Layson for giving them the opportunity to fulfill this project and lastly, to their friends, classmates, colleagues and everyone who were not mentioned who also, even in their small ways, helped in the improvement and fulfillment of the project, and supported the proponents until the end. They are forever in debt to everyone for their undying support, for without them, this project wouldn’t be completed. Abstract There had been a number of projects that focuses on the important aspects of a Public Addressing System.

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This study was then conducted in order to understand and appreciate the working principles of PA systems from their construction, functions and daily applications. Specifically, this research aimed to identify the role and reliability of PA Systems as a tool for communications. The design of the device was based on the perspectives of the instructors on how the system will satisfy the needs of the institution. The advantages and disadvantages of using the tool were also discussed. Weighted means were computed to analyze the significance of the project.

The results showed that the project is capable of being an optional sound reinforcement system since it can do mixing and amplifying signals of different inputs. This in turn benefits the student’s society as it enables them to have means of addressing with one another through a sound amplification system. This also helps in reducing the constraints of having a poor sense of communication in a limited range. Nonetheless, the students involved also agree that the accuracy of the data obtained from the test results are quite difficult to ensure considering that the knowledge about the device is limited.

Future researchers could easily take enhancements recommended for the betterment of the project. Moreover, legal consultation had been correlated to this tool. As stated from literatures, these finding clearly emphasizes the need for some additional resources from the previous studies and advices from instructors to ensure the reliability and validity of the results obtained. Items that point out to lack of available components must be taken out. Furthermore, outcomes of project enhancement and appraisal can be more successful by combining the concepts and ideas made based from the prototype versions.

Introduction Communication plays an important role in the development of a nation. It is an integral part of development. Societies cannot change and develop without communication, as it is a process of social interaction through which people are influenced by ideas, attitudes, knowledge and behavior of each other. Nowadays, communication has attained a great importance in the developmental programs. It is through the process of communication that people are made aware of the nature and objectives of the programs.

The useful developmental messages are conveyed to the target groups through various communication approaches. This helps people in acquiring new knowledge required for coping with fast changing society and in adoption of innovations for the improvement of their practices, methods and quality of life. Through the advancement of technology, electronics paved way for the development of communication systems. One of the innovations brought about these technologies is the Public Addressing System.

A Public Addressing System or simply PA System is an electronic sound amplification and distribution system. It is anything that amplifies sound so more people can hear it. Most basic systems these days include several different parts such as one or more microphones, one or more speakers, a mixer that allows the user to control the volume, tone and balance of different voices or instruments, an amplifier (built into the mixer, built into the speakers, or purchased separately) and stands to hold the speakers and microphones at appropriate height and angles.

From this documentation, the researchers were able to explore and delve deeper about the concepts on how a PA System work and how does it contribute to development in the field of communication systems. Background of the Study A Public Address (PA) system is a collection of audio equipment that allows broadcasts over a designated area. Often found in schools and office buildings, PA systems can be used for general announcements or emergency information, providing a simple way to get information out quickly. PA systems can be basic or advanced, and people can customize them to fit a variety of needs.

There are even personal models that can be less expensive, but allow for a much shorter range. The term is also used for systems which may additionally have a mixing console, amplifiers, and loudspeakers suitable for music as well as speech, used to reinforce a sound source, e. g. , recorded music or a person giving a speech, and distributing the sound throughout a venue or building. Sound reinforcement systems and PA systems may use some similar components, but with differing application, although the distinction between the two is not clear-cut.

Sound reinforcement systems are for live music or performance, whereas PA systems are primarily for reproduction of speech. The presence of the light weight components included in the circuit makes it easier to carry, and therefore, making it handy. Recently from the previous projects, we have used several components to amplify signals. Some of which are the bipolar junction transistor, field-effect transistor and metal-oxide semiconductor transistor, now we will use one of the best amplifying device, the IC OP-AMP. 41 OP-AMP is a versatile IC that can be used as a differential amplifier. From this, the researchers must be able to conceptualize and build effective Portable Public Addressing System using operational amplifiers and other electronic components as the center of the study. Statement of the Problem What is the purpose of a Public Addressing System? The purpose of a portable PA system is to provide an accessible way of addressing in a crowd. This is very useful when communications are to be made in a limited broadcasting range. Objective of the Study

To be able to conceptualize and build an effective public addressing system using IC-Operational Amplifiers and other electronic components and understand and appreciate its principles of operation as well as its primary function and applications. Scope and Limitations While a simple and portable PA system is often fairly expensive, it can provide a speaker with some options for addressing a crowd of people. This type of public announcement hardware provides someone with extremely limited broadcasting range, often including only a single speaker, but still serves to amplify the user's voice.

All PA systems are also delimited since they have a potential for audio feedback, which occurs when sound from the speakers returns to the microphone and is then re-amplified and sent through the speakers again. Another thing is, more advanced versions increase in price considerably, especially with numerous cords, wireless hubs, and adaptors that may be required. This all depends, however, on what a person or business needs in terms of PA system hardware and installation. Significance of the Study

The project is intended to enrich and upgrade the knowledge of the proponents about the different uses of IC Operational Amplifiers by constructing a simple portable Public Addressing System. This study will be a significant endeavor in promoting the construction of useful devices with the advancements of electronics. It will also be beneficial to the students and instructors in some applications employing conduction of gatherings, meetings, seminars and workshops for effective learning in their classroom setting particularly in different concepts related to electronics.

By understanding the needs of the students and benefits of quality education, these instructors and students are assured of a competitive advantage. Moreover, this project will provide recommendations on how to evaluate the performance of the researchers involved in accordance to the outcome of the study. Conceptual Framework A Public Address System is an electronic sound amplification and distribution system with an audio input, amplifier and an audio output. The Portable Public-Addressing System (PA systems) is capable of amplifying different input signals like microphone, audio, and guitar signals simultaneously.

Microphones The transmission can begin with a microphone, which is a device that can assist in magnifying an audio source's volume. A microphone is classified as a device that transforms sound into an electrical signal. Microphones used in PA systems are usually dynamic or condensers. Dynamic microphones are more rugged than condensers and are able to withstand the elements a little better. Condenser microphones utilize their own power source and produce better-quality audio signals, but can sometimes be so sensitive that they also receive background noises.

Mixers If a microphone or another audio source is used in a PA system, it is plugged into a mixer. The mixer allows for multiple channels of sound to be broadcast at different levels. This can help prevent feedback if a PA system will involve multiple microphones, instruments, or other audio sources. For example, someone may use a PA system to sing along with a pre-recorded CD. The CD track could be plugged into one channel, while the singer's voice would be broadcast through another. Amplifier The amplifier is usually side by side or incorporated with the mixer.

The amplifier's job is to magnify the audio signal by manipulating its varying frequency qualities. Gain in an amplifier refers to the decibel level of the sound coming out of the speakers. Another quality, Output Dynamic Range, refers to the loud and soft levels of a specific channel's sound. Too low of an output could result in just broadcasting noise; too high of an output can lead to distortion. Loudspeakers The loudspeaker is the output end of the PA system, transforming the electrical signal back into sound that a group can hear.

A good loudspeaker system will separate the differing sound frequencies and broadcast them through different sound channels for better quality output. Parts of a loudspeaker system include a woofer, which broadcasts low frequency sounds; and tweeters, the drivers of high frequency output. Some speakers also contain crossover systems that are responsible for separating these frequencies, reducing the electrical noise that can sometimes accompany a PA system broadcast. Discussions The design of the system internally contains three major stages. These stages are connected to each other to attain the circuit of a Portable Public Address System.

The first stage is the power supply of the circuit; has a center-tapped transformer with the primary set to 220Vac and secondary of 12-0-12Vac. This transformer is connected to diodes and capacitor which is responsible for filtering and to produce a full-wave output. This output will become a DC voltage which will serve as +VCC for the next stage. The second stage is for the Pre-amplifiers. There are three Pre-amplifiers which contain two inputs for the microphone and one for the guitar. The Pre-amplifiers in the project use an IC which is generally considered as one the most versatile component there is.

The purpose of the IC is to amplify the input sound signals to produce a sound suitable for speakers. Normally in the pre-amp, the output of the sound is not quite satisfying. An increase in the volume of the sound will be attained when it is connected into another stage which is the Power-Amplifier stage. This is the last stage of the circuit. The Power-Amplifier is one that drives the input sound coming from the pre-amplifier to produce an output through speakers. The Power-Amplifier uses an IC also. The loudness of the sound is produced by the Power-Amplifier. Schematic Diagrams * Audio * Guitar Microphone * Microphone Power Amplifier * Power Supply Parts list Label| Quantity| Description| R1, R2, R3| 3| 1K 1/4W Resistor| R4, R5, R6| 3| 10K Logarithmic Pot| R7| 1| 1Meg 1/4W Resistor| R8, R10| 2| 10K 1/4W Resistor| R9, R11| 2| 100K Linear Pot| C1, C2, C5, C6| 1| 0. 1uF Ceramic Disc Capacitor| C3, C4| 2| 22nF Ceramic Disc Capacitor| U1, U2| 2| 741 Op Amp| J1, J2, J3| 3| Input Jacks| MISC| 1| Board, Wire, Knobs, IC Sockets| Conclusion A Portable Public Address System is an electronic sound amplification and distribution system with a microphone, amplifier and loudspeakers used to allow a person to address a large public for example for announcements of ovements at large and noisy air and terminals. The PA system contains a mixing console where the amplifiers and loudspeakers are suitable for music and as well as speech used to reinforce a sound source and distributing the sound throughout a venue or building. It is often used in small areas such as school auditoriums, churches, small bars or other places. The significance of being portable is by means of you can carry it anywhere because it is lighter and useful for emergency or immediate announcements.

It also contains two systems combine in one module. The two systems may use some similar components but with different application. It has a sound reinforcement system which is the guitar input use for music performance and a PA system which is the microphone input use for speech purposes. Glossary A Amplify - to make larger, greater, or stronger; enlarge; extend. Audio – pertains to employed in the transmission, reception, reproduction of sound. B Bipolar junction transistor (BJT) - has three terminals connected to three doped semiconductor regions.

Board - piece of wood sawed thin, and of considerable length andbreadth compared with the thickness. C Condenser-lens or combination of lenses that gathers andconcentrates light in a specified direction, often used to direct light onto the projection lens in a projection system. Constraints - limitation or restriction. Circuit - the complete path of anelectric current, including the generating apparatus, intervening resistors, or capacitors. Capacitor - is a passive two-terminal electrical component used to store energy in an electric field.

Console - a physical device to operate a computer. D differential amplifier - a type of electronic amplifier that amplifies the difference between two voltages but does not amplify the particular voltages. F field-effect transistor (FET) is a transistor that uses an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material feedback - occurs when a sound loop exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for example, a loudspeaker).

H hub - makes the networking of multiple computers in the home or office easier. I Integrated circuit (IC) - the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material. Input - term denoting either an entrance or changes which are inserted into a system and which activate/modify a process. J Jack - is a small, round electrical connector found on audio and video products that is used to interconnect components. Junction - point where at least three circuit paths meet. K

Knob - a small rounded ornament or handle. M MOSFET (metal-oxide semiconductor field-effect transistor - special type of field-effect transistor ( FET ) that works by electronically varying the width of a channel along which charge carriers ( electron s or hole s) flow. Microphone - an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. N Noise - unwanted sound. O Operational-Amplifiers - widely used electronic devices today, being used in a vast array of consumer, industrial, and scientific devices.

Output - term denoting either an exit or changes which exit a system and which activate/modify a process. P Portable – denotes something that is handy. Plug - a male fitting for making an electrical connection to a live circuit by insertion in a receptacle (as an outlet). Pre-amplifier (pre-amp) - an electronic amplifier that prepares a small electrical signal for further amplification or processing Potentiometer - commonly used to control electrical devices such as volume controls on audio equipment. R

Resistor - is part of an electrical circuit that resists the flow of current. Reinforcement - is when a behavior is increased or maintained by its consequences. Rugged - having a rough uneven surface. S Signal - a detectable physical quantity or impulse (as a voltage, current, or magnetic field strength) by which messages or information can be transmitted. Speaker – an output device used specially for audio signals. T Transistor - a semiconductor device used to amplify and switch electronic signals and electrical power.

Terminal - a position in a circuit or device at which a connection can be made or broken. References Articles * Basic P. A. Systems: A Primer For Using P. A. Systems by Yorkville Sound Books * Electronic Devices and Circuit Theory by Robert L. Boylestad and Louis Nashelsky * Electronic Principles by Albert Paul Malvino * Teach Yourself Electricity and Electronics 5th Edition by Stan Gibilisco Websites * www. yorkville. com * www. wikipedia. com * www. circuitstoday. com * www. ehow. com * www. howstuffworks. com Appendices LM741 Operational Amplifier General Description

The LM741 series are general purpose operational amplifiers which feature improved performance over industry standards like the LM709. They are direct, plug-in replacements for the 709C, LM201, MC1439 and 748 in most applications. The amplifiers offer many features which make their application nearly foolproof: overload protection on the input and output, no latch-up when the common mode range is exceeded, as well as freedom from oscillations. The LM741C is identical to the LM741/LM741A except that the LM741C has their performance guaranteed over a 0°C to +70°C temperature range, instead of ? 5°C to +125°C. Connection Diagram Recommendations All PA systems have a potential for audio feedback, which occurs when sound from the speakers returns to the microphone and is then re-amplified and sent through the speakers again. Sound engineers take several steps to maximize gain before feedback. If you are setting up a sound system and want to avoid feedback, there are a few general measures that can help avoid such problem: * Keep a certain distance between the position of the microphone and the speakers. * Use a unidirectional microphone. If you have access to an equalizer, dampen the frequencies where feedback is occurring. * Ensure that both microphone and speakers are in good performance state. * Never place a mobile phone near the speakers or even at the microphone. Since the Power-Amplifier is responsible for the driving of the input sound (coming from the pre-amplifier), it is necessary to have an efficient circuit of a power amplifier with a sufficient wattage needed to obtain a desired output. The greater the wattage value of a power amplifier circuit, the better the output sound.

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