The Design of a Portable Public of Address System - Essay Example

THE DESIGN OF A PORTABLE PUBLIC OF ADDRESS SYSTEM Introduction 3 Background study3 Rectifier unit or DC adapter 3 The amplifier unit 4 The microphone unit 4 The mixer 4 Cables 4 Identification of the customer requirements 4 Public address system 4 Portable generator unit 4 Small mixer 4 Storage unit 4 Extension Cables 5 Fuel storage unit 5 Demand and wishes of the system to be developed 5 Demands of the clients 5 DESIGN SPECIFICATION 6 Specification for the Small generator 6 Functional analysis 18 Testing the product 24 Application 25 References 25 The Design of a Portable Public of Address System Introduction A public address system comprise of a combination of several units used for the amplification of audio voice for the purposes of enhancing audibility of spoken information. In addition to reinforcing the sound, the public address system is also used for recording music, distributing the sound in large venue system, for training in large institutions, in airports to broadcast vital information, in public building and large commercial centers for the purposes of broadcasting information at these centers. The public address systems have greatly improved the communication in the industrial and commercial sectors especially when it comes to transmitting verbal information to a group of people. Charities and other organizations such as health organizations, non governmental organization offering relief food, medicine and training often encounter large number of people who the need to train and educate. This necessities the use of a public address system(PA). The PA system requires special design as they must be tailor made to meet the client's specifications and wants. It is therefore necessary to design the PA systems using an organized procedure such as the Pahl and Beitz method. The process involves the surveying of the customer's needs and wants, generating some demands and wishes from the client, developing of the solution using a function analysis matrix and finally developing the product using the information from the demands and the function analysis. After the development of the product, it is tested for its overall suitability particular in satisfying the customers wants and needs, if the product is found unsuitable or with some limits, it is necessary to redesign and reconfigure the product to ensure that it satisfy the customer needs and promotes usability engineering and ergonomic principles. Background study The main components of a public address system include; The power supply: This is the system that supplies the public address unit with electrical power that is used to run the whole PA system. The most common types power supplied include the alternating current (AC) and the direct current (DC). Most PA system use direct current while most of the commercially available power is in form of AC supplied at 240 Volts or 110 volts. Rectifier unit or DC adapter This adapter is used for the conversion of AC power to DC power. Some of the PA systems incorporate this gadget inside the systems while others have the same system incorporated outside as a separate unit The amplifier unit The amplifier unit is used for amplification of the voice signal. The amplifier receives low power electrical signal and amplify the signals to high power and voltage which is fed to the loud speaker systems. Amplifier uses the transistors, MOSFET devices, field effects transistors (FET), CMOS and operational amplifiers circuit to provide gain to the input signal. The microphone unit The microphone unit is used for changing voice sound to an electrical signal that can be amplified by the amplifier. Upon receiving the sound signal, the crystal microphone vibrate generating a small electrical current that is fed to the amplifier The mixer The mixer is used for signal conditioning, this helps is controlling the voice produced by the amplifier unit. The mixer enhances the audibility of the sound produced and helps in tuning. Cables Cables are used to provide physical connections between different parts in a PA system Identification of the customer requirements From the design problem the main customer requirements are; Public address system The customer needs a public address system that can be used to convey messages to a group of people. The number of the listeners is not high as the system will serve approximately 60 people. Portable generator unit Due to the mobility of the health team, they need a generator unit; the generator unit is to provide power to the whole PA system. Small mixer The mixer will aid in fine tuning the sound produced by the PA unit. This is necessary as the health team will use different environments. For example, if the PA system is to be used in a room, then a lot of fine tuning is required to reduce reverberations and echo. Storage unit It is necessary to design a storage unit where all the appliances will be stored as they are transported from one place to another. The storage unit also protects the vital electronic equipment from adverse weather and shocks during transportation. Flexible platform: the platform is used for mounting an elevated stand where the tutor will stand. The platform must be flexible to allow it to be dismantled, packed, transported and reassembled with ease. Recording unit: for documentation purposes it is necessary for the health team to record all the information done during their tutorials. This necessities the use of a recording system. The recording system so chosen must record both the audio and video in order to enhance the clarity of the stored data. Extension Cables The client's also requires a flexible extension cable that can be elongated with ease and repacked. It is necessary to provide three to four extension cables due to variation of the distance for transmission between the amplifier and the speaker unit. Fuel storage unit The generator needs a fuel backup system to provide fuel storage facilities. It is necessary to provide the fuel back storage as the generator may run out of fuel in remote place where the is no gasohol or diesel filling station nearby. Demand and wishes of the system to be developed Demands of the clients A set of 6 wired microphones A set of 6 wireless microphones An amplifier unit A mixer unit A gasohol portable generator Extension cables Connection sockets and plugs Loud speaker systems (4 loud speaker units) 2 Adjustable long Microphone stands 10 Adjustable table microphone stands The audio recording unit Small Fuel storage tank Wishes A specially designed packing box The video recording unit Connection with the internet through wireless system Flexible platform stand Computer unit (preferably 3 laptops) The table below shows the clients demand and wishes Table 1 showing the clients demands and wishes Customers demands Customers wishes A set of 6 wired microphones A specially designed packing box A set of 6 wireless microphones The video recording unit An amplifier unit Flexible platform stand A mixer unit Computer unit (preferably 3 laptops) A gasohol portable generator Mouth loud speaker backup Extension cables Solar charging unit Connection sockets and plugs Loud speaker systems (4 loud speaker units) 2 Adjustable long Microphone stands 10 Adjustable table microphone stands The audio recording unit Small Fuel storage tank The customer demand are the necessary and the most vital equipment required by the PA system while the wishes shows a list of additional equipments that can be added to the PA system to enhance the performance of the system. Some of the wishes may not be provided for due the financial constrains. The customer must provide the funds to purchase the products listed in the demand section but can opt to leave the options listed in the wishes section, for example, the PA system cannot operate without a generator which provides power in remote areas. The client can also consider purchasing a hand held loud speaker which can be used at times when the PA system fails. The client can opt to buy computers to enhance the PA system or he can opt not to buy the laptops. DESIGN SPECIFICATION After the identification of the customer's needs and wants, the product specifications are highlighted. The specifications for the different elements of the public address system are as shown in the table below; Specification for the Small generator The specification for the generator units are highlighted in the table shown below Specification for a portable mini generator unit Function The main function for the generator is to supply AC power in remote places. The power is to be used to run the whole public address system and all its accessories Types of user interaction The generator has: (1)Digital display to show the power it is producing. The type of display is an Liquid crystal display (LCD) screen where all generator technical operating information can be retrieved, the information retrieved include (fuel level, the engine speed, the oil level, the AC voltage being produced, the engine temperature, the engine speed and the power factor (2) Generator has Emergency shut off button: this is a red button used to shut of the generator in times of emergencies. (3) the generator has an analogue voltmeter to indicate the voltage it is producing (4) The generator has an analogue ammeter to show the current it is producing. (4) The generator has an analogue clock which shows the number of hours it has run. This helps in scheduling for maintenance activities. The generator is also equipped with warning lights. Some of the warning lights include(low fuel, high engine speeds, high engine temperatures, low coolant levels, short circuit occurrences etc ) Physical form The generator unit is 30 kg with the physical dimension being 0.5 meters length, 0.35 meters width and a height of 0.3 meters. Operating environment The generator operates at room temperatures, it has a maximum engine temperature of 900 centigrade, beyond which it produces a high temperature alarm Power production The generator has a power rating of 1 kilowatt or 1KVA, the AC voltage produced is 240 V, frequency is 50 Hz, the power factor is 0.9. Safety Some of the safety measures include; Don't not operate the generate near a fire Always follow the instructions manual Connects all cable before powering the generator ON Always switch OFF the unit before performing any maintenance activity Generator should be operated by an engineer or a trained technician. Noise levels The generator unit is fitted with a silencer unit to reduce the noise generated by the engine. Additional features include adding a steel pipe to further reduce the noise. The noise level is below 2 decibels. Maintenance The generator requires regular maintenance operations; these operations include Changing the engine oil after every 300 running hours Changing the spark plug after every 300 running hours Changing the fuel filter after every 300 running hours Changing the oil filter after every 300 running hours Decarburizing the exhaust after 1000 hours Checking all mechanical and electrical connections after 3 months of operation irrespective of the number of hours it has been in used. Performing an engine overhaul after 10000 hours of operation. Regular check up of the alternator parts after every 3 weeks. Cost of the unit The cost of the generator is US $ 800 Schedule The time required for buying, configuration and installing a movable stand on it is three weeks Other aspects The generator will be fitted with a wheeled base to enable easy transportation and movement. The wheel can be locked to prevent it from sliding from one point to another. Table 3 showing the Amplifier Unit specifications Specification for amplifier unit Function The main function of the amplifier unit is to provide gain to the audio signal so that it can be heard by a group of people. Other functions include Tuning the sound Increasing or reducing the sound Controlling noise Types of user interaction The amplifier has several user interaction interfaces, these include; Well labeled buttons for increasing and reducing the volume. Well labeled ports for inserting the input and output devices Liquid crystal display showing the volume variation as the person speaks Tuning knob for controlling the treble, bass and other sounds. Contains a port where earphones are placed by the operator to allow for fine tuning. Has a USB port that allows it to be connected to a computer. Physical form The amplifier unit is 5 kilograms, with physical dimensions being 0.2m in length, 0.15m width and 0.1 m height Operating environment The amplifier operates at ambient temperatures, it has a maximum temperature of 500 C, the lowest temperature is 100 C. Power production The amplifier typically consumes 240 volts, 5 amperes. It has an in-built rectifier that converts the alternating current to direct current. Safety Some of the safety measures include; Don't not operate the amplifier near a fire Always follow the instruction manual Connect all cable before powering the amplifier ON Always switch OFF the unit before performing any maintenance activity Never open the amplifier cover when the amplifier is switched ON or the power cable are still connected The amplifier should be operated by an engineer or a trained technician. Noise levels The generator unit is fitted with a silencer unit to reduce the noise generated by the engine. Additional features include adding a steel pipe to further reduce the noise. The noise level is below 2 decibels. Maintenance The amplifier unit requires regular checking especially checking its performance. Also the maintenance technician should check for heat dissipation of the transistors and the integrated circuit located in the circuit boards. If the integrated circuit are producing excess heat, they should be changed or a more stronger cooling fan installed. Cost of the unit The cost the generator is US $ 225 Schedule The time required for buying, configuration and testing is 3 days. Other aspects The amplifier required a special casing so as to protect it from shock loads during transportation. Table 4 showing the mixer unit specification Specification for mixer unit Function The main function of the mixer is to aid in tuning the voice of the public address system. Some specific tasks include Tuning Volume control Inter-mixing the voice with other effects and audios. For example the team may want to incorporate the health tutorial with some sounds. The mixer can perform this task Types of user interaction The mixer unit has several user interaction interfaces, these include; Well labeled buttons for increasing and reducing the volume. Well labeled ports for inserting the input and output devices Liquid crystal display showing the volume variation as the person speaks Tuning knob for controlling the treble, bass and other sounds. Contains a port where earphones can be fitted by the operator to allow for fine tuning. Has a USB port that allows it to be connected to a computer. Has a well elaborated 24 buttons interface for controlling and altering the voice characteristics Physical form The mixer unit is 7 kilograms, with physical dimensions being 0.15m in length, 0.10m width and 0.05 m height Operating environment The mixer unit operates at ambient temperatures, it has a maximum temperature of 500 C, the lowest temperature is 100 C. Power production The mixer typically consumes 240 volts, 3 amperes. It has an in-built rectifier that converts the alternating current to direct current. Safety Some of the safety measures include; Always follow the instruction manual Connects all cable before powering the mixer ON Always switch OFF the unit before performing any maintenance activity Never open the mixer cover when the mixer is switched ON or the power cable are still connected The amplifier should be operated by an engineer or a trained technician. The mixer should be handled with care as it the electronic component can fail is exposed to sudden shocks. Noise levels The equipment does not produce any noise but electronic noise is produced causing distortion and unclear voice. When this happens the electronic IC need to be checked. Maintenance The mixer unit requires regular checking especially checking its performance. Also the maintenance technician should check for heat dissipation of the transistors and integrated circuit located in the circuit boards. If the integrated circuits are producing excess heat they should be changed or a stronger cooling fan installed. A blow fan should be used to remove excess dust Cost of the unit The cost the generator is US $ 356 Schedule The time required for buying, configuration and testing is 3 days. Table 5: specification for the computer unit Specification for computer unit Function The computer unit is used for recording information and storing of all data as well as helping in the production of the training program. Types of user interaction The computer has well designed programs that allow the user to perform multiple task. Some of the most important user interface include The keyboard: for imputing data The monitor: the output of information and also form a very versatile user interface The mouse: provides a simple way to input information The help command: helps in training the user about the methods of using particular programs Physical form The laptop computers are used. their size varies. Operating environment The computer unit operates at ambient temperatures, it has a maximum temperature of 500 C, the lowest temperature is 100 C. Power production The computer unit consumes 240 volts, 1 ampere. It has an in-built rectifier that converts the alternating current to direct current. Safety Some of the safety measures include; Always follow the instruction manual Connects all cable before powering the mixer ON Always switch OFF the unit before performing any maintenance activity Never open the mixer cover when the mixer is switched ON or the power cable are still connected The amplifier should be operated by an engineer or a trained technician. The mixer should be handled with care as it the electronic component can fail is exposed to sudden shocks. Noise levels The equipment does not produce any noise Maintenance The computer unit requires regular checking especially checking its performance. Computers requires regular checking and scanning for viruses Cost of the unit The cost the computer is US $ 350 Schedule The time required for buying, configuration and testing is 3 days. Table 6: Microphone unit Specification for Microphone unit Function The main function of the microphone unit is to change the sound to an electrical signal that will further be processed by the Amplifier and the mixer. It is one of the input device Types of user interaction Has a well illustrated button for switching it ON and OFF. Other allow for slight volume adjustment. Physical form Microphones have several shapes; some are rectangular in shape, others are conical while other are cylindrical. There are some wireless microphones that require a receiver and are always sold as a combination of the microphone and the receiver. Operating environment Operates at ambient temperatures. Power production Wireless microphones require a small Dc power produced by a small rechargeable DC battery. Wired microphone requires no power to operate. Safety Some of the safety measures include; Always follow the instruction manual Connects all cable before powering the mixer ON Always switch OFF the unit before performing any maintenance activity The equipment can only be opened by skilled technician Noise levels The equipment does not produce any noise but electronic noise is produced when the equipment malfunctions. Maintenance The microphone unit requires regular checking especially checking its performance. Cost of the unit The cost the microphone is US $ 20 Schedule The time required for buying, configuration and testing is 1day. Table 7: Loud speaker system Specification for Loud speaker system Function The main function of the loud speaker system is to produce the amplified audio sound that will be heard the people listening Some loud speakers have integrated amplifiers in them thus reduce the connections required. Types of user interaction Loud speaker has ports and connection well labeled as the input to the speaker unit. They are used to fit the jack plug so that the equipment can function. Other loud speaker systems have switches for putting it ON or OFF Physical form Each loud speaker unit is 10 kilograms, with physical dimensions being 0.35m in length, 0.35m width and 0.5 m height Operating environment The loud speaker unit operates at ambient temperatures, it has a maximum temperature of 500 C, the lowest temperature is 100 C. Power production The loud speaker uses power delivered to it by the amplifier unit Safety Some of the safety measures include; Always follow the instruction manual Connects all cable before powering the mixer ON Always switch OFF the unit before performing any maintenance activity The loud speaker should be operated and repaired by an engineer or a trained technician. Noise levels The equipment does not produce any noise but electronic noise is produced causing distortion and unclear voice. Maintenance The loud speaker unit requires regular checking after 6 to 8 months. Blowing of dust should be done regularly to remove dust particles. Cost of the unit The cost the generator is US $ 180 Schedule The time required for buying, configuration and testing is 2 days. Table 8 Recording unit Specification for Recording unit Function The main function of this unit is to record all the voice and video transaction during meeting and learning sessions. The video recorder is used for this function. Types of user interaction The equipment has well illustrated buttons for : Removing the storage media tape Putting in place a new storage media tape Performing the recording activities Has a full color digital display that allows the recorder to view what he/ she is recording Adjusting the image size, resolutions, and other image properties are done with ease Physical form The recorder is small equipment. Its shape resembles that of a cuboids with dimensions 7cm in length 4 cm widths and 4 cm height. It weight is approximately 500 grams. Operating environment The recorder should operates at ambient temperatures Power production The unit has a rechargeable battery that can be charged after a period. Safety Some of the safety measures include; Always follow the instruction manual The equipment requires a specialized operator to perform maintenance activities Noise levels No noise levels Maintenance Among the most frequent maintenance activity is cleaning of lens and other optical devices. This should be done weekly and using special cleaning fluid, supplied or specified by the unit manufacturer. Cost of the unit The cost the unit is US $ 200 Schedule The equipment is bought ready for use, however the users should be trained on how to use the equipment. This training takes 2 days. Table 9 Storage unit Specification for Storage unit Function The main function of this unit is to store all the facilities ready for transport using the four wheel drive vehicle. This is a metallic box with partitions inside. Its is lined with a shock absorber material to prevent the electronic components for being damaged during transportation of the equipment Types of user interaction Each partition is labeled with the equipment that is placed inside Physical form The storage container is a rectangular box. With dimensions of 1.25 meters length, 0.75 meters width and 0.45 meters width. The inside of the box is laminated with a foam material to prevent damage of the equipment being transported. Operating environment Can operate at all conditions Power production No power required Safety Handle the box with care Noise levels No noise levels Maintenance Check the box for any damage regularly. If a damage occur, repair the box Cost of the unit The cost the box is US $ 50 Schedule The design and construction of the box will be done after purchasing all the other equipments Table 10 Flexible Platform podium Specification for Flexible Platform podium Function The main function of this unit is to enable the trainer to stand at an elevated position when addressing a group of people. The unit comprise of several round hollow section tubes that are interconnected and interlinked together to form the stand. The stand can be dismantled to aid in carrying it from one point to another. Types of user interaction The ends are enlarged and all pipes have the same dimensions. The user just fits and connects the pipes to form a cuboids platform. Physical form Rectangular in shape. Operating environment Can operate at all conditions Power production No power required Safety Handle the metal bars with care Noise levels No noise levels. Maintenance Check the round hollow sections for any damages. Repair if any damage is noted. Cost of the unit The cost the platform unit is US $ 450 Schedule The unit will take two weeks to design and construct Functional analysis The main units used for this design and their functions are illustrated in the table below. The table also shows the functions of each of the units Table 11 showing the main functions of the PA system Item Function Generator To provide power to the whole equipment set. Microphone To change the audio sound produced by the tutor to an electrical signal that is then amplified by the amplifier Amplifier To amplify the sound so that it can be made audible to a group of people Loud speaker They are used to change the amplified electrical signal back to audio sound, however the resulting audio sound is much more powerful than the original sound Mixer unit Used for fine tuning the whole set Storage Used for storing all the equipment in one box Cables and plugs They are used for providing interconnection between different parts. Flexible Platform podium Used for providing an elevated ground to enable the tutor be seen by all those being educated or trained Recording unit Used for providing storage facilities for the education media. For each of the main functions, lists of equipments that can be used are outlined. The resulting table is as shown below Table 12 showing the list of solutions to the design problem Function List of solutions Power generation Diesels generators Gasohol generator Solar power charging Microphone Wired microphone Wireless microphone Amplification Amplifier with inbuilt mixers Amplifier with no inbuilt mixers Loud speaker Wired speakers with no inbuilt amplifier Wired speakers with no inbuilt amplifier Speakers only Mixer unit Ordinary mixer unit Storage Metallic box Wooden box Plastic box Cables and plugs Copper cables Flexible Platform podium Metallic platform Wooden platform Plastic platform Recording unit Audio recording integrated with the amplifier Audio recording plus video recording using a camcorder According to the Pahl and Beitz method, the list of options can be evaluated using numerical values assigned to them, some of these numerical values are illustrated in the table below Categories Numerical Values Completely Useless Solution 0 Very Inadequate Solution 1 Weak Solution 2 Tolerable Solution 3 Adequate Solution 4 Satisfactory Solution 5 Good Solution with some drawbacks 6 Good Solution 7 Very Good Solution 8 Solution Better Than Requirements 9 Ideal Solution 10 Table adapted from (Pahl, G., Beitz.1988. Engineering Design: A systematic approach, Springer publishers http://www.enge.vt.edu/terpenny/Smart/Virtual_econ/Module2/pahl_and_beitz_method.htm ) From the function table, each list of solution can be evaluated using the Pahl and Beitz method, based on this evaluation the different solutions were ranked. The results were outlined in the table below. The encircled number represents the solutions based on the Pahl and Beitz. Table showing the solution formulation using the Pahl and Beitz method Function List of solutions Power generation Diesels generators Gasohol generator Solar power charging Microphone Wired microphone Wireless microphone Amplification Amplifier with inbuilt mixers Amplifier with no inbuilt mixers Loud speaker Wired speakers with no inbuilt amplifier Wired speakers with inbuilt amplifier Mixer unit Ordinary mixer unit Don't use mixer unit Storage Metallic box Wooden box Plastic box Cables and plugs Copper cables Flexible Platform podium Metallic platform Wooden platform Plastic platform Recording unit Audio recording integrated with the amplifier Audio recording plus video recording using a camcorder The number in the blue box indicates the evaluation solution. The obtaining of this index depends upon The suitability of the material The efficiency of the material The cost of the material and equipment The size of the equipment or material The ability of the material to perform intended task with ease, ease of operation From the evaluation conducted it was found that the most suitable solutions for each of the components are as given in the table below Function Solution Power generation Gasohol generator Microphone Wireless microphone Amplification Amplifier with inbuilt mixers Loud speaker Wired speakers with no inbuilt amplifier Mixer unit Not incorporated Storage Plastic box Cables and plugs Copper cables Flexible Platform podium Metallic platform Recording unit Audio recording plus video recording using a camcorder From the solutions obtained in the above table the whole public address system can be designed. The functional diagram for the system is as shown in figure 1 below. The first design includes the major functional parts and their accessories From the figure shown above the wireless microphone pick the audio signals from the tutor, changes them to frequency modulated waves (FM) that are the transmitted in the air medium. The receiver unit receives the sounds and converts them to electrical signals that are fed to the amplifier unit. The amplifier unit boosts the electrical signal and also allows the operator to fine tune the sound produced. Once the sound has been fine tuned, it is passed to the loud speaker where it is converted back to audio signals that can be heard by the listener For the power supply systems, the block diagram is as shown in the figure below The generator set is used to provide power to the amplifier unit, the generator is also used to provide power to the microphone receiver set and the generator also provides power to the all other accessories such as charging the recording unit and providing power to all other equipments that are in use. Testing the product After the assembly of the whole set of equipment, it is tested to find if it will provide the best solution to the customer. After testing the equipment, necessary changes are made to ensure that the equipment developed satisfies the customer needs and wants. Redesigning the product is necessary in order to solve any anomalies that are encountered during the design stage Application The designed product can then be applied and recommended to the customer References Pahl, G., Beitz.1988. Engineering Design: A systematic approach, Springer publishers Malmqvist, J. 1996. A Comparative Analysis of the Theory of Inventive Problem-Solving and the Systematic Approach of Pahl and Beitz. USA Read More