A major crisis in my famouse company or shop with one of my Essay

A major crisis in my famouse company or shop with one of my customers> - Essay Example This was the first time any such complaint was brought into the notice of the company. Our company has been an established name in the clothing and accessories industry since many decades. To protect our image, we asked the woman to leave the shirt and her contact with us and if we found that the rash on her face was the result of our product she will surely be compensated. After the woman left a meeting was called where the senior most management was briefed about this unusual complaint faced for the first time by any customer. It was concluded in the meeting that action must be taken on this complaint before any other customers come to us with the same complaint. An inquiry commission was appointed to look over this case and presented a report to the senior management about the whole issue. The shirt of the customer was sent for examination in the lab. After few days the result of examination came and it was a shocked to hear that the company’s product was responsible for the rash. The report suggested that chemical named â€Å"formaldehyde† is found in the fabrics of the shirt. This chemical is mostly used for giving the clothes permanent press effect and also for increasing stain resistance. However this chemical can be harsh on skin if used in large quantity. The amount of formaldehyde found in fabric supplied by the supplier was more than the standard amount and this is the reason why the woman was complaining about skin irritation. Now that the company found the root cause of the problem, it was decided that it will be better for the firm to change the supplier, to avoid such problem in future. It was concluded that it is not solely the mistake of the supplier, but the inspection department of our firm also failed to detect the presence of such strong chemical in the raw material. The head of the inspection committee was also given a warning after this incidence and was asked to be act extra

Patriotic Sentiment in the Interwar Essay Example for Free

Patriotic Sentiment in the Interwar Essay The creation of the British Empire and its â€Å"contributions† to the welfare of its colonies was used by many English historians as a source of justification for its existence and future. Needless to say, many English historians would naturally put the British Empire as the â€Å"empire† that aspired for assimilation and multiculturalism, which had been absent in previous empires (although this is debatable) (Aldrich 1988:24). Added to that, because of the perceived inferiority of the colonized peoples, many of these historians usually attached to the â€Å"white man† the significant role of guardian (Aldrich 1988:25). In recent years however, this notion of racial superiority was replaced by the principles of equality and self-determinations. This was in lieu of the increasing surge of patriotic sentiments of the colonized peoples and a general compromise of the colonial powers over the future of the former colonies, as mandated by the United Nations. Modern English historians, while continuing to justify the existence and foundation of the British Empire, admitted some of the mistakes and grave errors usually attributed to the British Empire. Nonetheless, they argued that these mistakes were committed out of necessity. Other colonial powers were greedily aspiring to replace Britain in its role as a superpower. Germany for instance, before the onset of the First World War, was building a powerful navy to replace Britain as a sea power. France was busy eyeing British colonies in Central Africa for its own exploitation. In short, the errors committed by Great Britain to its colonies were a result of self-defense. Added to that, in order for the colonies to benefit from British colonial rule, the colonized peoples would have to sacrifice some of their outdated or â€Å"primitive† institutions and adopt institutions that are characterized by efficiency and commitment to public service. These justifications made by English historians on the role and future of the British Empire were imbued in the study of history. History as a Tool for Application of Theoretical Knowledge The use of history to justify the existence and foundation of the British Empire was not born out of prejudice or unsubstantiated truths. In fact, early English historians noted that history should be as scientific as possible in order to represent the true nature of world events. Added to that, these English historians viewed history as an application tool for upgrading the political, social, and economic systems of the world today. Specifically, knowledge of the end of the British Empire would naturally pave to greater solidarity and understanding between former colonies and the mother country (the colonizer); that they have a common history, and to some extent similar social, economic, and political structures. Although for the common viewer this might seem a little idealistic and devoid of historical verification, this was the practical side of the scientific discipline of history, if we accord them to these English historians. Thus, the extensive use of history as a tool for the political understanding of countries with a â€Å"common† history was the result of theoretical justification of English historians on the existence and rule of the British Empire to about a large portion of the Earth’s population. This was though a problem for many local historians in the former colonies. They extensively used history as a tool for demonizing their colonial oppressors: the justification of independence movements and revolutions. This dialectic aspect of history, depending on the one who views it, disoriented historical data, making the discipline of history itself the vantage point of uncertainty (Aldrich, 2000). Herein, we shall examine the various practices that were incorporated in a large, common society. Nonetheless, we shall also examine power relations between the mother country and its colonies as well as the issue of tolerance and cultural differences. Cultural Toleration in the British Empire When England finally defeated France and Spain in a series of colonial wars, it was able to establish colonies in North America and Asia (Africa was not the target of colonization since it was viewed as an inhabitable and inhospitable continent – although commercial bases were established to streamline trade and commerce with other European powers) (Baldwin, 2007). England was able to acquire Malacca from the Portuguese in the latter half of the 16th century. India and Canada fell into the hands of the British after France’s defeat in the Seven Years War (called French and Indian Wars in North America). The eastern coast of the present United States was colonized by England (the Thirteen Colonies) to foster greater trade between North America and England (it was known as New England). Australia and New Zealand were colonized to provide the British Empire penal colonies for the rouge elements of British society. Rebels and political prisoners were deported to these penal colonies. In the latter half of the 19th century, Britain was able to take possession of several Chinese ports after a series of wars with China, then under the rule of the Manchus (known as Opium Wars). In South America and the Caribbean, some islands were colonized by the British to offset Spanish and French power in the area (although in the early part of the 19th century, Spain controlled at least 2/3 of the land area of North, Central, and South America). In the European partition of Africa, Britain controlled a large portion of North, Central, and Southern Africa. These colonized areas minus the 13 colonies were known as the British Empire. The British fostered a policy of cultural toleration to discourage the native population from revolting. Moslems, Hindus, Taoists, Buddhists, and other Oriental religions existed side by side with Christianity in matters like trade and commerce. Temples of different religions were treated with respect and dignity by British authorities. Nonetheless, British rulers especially Queen Victoria even traveled to the colonies to inspect and inspire the native populations to support Great Britain in its economic undertakings, for the benefit of the mother country and the colonies, and its colonial wars with other European powers (especially France and Germany). Religious festivals were declared as holidays, with some exceptions, to foster greater solidarity with the native population. English was not an enforced language. This was done to preserve and enrich the culture of the native populations. The â€Å"British† educational system was introduced to stimulate greater economic efficiency in the colonies. The British parliament, in its sessions, declared that education was the only plausible and least risky way of opening the colonies to true development. The British parliament and to some extent the British rulers knew that there were form of British economic exploitation in the colonies, thus the only way for them to recreate the image of the â€Å"British Empire† was to encourage education. English was taught in the universities (other European powers loathed this type of strategy) established outside Britain. Economic and maritime schools were also established to stimulate the natives to increase their productivity yield and to participate in naval undertakings. Nonetheless, the British army was remodeled in order to include natives in the soldier payroll. At a specified rank, a native could rise to a prominent rank in the military. Needless to say, to fit in the global economy, Britain also created institutions that would politically and socially integrate the mother country and the colonies. The old models of exploitation and oppression were replaced by systems of mutual cooperation and commitment to a common economic goal. Thus, these contributions of the Britain to its colonies became the framework of early English historians for justifying the existence of the British Empire. Patriotism and Nationalism: The Beginning of Decline Nationalistic sentiment in the colonies grew in the latter beginning of the 20th century. Because of the relative prosperity of the colonies, some of its natives were able to study in European universities and able to acquire the increasing surge of ultra-nationalism (nationalism in Europe differs from the nationalism of the colonies on one count: nationalism in European countries focused on the acquisition of colonies to bring glory to the country, whereas in the colonies on independence) in Europe. When they returned to their homeland, they established organizations which aimed of attaining independence or self-governance status of their homelands. The British authorities naturally would quell these â€Å"uprisings† since this put into question the status quo, and generally the legitimacy of the British Empire. Power Relations But because of the involvement of Great Britain in the two World Wars, it was forced to grant self-governance status to many of its colonies in exchange for economic and military support (in India, Gandhi urged the Indians to fight on the side of the British). However, because of the changing political atmosphere in Britain at that time, the British authorities once more crushed these independence movements. Many were forced to go underground. Some seek political asylum in America or The Netherlands. Added to that, political theory and political education were deleted in the course curriculum of many universities for fear that the British might close the institutions. The purpose of the British authorities was always to preserve the rule of the British Crown on the colonies. All means were therefore necessary in order to dissipate these independence movements. Thus, while the British were open to cultural toleration, they loathed political development in the colonies. Political development is the measure of citizen participation in the affairs of the government. Political development is largely a relationship between the citizenry and the country to which they owe their citizenship. The British authorities were enforcing a policy of â€Å"mother dependency†, that is, the political, social, and economic future of the colonies should depend on the mother country. Later Vladimir Lenin expanded this concept and renamed it as the â€Å"dependency relations. † The mother country, according to Lenin, when its reaches the height of economic development experiences shortfalls and recessions due to overproduction. The surplus produce of the mother country is â€Å"dumped† to the colonies since colonies are potential markets. In this way, economic recessions in the mother country are kept in check, and the laboring class enjoys relative prosperity, at the expense of the colonies. This is a uni-directional type of development unlike the so-called â€Å"mutual development† that Britain was preaching (as exemplified in Africa, in Ramsay, 2000/1784). Practices and Institutions that Became Part of the Colonies’ Society: The Tragedy British colonies can be classified into two categories: 1) those that fully accepted British practices and institutions, 2) those who only accepted British political and educational institutions. India, Pakistan, former British African colonies, and former British Asian colonies adopted the political and educational institutions of Great Britain because of its efficiency and relative good organization. The parliamentary system became the standard system of government of most of the former colonies of Great Britain. It was noted that this type of government adheres to the principles of public accountability and stability. Most of the former colonies of Great Britain using this type of government experience relative stability and effective governance (Toynbee, 1987:401). The tragedy lies on the second type of former colonies. These colonies fully adopted British practices and institutions at the expense of native practices and customs. In Australia and New Zealand for example, most of the population is classified as of British or European descent. When the British came to New Zealand, they dispossessed the Maori through fraudulent land contracts and generally through war (that severely reduced the Maori population by 1/8. The British authorities encouraged immigration to these places (Australia and New Zealand) to reinvigorate economic activities to these places. The result was that New Zealand and Australia became an extension of British society: mirror images of England. The Maori who were the true owners of the country was exploited and dispossessed by the British. In the case of Canada, because of strong French influence (former French colony), the British authorities had the difficulty of making Canada a cultural sphere of influence of Britain. In fact, cultural differences in Canada serve as the marking definition of power relations in Canada. Conclusion While many English historians talk endlessly of a Commonwealth under the banner of Great Britain, they were not able to pinpoint the opportunity costs of the colonization on the part of the colonies. There is no such thing as a common society, for the British Empire created two types of societies in its sphere of geopolitics. The only intersection of these societies is the institutions bequeathed to them by the British Empire. Socially, these societies differ significantly because the British Empire was not able to fully integrate its customs and practices to most of its colonies due to the onset of nationalism and patriotic sentiments of the native populations (in Australia and New Zealand, there was no such thing as a â€Å"political† native population since they were able to reduce their populations through wars and enforced immigration policies). References Aldrich, Richard. 1988. Imperialism in the study and teaching of history. In Benefits Bestowed? Education and British Imperialism. Manchester and New York: Manchester University Press, pp. 23-38.

Microcontroller Based DC Motor Speed Controller

Microcontroller Based DC Motor Speed Controller In this report I present a microcontroller based DC motor speed controller. DC motors play a vital role in most of the industrial areas. They are mainly used for the mechanical movements of physical applications such as media drives, power plants, lifts, elevators, conveyers, belt driven loads (printing press) etc. The controller implements the control strategy governing the load and motor characteristics. To match the load and motor, the input to the microcontroller is manipulated by the controller. The purpose of a motor speed controller is to capture a signal representing the demanded speed, and to drive the motor at that speed. The controller may or may not actually measure the speed of the motor. If it does, it is called a Feedback Speed Controller or Closed Loop Speed Controller, if not it is called an Open Loop Speed Controller. Feedback speed control is better, but more complicated, and may not be required for a simple circuit design. The former (closed loop) is implemented in the presented controller design. The subject arrangement consisted of a tachometer attached to the shaft of the motor. A controller design cannot be more accurate than methods aimed at measuring actual motor speed. This is readily attained by coupling the motor shaft with a tachometer. The tachometer output signal is converted to a dc voltage signal acceptable to the microcontroller. The microcontroller is programmed to drive the motor accomplishing the load requirement. The operation of dc motor was studied. Several types of motors and various control types were investigated. The project also intends to familiarize us with the efficiency of PIC in control systems. To evaluate the effectiveness of the controller, analysis will be conducted driving variable load while maintaining constant speed of the motor. The advantages of using microcontrollers to control dc motor were studied. INTRODUCTION 1.1 MOTOR An electric motor is an electromechanical device that converts electrical energy to mechanical energy. The mechanical energy can be used to perform work such as rotating a pump impeller, fan, blower, driving a compressor, lifting materials etc. It is estimated that about 70% of the total electrical load is accounted by motors only. 1.2 CLASSIFICATION OF MOTORS Electric Motors Alternating Current (AC) Motors Direct Current (DC) Motors Synchronous Induction Three-Phase Single-Phase Self Excited Separately Excited Series Shunt Compound FIG-1.1 classification of motors 1.3 AC MOTORS An AC motor is a motor that is driven by an alternating current. It consists of two basic parts, an outside stationary stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft that is given a torque by the rotating field. 1.3.1 TYPES OF AC MOTORS There are two types of AC motors, depending on the type of rotor used. The first is the synchronous motor, which rotates exactly at the supply frequency or a sub multiple of the supply frequency. The magnetic field on the rotor is either generated by current delivered through slip rings or by a permanent magnet. The second type is the induction motor, which turns slightly slower than the supply frequency. The magnetic field on the rotor of this motor is created by an induced current. 1.3.2 TYPES OF INDUCTION MOTORS Squirrel-Cage Induction Motors The most simple and reliable of all electric motors. It is essentially a constant speed machine, which is adaptable for users under all but the most severe starting conditions. Requires little attention as there are no commutator or slip rings, yet operates with good efficiency. Wound-Rotor (Slip Ring) Induction motor It is used for constant speed-service requiring a heavier starting torque than is obtainable with squirrel cage type. Because of its lower starting current, this type is frequently used instead of the squirrel-cage type in larger sizes. These motors are also used for varying-speed-service. Speed varies with this load, so that they should not be used where constant speed at each adjustment is required, as for machine tools. Single Phase Induction Motors This motor is used mostly in small sizes, where polyphase current is not available. Characteristics are not as good as the polyphase motor and for size larger than 10 HP, the line disturbance is likely to be objectionable. These motors are commonly used for light starting and for running loads up to 1/3 HP Capacitor and repulsion types provide greater torque and are built in sizes up to 10 HP. Synchronous Motors Run at constant speed fixed by frequency of the system. Require direct current for excitation and have low starting torque. For large motor-generators sets, frequency changes, air compressors and similar apparatus which permits starting under a light load, for which they are generally used. These motors are used with considerable advantage, particularly on large power systems, because of their inherent ability to improve the power factor of the system. 1.4 DC MOTOR Direct-Current motors, as the name implies, use a direct-unidirectional current. A DC motor has three main components: Field pole. The interaction of two magnetic fields causes the rotation in a DC motor. The DC motor has field poles that are stationary and an armature that turns on bearings in the space between the field poles. A simple DC motor has two field poles: a north pole and a south pole. The magnetic lines of force extend across the opening between the poles from north to south. Armature. When current goes through the armature, it becomes an electromagnet. The armature, cylindrical in shape, is linked to a drive shaft in order to drive the load. The armature rotates in the magnetic field established by the poles, until the north and south poles of the magnets change location with respect to the armature. Once this happens, the current is reversed to switch the south and north poles of the armature. Commutator. This component is found mainly in DC motors. Its purpose is to overturn the direction of the electric current in the armature. The commutator also helps in the transmission of current between the armature and the power source. 1.4.1 OPERATION OF A DC MOTOR: When a dc motor is subject to dc voltage, the current flows through the armature coil. A wire carrying current also has a magnetic field around it. This magnetic field distorts the parallel magnetic field of stator to produce a force which causes the armature coil to turn. FIG-1.2 operation of motor Each coil of the armature is not only connected to the brushes but the brushes are connected first to one end and then to the other end of the coil. This commutating action is necessary to maintain the same direction of the current flow in the armature coils relative to the magnetic field lines in the field poles. The motor would never turn without commutation. FIG-1.3 cross section diagram of a motor 1.4.2 Types of Excitations There are two basic elements in a DC motor. The way in which these are connected results in various types of DC motors. SHUNT WOUND: The construction and principle of operation of a shunt motor is similar to any DC motor. This type of motor is called shunt because the field is in parallel or shunts the armature. The shunt field is directly connected in parallel with the armature circuit. Shunt windings require large number of turns to produce a strong magnetic field. SERIES WOUND: In a series wound motor, the field is connected in series with the armature. In this type, the speed tends to increase until the back EMF equals the impressed voltage. The EMF also decreases the current in the field and armature. As the field weakens more speed is required to maintain the counter EMF. Thus a series motor is used only where the load is attached e.g. A lift truck, an electric crane. Etc. COMPOUND WOUND: A compound motor has two field windings, the shunt field and series field. The shunt connected in parallel with the armature and the series field connected in series with the armature. The combination of both fields gives double advantages. It has a greater torque than the shunt motor due to the series field and fairly constant speed due to the series field winding. The compound motor has both shunt and series motor characteristics. These will be discussed along with their control techniques in the next chapter. 1.5 TACHOMETER A tachometer is an instrument that measures the rotational speed of the shaft of the motor. It functions in a similar fashion as compared to a speedometer on a car. It tells you the speed of the car. Similarly the tachometer is used to measure the motor speed. In a closed loop control system the information about the instantaneous state of the output is fed back and compared with the input and difference is used to modify the output in such manner as to achieve a desired condition. Similarly a tachometer is coupled to the shaft of the motor. Thus a signal representing the speed of the motor is produced. This signal is fed back to the input where it is compared to the speed command voltage. The error produced is actuated by the speed of the motor. In my designed controller the error actuating and motor control is achieved by programming the microcontroller. It is used to control the rotation of the motor. It senses the input and process it using the program burned in it and gives the required PWM output on the required port pins. This output controls the on/off time of the mosfet and thus controls the motor. This technique and mosfets will be discussed in the next chapter. As long as the speed command voltage is held constant, the motor will run at a proportional constant speed regardless of the mechanical load. The set speed control gives a dc voltage input, for example 12 volts for maximum speed and zero for stationary. This could be a potentiometer providing any voltage in a range from zero to +12 volts. The microcontroller (PIC) amplifies the difference between the two input voltages (tachometer and potentiometer) and the error is actuated. 1.6 MICROCONTROLLER (PIC) The name PIC initially referred to Programmable Interface Controller. Advantages of using PIC over other controlling devices for controlling the DC motor are given below: SPEED The execution of an instruction in PIC IC is very fast (in micro seconds) and can be changed by changing the oscillator frequency. One instruction generally takes 0.2 microseconds. COMPACT: The PIC IC will make the hardware circuitry compact. RISC PROCESSOR The instruction set consists of only 35 instructions. EPROM PROGRAM MEMORY Program can be modified and rewritten very easily. INBUILT HARDWARE SUPPORT Since PIC IC has inbuilt programmable timers, ports and interrupts, no extra hardware is needed. POWERFUL OUTPUT PIN CONTROL Output pins can be driven to high state, using a single instruction. The output pin can drive a load up to 25mA. INBUILT I/O PORTS EXPANSIONS This reduces the extra ICs which are needed for port expansion and port can be expanded very easily. INTEGRATION OF OPERATIONAL FEATURES Power on reset and brown/out protection ensures that the chip operates only when the supply voltage is within specification. A watchdog timer resets PIC if the chip ever malfunctions and deviates from its normal operation. The speed of motor is directly proportional to the DC voltage applied across its terminals. Hence, if we control the voltage applied across its terminal we actually control its speed. A PWM (Pulse Width Modulation) wave can be used to control the speed of the motor. Here the average voltage given or the average current flowing through the motor will change depending on the ON and OFF time of the pulses controlling the speed of the motor i.e. The duty cycle of the wave controls motor speed. This wave is generated by the PIC. . CHAPTER 2. 2.1 DC SHUNT MOTOR FIG -2.3 Shunt windings require large number of turns to produce a strong magnetic field. This is because a small gauge wire cannot handle heavy currents. As a result, when voltage is applied, very little current flows through the shunt coil. The interaction of the magnetic fields between the one from armature and the one from shunt coil causes the motor to rotate. The speed can be controlled by varying the field strength or armature voltage. Current is supplied from the stationary housing to the rotating armature through commutator brushes arrangement. As the stator is stationary, power is applied directly to it. 2.1.2 SPEED CONTROL OF A DC SHUNT MOTOR This type of motor runs at a constant speed practically, regardless of the load. It is the type generally used in commercial practice. Speed of the shunt wound motors may be varied in two ways: First, by inserting resistance in series with the armature, thus decreasing speed (FIG ) And second, by inserting resistance in the field circuit. In this case the speed will vary with each change in load. This normally works with any controller setting i.e. it maintains constant speed despite variable load. Therefore, a shunt motor has proved its efficiency in adjustable speed service and loads requiring a low starting torque. 2.2 DC SERIES MOTOR In a series motor, the field winding (shunt field) is connected in series with the armature winding (A) as shown in the figure. The field current is therefore equal to the armature current. Speed is restricted to 5000 RPM It must be avoided to run a series motor with no load because the motor will accelerate uncontrollably. FIG-2.5 V = Supply voltage E = Generated e.m.f I = Supply current RA = Armature resistance RF = Field resistance 2.2.2 SPEED CONTROL OF A DC SERIES MOTOR The speed of a series motor depends almost entirely on the flux. The stronger the field flux, the lower the speed. Likewise, decrease in load current and therefore in field current and field flux causes an increase in speed. This can be achieved by adding a resistor in parallel with the series field winding. This causes the field current to decrease and the flux drops accordingly. This causes the motor speed to increase. The speed can be decreased by adding an external resistor in series with the armature and the field winding. This would cause a reduction in the armature supply voltage causing the motor speed to decrease. 2.3 DC COMPOUND MOTOR A DC compound motor is a combination of shunt and series motor. In a compound motor, the field winding (shunt field) is connected in parallel in series with the armature winding (A). For this reason this motor has a good starting torque and a stable speed. The higher the percentage of compounding (i.e. percentage of field winding connected in series), the higher the starting torque this motor can handle. For example, compounding of 40-50% makes the motor suitable for hoists and cranes, but standard compound motors (12%) are not. There are 2 major types of compound motors. These are given below: Cumulative compound motors Differential compound motors FIF-2.6 CUMULATIVE COMPOUND MOTOR FIG-2.7 DIFFERENTIAL COMPOUND MOTOR 2.3.2 SPEED CONTROL OF A COMPOUND MOTOR The speed of a compound motor can easily be controlled by changing the voltage supply to the motor. A solid state AC variable frequency motor drive can also be used to vary the speed of an AC motor. 2.4 PWM (PULSE WIDTH MODULATION) PWM, or Pulse Width Modulation, is a method of controlling the amount of power to a load without having to dissipate any power in the load driver. Imagine a 10W light bulb load supplied from a battery. In this case the battery supplies 10W of power, and the light bulb converts this 10W into light and heat. No power is lost anywhere else in the circuit. If we wanted to dim the light bulb, so it only absorbed 5W of power, we could place a resistor in series which absorbed 5W and then the light bulb could absorb the other 5W. This would work, but the power dissipated in the resistor not only makes it get very hot, but is wasted. The battery is still supplying 10W. An alternative way is to switch the light bulb on and off very quickly so that it is only on for half of the time. Then the average power taken by the light bulb is still only 5W, and the average power supplied by the battery is only supplying 5W also. If we wanted the bulb to take 6W, we could leave the switch on for a little longer than the time it was off, then a little more average power will be delivered to the bulb. This on-off switching is called PWM. The amount of power delivered to the load is proportional to the percentage of time that the load is switched on. Pulse-width modulation (PWM) or duty cycle variations are commonly used in speed control of dc motor. The duty cycle is defined as the percentage of digital high to digital low and digital high pulse-width during a PWM period. Thus by varying the pulse width, we can vary the average voltage across a DC motor and hence its speed In my presented controller design the PWM (Pulse Width Modulation) function of PIC is used for the electric current control to drive a motor. PWM can change the duty of the pulse to output into CCP1 by the data. The duty of the pulse of CCP1 is controlled in the voltage (the control voltage). When the control voltage is higher than the regulation value, the H level time of the CCP1 pulse is made long and the number of rotations of the motor is lowered. When the control voltage is lower than the regulation value, the H level time of the CCP1 pulse is made short and the number of rotations of the motor is raised. This mechanism will be discussed and elaborated in the next chapter. 2.5 MOSFETS The speed controller works by varying the average voltage sent to the motor. Imagine a light bulb with a switch. When you close the switch, the bulb goes on and is at full brightness, say 100 Watts. When you open the switch it goes off (0 Watts). Now if you close the switch for a fraction of a second, and then open it for the same amount of time, the filament wont have time to cool down and heat up, and you will just get an average glow of 50 Watts. This is how lamp dimmers work, and the same principle is used by speed controllers to drive a motor. When the switch is closed, the motor sees 12 Volts, and when it is open it sees 0 Volts. If the switch is open for the same amount of time as it is closed, the motor will see an average of 6 Volts, and will run more slowly accordingly. As the amount of time that the voltage is on increases compared with the amount of time that it is off, the average speed of the motor increases. This on-off switching is performed by power MOSFETs. A MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) is a device that can turn very large currents on and off under the control of a low signal level voltage 2.5.1 TYPES OF MOSFETS. There are NPN type and PNP type as the semiconductor part. When no voltage is applied no electric current flows between the drain and the source. NPN type is called N-channel and PNP type is called P channel. An oxide film is put to the semiconductor of NPN or PNP and metal is put onto it as the gate. In case of NPN, the part of N is a source pole and a drain pole. In case of PNP, the part of P is the polar side. When positive voltage is applied to the gate of the N-channel MOS FET, the electrons of N-channel of source and drain are attracted to the gate and go into the P-channel semiconductor among both. With the movement of these electrons, it conditions itself like spans a bridge for electrons between drain and source. The size of this bridge is controlled by the voltage to apply to the gate. . This type (N CHANNEL) of mosfet is used in the presented controller. FIG 2.8 In case of P-channel MOS FET, the voltage is opposite but does similar operation. When negative voltage is applied to the gate of P-channel MOS FET, the holes of P-channel of source and drain are attracted to the gate and go into the N-channel semiconductor among both. With the movement of these holes, a bridge for holes is spanned and the electric current flows between drain and source. Transistor controls an output current by the input current. However, in case of FET, it controls an output current by input voltage (Electric field). The input current doesnt flow. To handle a MOS FET, needs attention because the oxidation insulation film is thin. This film is prone to the high voltage of the static electricity and so on. CHAPTER 3 The highlighted part in the figure represents the shaft which links the motor and the tachometer. The speed of the motor is directly proportional to the frequency of the tachometer. The dc voltage input is provided by the potentiometer. The microcontroller operates on a dc voltage. The output from the tachometer is a sine wave which has to be rectified in order to operate the pic. This is achieved using an F/V converter. The converter releases a dc logic signal which operates the pic. CIRCUIT EXPLANATION: The input voltage to the main motor is controlled by a potentiometer. This variable resistor could be adjusted manually to provide a 0-12 v input. This voltage sets the number of rotations of the main motor. The input voltage of PIC becomes low when bringing VR1 close to the side 1 and PIC increases the drive electric current of the motor. That is, the revolution of the motor rises. The input voltage of PIC becomes high when bringing VR1 close to the side 3 and PIC reduces the drive electric current of the motor. That is, the revolution of the motor slows down. Control voltage is defined as the feedback signal which is produced to rectify the error between the desired and controlled speed. This is provided by the tachometer in our case. The output from the tachometer is a sine wave which cannot operate the microcontroller to perform the programmed functions. This is converted to a dc voltage signal compatible with the pic microcontroller. This changed voltage is used to enable the CCP feature of the PIC resulting in motor drive. The CCP feature will be discussed in detail later in the chapter. The control voltage to PIC is thus governed by the fluctuations of the main motor. This control voltage (feedback signal) is directly proportional to the rotational speed of the motor. The PIC microcontroller is the brain of the circuit controlling all actions to be done and the output. PIC controls the electric drive current for the control voltage to become a regulation value. When the revolution of the motor slows down, i.e. control voltage goes down, the drive electric current of the motor is increased and number of rotations is raised. When the control voltage reaches a regulation value, a drive electric current at the point is held. When the number of rotations of the motor is high, i.e. the control voltage is high, the drive electric current of the motor is reduced and number of rotations is lowered D1 is used to protect PIC when the voltage of the detection motor is high. The voltage which is applied to the terminal of PIC is a maximum of +5V. This zener diode prevents the destruction of PIC when the speed detection voltage of the motor exceeds 5V. CCP FEATURE Capture, Compare and Pulse Width Modulation feature is abbreviated to form CCP. Capture This is the function to capture the 16 bits value of timer1 register when an event occurs on pin RC2/CCP1. This can be used for the measurement of the period time of the signal like the frequency counter and so on Compare Generate an interrupt, or change on output pin, when Timer 1 matches a pre-set comparison value PWM Create a re-configurable steady duty cycle square wave output at a user set frequency. The timer resource of the capture and compare is timer1 and the timer resource of PWM is timer2. The following steps should be taken when configuring the CCP module for PWM operation: Set the PWM period by writing to the PR2 register. PWM Period equals [(PR2+1)]*4Tosc*(timer 2 prescale value), and the resultant PWM frequency equals 1/ PWM_Period. Tosc stands for time period of the oscillations. Set the PWM duty cycle by writing to the CCPR1L register and CCP1X and CCP1Y bits of CCP1CON register. Duty Cycle is based on CCPRxL, most significant byte, and CCPxCON, least significant two bits. CCPRxL functions as a comparative value with timer 2 and a scaling factor to determine the number of counts of CCPx. PWM logic remains high, without considering CCPxCON. The two least significant bits, CCPxCON, determine the percentage of the maximum resolution the PWM duty cycle is extended. Make the CCP1 pin an output by clearing the TRISC. Set the TMR2 prescale value and enable Timer2 by writing to T2CON register. Configure the CCP1 module for PWM operation. PWM can change the duty of the pulse to output into CCP1 by the data. When the time period of the H level of the pulse of CCP1 is short, the time of ON (the L level) becomes long in TR2 which implies that the drive electric current of the motor increases. Oppositely, when the H level time of the pulse of CCP1 is long, the ON time of TR2 becomes short and the drive electric current of the motor decreases. The duty of the pulse of CCP1 is controlled by the control voltage (feedback signal) which was taken in with input circuit. When the control voltage is higher than the regulation value, the H level time of the CCP1 pulse is made long and the number of rotations of the motor is lowered. When the control voltage is lower than the regulation value, the H level time of the CCP1 pulse is made short and the number of rotations of the motor is raised. A three terminal regulator is used for getting the operate voltage for pic. PARTS PIC16F873 3 Terminal regulator ( 7805) Transistor for MOS FET drive ( 2SC1815 ) Power MOS FET ( 2SK3142 ) Zener diode ( RD5A ) IC socket Resonator Variable resistor for motor speed setting Resistors Capacitors Printed board VFC 320 (F/V CONV) Bipolar transistor 2N222 FURURE WORK: Dec: complete circuit design and order components. January: software design and circuit assembly February: Simulation and preparation of final report and presentation March: review and appendices April: submission.

History Of Cable Television :: Television TV

The History Of Cable Television The 1940's and 1950s Cable Television originated in 1948 as a service to households in mountainous or geographically remote areas where reception of over the air television signals was poor. Antennas were erected on mountaintops or other high points, and homes were wired and connected to these towers to receive the broadcast signals. By 1950, 70 cable systems served 14,000 subscribers nationwide. In late 1950s, when cable operators began to take advantage of their ability to pick up broadcast signals from hundreds of miles access to these "distant signals" changed the focus of cable's role from one of transmitting local broadcast signals to one of providing new programming choices. The 1960s by 1962, almost 800 cable systems serving 850,000 subscribers were in business. Not surprisingly, the growth of cable through the importation of distant signals was viewed as competition by local television stations. In response to broadcast industry concerns, the FCC expanded its jurisdiction and placed restrictions on the ability of cable system to import distant television signals. This action had the effect of freezing the development of cable systems in major markets. In the early 1970s, the FCC continued it's restrictive policies by enacting regulations that limited the ability of cable operators to offer movies, sporting events, and syndicated programming. The freeze on cable's development lasted until 1972, when a policy of gradual cable deregulation led to, among other things, modified restrictions on the importation of distant signals. Throughout the 1970s, concerted industry efforts at the federal, state and local levels resulted in continued lessening of cable restrictions. These changes, couples with cables pioneering to satellite communications technology, led to a pronounced growth of services to consumers and a substantial increase in cable subscribers. In 1972, Charles Dolan and Gerald Levin of Sterling Manhattan Cable launched the nation's first pay-TV network, Home Box Office (HBO). This venture led to the creation of a national satellite distribution system that used a newly approved domestic satellite transmission. Satellites changed the business dramatically, paving the way for the explosive growth of program networks. The second service to use the satellite was a local television station in Atlanta that broadcast primarily sports and classic movies. The station, owned by R.E Turner, substituted its existing microwave distribution with satellite distribution, and soon became known as the first "super station" WTBS.By the end of the decade, nearly 15 million households were cable subscribers. The 1980s while the delivery of programming via satellite was evolving, the 1984 Cable Act effectively deregulated the industry, stimulating investment in cable plant and programming on an unprecedented level.

Wounded Platoon

REACTION PAPER THE WOUNDED PLATOON Kevin Shields, a 24-year old Army Soldier, went out drinking with three Army buddies on November 30, 2007, from Fort Carson, Colorado, a base close to Colorado Springs. A few hours later, he was dead. He was shot twice in the head at close range and left by the side of the road by his army buddies. Shields' violent murder accentuated one of many violent attacks committed by the three Army buddies, who are now serving time in prison for Shield’s death and other crimes as well.Since the Iraq war began, a total of 18 soldiers from Fort Carson have been charged with or convicted of murder, manslaughter or attempted murder committed at home in the United States, and 36 Army soldiers have committed suicide. In the movie The Wounded Platoon, FRONTLINE investigate a single Fort Carson platoon of infantrymen, the 3rd Platoon, â€Å"Charlie Company† 1st Battalion, 506th Infantry, and finds that after a long period time away from home, serving th eir country, a group of young men changed by the war in Iraq and suffering from a range of psychiatric disorders that many blame for their violent and self-destructive behaviors.Since returning from Iraq, three members of the 3rd Platoon have been convicted on murder or attempted murder charges; one was jailed for drunk driving and another for assaulting his spouse; and the other one has attempted suicide. They could not stop bragging about the amount of innocent people they have murdered and they have gotten away with it. â€Å"There's a whole bunch of people in the unit that killed people they weren't supposed to,† according to Bruce Bastien, who, along with Louis Bressler and Kenny Eastridge, is now serving time for the murder of Kevin Shields.In a stunning confession recorded by police interviewers and shown for the first time on television, Mr. Bastien admits to his role in the murder of two U. S. soldiers and the stabbing of a young woman during a robbery in Colorado Sp rings, thefts and murders are being committed in our own backyard by our own Army soldiers whose work is to protect us and our country. Mr. Bastien also makes claims about more murders committed in Iraq during the surge. â€Å"It's easy to get away with that kind of s**t over there. You can just do it and be like, ‘Oh, he had a gun,' and nobody really looks into it. ‘F*** it, it's just another deadHaji. ‘† But that excuse did not go too well for them here. While the Army has concluded that there is no evidence to back up Bastien's allegations of soldiers killing innocent Iraqis, PBS, Fontline also speaks with platoon member Jose Barco, who makes a similar claim. â€Å"We were pretty trigger-happy,† he says of the soldiers' time in Iraq. â€Å"We'd open up on anything. We usually rolled three or four trucks, and if one of them got hit and there was any males around, we'd open up, and we'd shoot at them. They even didn't have to be armed. † They have extended their behaviors here at home and even turned on their own Army buddies.ScienceDaily (Sept. 15, 209) The Veterans’ Administration should expect a high volume of Iraq veterans seeking treatment of post traumatic stress disorder, with researchers anticipating that the rate among armed forces will be as high as 35%, according to the Management Insights feature in the current issue of Management Science, the flagship journal of the Institute for Operations Research and the Management Sciences (INFORMS ®). 35% of our soldiers suffer from PTSD. The VA system which is already experiencing significant delays for PTSD treatment provision, urgently needs to vamp up its mental health resource capacity.Our soldiers are becoming mass murderers abroad and at home. Is it PTSD, boredom or just because they can get away with it? Anything less than manditory PTSD therapy upon return should be considered less than acceptable to the American public. We ask these personnel to put t heir ordinary lives on hold, commit unspeakable acts of valor and return to America without support and understanding. We can not begin to imagine the horrors these people have witnessed or experienced. With manitory treatment by psychotherapists, the stigma would be removed and maybe they would have a regained sense of morality. Being from N.C. and witnessing the struggles of returning military personnel from wartime, we need to do so much more for them. This was an excellent film and is exactly what I expected from Frontline. No opinions or hidden agendas. Just the facts and the room for us to interpret. I think we need to step back and remove the original problem, which is waging illegal wars in other countries. We are sending our people in there to be damaged, then trying to â€Å"fix† them, most of the time so they can become functional enough to go back on a deployment and do violence upon others and be re-traumatized. That is insanity.Did you notice how the assistant c hief of staff to the army talks about the soldiers as though they are products or commodities to be shipped to the front based on â€Å"supply and demand? † That is, indeed, exactly what they are. Just another pair of boots on the ground, just like any iraqi is â€Å"just another haji, like cattle or a dog. † These soldiers are de-humanized in the same way they have de-humanized the alleged â€Å"enemy† and that may be the moral lesson for them all. This should give any person a lot of pause before they voluntarily (and remember everyone, it is voluntary) signs up for this irrational, cowardly work. This should give any person a lot of pause before they voluntarily (and remember everyone, it is voluntary) signs up for this irrational,cowardly work. † You need to jump back with your bad self,you and like minded others are as much to blame as the incompetent system I've had to deal with because of my own issues,you reek of the snide arrogant sort who spend t he day blaming America for every wrong in the world before going home to sleep at night under that blanket of safety provided by better men than you,the same men you call cowards.You're not fit to lick the mud off any of my brother's boots What ‘blanket of safety' did the War in Iraq provide for anyone? It was and is a complete disaster that has cost us over 4,000 soldiers lives and $1 trillion to US taxpayers. It was waged based on lies by ‘chicken hawks', men like Dick Cheney who got 5 deferments when it was his turn to fight in Vietnam yet has no problem sending young American men and women to die for ‘weapons of mass destruction and liberating the Iraqi people. What a joke. The ‘support the troops' campaign is nothing but a Pentagon marketing strategy to take the onus off of the government's awful policies. If you really want to support the troops, look at the policies themselves and the terrible decision making that when into waging them and make sure it never happens again. We can support the troops by avoiding the needless deaths of 4,000 soldiers and the countless wounded. Thats real patriotism, saving American lives from needless death.I’m sure many Americans are scared of the same thing happening to their soldiers coming home in their hometown who are now in Afghanistan. So far our media has not really made any connections between crimes at home and PTSD. It will only be time. I’m also sure that our Military is keeping quiet. Sending our young men into combat result to PTSD, Madness, and violence backhome. The VA will ne er have enough resources to take care of the broken minds and bodies that wars have created.

7 Ways to Kick Start the Writing Habit

7 Ways to Kick Start the Writing Habit 7 Ways to Kick Start the Writing Habit 7 Ways to Kick Start the Writing Habit By Daniel Scocco Sometime ago I came across an interesting post on Freelance Folder outlining seven ways to get your creative juices flowing. If you have been writing for a while, you know that getting out of the occasional writers block is a challenging task. Below you will find the seven tips, I am pretty sure they will be useful. Write nothing but headlines Write ‘crap’ without feeling guilty Schedule regular time and show up, even if you think you can’t write Write about how you solved a problem Edit older articles Type out other people’s articles Write something right now If you want more tips we have also covered this topic in the past, check out: How to Bypass Your Internal Editor Write Super Fast How to Start Writing When You Don’t Feel Like It Want to improve your English in five minutes a day? Get a subscription and start receiving our writing tips and exercises daily! Keep learning! Browse the Writing Basics category, check our popular posts, or choose a related post below:7 Types of Narrative Conflict20 Rules About Subject-Verb AgreementWords Often Misspelled Because of Double Letters