Types of Accountability Essay Example For Students

Types of Accountability Essay Bruce Stone, O. P. Dwivedi, and Joseph G. Jabbra list 8 types of accountability, namely: moral, administrative, political, managerial, market, legal/judicial, constituency relation, and professional. Leadership accountability cross cuts many of these distinctions. Political accountability Political accountability is the accountability of the government, civil servants and politicians to the public and to legislative bodies such as congress or parliament. In a few cases, recall elections can be used to revoke the office of an elected official. Generally, however, voters do not have any direct way of holding elected representatives to account during the term for which they have been elected. Additionally, some officials and legislators may be appointed rather than elected. Constitution, or statute, can empower a legislative body to hold their own members, the government, and government bodies to account. This can be through holding an internal or independent inquiry. We will write a custom essay on Types of Accountability specifically for you for only $16.38 $13.9/page Order now Inquiries are usually held in response to an allegation of misconduct or corruption. The powers, procedures and sanctions vary from country to country. The legislature may have the power to impeach the individual, remove them, or suspend them from office for a period of time. The accused person might also decide to resign before trial. Impeachment in the United States has been used both for elected representatives and other civil offices, such as district court judges. In parliamentary systems, the government relies on the support or parliament, which gives parliament power to hold the government to account. For example, some parliaments can pass a vote of no confidence in the government. Ethical accountability Ethical accountability is the practice of improving overall personal and organizational performance by developing and promoting responsible tools and professional expertise, and by advocating an effective enabling environment for people and organizations to embrace a culture of sustainable development. Ethical accountability may include the individual, as well as small and large businesses, not-for-profit organizations, research institutions and academics, and government. One scholarly paper has posited that it is unethical to plan an action for social change without excavating the knowledge and wisdom of the people who are responsible for implementing the plans of action and the people whose lives will be affected. Administrative accountability Internal rules and norms as well as some independent commission are mechanisms to hold civil servant within the administration of government accountable. Within department or ministry, firstly, behavior is bounded by rules and regulations; secondly, civil servants are subordinates in a hierarchy and accountable to superiors. Nonetheless, there are independent â€Å"watchdog† units to scrutinize and hold departments accountable; legitimacy of these commissions is built upon their independence, as it avoids any conflicts of interest. Apart from internal checks, some â€Å"watchdog† units accept complaints from citizens, bridging government and society to hold civil servants accountable to citizens, but not merely governmental departments. Market accountability Under voices for decentralization and privatization of the government, services provided are nowadays more â€Å"customer-driven† and should aim to provide convenience and various choices to citizens; with this perspective, there are comparisons and competition between public and private services and this, ideally, improves quality of service. As mentioned by Bruce Stone, the standard of assessment for accountability is therefore â€Å"responsiveness of service providers to a body of ‘sovereign’ customers and produce quality service. Outsourcing service is one means to adopt market accountability. Government can choose among a shortlist of companies for outsourced service; within the contracting period, government can hold the company by rewriting contracts or by choosing another company. Constituency relations Within this perspective, a particular agency or the government is accountable f voices from agencies, groups or institutions, which is outside the public sector and representing citizens’ interests in a particular constituency or field, are heard. Moreover, the government is obliged to empower members of agencies with political rights to run for elections and be elected; or, appoint them into the public sector as a way to hold the government representative and ensure voices from all constituenc ies are included in policy-making process. Public/private overlap .u799818a64502ecdac66910a93b8d0743 , .u799818a64502ecdac66910a93b8d0743 .postImageUrl , .u799818a64502ecdac66910a93b8d0743 .centered-text-area { min-height: 80px; position: relative; } .u799818a64502ecdac66910a93b8d0743 , .u799818a64502ecdac66910a93b8d0743:hover , .u799818a64502ecdac66910a93b8d0743:visited , .u799818a64502ecdac66910a93b8d0743:active { border:0!important; } .u799818a64502ecdac66910a93b8d0743 .clearfix:after { content: ""; display: table; clear: both; } .u799818a64502ecdac66910a93b8d0743 { display: block; transition: background-color 250ms; webkit-transition: background-color 250ms; width: 100%; opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #95A5A6; } .u799818a64502ecdac66910a93b8d0743:active , .u799818a64502ecdac66910a93b8d0743:hover { opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #2C3E50; } .u799818a64502ecdac66910a93b8d0743 .centered-text-area { width: 100%; position: relative ; } .u799818a64502ecdac66910a93b8d0743 .ctaText { border-bottom: 0 solid #fff; color: #2980B9; font-size: 16px; font-weight: bold; margin: 0; padding: 0; text-decoration: underline; } .u799818a64502ecdac66910a93b8d0743 .postTitle { color: #FFFFFF; font-size: 16px; font-weight: 600; margin: 0; padding: 0; width: 100%; } .u799818a64502ecdac66910a93b8d0743 .ctaButton { background-color: #7F8C8D!important; color: #2980B9; border: none; border-radius: 3px; box-shadow: none; font-size: 14px; font-weight: bold; line-height: 26px; moz-border-radius: 3px; text-align: center; text-decoration: none; text-shadow: none; width: 80px; min-height: 80px; background: url(https://artscolumbia.org/wp-content/plugins/intelly-related-posts/assets/images/simple-arrow.png)no-repeat; position: absolute; right: 0; top: 0; } .u799818a64502ecdac66910a93b8d0743:hover .ctaButton { background-color: #34495E!important; } .u799818a64502ecdac66910a93b8d0743 .centered-text { display: table; height: 80px; padding-left : 18px; top: 0; } .u799818a64502ecdac66910a93b8d0743 .u799818a64502ecdac66910a93b8d0743-content { display: table-cell; margin: 0; padding: 0; padding-right: 108px; position: relative; vertical-align: middle; width: 100%; } .u799818a64502ecdac66910a93b8d0743:after { content: ""; display: block; clear: both; } READ: Child Labor and Academic Performance EssayWith the increase over the last several decades in public service provision by private entities, especially in Britain and the United States, some have called for increased political accountability mechanisms to be applied to otherwise non-political entities. Legal scholar Anne Davies, for instance, argues that the line between public institutions and private entities like corporations is becoming blurred in certain areas of public service provision in the United Kingdom and that this can compromise political accountability in those areas. She and others argue that some administrative law reforms are necessary to address this accountability gap. With respect to the public/private overlap in the United States, public concern over the contracting out of government (including military) services and the resulting accountability gap has been highlighted recently following the shooting incident involving the Blackwater security firm in Iraq.

Asian Brown Cloud essays

Asian Brown Cloud essays The report by the United Nations Environmental Programme (UNEP) on the three-kilometre brown cloud hanging over Asia zeroes in on this kind of fuel burning as the source of the cloud that is disrupting monsoons, lowering agricultural output and creating air pollution leading to respiratory diseases. "The big problem here could be cooking at home," says Nobel laureate Paul Crutzen of the Max-Planck Institute for Chemistry in Germany. Crutzen won the Nobel Prize for his work on discovering the ozone hole. It is a problem that will now have to be addressed by governments in South Asia, says Prof V. Ramanathan of the Scripps Institute of Oceanography, one of the leading scientists involved in the study, conducted between 1995 and 1999 at a cost of about $40 million. "The sliver lining to this cloud is that it can be tackled relatively soon if the correct policy decisions are taken," he says. The Supreme Court of India took the lead in introducing compressed Natural gas (CNG) in buses, taxis and auto-rickshaws in the country. But the court had no idea of the magnitude of the cloud hanging overhead which its order could do nothing to remove. The cloud cannot be tackled at the level of handling pollution in New Delhi or some other cities. Ramantahan says: "We are seeing great variation in this cloud not just across Asia but over parts of India as well." The Asian Brown Cloud, as the scientists are calling it, "should not be seen as something static," he said. "It is moving about all the time." Scientists indicate a revolution of lifestyles will be needed across India, Pakistan and China acting together. This will mean common policies against burning of fossil fuels, of agricultural wastes, against emissions from industries and power stations, and above all, against emissions from the millions of inefficient cookers in homes using fuels like wood and cow dung. The brown clouds these fuels have created over Asia have ...

System Analysis and Design Assignment Example | Topics and Well Written Essays - 750 words - 1

System Analysis and Design - Assignment Example Additionally, in terms of their real-world modeling, the system models the real world to a complete fashion compared to the traditional technique. The objects are categorized into object’s classes and the objects are associated with the behavior, this is because it is not based on processing and data but rather on objects. The object-oriented method is more reliable compared to the traditional system. This is because new behaviors can be developed from the existing projects. This is because the objects can be accessed and called dynamically. The object-oriented approach has high code reusability. After creating new objects, the project will automatically update the data characteristics and attributes of the previous project. There will also be data inheritance from the super classes that participated. When users create a new widget, the created project will behave â€Å"witty†. The analyst needs to start learning object-oriented techniques first. Learning the technique first will expose the analyst to promote greater maintainability and flexibility in the field of analysis. The technology has also proven to be popular in almost every field of software development. There the analysts need to have a basic understanding of the technology paradigm in order to develop sustainable software solutions. Therefore, the analyst needs to start learning the object-oriented techniques (Rosenblatt, 240). In the field, the analyst will be required to describe the functionality of the object-oriented system, and how the object-oriented system should be developed in ways that are conducive to flexibility and maintainability. Here, the analyst will be guided through using case survey, creating UML diagrams, applying high cohesion and low coupling, and produce codes from the design, and later understand time for creating design artifacts and analysis.

Guillermo Furniture Store Scenario Essay Example | Topics and Well Written Essays - 500 words

Guillermo Furniture Store Scenario - Essay Example This case study concerns the strategic challenges faced by a relatively small but successful local furniture maker in the face of a large foreign competitor with superior technology and lower prices. The salient facts are as follows. a. A new competitor entered from overseas, with high tech methods and low prices. The plant in Norway was highly automated, used very little labour (used robotics). Production could move between products quickly, and runs on a 24- hour basis (shift-differentials could be more than offset by reduction in labor). 1. Guillermo may tie up with a Norwegian competitor which did not want to operate retail outlets locally but preferred to rely on chain distributors. Guillermo, while retaining the high-end custom work, intends to represent the Norwegian company, converting his company’s primary focus from manufacturing to distribution. 2. Guillermo had a patented process for creating a coating for his furniture which was flame-retardant and, with further processing, stain resistant. There was market for the flame-retardant but not the finished coating. Budgets represent short-term financial forecast, particularly of expected cash flows, based on the business plans drawn by the company, to see if forecasted cash outflows and their timing could be sufficiently covered by cash inflows (revenues and liabilities), and if not, to allocate for future financing at the time they would be needed. Past performance reports to see the history of costs and sales, and to draw insights as to the behavior of costs and revenues given the environmental indicators. Ratios, trends and sensitivity analyses of costs and revenues compared to each other and to economic indicators is important in determining how the company will be affected by a prospective decision. Ratio analysis of historical and cross-sectional accounts are helpful

Assignment Example | Topics and Well Written Essays - 750 words - 70

Assignment Example It is not true that cabbage is cheaply made and is of low quality. Red wine and beef steak are complimentary goods. The goods complement each other. A complementary good is one whose cross elasticity of demand is negative. That is, the demand of a complementary good will increase if the price of another good decreases. Similarly, the demand of a complementary good falls when the price of another good is increased. As such, because red wine and beef steak are complimentary goods (are consumed together), an increase in the price of red wine will discourage people from buying beef steak and thus a fall in demand for beef steak. Red wine has a negative cross elasticity of demand with respect to beef steak. The sales of generic frozen orange juice soared during recession because it is an inferior good. Inferior goods are those that provide an alternative for consumers to reducing their expenditure during harsh economic times. The demand for inferior goods soars with a decrease in the level of disposable income. On the other hand, the sales of freshly squeezed orange juice declined because it is a normal good. The demand for normal goods falls with a fall in income level. As such, during 2007/2008 recession, people turned to generic frozen orange juice to cut their expenditure and thus high sales recorded. On the other hand, the number of people buying freshly squeezed orange juice declined as their disposable income fell. At point A, change in price produces equal change in quantity demanded and hence elastic. At point B, the demand is probably inelastic because a change in price yields less percentage change in quantity demanded. The firm’s products have elastic demand. For goods with elastic demand, a small change in price will cause a big change in quantity demanded. Therefore, every time the firm increased the price, it Assignment Example | Topics and Well Written Essays - 250 words - 185 Assignment Example Joycelyn’s objective of career development has been key to her high performance and provision of a worker friendly environment has enabled her to achieve a lot in her career (Mondy, Noe, & Gowan, 2005). Joycelyn has no longer taken human resource as a an administrative duty but as a responsibility to ensure that workers feel that their place of work as the right place to spend time due to the conditions that are provided by the employer. Worker motivation is a major driver to any institution that would want to get the maximum of the employees’ capability. A motivated worker has all his/her welfare well taken care of and it trickles down to the human resource to ensure that they motivate workers by providing them with essential services such as schools for their children, insurance covers etc and rewarding them fairly for the work they have done (Mondy, Noe, & Gowan, 2005). Madam Joycelyn success has come as a result of combination of various factors the work together and is geared towards the workers

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.

The Problem with 6 Digits Dating

What started of as a noble act of saving some memory space turned out to be a quake, capable of trembling the world to its core. When maiden inventors set the year with two digits instead of four, little did they realize that by 1st January 2000 it would cause arithmetic delinquencies and confuses the entire system. For example, a bank transaction on the 25th of July 1997 would be recorded as 07/25/97. Many software add the value 1900 to the two digits code to calculate the actual year. A credit card charged on 1st of January 2000 would have to bear the interest of 99 years because the transaction date would read 01/01/00. This means the computers assume that the same transaction took place on 01/01/1900. Another major problem with six digits dating occurs when we tend to compare the pre and post – 2000 dates. For example, 01/09/99 and 01/01/00, when converted into a simple code they would read 990901 and 000101 respectively. Obviously 990901 is older than 000101, which in reality is not true. As the computers cannot process the current date as year 2000 marches in, it is also unable to calculate the leap year. All years divisible by 4 is considered as a leap year except for centuries. A century will be considered as a leap year only if it is divisible by 400. For example, 1996 is considered as a leap year because it is divisible by 4 (1996 4 = 499) wherelse 1997 is not (1997/4 = 499.25). On the hand the hand, 1900 is not a leap year for it is not divisible by 400 (1900/400=4.75). Year 2000 is a leap year for it is divisible by 400 (2000/400 = 5) (with reference to explanation from: http://www.ast.cam.ac.uk/RGO/leaflets/leapyear/leapyear.html). As we step into the year 2000, existing computers will not be able to differentiate the two digits year anymore. The â€Å"00† date field might be assumed as 1900 instead of 2000. Thus calculations that involve a date would provide wrong answers. On the 1st of January 2000, computers will define this day as 01/01/00 and regards the year as 1900, leaving us 99 years behind time. This will interrupt public services, bank transactions, loan interest calculations and many more, causing formidable loss of billions of dollars. Only a few systems could be spared from the Y2K and it has been estimated that there are 500 billion lines of application code worldwide, with some 85% of which needs to be corrected. Various reports stated that by the turn of the millennium, as much as 50% of all businesses which failed to address the year 2000 challenge would fall apart. Besides being deadly, expensive and extensive, the year 2000 problem affects hardware (BIOS, real-time clocks), embedded firmware, languages and compilers, operating systems, random number generators, database management systems, transaction-processing systems, banking systems, PBX, flight scheduling and any other system that deals with dates. Surfing the net would prove that the Y2K's awareness level is growing with more more sites dedicated to this problem. Managers and IT resources are becoming heavy-hearted thinking about their future as 31st December 1999 rolls in. Knowing that there is going to be an IT disaster does not help much especially when there are few resources to handle the problem. A rough estimation to create solutions for the Y2K issue concentrated on something like US $400 -600 billion dollars worldwide. An additional 200,000 COBOL programmers will also be required. Organizations are not the only ones that are going to suffer from the virulent millennium bug, it can be anyone, even a personal computer user.