google-site-verification: google1c0c3254b0a96609.html October 2012 ~ Trending World

Sunday 21 October 2012

DD Delhi Daredevils CLT20 2012 Champions League Live scorecard Images Latest Score V Sehwag

DD Delhi Daredevils CLT20 2012.DD Delhi Daredevils Champions League.DD Delhi Daredevils Live scorecard.DD Delhi Daredevils Images.DD Delhi Daredevils Latest Score.DD Delhi Daredevils V Sehwag.Delhi Daredevils is the Delhi franchise of the Indian Premier League in cricket. The franchise is owned by the GMR Group. Founded in 2008, the team is currently captained by Mahela Jayawardene and coached by former South African cricketer Eric Simons. They play all their home matches at the historic Feroz Shah Kotla Ground.
Delhi quicks keep Perth to 121
The clouds hung heavy over Newlands but the rain that has blighted much of this Champions League Twenty20 stayed away, allowing the first game of the group in four days. Perth Scorchers, needing to win both their remaining matches to stay alive, struggled for momentum and were kept down to 121 for 5 by Delhi Daredevils.
Daredevils, the only IPL team with a chance of reaching the semi-finals, made the most of winning the toss on a track which wasn't the easiest to bat on. Each of their four-pronged pace attack played their part in keeping Perth down to what should be a gettable target.
The batting is Scorchers' strength but they were unable to impose themselves on the Daredevils quicks. Their troubles were highlighted by Shaun Marsh's lack of fluency. A career average above 40 and a strike-rate above 130 show Marsh's Twenty20 credentials, but he wasn't able to find the boundaries with any regularity today. After facing 25 deliveries, he had made only 15, and though he rebuilt the innings with Simon Katich after the early loss of Herschelle Gibbs, the pair couldn't shift to a higher gear.
DD Delhi Daredevils CLT20 2012 Champions League Live scorecard Images Latest Score V Sehwag
DD Delhi Daredevils 
Ajit Agarkar, regularly pilloried for his high economy-rates, removed both batsmen on his way to superb figures of 4-0-14-2. The strikes came just after a couple of Marsh boundaries in the 12th over which finally lifted Perth's run-rate over six, and suggested the start of an extended period of big strokes from Perth.
The double-blow again sucked the flow out of the innings, and Morne Morkel, Daredevils' bowler of the tournament in the IPL, returned to inflict more damage. The highlight was the 19th over, when with Perth looking to swing at everything, he conceded just a single and dismissed the dangerous Mitchell Marsh.
All right that's it from this game. We are working frenetically to get the furniture ready for the next match. See you on the flip side
Quotes from presentation
"140 was where we needed to be," says Marcus North. "Looking at how it panned out, 140 looks like a good score. We had chances to get there, but we lost our way, losing Shaun and Simon in the middle. Still a lot of pride to play for and get our first win up."
"We haven't played for a week," says Mahela Jayawardene, "so good to get out and play a good game. We made a few mistakes, which nearly cost us the game. We didn't handle a few situations well. We will have a chat, but our bowlers and fielders did really well. Ajit batted really well, the experience showed. Credit to them, they fought really hard."
"It's a good thing following them because Irfan, Morke and Umesh have been bowling really well," says MoM Ajit Agarkar, who is yet to remove his pads. "Some days it works for you in T20, some days it doesn't. As long as your ideas are right, you can hope for the best. Some times it is nice to get over the line the hard way. Hopefully we will win a few easy ones later."

Scorchers tried hard to stay alive with the ball, but their batsmen didn't give them enough to defend. They kept taking wickets, but all it took to tip scales was two good shots from Agarkar in the end. Scorchers will be heart-broken, but they are out of the running for the semi-final.
"Sorry Tim, Today is the day of Bombay Ducks with Beer.Cheers" Ronald, as I always keep saying, it ain't over until Ajit has had his say. And that applies either way. However, I am surprised the BCCI hasn't pulled Ajit out yet, fearing workload before the upcoming Test series
"Shane Watson is the Ajit Agarkar of Sydney Sixers." Vignesh, tributes to the only Mumbai centurion at Lord's since the glory days of Dilip Vengsarkar are flowing thick and fast....,

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Azhar Mahmood Sagar Profile Career Images Statistics Rawalpindi Punjab Auckland Kings XI Cricket

Azhar Mahmood Sagar  Profile. Azhar Mahmood Sagar  Career. Azhar Mahmood Sagar Images. Azhar Mahmood Sagar  Statistics. Azhar Mahmood Sagar Rawalpindi. Azhar Mahmood Sagar Punjab. Azhar Mahmood Sagar Auckland. Azhar Mahmood Sagar Life.Azhar Mahmood is a mentally tough allrounder and belligerent batsman, who began his career with three Test centuries against South Africa.

In one-day cricket he invariably raises the tempo in the lower middle-order. He is strong off his legs and relishes short bowling. But he pushes at the ball too firmly in defence, and is particularly vulnerable against legspin. 
 Azhar Mahmood 
In a team of reverse-swingers he is the only English-type seamer, virtuous in his pursuit of line and length. He is a useful fielder and, close in, he rarely misses an opportunity to enquire about the batsman's health. During a one-month stint as a Surrey overseas player in 2002 he took 8 for 61 against Lancashire, then turned out for them for two seasons full-time as Pakistan's mercurial lost faith in him for reasons that have never quite been made clear. 
 Azhar Mahmood Sagar Profile Career Images Statistics Rawalpindi Punjab Auckland Kings XI
 Azhar Mahmood Sagar

He signed with Surrey again for 2005, and later applied for British citizenship after marrying his British wife. He signed for Kent in late 2007. He extended his contract with Kent for two years, at the end of the 2011 season. His Twenty20 hitting also earned him a call-up to the Auckland squad as their overseas pro for the 2011-12 HRV Cup. 
 Azhar Mahmood Sagar Profile Career Images Statistics Rawalpindi Punjab Auckland Kings Cricket
 Azhar Mahmood Sagar Profile 
 Azhar Mahmood Sagar Profile Career Images Statistics Rawalpindi Auckland Kings XI Cricket
 Azhar Mahmood Sagar Rawalpindi 
 Azhar Mahmood Sagar Profile Career Images Statistics Rawalpindi Punjab Kings XI Cricket
 Azhar Mahmood Sagar Career

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Wednesday 17 October 2012

PLC Programmable Logic Controller Definition Advantages Dis-Advantages Applications Major Components

Programmable Logic Controller (PLC) Definition. Programmable Logic Controller (PLC) Advantages. Programmable Logic Controller (PLC) Dis-Advantages. Programmable Logic Controller (PLC) Applications. Programmable Logic Controller (PLC) Major Components. Programmable Logic Controller (PLC) Images. Programmable Logic Controller (PLC) Photos.
PROGRAMMABLE LOGIC CONTROLLER
A programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory. A PLC is an example of a hardreal time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result.
Programming:
Early PLCs, up to the mid-1980s, were programmed using proprietary programming panels or special-purpose programming terminals, which often had dedicated function keys representing the various logical elements of PLC programs. Programs were stored on cassette tape cartridges. Facilities for printing and documentation were minimal due to lack of memory capacity. The very oldest PLCs used non-volatile magnetic core memory.
More recently, PLCs are programmed using application software on personal computers. The computer is connected to the PLC through EthernetRS-232RS-485 or RS-422 cabling. The programming software allows entry and editing of the ladder-style logic. Generally the software provides functions for debugging and troubleshooting the PLC software, for example, by highlighting portions of the logic to show current status during operation or via simulation. The software will upload and download the PLC program, for backup and restoration purposes. In some models of programmable controller, the program is transferred from a personal computer to the PLC through a programming board which writes the program into a removable chip such as an EEPROM or EPROM.
PLC Programmable Logic Controller 
Functionality:
The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control, distributed control systems and networking. The data handling, storage, processing power and communication capabilities of some modern PLCs are approximately equivalent to desktop computers. PLC-like programming combined with remote I/O hardware, allow a general-purpose desktop computer to overlap some PLCs in certain applications. Regarding the practicality of these desktop computer based logic controllers, it is important to note that they have not been generally accepted in heavy industry because the desktop computers run on less stable operating systems than do PLCs, and because the desktop computer hardware is typically not designed to the same levels of tolerance to temperature, humidity, vibration, and longevity as the processors used in PLCs. In addition to the hardware limitations of desktop based logic, operating systems such as Windows do not lend themselves to deterministic logic execution, with the result that the logic may not always respond to changes in logic state or input status with the extreme consistency in timing as is expected from PLCs. Still, such desktop logic applications find use in less critical situations, such as laboratory automation and use in small facilities where the application is less demanding and critical, because they are generally much less expensive than PLCs.
In more recent years, small products called PLRs (programmable logic relays), and also by similar names, have become more common and accepted. These are very much like PLCs, and are used in light industry where only a few points of I/O (i.e. a few signals coming in from the real world and a few going out) are involved, and low cost is desired. These small devices are typically made in a common physical size and shape by several manufacturers, and branded by the makers of larger PLCs to fill out their low end product range. Popular names include PICO Controller, NANO PLC, and other names implying very small controllers. Most of these have between 8 and 12 digital inputs, 4 and 8 digital outputs, and up to 2 analog inputs. Size is usually about 4" wide, 3" high, and 3" deep. Most such devices include a tiny postage stamp sized LCD screen for viewing simplified ladder logic (only a very small portion of the program being visible at a given time) and status of I/O points, and typically these screens are accompanied by a 4-way rocker push-button plus four more separate push-buttons, similar to the key buttons on a VCR remote control, and used to navigate and edit the logic. Most have a small plug for connecting via RS-232 or RS-485 to a personal computer so that programmers can use simple Windows applications for programming instead of being forced to use the tiny LCD and push-button set for this purpose. Unlike regular PLCs that are usually modular and greatly expandable, the PLRs are usually not modular or expandable, but their price can be two orders of magnitude less than a PLC and they still offer robust design and deterministic execution of the logic.
PLC Topics:
Features:
The main difference from other computers is that PLCs are armored for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements. These connect the PLC to sensors and actuators. PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of complex positioning systems. Some use machine vision. On the actuator side, PLCs operate electric motorspneumatic or hydraulic cylinders, magnetic relayssolenoids, or analog outputs. The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC.

Scan time:
A PLC program is generally executed repeatedly as long as the controlled system is running. The status of physical input points is copied to an area of memory accessible to the processor, sometimes called the "I/O Image Table". The program is then run from its first instruction rung down to the last rung. It takes some time for the processor of the PLC to evaluate all the rungs and update the I/O image table with the status of outputs. This scan time may be a few milliseconds for a small program or on a fast processor, but older PLCs running very large programs could take much longer (say, up to 100 ms) to execute the program. If the scan time was too long, the response of the PLC to process conditions would be too slow to be useful.
As PLCs became more advanced, methods were developed to change the sequence of ladder execution, and subroutines were implemented. This simplified programming and could also be used to save scan time for high-speed processes; for example, parts of the program used only for setting up the machine could be segregated from those parts required to operate at higher speed.
Special-purpose I/O modules, such as timer modules or counter modules, could be used where the scan time of the processor was too long to reliably pick up, for example, counting pulses from a shaft encoder. The relatively slow PLC could still interpret the counted values to control a machine, but the accumulation of pulses was done by a dedicated module that was unaffected by the speed of the program execution.
System scale:
A small PLC will have a fixed number of connections built in for inputs and outputs. Typically, expansions are available if the base model has insufficient I/O.
Modular PLCs have a chassis (also called a rack) into which are placed modules with different functions. The processor and selection of I/O modules are customized for the particular application. Several racks can be administered by a single processor, and may have thousands of inputs and outputs. A special high speed serial I/O link is used so that racks can be distributed away from the processor, reducing the wiring costs for large plants.

User interface:

PLCs may need to interact with people for the purpose of configuration, alarm reporting or everyday control. A human-machine interface (HMI) is employed for this purpose. HMIs are also referred to as man-machine interfaces (MMIs) and graphical user interface (GUIs). A simple system may use buttons and lights to interact with the user. Text displays are available as well as graphical touch screens. More complex systems use programming and monitoring software installed on a computer, with the PLC connected via a communication interface.
Communications:
PLCs have built in communications ports, usually 9-pin RS-232, but optionally EIA-485 or EthernetModbusBACnet or DF1 is usually included as one of the communications protocols. Other options include various fieldbuses such as DeviceNet or Profibus. Other communications protocols that may be used are listed in the List of automation protocols.
Most modern PLCs can communicate over a network to some other system, such as a computer running a SCADA (Supervisory Control And Data Acquisition) system or web browser.
PLCs used in larger I/O systems may have peer-to-peer (P2P) communication between processors. This allows separate parts of a complex process to have individual control while allowing the subsystems to co-ordinate over the communication link. These communication links are also often used for HMI devices such as keypads or PC-type workstations.
Programming:
PLC programs are typically written in a special application on a personal computer, then downloaded by a direct-connection cable or over a network to the PLC. The program is stored in the PLC either in battery-backed-up RAM or some other non-volatile flash memory. Often, a single PLC can be programmed to replace thousands of relays.
 Under the IEC 61131-3 standard, PLCs can be programmed using standards-based programming languages. A graphical programming notation called Sequential Function Charts is available on certain programmable controllers. Initially most PLCs utilized Ladder Logic Diagram Programming, a model which emulated electromechanical control panel devices (such as the contact and coils of relays) which PLCs replaced. This model remains common today.
IEC 61131-3 currently defines five programming languages for programmable control systems: function block diagram (FBD), ladder diagram (LD), structured text (ST; similar to the Pascal programming language), instruction list (IL; similar to assembly language) and sequential function chart (SFC). These techniques emphasize logical organization of operations.
While the fundamental concepts of PLC programming are common to all manufacturers, differences in I/O addressing, memory organization and instruction sets mean that PLC programs are never perfectly interchangeable between different makers. Even within the same product line of a single manufacturer, different models may not be directly compatible.
PLC compared with other control systems:
PLCs are well-adapted to a range of automation tasks. These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation, and where changes to the system would be expected during its operational life. PLCs contain input and output devices compatible with industrial pilot devices and controls; little electrical design is required, and the design problem centers on expressing the desired sequence of operations. PLC applications are typically highly customized systems so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. On the other hand, in the case of mass-produced goods, customized control systems are economic due to the lower cost of the components, which can be optimally chosen instead of a "generic" solution, and where the non-recurring engineering charges are spread over thousands or millions of units.
For high volume or very simple fixed automation tasks, different techniques are used. For example, a consumer dishwasher would be controlled by an electromechanical cam timer costing only a few dollars in production quantities.
A microcontroller-based design would be appropriate where hundreds or thousands of units will be produced and so the development cost (design of power supplies, input/output hardware and necessary testing and certification) can be spread over many sales, and where the end-user would not need to alter the control. Automotive applications are an example; millions of units are built each year, and very few end-users alter the programming of these controllers. However, some specialty vehicles such as transit buses economically use PLCs instead of custom-designed controls, because the volumes are low and the development cost would be uneconomic.
Very complex process control, such as used in the chemical industry, may require algorithms and performance beyond the capability of even high-performance PLCs. Very high-speed or precision controls may also require customized solutions; for example, aircraft flight controls. Single-board computers using semi-customized or fully proprietary hardware may be chosen for very demanding control applications where the high development and maintenance cost can be supported. "Soft PLCs" running on desktop-type computers can interface with industrial I/O hardware while executing programs within a version of commercial operating systems adapted for process control needs.
Programmable controllers are widely used in motion control, positioning control and torque control. Some manufacturers produce motion control units to be integrated with PLC so that G-code (involving a CNC machine) can be used to instruct machine movements PLCs may include logic for single-variable feedback analog control loop, a "proportional, integral, derivative" or "PID controller". A PID loop could be used to control the temperature of a manufacturing process, for example. Historically PLCs were usually configured with only a few analog control loops; where processes required hundreds or thousands of loops, a distributed control system (DCS) would instead be used. As PLCs have become more powerful, the boundary between DCS and PLC applications has become less distinct.
PLCs have similar functionality as Remote Terminal Units. An RTU, however, usually does not support control algorithms or control loops. As hardware rapidly becomes more powerful and cheaper,RTUs, PLCs and DCSs are increasingly beginning to overlap in responsibilities, and many vendors sell RTUs with PLC-like features and vice versa. The industry has standardized on the IEC 61131-3 functional block language for creating programs to run on RTUs and PLCs, although nearly all vendors also offer proprietary alternatives and associated development environments.
In recent years "Safety" PLCs have started to become popular, either as standalone models (Pilz PNOZ Multi, Sick etc.) or as functionality and safety-rated hardware added to existing controller architectures (Allen Bradley Guardlogix, Siemens F-series etc.). These differ from conventional PLC types as being suitable for use in safety-critical applications for which PLCs have traditionally been supplemented with hard-wired safety relays. For example, a Safety PLC might be used to control access to a robot cell with trapped-key access, or perhaps to manage the shutdown response to an emergency stop on a conveyor production line. Such PLCs typically have a restricted regular instruction set augmented with safety-specific instructions designed to interface with emergency stops, light screens and so forth. The flexibility that such systems offer has resulted in rapid growth of demand for these controllers.
Digital and Control Signals:
Digital or discrete signals behave as binary switches, yielding simply an On or Off signal (1 or 0, True or False, respectively). Push buttons, limit switches, and photoelectric sensors are examples of devices providing a discrete signal. Discrete signals are sent using either voltage or current, where a specific range is designated as On and another as Off. For example, a PLC might use 24 V DC I/O, with values above 22 V DC representing On, values below 2VDC representing Off, and intermediate values undefined. Initially, PLCs had only discrete I/O.
Analog signals are like volume controls, with a range of values between zero and full-scale. These are typically interpreted as integer values (counts) by the PLC, with various ranges of accuracy depending on the device and the number of bits available to store the data. As PLCs typically use 16-bit signed binary processors, the integer values are limited between -32,768 and +32,767. Pressure, temperature, flow, and weight are often represented by analog signals. Analog signals can use voltage or current with a magnitude proportional to the value of the process signal. For example, an analog 0 - 10 V input or 4-20 mA would be converted into an integer value of 0 - 32767.
Current inputs are less sensitive to electrical noise (i.e. from welders or electric motor starts) than voltage inputs.
Example:
As an example, say a facility needs to store water in a tank. The water is drawn from the tank by another system, as needed, and our example system must manage the water level in the tank.
Using only digital signals, the PLC has two digital inputs from float switches (Low Level and High Level). When the water level is above the switch it closes a contact and passes a signal to an input. The PLC uses a digital output to open and close the inlet valve into the tank.
When the water level drops enough so that the Low Level float switch is off (down), the PLC will open the valve to let more water in. Once the water level rises enough so that the High Level switch is on (up), the PLC will shut the inlet to stop the water from overflowing. This rung is an example of seal-in (latching) logic. The output is sealed in until some condition breaks the circuit.
|                                                                                  |
|   Low Level      High Level                 Fill Valve    |
|------[/]------|------[/]----------------------(OUT)--------|
|               |                                                                  |
|               |                                                                  |
|               |                                                                  |
|   Fill Valve  |                                                            |
|------[ ]------|                                                              | 
|                                                                                   |
|                                                                                   |

An analog system might use a water pressure sensor or a load cell, and an adjustable (throttled) control (e.g. by a valve) of the fill of the tank.
In this system, to avoid 'flutter' adjustments that can wear out the valve, many PLCs incorporate "hysteresis" which essentially creates a "deadband" of activity. A technician adjusts this dead band so the valve moves only for a significant change in rate. This will in turn minimize the motion of the valve, and reduce its wear.
A real system might combine both approaches, using float switches and simple valves to prevent spills, and a rate sensor and rate valve to optimize refill rates and prevent water hammer. Backup and maintenance methods can make a real system very complicated.

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