PLC

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Next Attraction : Progamming in PLC

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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 lighting fixtures. PLCs are used in many industries and machines, such as packaging and semiconductor 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 or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result.

PROGRAMING OF PLC : MAKE SNIDER

Features:
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Control panel with PLC (grey elements in the center). The unit consists of separate elements, from left to right; power supply, controller, relay units for in- and outputThe 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 motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, 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.

PLC CARDS : IN THE CENTER, SIEMENS S7

System scale:
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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 is customised 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:
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See also: List of human-computer interaction topics
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 MMIs (Man Machine Interface) and GUI (Graphical User Interface).

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 a programming and monitoring software installed on a computer, with the PLC connected via a communication interface.


Communications:
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PLCs have built in communications ports usually 9-Pin RS232, and optionally for RS485 and Ethernet. Modbus, BACnet or DF1 is usually included as one of the communications protocols. Others' 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. Some of today's PLCs can communicate over a wide range of media including RS-485, Coaxial, and even Ethernet.
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 in ladder logic (or function chart) notation. 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 and input/output hardware) 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 busses 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.

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.

Digital and analog signals:
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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 4-20 mA or 0 - 10 V input 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:
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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 logic. The output is sealed in until some condition breaks the circuit.


Low Level High Level Fill Valve
------[/]------------[/]----------------------(OUT)---------



Fill Valve
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An analog system might use a water pressure sensor or a load cell, and an adjustable (throttling) dripping out of the tank, the valve adjusts to slowly drip water back into 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 deadband 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.

ROBBED by "SYSTEM".

Hi all, My friend sushant Danekar, the things which happened with him was fear ful not for him only but for all of us.
BECAUSE THE PERSON WHO WORKING IN HIS OFFICE AND AT THE SAME TIME SOME ONE MADE TRANSACTION FROM HIS ACOUNT, EVEN THE CARD IS IN HIS WALLET.
In a strange incident, a man lost Rs 23,000 from his Punjab National Bank (PNB) account while his ATM card was with him.

And the Bank is not responding him, and the POLICE are not taking the FIR! Because he did not have enough things to present in front of cops.
Dear al my friends it may be u r number Next!

PLEASE VISIT THIS POST OF PUNE MIRRIR! & circulate this thing as U can! He Needs U r Help!
http://www.punemirror.in/index.aspx?Page=article§name=News-%20City§id=2&contentid=2009071120090711022022157f48e124

by
Abhijeet Joshi
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Lost in transaction
Here’s the curious case of money being siphoned off a man’s bank account through the bank’s ATM, although owner has the ATM card! Cops won’t register a case because it’s odd, bank is clueless

By Vishakha Sharma
Posted On Saturday, July 11, 2009 at 02:20:22 AM


In a strange incident, a man lost Rs 23,000 from his Punjab National Bank (PNB) account while his ATM card was with him.

25-year-old Sushant Danekar, a resident of Karve Nagar was unable to file an FIR as the police refused to register his complaint.

“On June 3, Rs 10,000 was withdrawn from my account even though my ATM card was safe with me.

I informed PNB, Deccan Gymkhana branch where the manager Anil D Sawant arranged for the CCTV clippings.

There was a girl who made the transaction, but she was wearing a scarf around her face and it was impossible to identify her.”

“The bank as well as the police could not believe how money could be transacted while the ATM card was with me at the time of the transaction. But it happened and I don’t know how.

While I continuously followed up with the bank, on June 26, Rs 13,000 was withdrawn from my account while the ATM card was with me and I was at work. It is not only confusing for me but very wrong.

My ATM pin is not even shared with anybody. When I went to file the FIR at Prabhat police chowky, PSI Patil heard my case patiently and directed me to File an FIR at the Deccan Gymkhana police station.” added Sushant.

But when Sushant reached Deccan Gymkhana police station, he was made to understand that police wouldn’t be able to help him.

“When I narrated the incident in the police station to four or five police officials, they all said that they coundn’t help me as this case is not proper.

They advised me further to deal with the bank and find the culprit. They also told me that they could help me only if I gave them the names of those I suspected in writing.

They were hinting to my roommate. But I trust him. He is the only one helping me with this case,” said Sushant.

When Pune Mirror spoke to PSI Patil from Prabhat police chowky, he said, “I had directed Sushant to Deccan Gymkhana police station to lodge an FIR.

His case is a little confusing, but we can’t help unless there is an FIR. Its hard to believe that his money has been withdrawn when his ATM card was with him. There has to be someone who knew his PIN or may be a duplicate card was used.”

Anil D Sawant, manager, PNB, Deccan Gymkhana branch said, “The ATM used for the first transaction of Rs 10,000 was our PNB ATM in Deccan (ATM no DD13) for which we provided the CCTV clippings.

For the second transaction, our ATM was not used, therefore, I can’t provide the CCTV clippings.”

“I don’t know who this intelligent hacker is. I don’t even think I’ll get my money back. I have frozen my account for debit but the case remains unsolved.

This is either the bank’s fault or a duplicate ATM fraud. I’m also following up with the Lakshmi Road branch of PNB for the CCTV clippings for the second theft.

They have told me that they might take two or three weeks to provide the clippings. The bottom line is, this is a non-supporting environment for an extra-ordinary case,” said Sushant.


If you have any info or have had such an experience, tell us at editfeedback@indiatimes.com

Automation

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Next Attraction : in Next Few Days Read :
{What is PLC? } PROGRAMABLE LOGIC CONTROLLER.
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Automation is the use of control systems (such as numerical control, programmable logic control, and other industrial control systems), in concert with other applications of information technology (such as computer-aided technologies [CAD, CAM, CAx]), to control industrial machinery and processes, reducing the need for human intervention.In the scope of industrialization, automation is a step beyond mechanization. Whereas mechanization provided human operators with machinery to assist them with the physical requirements of work, automation greatly reduces the need for human sensory and mental requirements as well. Processes and systems can also be automated.

Automation plays an increasingly important role in the global economy and in daily experience. Engineers strive to combine automated devices with mathematical and organizational tools to create complex systems for a rapidly expanding range of applications and human activities.

Many roles for humans in industrial processes presently lie beyond the scope of automation. Human-level pattern recognition, language recognition, and language production ability are well beyond the capabilities of modern mechanical and computer systems. Tasks requiring subjective assessment or synthesis of complex sensory data, such as scents and sounds, as well as high-level tasks such as strategic planning, currently require human expertise. In many cases, the use of humans is more cost-effective than mechanical approaches even where automation of industrial tasks is possible.

Specialised hardened computers, referred to as programmable logic controllers (PLCs), are frequently used to synchronize the flow of inputs from (physical) sensors and events with the flow of outputs to actuators and events. This leads to precisely controlled actions that permit a tight control of almost any industrial process.

Human-machine interfaces (HMI) or computer human interfaces (CHI), formerly known as man-machine interfaces, are usually employed to communicate with PLCs and other computers, such as entering and monitoring temperatures or pressures for further automated control or emergency response. Service personnel who monitor and control these interfaces are often referred to as stationary engineers.
Impact :
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Automation has had a notable impact in a wide range of highly visible industries beyond manufacturing. Once-ubiquitous telephone operators have been replaced largely by automated telephone switchboards and answering machines. Medical processes such as primary screening in electrocardiography or radiography and laboratory analysis of human genes, sera, cells, and tissues are carried out at much greater speed and accuracy by automated systems. Automated teller machines have reduced the need for bank visits to obtain cash and carry out transactions. In general, automation has been responsible for the shift in the world economy from agrarian to industrial in the 19th century and from industrial to services in the 20th century.
The widespread impact of industrial automation raises social issues, among them its impact on employment. Historical concerns about the effects of automation date back to the beginning of the industrial revolution, when a social movement of English textile machine operators in the early 1800s known as the Luddites protested against Jacquard's automated weaving looms— often by destroying such textile machines— that they felt threatened their jobs. One author made the following case. When automation was first introduced, it caused widespread fear. It was thought that the displacement of human operators by computerized systems would lead to severe unemployment.

Critics of automation contend that increased industrial automation causes increased unemployment; this was a pressing concern during the 1980s. One argument claims that this has happened invisibly in recent years, as the fact that many manufacturing jobs left the United States during the early 1990s was offset by a one-time massive increase in IT jobs at the same time. Some authors argue that the opposite has often been true, and that automation has led to higher employment. Under this point of view, the freeing up of the labour force has allowed more people to enter higher skilled managerial as well as specialised consultant/contractor jobs (like cryptographers), which are typically higher paying. One odd side effect of this shift is that "unskilled labour" is in higher demand in many first-world nations, because fewer people are available to fill such jobs.

At first glance, automation might appear to devalue labor through its replacement with less-expensive machines; however, the overall effect of this on the workforce as a whole remains unclear. Today automation of the workforce is quite advanced, and continues to advance increasingly more rapidly throughout the world and is encroaching on ever more skilled jobs, yet during the same period the general well-being and quality of life of most people in the world (where political factors have not muddied the picture) have improved dramatically. What role automation has played in these changes has not been well studied.

Current emphasis:-
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Currently, for manufacturing companies, the purpose of automation has shifted from increasing productivity and reducing costs, to broader issues, such as increasing quality and flexibility in the manufacturing process.

The old focus on using automation simply to increase productivity and reduce costs was seen to be short-sighted, because it is also necessary to provide a skilled workforce who can make repairs and manage the machinery. Moreover, the initial costs of automation were high and often could not be recovered by the time entirely new manufacturing processes replaced the old. (Japan's "robot junkyards" were once world famous in the manufacturing industry.)

Automation is now often applied primarily to increase quality in the manufacturing process, where automation can increase quality substantially. For example, automobile and truck pistons used to be installed into engines manually. This is rapidly being transitioned to automated machine installation, because the error rate for manual installment was around 1-1.5%, but has been reduced to 0.00001% with automation. Hazardous operations, such as oil refining, the manufacturing of industrial chemicals, and all forms of metal working, were always early contenders for automation.

Another major shift in automation is the increased emphasis on flexibility and convertibility in the manufacturing process. Manufacturers are increasingly demanding the ability to easily switch from manufacturing Product A to manufacturing Product B without having to completely rebuild the production lines. Flexibility and distributed processes have led to the introduction of Automated Guided Vehicles with Natural Features Navigation.


Advantages and disadvantages:
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The main advantage of automation are:

>Replacing human operators in tedious tasks.
>Replacing humans in tasks that should be done in dangerous environments (i.e. >Fire, space, volcanoes, nuclear facilities, under the water, etc)
>Making task that are beyond the human capabilities such as handle too heavy loads, too large objects, too hot or too cold sustances or the requirement to make things too fast or too slow.
>Economy improvement. Sometimes and some kinds of automation implies improves in economy of enterprices, society or most of the humankind. For example, when an enterprice that have invested in automation technology recover its investment; when a state or country increase its incomes due to automation like Germany or Japan in the XX Century or when the humankind can use the internet which in turn use satellites and other automated engines.

The main disadvantages of automation are:
>Technology limits. Nowadays technology is not able to automatizate all the desired tasks.
>Initial costs are relative high. The automation of a new product required a huge initial investment in comparison with the unit cost of the product, although the cost of automation is spread in many product batches. The automation of a Plant required a great initial investment too, although this cost is spread in the products to be produced.

Controversial factors:-
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Unemployment. It is commonly thought that automation implies unemployment due to the fact that the work of a human being is replaced in part or completely by a machine. Nevertheless, the unemployment is caused by the economical politics of the administration like dismissing the workers instead of changing their tasks. Since the general economical policies of most of the industrial plants are to dismiss people, nowadays automation implies unemployment. In different scenarios without workers, automation implies more free time instead of unemployment like the case with the automatic washing machine at home. Automation does not imply unemployment when it makes tasks unimaginable without automation such as exploring mars with the Sojourner or when the economy is fully adapted to an automated technology as with the Telephone switchboard.
Environment. The costs of automation to the environment are different depending on the technology, product or engine automated. There are automated engines that consume more energy resources from the Earth in comparison with previous engines and those that do the opposite too.
Human being replacement. In the future there is a possibility that the Artificial intelligence could replace and improve a human brain and the robots would become not only fully automated but fully autonomous from the human beings (Technological singularity)

Automation tools:
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Different types of automation tools exist:

ANN - Artificial neural network
DCS - Distributed Control System
HMI - Human Machine Interface
SCADA - Supervisory Control and Data Acquisition
PLC - Programmable Logic Controller
PAC - Programmable Automation Controller
Instrumentation - Instrumentation
Motion Control - Motion Control
Robotics - Robotics

Automated manufacturing:
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Automated manufacturing refers to the application of automation to produce things in the factory way. Most of the advantages of the automation technology has its influence in the manufacture processes.

The main advantage of the automated manufacturing are: more quality, reduce the lead times, simplification of production, reduce handling, improve work flow and increase the moral of workers when a good implementation of the automation is made.

INSTRUMENTATION & CONTROL

"Instrumentation is the branch of engineering that deals with measurement and
control."
An instrument is a device that measures or manipulates variables such as flow, temperature, level, or pressure. Instruments include many varied contrivances which can be as simple as valves and transmitters, and as complex as analyzers. Instruments often comprise control systems of varied processes. The control of processes is one of the main branches of applied instrumentation..

Control instrumentation includes devices such as solenoids, Valves, breakers, relays, etc. These devices are able to change a field parameter, and provide remote and/or automated control capabilities.

Transmitters are devices which produce an analog signal, usually in the form of a 4-20 mA electrical current signal, although many other options are possible using voltage, frequency, or pressure. This signal can be used to directly control other instruments, or sent to a PLC, DCS, SCADA system or other type of computerized controller, where it can be interpreted into readable values, or used to control other devices and processes in the system.

Instrumentation plays a significant role in both gathering information from the field and changing the field parameters, and as such are a key part of control loops.

Measurement:
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Instrumentation can be used to measure certain field parameters (physical values):

These measured values include:
pressure, either differential or static
flow
temperature - Temperature_measurement
level - Level Measurement
density
viscosity
radiation
current
voltage
inductance
capacitance
frequency
resistivity
conductivity
chemical composition
chemical properties
various physical properties

Control :
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Control valve.In addition to measuring field parameters, instrumentation is also responsible for providing the ability to modify some field parameters.

Some examples include:

Device <=====>Field Parameter(s)
1)Valve ======Flow, Pressure
2)Relay ======Voltage, Current
3)Solenoid ====Physical Location, Level
4)Circuit breaker ==Voltage, Current

Instrumentation engineering :

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Instrumentation engineering is the engineering specialization focused on the principle and operation of measuring instruments which are used in design and configuration of automated systems in electrical, pneumatic domains etc. They typically work for industries with automated processes, such as chemical or manufacturing plants, with the goal of improving system productivity, reliability, safety, optimization and stability. To control the parameters in a process or in a particular system Microprocessors , Micro controllers ,PLC's etc are used. But their ultimate aim is to control the parameters of a system.


Instrumentation technologists and mechanics :-
Instrumentation technologists, technicians and mechanics specialize in troubleshooting and repairing instruments and instrumentation systems. This trade is so intertwined with electricians, pipefitters, power engineers, and engineering companies, that one can find him/herself in extremely diverse working situations. An over-arching term, "Instrument Fitter" is often used to describe people in this field, regardless of any specialization. oo nga.

Four Steps!

Four steps,
we'll go together
Will see,
The Voice come together?

If Possible,
then only come!
I'll never Force;
to come Together!

coz its better to Express Feelings
than suppres the things in mind!

Who likes whom
cant say
to ask, and then give the heart;
its not the way

The things happened are so bad
but things happening are so glad
to say the truth is crime
now that get in my mind!

Forget the things
which happened
Dont turn back
and see me again

Hey,"Please Forget me",
I will never say this!
But Stil U try,
To forget me and that!

STOP!
From here i need to go alone
But thanks u came, up to here!
Not in the whole life,
but "Four stepS You was Mine"!

BlueBird-7!
*- translated