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programmable logic controller plc full report

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1. INTRODUCTION
Programmable logic controllers (PLCs) are members of the computer family capable of storing instructions to control functions such as sequencing, timing, and counting, which control a machine or a process. The PLC is composed of two basic sections, the Central Processing Unit (CPU) and the Input/Output (I/O) interface system. The PLC measures input signals coming from a machine and through the internal program provides output or control back to the machine.
Ladder logic is the programming language used to represent electrical sequences of operation. In hardwired circuits the electrical wiring is connected from one device to another according to logic of operation. In a PLC the devices are connected to the input interface, the outputs are connected to the output interface and the actual wiring of the components is done electronically inside the PLC using ladder logic. This is known as soft wired.
PLC is a device that is capable of being programmed to perform a controlling function. Before the advent of PLC, the problem of industrial control was usually solved by relays or hardwired solid-state logic blocks. These are very flexible in design and easy for maintenance personal to understand. However, they involved a vast amount of interconnection. For the wiring cost to be minimized, relays and logic blocks had to be kept together. This led to development of control panel concept for larger and more complex logic control system.
The PLC was first conceived by group of engineers from hydramatic division of GM in 1968.This was designed to provide flexibility in control based on programming and executing logic instruction. Adopting the ladder diagram programming language, simplifying maintenance and reducing the cost of spare parts inventories realized major advantages.
2. PLC HISTORY
In the late 1960's PLCs were first introduced. The primary reason for designing such a device was eliminating the large cost involved in replacing the complicated relay based machine control systems. Bedford Associates (Bedford, MA) proposed something called a Modular Digital Controller (MODICON) to a major US car manufacturer. Other companies at the time proposed computer based schemes, one of which was based upon the PDP-8. The MODICON 084 brought the world's first PLC into commercial production.
When production requirements changed so did the control system. This becomes very expensive when the change is frequent. Since relays are mechanical devices they also have a limited lifetime which required strict adhesion to maintenance schedules. Troubleshooting was also quite tedious when so many relays are involved. Now picture a machine control panel that included many, possibly hundreds or thousands, of individual relays. The size could be mind boggling. How about the complicated initial wiring of so many individual devices! These relays would be individually wired together in a manner that would yield the desired outcome. Were there problems You bet!
These "new controllers" also had to be easily programmed by maintenance and plant engineers. The lifetime had to be long and programming changes easily performed. They also had to survive the harsh industrial environment. That's a lot to ask! The answers were to use a programming technique most people were already familiar with and replace mechanical parts with solid-state ones.
In the mid70â„¢s the dominant PLC technologies were sequencer state-machines and the bit-slice based CPU. The AMD 2901 and 2903 were quite popular in Modicon and A-B PLCs. Conventional microprocessors lacked the power to quickly solve PLC logic in all but the smallest PLCs. As conventional microprocessors evolved, larger and larger PLCs were being based upon them. However, even today some are still based upon the 2903.(ref A-B's PLC-3) Modicon has yet to build a faster PLC than their 984A/B/X which was based upon the 2901.
Communications abilities began to appear in approximately 1973. The first such system was Modicon's Modbus. The PLC could now talk to other PLCs and they could be far away from the actual machine they were controlling. They could also now be used to send and receive varying voltages to allow them to enter the analog world. Unfortunately, the lack of standardization coupled with continually changing technology has made PLC communications a nightmare of incompatible protocols and physical networks. Still, it was a great decade for the PLC!
The 80â„¢s saw an attempt to standardize communications with General Motor's manufacturing automation protocol(MAP). It was also a time for reducing the size of the PLC and making them software programmable through symbolic programming on personal computers instead of dedicated programming terminals or handheld programmers. Today the world's smallest PLC is about the size of a single control relay!
The 90â„¢s have seen a gradual reduction in the introduction of new protocols, and the modernization of the physical layers of some of the more popular protocols that survived the 1980's. The latest standard (IEC 1131-3) has tried to merge plc programming languages under one international standard. We now have PLCs that are programmable in function block diagrams, instruction lists, C and structured text all at the same time! PC's are also being used to replace PLCs in some applications. The original company who commissioned the MODICON 084 has actually switched to a PC based control system.
3. PLC HARDWARE
A programmable logic controller consists of the following components:
¢ Central Processing Unit (CPU).
¢ Memory.
¢ Input modules.
¢ Output modules and
¢ Power supply.
A PLC hardware block diagram is shown in Figure. The programming terminal in the diagram is not a part of the PLC, but it is essential to have a terminal for programming or monitoring a PLC. In the diagram, the arrows between blocks indicate the information and power flowing directions.



Fig: PLC Hardware Block Diagram
CPU
Like other computerized devices, there is a Central Processing Unit (CPU) in a PLC. The CPU, which is the brain of a PLC, does the following operations:
¢ Updating inputs and outputs. This function allows a PLC to read the status of its input terminals and energize or deenergize its output terminals.
¢ Performing logic and arithmetic operations. A CPU conducts all the mathematic and logic operations involved in a PLC.
¢ Communicating with memory. The PLC™s programs and data are stored in memory. When a PLC is operating, its CPU may read or change the contents of memory locations.
¢ Scanning application programs. An application program, which is called a ladder logic program, is a set of instructions written by a PLC programmer. The scanning function allows the PLC to execute the application program as specified by the programmer.
¢ Communicating with a programming terminal. The CPU transfers program and data between itself and the programming terminal.
A PLCâ„¢s CPU is controlled by operating system software. The operating system software is a group of supervisory programs that are loaded and stored permanently in the PLCâ„¢s memory by the PLC manufacturer.
Memory
Memory is the component that stores information, programs, and data in a PLC. The process of putting new information into a memory location is called writing. The process of retrieving information from a memory location is called reading.
The common types of memory used in PLCs are Read Only Memory (ROM) and Random Access Memory (RAM). A ROM location can be read, but not written. ROM is used to store programs and data that should not be altered. For example, the PLCâ„¢s operating programs are stored in ROM.
A RAM location can be read or written. This means the information stored in a RAM location can be retrieved and/or altered. Ladder logic programs are stored in RAM. When a new ladder logic program is loaded into a PLCâ„¢s memory, the old program that was stored in the same locations is over-written and essentially erased.
The memory capacities of PLCs vary. Memory capacities are often expressed in terms of kilo-bytes (K). One byte is a group of 8 bits. One bit is a memory location that may store one binary number that has the value of either 1 or 0. (Binary numbers are addressed in Module 2). 1K memory means that there are 1024 bytes of RAM. 16K memory means there are 16 x 1024 =16384 bytes of RAM.
Input modules and output modules

A PLC is a control device. It takes information from inputs and makes decisions to energize or de-energize outputs. The decisions are made based on the statuses of inputs and outputs and the ladder logic program that is being executed.
The input devices used with a PLC include pushbuttons, limit switches, relay contacts, photo sensors, proximity switches, temperature sensors, and the like. These input devices can be AC (alternating current) or DC (direct current). The input voltages can be high or low. The input signals can be digital or analog. Differing inputs require different input modules. An input module provides an interface between input devices and a PLCâ„¢s CPU, which uses only a low DC voltage. The input moduleâ„¢s function is to convert the input signals to DC voltages that are acceptable to the CPU. Standard discrete input modules include 24 V AC, 48 V AC, 120 V AC, 220 V AC, 24 V DC, 48 V DC, 120 V DC, 220 V DC, and transistor-transistor logic (TTL) level.
The devices controlled by a PLC include relays, alarms, solenoids, fans, lights, and motor starters. These devices may require different levels of AC or DC voltages. Since the signals processed in a PLC are low DC voltages, it is the function of the output module to convert PLC control signals to the voltages required by the controlled circuits or devices. Standard discrete output modules include 24 V AC, 48 V AC, 120 V AC, 220 V AC, 24 V DC, 48 V DC, 120 V DC, 220 V DC, and TTL level.
Power Supply
PLCs are powered by standard commercial AC power lines. However, many PLC components, such as the CPU and memory, utilize 5 volts or another level of DC power. The PLC power supply converts AC power into DC power to support those components of the PLC.
Programming Terminal
A PLC requires a programming terminal and programming software for operation. The programming terminal can be a dedicated terminal or a generic computer purchased anywhere. The programming terminal is used for programming the PLC and monitoring the PLCâ„¢s operation. It may also download a ladder logic program (the sending of a program from the programming terminal to the PLC) or upload a ladder logic program (the sending of a program from the PLC to the programming terminal). The terminal uses programming software for programming and talking to a PLC.
4. WORKING OF PLC
Bringing input signal status to the internal memory of CPU
¢ The field signals are connected to the I/P module. At the output of I/P module the field status converted into the voltage level required by the CPU is always available.
¢ At the beginning of each cycle the CPU brings in all the field I/P signals from I/P module & stores into its internal memory called as PII, meaning process image input.
¢ The programmable controller operates cyclically meaning when complete program has been scanned; it starts again at the beginning of the program.

I/O BUS
A PLC works by continually scanning a program. We can think of this scan cycle as consisting of 3 important steps. There are typically more than 3 but we can focus on the important parts and not worry about the others. Typically the others are checking the system and updating the current internal counter and timer values.

Step 1-Check Input Status-First the PLC takes a look at each input to determine if it is on or off. In other words, is the sensor connected to the first input on How about the second input How about the third... It records this data into its memory to be used during the next step.
Step 2-Execute Program-Next the PLC executes your program one instruction at a time. Maybe your program said that if the first input was on then it should turn on the first output. Since it already knows which inputs are on/off from the previous step it will be able to decide whether the first output should be turned on based on the state of the first input. It will store the execution results for use later during the next step.
Step 3-Update Output Status-Finally the PLC updates the status of the outputs. It updates the outputs based on which inputs were on during the first step and the results of executing your program during the second step. Based on the example in step 2 it would now turn on the first output because the first input was on and your program said to turn on the first output when this condition is true.
Process Control and Automation
Process Control

The process of recognizing the state of the process at all times, analyze the information according to the set rules and guidelines and accordingly actuate the control elements is referred to as process control.

RECOGNISING
THE
STATUS

In control of process all these actions can be taken manually with human involvement or in a semiautomatic or fully automatic manner.
Automation

Automation is basically the delegation of human control functions to technical equipment aimed towards achieving:
¢ Higher productivity.
¢ Superior quality of end product.
¢ Efficient usage of energy and raw materials.
¢ Improved safety in working conditions etc.
Methods adopted for Process Control and Automation
¢ Manual control
¢ Hard wired logic control
¢ Electronics control
¢ PLC control
¢ Manual Control
Hardwired Control
¢ This was considered to be the first step towards automation.
¢ Here the contractor & relays together with timers & counters were used.
Electronics Control
¢ With the advent of electronics, the logic gates started replacing the relays & auxiliary contractors in the control circuits & timers.
¢ With changes, the benefits are:
¢ 1) Reduced space requirements
2) Energy saving
3) Less maintenance and hence greater reliability etc.
¢ With electronics, the implementation of changes in the control logic as well as reducing the project lead-time was not possible.
Programmable Logic Controller
¢ With microprocessor and associated peripherals chips, the process of control and automation went a radical change.
¢ Instead of achieving the desired control or automation through physical wiring of control devices, in PLC it is through a program or software. Thus these controllers are referred to as programmable logic controllers.
¢ The programmable controllers have experienced an unprecedented growth as universal element. It can be effectively used in applications ranging from simple control like replacing small number relays to complex automation problem.
5. PROGRAMMING THE PLC
Ladder Logic
Ladder logic is the main programming method used for PLCs. The ladder logic has been developed to mimic relay logic. The decision to use the relay logic diagrams was a strategic one. By selecting ladder logic as the main programming method, the amount of retraining needed for engineers and trades people was greatly reduced.
Modern control systems still include relays, but these are rarely used for logic. A relay is a simple device that uses a magnetic field to control a switch, as pictured in Fig. When a voltage is applied to the input coil, the resulting current creates a magnetic field. The magnetic field pulls a metal switch (or reed) towards it and the contacts touch, closing the switch. The contact that closes when the coil is energized is called normally open. The normally closed contacts touch when the input coil is not energized. Relays are normally drawn in schematic form using a circle to represent the input coil. The output contacts are shown with two parallel lines. Normally open contacts are shown as two lines, and will be open (non-conducting) when the input is not energized. Normally closed contacts are shown with two lines with a diagonal line through them. When the input coil is not energized the normally closed contacts will be closed (conducting).

Fig: Simple Relay Layouts and Schematics
Relays are used to let one power source close a switch for another (often high current) power source, while keeping them isolated. An example of a relay in a simple control application is shown in Figure. In this system the first relay on the left is used as normally closed, and will allow current to flow until a voltage is applied to the input A. The second relay is normally open and will not allow current to flow until a voltage is applied to the input B. If current is flowing through the first two relays then current will flow through the coil in the third relay, and close the switch for output C. This circuit would normally be drawn in the ladder logic form. This can be read logically as C will be on if A is off and B is on.

Fig: A Simple Relay Controller
The example in Figure does not show the entire control system, but only the logic. When we consider a PLC there are inputs, outputs, and the logic. Figure 4 shows a more complete representation of the PLC. Here there are two inputs from push buttons. We can imagine the inputs as activating 24V DC relay coils in the PLC. This in turn drives an output relay that switches 115V AC that will turn on a light. Note, in actual PLCs inputs are never relays, but outputs are often relays. The ladder logic in the PLC is actually a computer program that the user can enter and change. Notice that both of the input push buttons are normally open, but the ladder logic inside the PLC has one normally open contact, and one normally closed contact. Do not think that the ladder logic in the PLC needs to match the inputs or outputs. Many beginners will get caught trying to make the ladder logic match the input types.

Fig: A PLC Illustrated With Relays
Many relays also have multiple outputs (throws) and this allows an output relay to also be an input simultaneously. The circuit shown in Figure 5 is an example of this; it is called a seal in circuit. In this circuit the current can flow through either branch of the circuit, through the contacts labeled A or B. The input B will only be on when the output B is on. If B is off, and A is energized, then B will turn on. If B turns on then the input B will turn on and keep output B on even if input A goes off. After B is turned on the output B will not turn off.

Fig: A Seal-in Circuit
Programming

The first PLCs were programmed with a technique that was based on relay logic wiring schematics. This eliminated the need to teach the electricians, technicians and engineers how to program a computer - but, this method has stuck and it is the most common technique for programming PLCs today. An example of ladder logic can be seen in Fig. To interpret this diagram imagines that the power is on the vertical line on the left hand side, we call this the hot rail. On the right hand side is the neutral rail. In the figure there are two rungs, and on each rung there are combinations of inputs (two vertical lines) and outputs (circles). If the inputs are opened or closed in the right combination the power can flow from the hot rail, through the inputs, to power the outputs, and finally to the neutral rail. An input can come from a sensor, switch, or any other type of sensor. An output will be some device outside the PLC that is switched on or off, such as lights or motors. In the top rung the contacts are normally open and normally closed. Which means if input A is on and input B is off, then power will flow through the output and activate it Any other combination of input values will result in the output X being off.

Fig: A Simple Ladder Logic Diagram

There are other methods for programming PLCs. One of the earliest techniques involved mnemonic instructions. These instructions can be derived directly from the ladder logic diagrams and entered into the PLC through a simple programming terminal. An example of mnemonics is shown in Figure. In this example the instructions are read one line at a time from top to bottom. The first line 00000 has the instruction LDN (input load and not) for input A. This will examine the input to the PLC and if it is off it will remember a 1 (or true), if it is on it will remember a 0 (or false). The next line uses an LD (input load) statement to look at the input. If the input is off it remembers a 0, if the input is on it remembers a 1 (note: this is the reverse of the LDN). The AND statement recalls the last two numbers remembered and if they are both true the result is a 1; otherwise the result is a 0. This result now replaces the two numbers that were recalled, and there is only one number remembered. The process is repeated for lines 00003 and 00004, but when these are done there are now three numbers remembered. The oldest number is from the AND, the newer numbers are from the two LD instructions. The AND in line 00005 combines the results from the last LD instructions and now there are two numbers remembered. The OR instruction takes the two numbers now remaining and if either one is a 1 the result is a 1; otherwise the result is a 0. This result replaces the two numbers, and there is now a single number there. The last instruction is the ST (store output) that will look at the last value stored and if it is 1, the output will be turned on; if it is 0 the output will be turned off.

Fig: An Example of a Mnemonic Program and Equivalent Ladder Logic
The ladder logic program in Figure is equivalent to the mnemonic program. Even if you have programmed a PLC with ladder logic, it will be converted to mnemonic form before being used by the PLC. In the past mnemonic programming was the most common, but now it is uncommon for users to even see mnemonic programs.
Sequential Function Charts (SFCs) have been developed to accommodate the programming of more advanced systems. These are similar to flowcharts, but much more powerful. The example seen in Figure is doing two different things. To read the chart, start at the top where is says start. Below this there is the double horizontal line that says follow both paths. As a result the PLC will start to follow the branch on the left and right hand sides separately and simultaneously. On the left there are two functions the first one is the power up function. This function will run until it decides it is done, and the power down function will come after. On the right hand side is the flash function; this will run until it is done. These functions look unexplained, but each function, such as power up will be a small ladder logic program. This method is much different from flowcharts because it does not have to follow a single path through the flowchart.

Fig: An Example of a Sequential Function Chart
Structured Text programming has been developed as a more modern programming language. It is quite similar to languages such as BASIC. A simple example is shown in Figure 9. This example uses a PLC memory location i. This memory location is for an integer, as will be explained later in the book. The first line of the program sets the value to 0. The next line begins a loop, and will be where the loop returns to. The next line recalls the value in location i, adds 1 to it and returns it to the same location. The next line checks to see if the loop should quit. If i is greater than or equal to 10, then the loop will quit, otherwise the computer will go back up to the REPEAT statement continue from there. Each time the program goes through this loop i will increase by 1 until the value reaches 10.
i: = 0;
REPEAT
i: = i + 1;
UNTIL i >= 10
END_REPEAT;
Fig: An Example of a Structured Text Program
PLC Connections
When a process is controlled by a PLC it uses inputs from sensors to make decisions and update outputs to drive actuators, as shown in Figure. The process is a real process that will change over time. Actuators will drive the system to new states (or modes of operation). This means that the controller is limited by the sensors available, if an input is not available, the controller will have no way to detect a condition.

Fig: The Separation of Controller and Process
The control loop is a continuous cycle of the PLC reading inputs, solving the ladder logic, and then changing the outputs. Like any computer this does not happen instantly. Figure shows the basic operation cycle of a PLC. When power is turned on initially the PLC does a quick sanity check to ensure that the hardware is working properly. If there is a problem the PLC will halt and indicate there is an error. For example, if the PLC power is dropping and about to go off this will result in one type of fault. If the PLC passes the sanity checks it will then scan (read) all the inputs. After the inputs values are stored in memory the ladder logic will be scanned (solved) using the stored values - not the current values. This is done to prevent logic problems when inputs change during the ladder logic scan. When the ladder logic scan is complete the outputs will be scanned (the output values will be changed). After this the system goes back to do a sanity check, and the loop continues indefinitely. Unlike normal computers, the entire program will be run every scan. Typical times for each of the stages are in the order of milliseconds.


Fig: The Scan Cycle of a PLC
Ladder Logic Inputs
PLC inputs are easily represented in ladder logic. In Figure there are three types of inputs shown. The first two are normally open and normally closed inputs, discussed previously. The IIT (Immediate Input) function allows inputs to be read after the input scan, while the ladder logic is being scanned. This allows ladder logic to examine input values more often than once every cycle.

Fig: Ladder Logic Inputs
Ladder Logic Outputs
In ladder logic there are multiple types of outputs, but these are not consistently available on all PLCs. Some of the outputs will be externally connected to devices outside the PLC, but it is also possible to use internal memory locations in the PLC. Six types of outputs are shown in Figure 13. The first is a normal output, when energized the output will turn on, and energize an output. The circle with a diagonal line through is a normally on output. When energized the output will turn off. This type of output is not available on all PLC types. When initially energized the OSR (One Shot Relay) instruction will turn on for one scan, but then be off for all scans after, until it is turned off. The L (latch) and U (unlatch) instructions can be used to lock outputs on. When an L output is energized the output will turn on indefinitely, even when the output coil is deenergized. The output can only be turned off using a U output. The last instruction is the IOT (Immediate Output) that will allow outputs to be updated without having to wait for the ladder logic scan to be completed.
When power is applied (on) the output x is activated for the left output, but turned off for the output on the right.
An input transition on will cause the output x to go on for one scan. (This is also known as a one shot relay)

When the L coil is energized, x will be toggled on; it will stay on until the U coil is energized. This is like a flip-flop and stays set even when the PLC is turned off.

Some PLCs will allow immediate outputs that do not wait for the program scan to end before setting an output.

Fig: Ladder Logic Outputs
Basic Instructions
Load
The load (LD) instruction is a normally open contact. It is sometimes also called examine if on. (XIO) (As in examine the input to see if itâ„¢s physically on) The symbol for a load instruction is shown below.

A Load (contact) symbol
This is used when an input signal is needed to be present for the symbol to turn on. When the physical input is on we can say that the instruction is true. We examine the input for an on signal. If the input is physically on then the symbol is on. An on condition is also referred to as logic 1 state.
This symbol normally can be used for internal inputs, external inputs and external output contacts. Remember that internal relays don't physically exist. They are simulated (software) relays.
Load Bar
The Load Bar instruction is a normally closed contact. It is sometimes also called Load Not or examine if closed. (XIC) (as in examine the input to see if itâ„¢s physically closed) the symbol for a load bar instruction is shown below.

A Load Not (normally closed contact) symbol
This is used when an input signal does not need to be present for the symbol to turn on. When the physical input is off we can say that the instruction is true. We examine the input for an off signal. If the input is physically off then the symbol is on. An off condition is also referred to as a logic 0 state.
This symbol normally can be used for internal inputs, external inputs and sometimes, external output contacts. Remember again that internal relays don't physically exist. They are simulated (software) relays. It is the exact opposite of the Load instruction.
Logic State Load Load Bar
0 False True
1 True False
Out
The Out instruction is sometimes also called an Output Energize instruction. The output instruction is like a relay coil. Its symbol looks as shown below.

An OUT (coil) symbol
When there is a path of True instructions preceding this on the ladder rung, it will also be true. When the instruction is true it is physically on. We can think of this instruction as a normally open output. This instruction can be used for internal coils and external outputs.
Out bar
The Out bar instruction is sometimes also called an Out Not instruction. Some vendors don't have this instruction. The out bar instruction is like a normally closed relay coil. Its symbol looks like that shown below.

An Out Bar (normally closed coil) symbol
When there is a path of false instructions preceding this on the ladder rung, it will be true. When the instruction is true it is physically on. We can think of this instruction as a normally closed output. This instruction can be used for internal coils and external outputs. It is the exact opposite of the Out instruction.
Logic State Out Out Bar
0 False True
1 True False
6. ADVANTAGES OF PLC
¢ Reduced space.
¢ Energy saving.
¢ Ease of maintenance.
¢ Economical.
¢ Greater life and reliability.
¢ Tremendous flexibility.
¢ Shorter project time.
¢ Easier storage, archiving and documentation.
¢ PLCs are armored for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements.
¢ PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of complex positioning systems.
¢ PLCs are used in many "real world" applications. If there is industry present, chances are good that there is a plc present. If you are involved in machining, packaging, material handling, automated assembly or countless other industries you are probably already using them. If you are not, you are wasting money and time. Almost any application that needs some type of electrical control has a need for a plc.
7. APPLICATIONS OF PLC SYSTEM

¢ In industry, there are many production tasks, which are of highly repetitive nature. Although repetitive & monotonous, each stage needs careful attention of operator to ensure good quality of final product.
¢ Many times, a close supervision of the processes cause high fatigue on operator resulting in loss of track of process control.
¢ Sometimes it™s hazardous also as in the case of potentially explosive chemical processes.
¢ Under all such conditions we can use PLCs effectively in totally eliminating the possibilities of human error.
¢ Some capabilities of PLCs are as follows:
1. Logic control
2. PID control
3. Coordination & automation
4. Operator control
5. Signaling and listing etc.
¢ In short, wherever sequential logic control & automation is desired the PLCs are the best suited to meet the task. It includes simple interlocking functions to complicated analog signal processing to PID control action in closed loop control etc.
¢ Few examples of industries where PLCs are used for control & automation purpose are listed below: -
1. Tyre industry.
2. Blender reclaimer.
3. Bulk material handling system at ports.
4. Ship unloader.
5. Wagon loaders.
6. Steel plants.
7. Blast furnace charging.
8. Brick-moulding press in refectories.
9. Galvanizing plant.
10. Dairy automation.
11. Pulp factory.
12. Printing industry etc.

¢ Today the PLCs are used for control and automation job in a single machine and it increases up to full automation of manufacturing or testing process in a factory.
In robotics:

PLC is used for two tasks in robotics:
1) As the controller or unprogrammble part of robot.
2) As an overall system controller.
In flexible manufacturing system:
The logical development from linking machines in this manner is to group programmable machines into flexible manufacturing cells, each capable of machining a variety of products under fully automatic control.
In factory automation:

The Austin-rover assembling plant.
The plant produces multi style car body from individual body panels .The process consists of following activities:
1. Make up of sub assemblies from panels. Eg: doors, under frames
2. Tag sub assemblies together.
3. Pass tagged bodies to a main jig for automatic alignment & framing.
4. Conduct material transfer in which sub assemblies are selected, transported & distributed to workstation by conveyor system
5. Maintain quality control by automatic monitoring & manual inspection of each process.
The PLC tracks each component as it moves through the production area, communicating this information to each appropriate robot as necessary. Data send between PLC & robot includes handshaking signals to indicate robot busy parked, action complete etc. Data in binary coded decimal form is used to send component information & weld sequences from the PLC to root, which must acknowledge receipt of the correct data before the PLC will allow it to commence operation.
Overall planning & control: control
Plant mainframe computer main database


2 production & scheduling data
Centers minicomputer or powerful computer
3 coordination of multiple stations
Cells large PLC or computer

4 controlling plant & machinery
Stations PLC or computer
5 machinery & processes
Machinery I/P &O/P interfacing

Pyramid control hierarchy in an automated factory
8. PLC VS COMPUTER
PLC
¢ Designed for extreme industrial environments.
¢ Can operation in high temperature and humidity. Er
¢ High immunity to noise.
¢ Integrated command interpreter (proprietary).
¢ No secondary memory available (in the PLC).
¢ Optimized for Single task.Optimized
¢ Task
Computer
Computer
¢ Designed mainly for data processing and calculation.
¢ Optimized for speed.
¢ Can™t operate in extreme environments.
¢ Can be programmed in different languages.
¢ Lost of secondary memory available.
¢ Multitasking capability.
9. PLC DISADVANTAGES
¢ In contrast to microcontroller systems that have what is called an open
architecture, most PLCs manufacturers offer only closed architectures
for their products.
¢ PLC devices are proprietary, which means that parts and software from
one manufacturer can t easily be used in combination with parts of
another manufacturer, which limits the design and cost options.
10. CONCLUSION
PLC is a device that is capable of being programmed to perform a controlling function. The PLC was designed to provide flexibility in control based programming and executing logic instruction. PLC allowed for shorter installation time and faster commissioning through programming rather than wiring.
The PLC have in recent years experienced an unprecedented growth as universal element in industrial automation .It can be effectively used in applications ranging from simple control like replacing a small number of relays to complex automation problems.
Today the PLCs are used for control & automation job in a single machine & it increases up to full automation of manufacturing / testing process in a factory.
11. REFERENCE
http://www.plcs.net
http://www.sea.siemens.com/step/template...plcs:1:1:1
http://en.wikipedia.org/wiki/Programmabl...controller

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05-05-2010, 11:28 AM
Post: #2
RE: programmable logic controller plc full report

.ppt  P-L-C-General.ppt (Size: 881.5 KB / Downloads: 684)


Control Systems Types

Programmable Logic Controllers
Distributed Control System
PC- Based Controls

PLC

The PLC is an assembly of solid state digital logic elements design to make logical decisions and provide outputs.
PLC is programmed interface between input sensor &output device.


Programmable Logic Controllers

Sequential logic solver
PID Calculations.
Advanced Subroutines
BIT Operations.
Data Transfer.
Text Handling.


Programmable Logic Controllers

Applications :

Machine controls, Packaging, Material handling, similar Sequential task as well as Process control

Advantages of PLC :

They are fast and designed for the rugged industrial environment.
They are attractive on Cost-Per-Point Basis.
These Devices are less Proprietary ( E.g.. Using Open Bus Interface.)
These Systems are upgraded more Capabilities with dedicated PID and Ethernet Modules.

Disadvantages of PLC :

PLC one time cost is high
To maximize PLC performance a number of IO Modules to be added.
PLC hold only one copy of program.

P L C Components(Hardware)

Central Processing Unit (CPU)
Input Modules
Output Modules
Power Supply
Bus system
Rack(Rail)


Central Processing Unit

It is a micro-controller based circuitry. The CPconsists of following blocks :
Arithmetic Logic Unit (ALU), Program memory
Process image memory (Internal memory of CPU)
Internal timers ,counters and Flags .
CPperforms the task necessary to fulfill the PLC functions. i.e. Scanning I/O bus traffic control, Program execution, Peripheral and External device communication, data handling and self diagnostics.



Input module

These modules act as interface between real-time status of process variable and the CPU.
Analog input module : Typical input to these modules is
4-20 mA, 0-10 V
Ex : Pressure, Flow, Level Tx, RTD (Ohm), Thermocouple (mV)
Digital input module : Typical input to these modules is 24 V DC, 115 V AC, 230 V AC
Ex. : Switches, Pushbuttons, Relays, pump valve on off status
These modules act as link between the CPand the output devices in the field.
Analog output module : Typical output from these modules is 4-20 mA, 0-10 V
Ex : Control Valve
Digital output module : Typical output from these modules is 24 V DC, 115 V AC, 230 V AC
Ex. : Solenoid Valves, lamps, Actuators, Pump valve on off control


I/O MODULE SPECIFICATION

COST
INPUT VOLTAGE
ON-STATE INPUT VOLTAGE RANGE
AMBIENT TEMP RATING
INPUT DELAY “
NOMINAL OUTPUT VOLTAGE
MAX O/P CURRENT
ELECTRICAL ISOLATION “


Power Supply

The power supply gives the voltage required for electronics module (I/O, CPU, memory unit) of the PLC from the line supply.
The power supply provides isolation necessary to protect the solid state devices from most high voltage line spikes.
As I/O is expanded, some PLC may require additional power supplies in order to maintain proper power levels.


Bus System

It is path for the transmission of the signal between power supply module,processor and I/O modules.
The bus comprise of several single line i.e. wires /tracks


Advantage of PLC Over Relay
RELAY PLC

1-More wiring 1-Less wiring
2-Changes difficult 2-Changes easy
3-More power 3-Low power
4-More maintenance 4-Solid state reliability
5-Difficult to expand 5 -Easy to expand



PLC Cycle

Sense the Input
Process the Logic
Give Output
PLC Signal Flow
PLC Architecture Evolution
1970s : Discrete Machine Control
1985 : Discrete and Process Control
PLC Architecture Evolution
PLC Systems of various vendors
Siemens
S5 -110U, 115U, 135U
S7 - 200, 300, 400
Allen Bradley

Micrologix 1000, 1200, 1500
SLC 5/01, 5/02, 5/03
LOGIX PLATFORM
Modicon

Nano
Micro
Premium
Quantum
Configuration of PLC : Modicon
Configuration of PLC : Siemens
Configuration of PLC : Allen Bradley
Configuration of PLC : GE FANUC
PLC Programming Standards

Ladder Diagram

Function Block Diagram
Sequential Function Chart
Structured Text Language



Scan Rate

The completion of one cycle of the sequence is called- SCAN
Time required for one cycle is called SCAN TIME


PLC Selection Criteria

Cost of hardware,
I/O requirement
CPmemory
Spare parts& Maintenance,
Reliability,
Flexibility&
Integration of High-level Application.
Compatible Protocol


Memory Types

ROM (Read Only Memory)
RAM (Random Access Memory)
PROM (Programmable ROM)
EPROM (Erasable PROM)
EAROM- Electrically alterable ROM
EEPROM-Electrically erasable PROM


Binary System

BIT “ Each digit of a binary number i.e.0 or1
BYTE “ Group of 8 bits
WORD = Two bytes=16 bits
DOUBLE WORD =Two word =4bytes=32bits


PLC : Terminology

INPUT is referred by “ I
OUTPUT is referred by “ Q or O
TIMER is referred by “ T
FLAGS are referred by “ M or B
COUNTERS are referred by “ C


PLC : Protocol

It is a set of rules for data transmission when PLC is connected to network
RS-232 (Recommended standard)
RS-485
MPI(Multi point Interface)
Profibus
DH(Data Highway)
Ethernate
Controlnet

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30-05-2010, 07:42 AM
Post: #3
RE: programmable logic controller plc full report
please read http://www.seminarprojects.com/Thread-pr...ull-report for getting more information of PROGRAMMABLE LOGIC CONTROLLERS AND SCADA full report

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30-05-2010, 07:49 AM
Post: #4
RE: programmable logic controller plc full report

.pptx  PLC Presentation.pptx (Size: 1.01 MB / Downloads: 315)


SEMINAR ON P.L.C.

SUBMITTED BY
HRIDAY MUKHERJEE 08144003062
AMIT DEBNATH 08144003063
SOMNATH SHIL 08144003064





INTRODUCTION TO PLC
PROGRAMMABLE LOGIC CONTROLLER

A digitally operating electronic apparatus which uses a programming memory for the internal storage of instructions for implementing specific functions such as logic, sequencing, timing, counting and arithmetic to control through digital or analog modules, various types of machines or process.




PROGRAMMABLE CONTROLLER DEVELOPMENT

1968 Programmable concept developed
1974 Use of several (multi) processors within a
PLC - timers and counters; arithmetic
operations.
1977 Microprocessors - based PLC introduced
1983 Low - cost small PLCâ„¢s introduced
1985 on Networking of all levels of PLC, computer and machine using software




COMPONENT OF PLC
POWER SUPPLY


Provides the voltage needed to run the primary PLC component
I/O MODULES
Provides signal conversion and isolation between the internal logic- level signals inside the PLC and the fieldâ„¢s high level signal


PROCESSOR

Provides intelligence to command and govern the activities of the entire PLC systems

PROGRAMMING DEVICE

Used to enter the desired program that will determine the sequence of operation and control of process equipment or driven machine




PLC OPERATION

CHECK INPUT STATUS
First the PLC scans each input to determine if it is ON or OFF. It records this data into its memory to be used the next steps.

EXECUTE PROGRAM

Next the PLC executes the program one at a time.
UPDATE OUTPUT STATUS

Finally the PLC updates the status of the outputs.



CONFIGURATION

RELAYS: This are connected to the outside world. They are physically exist.
COUNTERS: They do not physically exist. They are simulated and can be programmed to count pulses.
TIMERS: They also do not physically exist. Common type are ON delay and OFF delay.
DATA STORAGE: Typically there are register to store data.



PLC PROGRAMMING
LADDER LOGIC:

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.



ELEMENTS OF LADDER LOGIC

Power flows through these contacts when they are closed. The normally open (NO) is true when the input or output status bit controlling the contact is 1. The normally closed (NC) is true when the input or output status bit controlling the contact is 0.



ELEMENTS OF LADDER LOGIC

Coils represent relays that are energized when power flows to them. When a coil is energized it causes a corresponding
output to turn on by changing the state of the status bit controlling the output to 1. That same output status bit maybe used to control normally open or normally closed contact anywhere in the program.



PLC MEMORY

The memory system in the processor module has two parts:
1. PROGRAM FILE
2. DATA FILE
3. The user program area is where the programmed instructions entered by the user are stored as an application control program
4. Data files are used for stored different information types. In the input and output which interface to outside world, and the other part of data file is fixed types of data files. The content of program memory cannot be changed while the PLC is running.




SELECTING A PLC

Criteria
Number of logical inputs and outputs.
Memory
Number of special I/O modules
Scan Time
Communications
Software



PLC AS A TOOL

achieve consistency in manufacturing.
improve quality and accuracy
increase productivity
shorten the time to the market
quick change over from one product to another
control inventry



USER INTERFACE

PLCs may need to interact with people for the purpose of configuration, alarm reporting or everyday control.



PLC COMMUNICATION

Changing resident PLC programs - uploading/downloading from a supervisory controller (Laptop or desktop computer).

Forcing I/O points and memory elements from a remote terminal.

Linking a PLC into a control hierarchy containing several sizes of PLC and computer.
Monitoring data and alarms, etc. via printers or Operator Interface Units.



PLC COMMUNICATION

Common Standards
RS 232
RS 485
LAN


TYPES OF PLC

Rack: A rack is often large (up to 18 by 30 by 10) and can hold multiple cards. When necessary, multiple racks can be connected together.
Mini: these are similar in function to PLC racks, but about half the size.
Micro: these units can be as small as a deck of cards. They tend to have fixed quantities of I/O and abilities, but cost will be the lowest.
Software: A software based PLC requires a computer with an interface card, but allows the PLC to be connected to sensor and other PLCs across a network.



LIST OF ITEMS REQUIRED WORKING WITH PLC

Programming Terminal - laptop or desktop PC.
PLC Software
Communication cable for connection from Laptop to PLC.
Backup copy of the ladder program (on diskette, CDROM,
hard disk, flash memory).
Documentation- (PLC manual, Software manual, drawings,
ladder program printout, and Seq. of Operations manual.)



AREA OF APPLICATION

Manufacturing / Machining
Food / Beverage
Metals
Power
Mining
Petrochemical / Chemical



ADVANTAGE OF PLC

Cost effective for controlling complex system.
Smaller physical size than hard-wired solutions.
Flexible and can be reapplied to control other systems quickly.
PLCs have integrated diagnostics and override functions.
Computational abilities allow more sophisticated control.
Diagnostics are centrally available.
Troubleshooting aids make programming easier and
reduce downtime.
Applications can be immediately documented.
Applications can be duplicated faster and less
expensively.
Reliable components make these likely operate for
several years successfully.
Communication is possibilities.


DISADVANTAGE OF PLC

Programmable controllers are not equipped with enough memory to store big amounts of data.
In this field the communication system need to be more developed.



CONCLUSION

Programmable Logic Control, or PLC as it is universally called, is the Ëœwork horseâ„¢ of industrial automation.
PLCs have been gaining popularity on the factory floor and will probably remain predominant for some time to come.
PLCs are an application area where much can be done.

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12-08-2010, 11:13 AM
Post: #5
RE: programmable logic controller plc full report
thanks buddy..
ur dis post helpsea lot to get sm knowledge about plc
19-09-2010, 07:48 PM
Post: #6
Sad RE: programmable logic controller plc full report
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03-10-2010, 01:13 PM
Post: #7
Lightbulb RE: programmable logic controller plc full report
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06-10-2010, 02:05 PM
Post: #8
RE: programmable logic controller plc full report

.doc  report.doc (Size: 738 KB / Downloads: 703)
PROGRAMMABLE
LOGIC
CONTROLLER


Prepared by:

DESAI PIYUSH (96EL424)
DESAI SAPAN (96EL425)
MEHTA PRAKSHEP (96EL441)
PATEL AKSHAY (96EL489)

Guided by:

SHRI. V.D. PATEL
SHRI. V. K. THAKAR
SHRI. K. D. PATEL

B V M ENGINEERING COLLEGE

SARDAR PATEL UNIVERSITY

VALLABH VIDYANAGAR

INTRODUCTION



Simplification of engineering and precise control of manufacturing process can result in significant cost savings. The most cost-effective way, which can pay big dividends in the long run, is flexible automation; a planned approach towards integrated control systems. It requires a conscious effort on the part of plant managers to identify areas where automation can result in better deployment/utilization of human resources and savings in man-hours, down time. Automation need not be high ended and too sophisticated; it is the phased, step-by-step effort to automate, employing control systems tailored to one’s specific requirements that achieves the most attractive results. That is where Industrial electronics has been a breakthrough in the field of automation and control techniques.


ROLE OF ELECTRONICS IN AUTOMATION

A constant demand for better and more efficient manufacturing and process machinery has led to the requirement for higher quality and reliability in control techniques. With the availability of intelligent, compact solid state electronic devices, it has been possible to provide control systems that can reduce maintenance, down time and improve productivity to a great extend. By installing efficient and user friendly industrial electronics systems for manufacturing machinery or processors, one can obtain a precise, reliable and prolific means for generating quality products.
Considering the varied demand and increasing competition, one has to provide for flexible manufacturing process. One of the latest techniques in solid state controls that offers flexible and efficient operation to the user is “PROGRAMMABLE CONTROLLERS”. The basic idea behind these programmable controllers was to provide means to eliminate high cost associated with inflexible, conventional relay controlled systems. Programmable controllers offer a system with computer flexibility:
26-10-2010, 05:10 PM
Post: #9
RE: programmable logic controller plc full report

.ppt  NITESH.ppt (Size: 2.33 MB / Downloads: 220)
PROGRAMMABLE LOGIC CONTROLLER

Submitted By:
Nitesh Agarwal
(4th year, E.C.E, EC/07/64)




Contents

Company Profile
Company Vision
Milestones
Collaboration
Other plants
Departments
Products
Application of bearings
Major customers
Programmable logical controller
Working Principle
Conclusion & Key learning
24-11-2010, 03:22 PM
Post: #10
RE: programmable logic controller plc full report

.docx  SCADA_Primer.docx (Size: 361.39 KB / Downloads: 87)
SCADA Primer



This document discusses the basics of SCADA systems. It
serves as introduction for those who are not familiar with it,
and as a reviewer for those who are already
knowledgeable about the SCADA Systems.

What is SCADA?

What is Telemetry?

What is Data Acquisition?

Differences between SCADA and DCS?

Components of SCADA

Field Instrumentation

Remote Station

Communication Network

Central Monitoring System (CMS)

Typical System Configuration

Modes of Communication





































SCADA Primer

What is SCADA?

SCADA (Supervisory Control And Data Acquisition) system
refers to the combination of telemetry and data acquisition.
It consists of collecting information, transferring it back to a
central site, carrying out necessary analysis and control,
and then displaying this data on a number of operator
screens.The SCADA system is used to monitor and control
a plant or equipment. Control may be automatic or can be
initiated by operator commands.



SCADA Primer

What is telemetry?

Telemetry is usually associated with SCADA systems. It is
a technique used in transmitting and receiving information
or data over a medium. The information can be
measurements, such as voltage, speed or flow. These data
are transmitted to another location through a medium such
as cable, telephone or radio. Information may come from
multiple locations. A way of addressing these different sites
is incorporated in the system.



SCADA Primer

What is data acquisition?

Data acquisition refers to the method used to access and
control information or data from the equipment being
controlled and monitored. The data accessed are then

Contact us at: compusystems2002[at]yahoo.com









forwarded onto a telemetry system ready for transfer to the
different sites. They can be analog and digital information
gathered by sensors, such as flowmeter, ammeter, etc. It
can also be data to control equipment such as actuators,
relays, valves, motors, etc.

SCADA Primer

What are the differences between SCADA and DCS?

Similar to the SCADA systems are the Distributed Control
Systems (DCS). The DCS is usually used in factories and
located within a more confined area. It uses a high-speed
communications medium, such as local area network
(LAN). A significant amount of closed loop control is
present on the systemThe SCADA system covers
larger.geographical areas. It may rely on a variety of
communication links such as radio and telephone. Closed
loop control is not a high priority in this system.



SCADA Primer




Components of SCADA System

Components of a SCADA System A SCADA
system are composed of the following:
1. Field Instrumentation
2. Remote Stations
3. Communications Network
4. Central Monitoring Station









Compusystems: Engineering training center services group of:
NASC: National Automation &Systems Co.
NTC: National Technical Company.

Tec-Edge

Electrical contracting Co.

Contact us at: compusystems2002[at]yahoo.com





















Components of SCADA System

Field Instrumentation refers to the sensors and actuators that
are directly interfaced to the plant or equipment. They
generate the analog and digital signals that will be monitored
by the Remote Station. Signals are also conditioned to make
sure they are compatible with the inputs/outputs of the RTU
or PLC at the Remote Station.

The Remote Station is installed at the remote plant or
equipment being monitored and controlled by the central host
computer. This can be a Remote Terminal Unit (RTU) or a
Programmable Logic Controller (PLC).

The Communications Network is the medium for transferring
information from one location to another. This can be via
telephone line, radio or cable.

The Central Monitoring Station (CMS) refers to the location of
the master or host computer. Several workstation may be
configured on the CMS, if necessary. It uses a Man Machine
Interface (MMI) program to monitor various types data
needed for the operation. The following is a sample
configuration of a SCADA system for water distribution.













Compusystems: Engineering training center services group of:
NASC: National Automation &Systems Co.
NTC: National Technical Company.

Tec-Edge

Electrical contracting Co.

Contact us at: compusystems2002[at]yahoo.com





































SCADA System for Water Distribution















SCADA Primer

SCADA Component:
Field Instrumentation

Field Instrumentation refers to the devices that are
connected to the equipment or machines being controlled
and monitored by the SCADA system. These are sensors
for monitoring certain parameters; and actuators for
controlling certain modules of the system.


Compusystems: Engineering training center services group of:
NASC: National Automation &Systems Co.
NTC: National Technical Company.

Tec-Edge

Electrical contracting Co.

Contact us at: compusystems2002[at]yahoo.com














These instruments convert physical parameters (i.e., fluid
flow, velocity, fluid level, etc.) to electrical signals (i.e.,
voltage or current) readable by the Remote Station
equipment. Outputs can either be in analog (continuous
range) or in digital (discrete values). Some of the industry
standard analog outputs of these sensors are 0 to 5 volts, 0
to 10 volts, 4 to 20 mA and 0 to 20 mA. The voltage
outputs are used when the sensors are installed near the
controllers (RTU or PLC). The current outputs are used
when the sensors are located far from the controllers.

Digital outputs are used to differentiate the discrete status
of the equipment. Usually, <1> is used to mean
EQUIPMENT ON and <0> for EQUIPMENT OFF status.
This may also mean <1> for FULL or <0> for EMPTY.

Actuators are used to turn on or turn off certain equipment.
Likewise, digital and analog inputs are used for control. For
example, digital inputs can be used to turn on and off
modules on equipment. While analog inputs are used to
control the speed of a motor or the position of a motorized
valve.






















Compusystems: Engineering training center services group of:
NASC: National Automation &Systems Co.
NTC: National Technical Company.

Tec-Edge

Electrical contracting Co.

Contact us at: compusystems2002[at]yahoo.com


















SCADA Primer




SCADA Component:
Remote Station

Field instrumentation connected to the plant or equipment
being monitored and controlled are interfaced to the
Remote Station to allow process manipulation at a remote
site. It is also used to gather data from the equipment and
transfer them to the central SCADA system. The Remote
Station may either be an RTU (Remote Terminal Unit) or a
PLC (Programmable Logic Controller). It may also be a
single board or modular unit.

RTU versus PLC

The RTU (Remote Terminal Unit) is a ruggedized computer
with very good radio interfacing. It is used in situations
where communications are more difficult. One
disadvantage of the RTU is its poor programmability.
However, modern RTUs are now offering good
programmability comparable to PLCs.

The PLC (Programmable Logic Controller) is a small
industrial computer usually found in factories. Its main use
is to replace the relay logic of a plant or process. Today,
the PLC is being used in SCADA systems to due its very
good programmability. Earlier PLC’s have no serial
communication ports for interfacing to radio for transferring
of data. Nowadays, PLC's have extensive communication
features and a wide support for popular radio units being used for SCADA system. In the near future we are seeing
the merging of the RTUs and the PLC’s.

Micrologic is offering an inexpensive RTU for SCADA
system wherein the PLC may be an overkill solution. It is a
microcontroller-based RTU and can be interfaced to radio
modems for transmitting of data to the CMS.

Single Board versus Modular Unit

The Remote Station is usually available in two types,
namely, the single board and the modular unit. The single
board provides a fixed number of input/output (I/O)
interfaces. It is cheaper, but does not offer easy
expandability to a more sophisticated system. The modular
type is an expandable remote station and more expensive
than the single board unit. Usually a back plane is used to
connect the modules. Any I/O or communication modules
needed for future expansion may be easily plugged in on
the backplane.
The use of telephone lines (i.e., leased or dial-up) is a
cheaper solution for systems with large coverage. The
leased line is used for systems requiring on-line connection
with the remote stations. This is expensive since one
telephone line will be needed per site. Besides leased lines
are more expensive than ordinary telephone line. Dial-up
lines can be used on systems requiring updates at regular
intervals (e.g., hourly updates). Here ordinary telephone
lines can be used. The host can dial a particular number of
a remote site to get the readings and send commands.

Remote sites are usually not accessible by telephone lines.
The use of radio offers an economical solution. Radio
modems are used to connect the remote sites to the host.
An on-line operation can also be implemented on the radio
system. For locations wherein a direct radio link cannot be
established, a radio repeater is used to link these sites.




SCADA Primer

SCADA Component:
Central Monitoring Station (CMS)



The Central Monitoring Station (CMS) is the master unit of
the SCADA system. It is in charge of collecting information
gathered by the remote stations and of generating
necessary action for any event detected. The CMS can
have a single computer configuration or it can be
networked to workstations to allow sharing of information
from the SCADA system.

A Man-Machine Interface (MMI) program will be running on
the CMS computer. A mimic diagram of the whole plant or
process can be displayed onscreen for easier identification
with the real system. Each I/O point of the remote units can
be displayed with corresponding graphical representation
and the present I/O reading. The flow reading can be
displayed on a graphical representation of a flowmeter. A
reservoir can be displayed with the corresponding fluid
contents depending on the actual tank level.

Set-up parameters such as trip values, limits, etc. are
entered on this program and downloaded to the
corresponding remote units for updating of their operating
parameters.

The MMI program can also create a separate window for
alarms. The alarm window can display the alarm tag name,
description, value, trip point value, time, date and other
pertinent information. All alarms will be saved on a
separate file for later review.

A trending of required points can be programmed on the
system. Trending graphs can be viewed or printed at a
later time. Generation of management reports can also be
scheduled on for a specific time of day, on a periodic basis,
upon operator request, or event initiated alarms.

Access to the program is permitted only to qualified
operators. Each user is given a password and a privilege
level to access only particular areas of the program.. All
actions taken by the users are logged on a file for later
review.
22-12-2010, 05:01 PM
Post: #11
RE: programmable logic controller plc full report
Prepared by:ABHISHEK BIRLA


.ppt  PLC.PPT (Size: 246.5 KB / Downloads: 237)



Introduction
PLCs are members of computer family.
PLC is a device which can control the whole machinery process through s/w programming.
PLC is composed of two basic sections CPU and INPUT/OUTPUT (I/O) interface system.
“LADDER LOGIC” programming language used to represent electrical sequences of operations.
PLC was designed to provide flexibility in control based programming.

PLC Definition
It is a medium to interface b/w input field elements & output field elements.
A PLC is a control device it takes information from inputs and makes decisions to energize or de-energize outputs the decisions are made based on the status of inputs &outputs and the ladder logic program that is being executed.

PLC HARDWARE
A programmable logic controller consists of the following components
Central Processing Unit (CPU).
Memory.
Input modules.
Output modules.
Power Supply.

PLC Hardware Block Diagram

Working of PLC
Steps of working
Types of PLC
COMPACT-: In which i/o modules are integrated
we can not connect extra i/o modules.

MODULAR-: In which we can connect i/o modules as per our requirement.
Companies Make PLC


Allen Bradely.
Siemens.
Modicon.
Mitsubishi.
Ge fanuc.
PROGRAMMING THE PLC

LADDER LOGIC INPUTS
LADDER LOGIC OUTPUTS
FUNCTIONING OF LADDER LOGIC

LOGIC GATES BY LADDER
APPLICATIONS OF PLC
ADVANTAGES OF PLC
Reduced space.
Energy saving.
Ease of maintenance.
Economical.
Greater life and reliability.
Tremendous flexibility.
Shorter project time.

DISADVANTAGES OF PLC
contrast to microcontroller systems that have what is called an open architecture, most PLCs manufacturers offer only closed architectures for their products.
PLC devices are proprietary, which means that parts and software from one manufacturer can t easily be used in combination with parts of another manufacturer, which limits the design and cost options.


03-01-2011, 03:38 PM
Post: #12
RE: programmable logic controller plc full report



.doc  ( Programmable Logic Controller) .doc (Size: 1.25 MB / Downloads: 163)

PROGRAMMABLE LOGIC CONTROLLERS

A PLC ( Programmable Logic Controller) is a device that was invented to replace the necessary sequential relay circuits for machine control. The PLC works by looking at its inputs and depending upon their state, turning on/off its outputs. The user enters a program, usually via software, that gives the desired results.

A digitally operating electronic apparatus which uses a programmable memory for the internal storage of instructions by implementing specific functions such as logic sequencing, timing, counting, and arithmetic to control, through digital or analog input/output modules, various types of machines or processes.

The digital computer which is used to perform the functions of a programmable controller is considered to be within this scope. Excluded are drum and other similar mechanical sequencing controllers.” Control engineering has evolved over time .in past humans was the main method for controlling system .More recently electricity has been used of control and early electrical control was based on relays .These relays allow power to be switched on and off without a mechanical switch.Controls. PLCs have been gaining popularity on the factory floor and will probably remain predominant for some time to come.

• Most of this is because of the advantages they offer. Flexible and can be reapplied to control other systems quickly and easily.
• Computational abilities allow more sophisticated control.
• Trouble shooting aids make programming easier and reduce downtime.

PLC BASICS:
In the 1960s and 1970s, industry was beginning to see the need for automation. Industry saw the need to improve quality and increase productivity. Flexibility had also become a major concern. Industry needed to be able to change processes quickly to meet the needs of the consumer.

OLD WAYS:
• There was always a huge wiring panel to control the system.
• Inside the panel there were masses of electromechanical relays.
• These relays were all hardwired together to make the system work.
• Hardwiring means that an electrician had to install wires between the connections of the relays.
• An engineer would design the logic of the system and electricians would be given a blueprint of the logic and would have to wire the components together.
• That the engineer made a few small errors in his/her design.
• That the electrician may have made a few errors in wiring the system.
• That there are few bad components in the system.

EARLIER WAYS:
• The only way to see everything was correct was to run the system.
• Troubleshooting was done by running the actual system. This was a very time-consuming process.
• No product could be manufactured while the wiring was being changed and system had to be disabled for wiring changes. This means that all the production personnel associated with that production line were without work until the system was repaired.
• The control system was based on mechanical relays.Mechanical devices are usually the weakest links in the systems. Mechanical devices have moving parts
• that can wear out. If one relay failed, the electrician might have to troubleshoot the whole system again. The system was down again until the problem was found and corrected.
• Another problem with hardwired logic is that if a change must be made, the system must be shutdown and the panel rewired. If a company decided to change the sequence of operations (even a minor change), it was a major expense and loss of production time while the system was not producing parts.
• Due to the disadvantages of the hardwired control panels industry saw the need to replace them and introduce PLCs.
• Increased competition to manufacturers to improve both quality and Productivity.
• Flexibility, rapid changeover and reduced downtime became important.
• Industry realized that a computer could be used for logic instead of hardwired relays. Computer could take the place of huge, costly, inflexible, hardwired control panels.
• If changes in the system logic or sequence of operations were needed, the program of the computer could be changed instead of rewiring.
• Imagine eliminating all the downtime associated with wiring changes.
• Imagine being able to completely change how a system operated by simply changing the software in the computer.
ADVANTAGES OF PLC:
• High reliability
• Small space requirements
• Computing capabilities
• Reduced costs
• Ability to withstand harsh environments
• Expandability
• Easy trouble shooting
• Less maintanence




26-03-2011, 03:03 PM
Post: #13
RE: programmable logic controller plc full report
PRESENTED BY:
Rajiv Nigam


.ppt  rajiv sir.ppt (Size: 2 MB / Downloads: 169)
objective
To understand the Basic concepts of programmable logic controller (PLC) or programmable controller, its Features , Communications and Programming, the advantages of the PLC over hard-wired control systems, its practical applications
 PLC
 Conclusion
What is PLC
The automation of many different processes, such as controlling machines or factory assembly lines, is done through the use of small computers called a programmable logic controllers (PLCs).
POWER SUPPLY
Provides the voltage needed to run the primary PLC components
Applications of PLC
 Plastics Industry
- Extruder factory, silo feeding control system
- Injection molding control system.
• Textile Industry
- Industrial batch washing machine control system
- Closed loop textile shrinkage system.
• Manufacturing Industry
- Lead acid battery plant, complete manufacturing system.
- Extruder factory, silo feeding control system
Travel Industry
- Escalator operation, monitored safety control system.
- Lift operation, monitored safety control system.
• Aerospace
- Water tank quenching system
• Printing Industry
- Offset web press print register control system.
- Multi stage screen washing system.
• Food Industry
- Filling machine control system
- Main factory feed water pump duty changeover system
Conclusion
PLC is a device that is capable of being programmed to perform a controlling function. The PLC was designed to provide flexibility in control based programming and executing logic instruction. PLC allowed for shorter installation time and faster commissioning through programming rather than wiring.
Today the PLCs are used for control & automation job in a single machine & it increases up to full automation of manufacturing / testing process in a factory.
18-07-2011, 04:47 PM
Post: #14
RE: programmable logic controller plc full report

.doc  report.doc (Size: 738 KB / Downloads: 230)
INTRODUCTION
Simplification of engineering and precise control of manufacturing process can result in significant cost savings. The most cost-effective way, which can pay big dividends in the long run, is flexible automation; a planned approach towards integrated control systems. It requires a conscious effort on the part of plant managers to identify areas where automation can result in better deployment/utilization of human resources and savings in man-hours, down time. Automation need not be high ended and too sophisticated; it is the phased, step-by-step effort to automate, employing control systems tailored to one’s specific requirements that achieves the most attractive results. That is where Industrial electronics has been a breakthrough in the field of automation and control techniques.
ROLE OF ELECTRONICS IN AUTOMATION
A constant demand for better and more efficient manufacturing and process machinery has led to the requirement for higher quality and reliability in control techniques. With the availability of intelligent, compact solid state electronic devices, it has been possible to provide control systems that can reduce maintenance, down time and improve productivity to a great extend. By installing efficient and user friendly industrial electronics systems for manufacturing machinery or processors, one can obtain a precise, reliable and prolific means for generating quality products.
Considering the varied demand and increasing competition, one has to provide for flexible manufacturing process. One of the latest techniques in solid state controls that offers flexible and efficient operation to the user is “PROGRAMMABLE CONTROLLERS”. The basic idea behind these programmable controllers was to provide means to eliminate high cost associated with inflexible, conventional relay controlled systems. Programmable controllers offer a system with computer flexibility:
1. Suited to withstand the industrial environment
2. Has simplicity of operation
3. Maintenance by plant technicians and
4. Reduce machine down time and provide expandability for future.
DEFINATION OF PLC
A Programmable controller is a solid state user programmable control system with functions to control logic, sequencing, timing, arithmetic data manipulation and counting capabilities. It can be viewed as an industrial computer that has a central processor unit, memory, input output interface and a programming device. The central processing unit provides the intelligence of the controller. It accepts data, status information from various sensing devices like limit switches, proximity switches, executes the user control program store in the memory and gives appropriate output commands to devices like solenoid valves, switches etc.
Input output interface is the communication link between field devices and the controllers; field devices are wired to the I/O interfaces. Through these interfaces the processor can sense and measure physical quantities regarding a machine or process, such as, proximity, position, motion, level, temperature, pressure, etc. Based on status sensed, the CPU issues command to output devices such as valves, motors, alarms, etc.
Programmer unit provides the man machine interface. It is used to enter the application program, which often uses a simple user-friendly logic.
BENEFITS OF PROGRAMMABLE CONTROLLERS
1. Programmable controllers are made of solid state components and hence provide high reliability.
2. They are flexible and changes in sequence of operation can easily be incorporated due to programmability. They may be modular in nature and thus expandability and easy installation is possible.
3. Use of PLC results in appreciable savings in Hardware and wiring cost.
4. They are compact and occupy less space.
5. Eliminate hardware items like Timers, counters and Auxiliary relays. The presence for timers and counters has easy accessibility.
6. PLC can control a variety of devices and eliminates the need for customized controls.
7. Easy diagnostic facilities are provided as a part of the system. Diagnosis of the external systems also becomes very simple. Thus easy service/maintenance.
8. Programming devices provide operator friendly interface with the machine. Being an outcome of the latest art of electronics technology, Programmable controllers provide higher level of performance with computers is possible. Useful management data can be obtained and maintained.
9. It has total protections against obsolescence and has wide scope for upgradation.
19-07-2011, 03:35 PM
Post: #15
RE: programmable logic controller plc full report
Ladder logic is the programming language used to represent electrical sequences of operation. In hardwired circuits the electrical wiring is connected from one device to another according to logic of operation. In a PLC the devices are connected to the input interface, the outputs are connected to the output interface and the actual wiring of the components is done electronically inside the PLC using ladder logic. This is known as soft wired.
12-03-2012, 03:59 PM
Post: #16
RE: programmable logic controller plc full report
programmable logic controller plc


.doc  plc.doc (Size: 22 KB / Downloads: 29)

Aim- Study of Programmable Logic Controller.
A Programmable Logic Controller, PLC, or Programmable Controller or Logic Box is
an electronic device used for Automation of industrial processes, such as control of machinery on factory assembly lines. 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.



Digital Input / Output of PLC
Digital Input signals behave as binary switches, yielding simply an ON or OFF signal (1 or 0, True or False, respectively). Pushbuttons, limit switches, and photo electric sensor are examples of Input devices providing a discrete signal.
Discrete Output signals are sent using either voltage or current, where a specific range is designated as ON and another as OFF. A PLC might use 24 V DC I/O, with values above 19 VDC representing ON and values below 11 VDC representing OFF. Relay Coil, Solonoide valve etc are example of Output devices.
The maximum number of I/O that can be configured in our system is 8 192 I/O with XP series.
07-12-2012, 11:42 AM
Post: #17
RE: programmable logic controller plc full report
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22-02-2014, 02:07 PM
Post: #18
RE: programmable logic controller plc full report
Who has the interest to do project by own, without any help of consultancy's....? I'm doing my project by my own.. Add me for idea's..

Who has the interest to do project by own, without any help of consultancy's....? I'm doing my project by my own.. Add me for idea's..
Who has the interest to do project by own, without any help of consultancy's....? I'm doing my project by my own.. Add me for idea's..
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