plc workshop 1-2 day

Basics of Programmable Logic Controllers

SAJID ALI

DAY - 1PLC WORKSHOP

Presentation Sequence

Functions of PLCs Applications of PLCs Components of PLCs Programming Devices Symbols Programming modes PLC program creation Documentation PLC addressing Programming logic

functions Q&A

Basics of PLCs

Functions of PLC

Applicationsof PLC

Components of PLC

Programming Devices

Programming Modes

Symbols

PLC Program creation

Documentation

PLC addressing

Programming Logic Functions Q & A

Programmable Logic Controllers PLC( programmable logical controller) is a computer type device used in an industrial environment to control various types of machines or processes through digital or analogue inputs and outputs.

PLCs are similar to computers except, computers are optimised for calculation and display, PLCs are optimised for control tasks and the industrial environment. Thus PLCs are:

• Rugged and designed to withstand vibrations, temperature, humidity and noise.

• Have interfacing for inputs and outputs already inside the controller.

• Easily programmed and have an easily understood programming language which primarily concerned with logic and switching operations

Why PLCs

PLC is a microprocessor based, reprogrammable device that is used for Industrial Automation

In addition to the programming flexibility PLCs offer other advantages over traditional control systems. These advantages include:

high reliability small space requirements computing capabilities reduced costs ability to withstand harsh environments expandability

History

Conventional control panelAt the outset of industrial

revolution, especially during sixties and seventies, relays were used to operate automated machines, and these were interconnected using wires inside the control panel.

In some cases a control panel covered an entire wall.

History

Disadvantages of Conventional control panel

Too many wiring work. Difficult to modify and troubleshoot => Long down time. Power consumption can be quite high Drawings are usually not updated. Lifetime of relay contacts was limited, so some relays had to be replaced. If replacement was required, machine had to be stopped and production too. Also, it could happen that there was not enough room for necessary changes. As far as maintenance, electricians had to be very skillful in finding errors. When a problem occurs, hold-up time is indefinite, usually long.

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.

In the mid70's the dominant PLC were Modicon and A-B PLCs. The AMD 2901 and 2903 were quite popular in these PLCs

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.

History

The 80'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.

The 90'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.

http://www.plcopen.org/

History

Advantages of PLC based control system

Compared to a conventional process control system, number of wires needed for connections is reduced by 80%

Diagnostic functions of a PLC controller allow for fast and easy error detection. Change in operating sequence or application of a PLC controller to a different

operating process can easily be accomplished by replacing a program through a console or using a PC software (not requiring changes in wiring, unless addition of some input or output device is required).

Needs fewer spare parts. It is much cheaper compared to a conventional system, especially in cases

where a large number of I/O instruments are needed and when operational functions are complex.

Reliability of a PLC is greater than that of an electro-mechanical relay or a timer.

PLC ArchitectureTypically a PLC system has five basic components. These are the processor unit, memory, the power supply unit, input/output interface section and the programming device. Figure shows the basic arrangement. Programming

Device

Memory

Power Supply

Input Interface

Output InterfaceProcessor

PLC Architecture

PLC Architecture

CPUThe processor unit or central processing unit (CPU) is the unit containing the microprocessor and this interprets the input signals and carries out the control actions, according to the program stored in its memory, communicating decisions as a action signals to the output.

Power Supply UnitThe power supply unit is needed to convert the main a.c. voltage to the low d.c. voltage (5V,24V etc) necessary for the processor and the circuits in the input and output interface modules.

PLC Architecture

Programming DeviceThe Programming device is used to enter/edit the required program into the memory of the processor. The program is developed in the device and then transferred to the memory unit of the PLC.

Memory UnitProgram is stored in memory unit, and is used for the control actions to be exercised by the microprocessor.

Input and Output SectionsThe input and output sections are where the processor receives information form external devices and communicates information to external devices

PLC Architecture

The essential elements of a CPU are:RegistersA register is a byte (8 bits), word ( 16 bits ) or long word (32 bits) of memory which is part of the microprocessor as opposed to general purpose memory. A register is used for temporary storage of data and addresses within the CPU.

ALUThe ALU performs arithmetic and logical operations such as addition and subtraction on data stored in registers.

Control UnitThe control unit is basically a set of counters and logic gates which is driven by the block. Its function is to control the units within the microprocessor to ensure that operations are carried out in the correct order.

Functions of PLCs Functions of PLC:

Function of a PLC is to provide a reprogrammable, reliable, upgradable control solution for Industrial Automation

The function of an input module is to convert incoming signals into signals, which can be processed by the PLC, and to pass these to the central control unit. The reverse task is performed by an output module. This converts the PLC signal into signals suitable for the actuators

Conveyor systems

Filling plants

Woodworking

Pump controls

Vacuum suction systems/elevators

...over 1,000,000 applications world wide

Overview

Applications of PLCs

Applications of PLC are wide ranging as it is designed for Industrial Applications

As the Industry is diversified so is the application of PLC. A reliable controller for every machine & system . Where frequent process changes are required. In harsh environments. Where the whole plant is to be controlled by central controller

with multiple loops. Accurate Timer and counter functions, memory setting and

resetting, mathematical computing operations when required. For reliable, accurate and economical automation

Application examples

Control of a Sequence (Conveyor Unit)

Here a PLC is controlling the conveyor unit (Diversion & Speed)

PLC is getting info from: Sensors for workpiece

detection Sensors for conveyor

speed detection And controlling:

1. Diversion device (pneumatic based)

2. Conveyor speed

Monitoring a Chemical Plant

Here a PLC is controlling a process

PLC gathers information from level sensors

According to the level definition of the reservoirs opens or closes the respective valves

All of the actions are executed according to the program that is written in the PLC

PLC can also control the flowrate of the fluids.

Interface Control in CNC machine

A CNC machine requires a variety of sequential control applications like: Coolant on / off Door open / close Tool changing Vise / chuck open / close

A PLC is used here in connection with CNC controller that enables the machine to execute the fore stated steps

Interface control in CNC machine

PLCInterfaceControl

CNC-Controller

MachineTool

Program Program

Replacing Relays by PLC

Replacing Relays by PLC Continue:

Components of a PLC

Hardware Power supply Processor Input module Output module Special modules

Temperature sensing Motor control

Software PLC programming software Linking software HMI development software

Basics of PLC

Functions of PLC

Applicationsof PLC

Components of PLC

Programming Devices

Programming Modes

Symbols


Documentation

PLC addressing


The Base For PLC

Components of a PLC

The Power Supply Mounted On The Base Plate

Components of a PLC

The Processor Module Mounted on the Base Plate

Components of a PLC

The Input Module Mounted on the Base Plate

Components of a PLC

The Output Module Mounted on the Base Plate

Components of a PLC

Block Diagram of PLC

Types of PLCThere are two types of PLC 1) Fixed PLC Fixed PLC combine all of the main

components into a single unit that contains the CPU, input/output sections, and power supply. The number of inputs and outputs cannot be expanded.

2) Modular PLC A PLC configuration in which each

component is split into a separate unit. A modular PLC lets you have as many inputs and outputs as you want.

PLC Available in market

Following models of PLC are commonly available in the market.

Basics of PLC

Functions of PLC

Applicationsof PLC

Components of PLC

Programming Devices

Programming Modes

Symbols


Documentation

PLC addressing


Programming Devices

Processor Module can be programmed via Computer PLC programmer Hand Held Programmer

Processor Module can give output to Printer HMI panel Computer

It can communicate with other devices as well

Basics of PLC

Functions of PLC

Applicationsof PLC

Components of PLC

Programming Devices

Programming Modes

Symbols


Documentation

PLC addressing


Programming languages

Ladder Diagram Function Block Diagram Instruction List Structured Text Sequential Function Chart

Basics of PLC

Functions of PLC

Applicationsof PLC

Components of PLC

Programming Devices

Programming Modes

Symbols


Documentation

PLC addressing


Ladder diagram

A graphic programming language

Derived from relay logic Contact Rails to the left and

the right These contact rails are

connected to switching elements

Function block diagram

Graphical Method of programming

Various Function blocks are provided for the ease of programmer, e.g. Logic Functions Math Functions Special Functions

Functions blocks are interconnected into networks, to form a PLC program.

Even Ladder Diagram can be used with function blocks

Instruction List

Instruction list is a textual assembler-type language

Instruction list is formulated from control instructions consisting of an operator and an operand.

LD Part_TypeAOR Part_TypeBAND Part_presentAND Drill_okST Sleeve_in

Structured Text

Structured text programming is similar to high-level language Loops, control statements and function blocks can be used Structured text enables the formulation of numerous

applications, beyond pure function technology, algorithmic problems (Control) data handling (data analysis, processing of complex data

structures etc.).

Sleeve_in :- (Part_TypeA OR Part_TypeB) And Part_present AND Drill_ok;

Used for structuring of sequence-oriented control programs.

The elements SFC are steps, transitions, alternative and parallel branching.

Hierarchical structure of a control program is developed.

Sequential Function Chart

To gain popularity!

Why there are a number of programming options for a

PLC?

Basics of PLC

Functions of PLC

Applicationsof PLC

Components of PLC

Programming Devices

Programming Modes

Symbols


Documentation

PLC addressing


Specification: Description of the task

Design: Description of the solution

Realization: Implementation of the

solution Integration / commissioning:

Incorporating into environment and testing

Procedure for Creating a PLC Program

Documentation One important and crucial component of a system is

documentation, Documentation is required for

Maintenance Expansion of the system Troubleshooting

Individually these are: Problem description Positional sketch or technology pattern Circuit diagram Terminal diagram Printouts of control programs in SFC, FBD etc.. Allocation list of inputs and outputs Additional documentation


Documentation

PLC addressing

Input and output Assignment Electrical and pneumatic

circuit diagrams

Basics of PLC

Functions of PLC

Applicationsof PLC

Components of PLC

Programming Devices

Programming Modes

Symbols


Documentation

PLC addressing


PLC addressing

Memory Area Structure OF FATEK PLC

PLC addressing

Memory Area Structure OF SIEMENS PLC

PLC addressingMemory Area Structure OF SIEMENS

PLC

PLC addressing

Memory Area Structure OF SIEMENS PLC

Physical Input Contacts()-These are the external physical inputs contacts of the PLC. Its Address in Siemens PLC is I0….. In and for Fatek PLC is X0….Xn.

Physical Output Coils()-These are the external physical Outputs Coils/Relays of the PLC. Its Address in Siemens PLC is Q0….. Qn and for Fatek is Y0….Yn.

PLC addressing

Memory Area Structure PLC Internal Relay ()- Do not have any specific function, and they can be freely used within the program (except those assigned to Input or Output Cards and Special I/O Cards). Known as M area in Fatek PLC.

Retentive M(M800-1399), Internal Relay(M0-799) and Special relays (M1912-2001)

Work Area/Data Register (D) – can be used only in the program; not for I/O exchange with external I/O terminals.

D (D0-D4095), R(R0-4168)

PLC addressing

Memory Area Structure PLC

Step Relays (S) – These are the step relays of PLC. Known as

Retentive S(S500-999) and S(0-499) of Fatek PLC.

Timers(T)/ Counters(C)-

I/O Assignment

The I/O assignment table indicates which PLC inputs are connected to which input devices

And which PLC outputs drive which output devices.

The assignment of internals, including timers and counters also takes place here.

Electrical and pneumatic circuit diagrams

Integration of PLC with mechanical system. the electrical circuit is

replaced with the ladder diagram of PLC

and is connected to the pneumatic circuit accordingly

Here a solenoid operated valve is connected to the PLC.

Basics of PLC

Functions of PLC

Applicationsof PLC

Components of PLC

Programming Devices

Programming Modes

Symbols


Documentation

PLC addressing


Programming of logic functionsLadder Diagram

• A graphical representation use by engineers for their relay logic.

• Adopted by PLC makers as a programming language due to its simplicity. Thus the term Ladder Programming shown in figure.

• Fatek PLC programmer WinProLadder.

Symbols of Ladder Diagram

Symbols of Ladder Diagram

This is a representation of a relay coil. The number represents the relay.

This is a normally open contact symbol. It will be closed if the coil of the same number is energised.

This is a normally closed contact symbol. It will open upon the energising of the coil of the same number

Y0

X0

X0

SIMATIC S7-200SIMATIC S7-200

S7-200 Second Generation OverviewCPU 221

(10 I/O Points)CPU 222

(14 I/O Points)

CPU 226(40 I/O Points)

) CPU 224(24 I/O Points)

CPU 224XP(24 I/O Points)

Overview

Built-in Features

Removable Terminal Blocks (224(XP),226)

Communication Port(s)

24V Sensor Power Output

Mounting Holes for Panel Installation

Snap-On Clipfor DIN Rail Mounting

Cartridge Slot

CPU Status LEDs

Internal:- Power Supply- Super Capacitor- Clock (224(XP),226)

I/O Point Status LEDs

Overview

Please sit infront of Individual PCs and Open WinProLadder placed on DeskTop.

Practice on Simple Ladder Logic Programming

Review on Logic Gates

NOT Gate, OR Gate, Nor Gate, And Gate, Nand Gate, XOR Gate, Multiplexers Etc.

Equation & Truth Table of Gates

Practice Session

Programming of logic functions

Basic Logic Functions Not Or And Memory

The figure is showing the relay logic for AND and OR operation

Negation (NOT Gate)

The output signal assumes the value 1, if the input signal has the value 0 and vice versa.

Negation (NOT Gate)

Exercise 1: Lamp H1 is illuminated as

long as switch S1 is not actuated;

It is extinguished, if the switch is closed. The purpose of S1 is therefore to switch off the lamp.

Negation (NOT Gate)

Solution:

AND-Operation

The output signal only assumes the value 1, if all input signals have the value 1.

AND-Operation

Exercise 2:

Lamp H1 is to be switched on only if the two switches S1 and S2 are actuated.

AND-Operation

Solution:

NAND-Operation

The output signal only assumes the value 1, if all input signals have the value 1.

NAND-Operation

Exercise 3: The output signal only

assumes the value 1, if all input signals have the value 1.

Lamp H1 is to be switched on only if the two switches S1 and S2 are actuated.

NAND-Operation

Solution 3:

OR-Operation

The output signal assumes the value 1, if at least one input signal has the value 1.

OR-Operation

Example 4:

Lamp H1 is to be switched on, if at least one switch, S1 or S2 is actuated.

OR-Operation

Solution 4:

NOR-Operation


NOR-Operation

Example 5:


NOR-Operation

Solution 5:

Exclusive OR-Operation



Example 6:



Solution 6:

Memory Function The standard function block

SR a dominant setting flipflop

(bistable memory with preferred status 1).

A 1-signal at S1 sets the value of Q1

A 1-signal at R only brings output Q1 to value 0

The standard function block RS a dominant resetting flipflop

(bistable memory with preferred status 0).

Memory Function

Exercise: If sensor B1 has a 1-Signal, this indicates an error status in

the system. A horn H1 is sounded. The horn can only be switched off by actuating push-button

S1. It is possible to switch off the horn, even if the B1- signal continues to be applied.

Memory Function

National Institute of Design & Analysis 88

DAY-2 Programming Techniques

• Symbolic Addressing• Latches• Timers• Single Shot Pulse• Counters


Symbolic Addressing


LatchesLatch circuit is used to maintain the status of output based on two execution conditions. These conditions are SET & RESET. When SET condition is true, output turns ON and stay ON, until reset condition is true. When RESET condition is true, output turns OFF and stay OFF, until SET condition is true.

SET condition

Output

RESET condition


Latches


TIMER

National Institute of Design & Analysis97

Timers and Creating Delay

A timer is activated when its execution condition goes ON. If the execution condition remains ON long enough for TIM to time down to zero, the output for the TC number used will turn ON and will remain ON, until TIM is reset. TIM measures in units of 0.1 second from the Set Value.

Input Condition

OutputT1


Timers and Creating Delay


DELAY ON TIMER


DELAY ON TIMER

EXAMPLE: Write a program to on a motor after 10 seconds

When switch S1 is on


DELAY ON TIMERSolution:


DELAY OFF TIMER

EXAMPLE: Write a program to on a motor for 100 seconds

When switch S1 is on.


DELAY OFF TIMER Solution:


Retentive or Accumulating timer


Retentive or Accumulating timer Example:


TIMER


Single-Shot Circuit This circuit is used to keep the ON time of an

input signal.

Input Signal

OutputT1 T1


Single-Shot Circuit


COUNTER


COUNTER

EXAMPLE: Write a program to count a number of samples ( box, apples, bottles etc) up to 10 and then stop the conveyor motor.


COUNTER


Retentive or Accumulating timer

EXAMPLE: Write a program to count the existing bottles on a conveyor belt by using S1 at the entrance and S2 at outlet. If bottles are 4 then on alarm AL1. Use S3 pushbutton for reset.


COUNTER

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