GITAM INSTITUTE OF TECHNOLOGY (Department of Electronics and Communication Engineering) GITAM UNIVERSITY VISHAKAPATNAM REPORT ON "STUDY OF PROGRAMMABLE LOGIC CONTROLLER" submitted as a part of industrial training done by Y.MADHAVA REDDY Regd no:1210409365
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GITAM INSTITUTE OF TECHNOLOGY
(Department of Electronics and Communication Engineering)
GITAM UNIVERSITY
VISHAKAPATNAM
REPORT ON
"STUDY OF PROGRAMMABLE LOGIC CONTROLLER"
submitted as a part of industrial training done by
Y.MADHAVA REDDY
Regd no:1210409365
BHARAT HEAVY ELECTRICALS LIMITED.
Ramachandra Puram,Hyderabad
ACKNOWLEDGEMENT
We would like to take this opportunity and express our heartfelt thanks to all those who helped
us in the course of this project work.
We are very much grateful to BHARAT HEAVY ELECTRICALS LIMITED for providing with real
data regarding the functioning of organization and we take this opportunity to express our
heartfelt gratitude to Mr.L.SHANKAR SINGH, ENGINEER (M&S), B.H.E.L., for having permitted
us to undertake the project in the organization and encouraging in completing this project
successfully.
We would like to convey our thanks to other staff members, who also guided us in our
endeavors and also extending their helping hands.
1. INTRODUCTION TO BHEL
BHEL is the largest engineering and manufacturing enterprise in India in the energy related/infrastructure sector today. BHEL was established more than 40 years ago ushering in the indigenous Heavy Electrical Equipment industry in India, a dream that has been more than realized with a well-recognized track record of performance. It has been earning profits continuously since 1971-72 and paying dividends since 1976-77.
BHEL manufactures over 180 products under 30 major product groups and caters to core sectors of the Indian Economy viz., Power Generation & Transmission, Industry, Transportation, Telecommunication, Renewable Energy, etc. The wide network of BHEL's 14 manufacturing divisions, four Power Sector regional centers, over 100 project sites, eight service centers and 18 regional offices, enables the Company to promptly serve its customers and provide them with suitable products, systems and services - efficiently and at competitive prices.
The quality & reliability of its products is due to the emphasis on design, engineering and manufacturing to international standards by acquiring and adapting some of the best technologies from leading companies in the world, together with technologies developed in its own R&D centers.
BHEL has acquired certifications to Quality Management Systems – ISO 9001, Environmental Management Systems – ISO 14001 and Occupational Health & Safety Management Systems – OHSAS 18001 and has also adopted the concepts of Total Quality Management.
BHEL has Installed equipment for over 90,000 MW of power generation - for Utilities, Captive and Industrial users.
Supplied over 2,25,000 MVA transformer capacity and sustained equipment operating in Transmission & Distribution network upto 400 KV - AC & DC.
Supplied over 25,000 Motors with Drive Control System to Power projects, Petrochemicals, Refineries, Steel, Aluminum, Fertilizer, Cement plants, etc.
Supplied Traction electrics and AC/DC locos to power over 12,000 Kms Railway network.
Supplied over 2,25,000 MVA transformer capacity and sustained equipment operating in Transmission & Distribution network upto 400 KV - AC & DC.
Supplied over one million Valves to Power Plants and other Industries.
BHEL's operations are organized around three business sectors, namely Power, Industry including Transmission, Transportation, Telecommunication & Renewable Energy and Overseas Business. This enables BHEL to have a strong customer orientation, to be sensitive to his needs and respond quickly to the changes in the market.
BHEL's vision is to become a world class engineering enterprise, committed to enhance stakeholder value. The company is striving to give shape to its aspirations and fulfill the expectations as a ‘Navratna' Company.
The greatest strength of BHEL is its highly skilled and committed 44,000 employees. Every employee is given an equal opportunity to develop himself and improve his position. Continuous training and retraining, career planning, a positive work culture and participative style of management have engendered development of a committed and motivated work force leading to enhanced productivity and higher levels of quality.
Project Engineering Department in BHEL Hyderabad Unit is mainly performing the engineering, procurement, inspection activities for Balance of Plant equipments for Captive and Utility power plants mainly Gas Turbine based.
Control & Instrumentation Group is involved in engineering, procurement, inspection of various field instruments, safety & control valves, cables, etc for the power plants. Also involved in providing overall plant control system using various makes of Distributed Control Systems (DCS) and Programmable Logic Controllers (PLCs).
A programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures . PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory. A PLC is an example of a hard real time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result.
The main difference from other computers is that PLCs are armoured for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements. These connect the PLC to sensors and actuators. PLCs read limit switches, analogy process variables (such as temperature and pressure), and the positions of complex positioning systems. Some use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analogy outputs. The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC
PROGRAMMABLE LOGIC CONTROLLER(PLC)
CONTENTS:
BHEL-An Over View
-Power Generation
-Power Transmission And Distribution
-Industries
-Transportation
-Technology Up -gradation And R & D
PLC Organisation
PLC Resources
Programming Structures
Introduction To NHCNC Machines &
Introduction To FAGOR 8040 CNC Systems
Technical specifications of FAGOR 8040
FAGOR 8040 Module Structure
-Directing Instructions
-Axes & Coordinate System
PLC Programming Examples
-Motor Starter Example
-Program Instructions
Expanding The Application
PLC Resources Of FAGOR 8040
PLC Program
PLC ORGANISATION
PLC (Programmable logic controller):
PLC is a digitally operating electronic apparatus which uses a programmable memory for
the internal storage of instructions for implementing specific functions such as logic,
sequencing, timing, counting and arithmetic to control various types of machines and
processors. A PLC monitors inputs, makes decisions based on its program, and controls outputs
to automate a process or machine. The inputs can be from sensors like push buttons, switches
etc. and the outputs go to devices like lamps, motors, pumps etc.
Block diagram of PLC:
PLCs consist of input modules or points, a Central Processing Unit (CPU) and output
modules or points. An input accepts a variety of digital or analog signals from various field
devices (sensors) and converts them into a logic signal that can be used by the CPU. The CPU
makes decisions and executes control instructions based on program instructions in memory.
Output modules convert control instructions from the CPU into a digital or analog signal that
can be used to control various field devices (actuators). A programming device is used to input
the desired instructions. These instructions determine what the PLC will do for a specific input.
An operator interface device allows process information to be displayed and new control
parameters to be entered.
It consists of various buses for transmission of information from one module to another
module. They are:
Address Bus: select the address (memory locations) on the individual members)
Data Bus: It carries data (content of the memory location
Control bus: Transfers control and timing signals for the synchronization of CPU’s
activities within the programmable controller
PLC RESOURCES
(All the values like number of inputs, outputs, marks, etc. refer to the FAGOR 8040 machine
specifications)
1. Inputs:
These are elements which supply information to the PLC from signals received from the
outside world. The inputs are basically from devices called sensors which can be defined as the
devices which convert a physical condition into an electrical signal like push buttons, limit
switches, proximity switches etc. They are represented by the letter I followed by the input
number which is desired to reference, for example I1, I25, I102, etc.
The PLC may control 512 inputs although when communicating with the outside world it can
only access the physical ones. Local physical inputs are the ones corresponding to the central
unit. Remote physical inputs are the ones corresponding to the remote modules
2. Outputs:
These are elements which allow the PLC to activate or deactivate the different devices in
the electrical cabinet. They are represented by the letter O followed by the output number
which is desired to reference, for example O1, O25, O102, etc.
The PLC may control 512 outputs although when communicating with the outside world it
can only access the physical ones. Local physical outputs are the ones corresponding to the
central unit. Remote physical outputs are the ones corresponding to the remote modules.
Output O1 coincides with the emergency output of the CNC (connector); thus, it must be kept
high (logic level 1).
I/O Numbering: The numbering conventions can differ from one manufacturer to another.
For example, the above convention is from FAGOR. In SIEMENS, I designate a discrete input
and Q designates a discrete output. The first number identifies the byte; the second number
identifies the bit. Input I0.0, for example, is byte 0, bit 0. Both the above conventions are used
throughout the remaining of this text.
3.Marks:
These are elements capable of memorizing in one bit (as if they were an internal relay) \
information defined by the user, their value being inalterable even when the power supply to
the system is turned off. This will be programmed by the letter M followed by the number of
the mark which it is wished to reference, for example, M1, M25, M102, etc.
The PLC controls the following marks:
User marks M1 - M2000
Arithmetic flag marks M2003
Clock marks M2009 - M2024
Fixed status marks M2046 and M2047
Marks associated with messages M4000 - M4127
Marks associated with errors M4500 - M4563
Screen marks M 4700 - M4955
CNC communication marks M5000 - M5957
Marks M1 thru M2047 have image values unlike the remainder of the marks, and so the PLC
will always work with their real values.
The arithmetic flag mark available at the PLC is:
M2003 Is the Zero flag and is set to 1 (high logic level) when the result of an AND, OR,
XOR operation is 0.
The clock marks M2009 to M2024, make up internal clocks of different periods which can be
used by the user.
The fixed status marks available at the PLC are:
M2046 Always has a value of 0.
M2047 Always has a value of 1.
The PLC allows, by means of the activation of a series of message marks, the PLC message
corresponding to the PLC message table to be displayed on the CNC screen. They can be named
by means of the mark M4000 - M4127 or by means of their associated mnemonic MSG1 -
MSG128:
Likewise, 64 error marks are available which allow the error corresponding to the PLC error
table to be displayed on the CNC screen as well as to interrupt the execution of the CNC
program, stopping axis feed and spindle rotation. Activating any of these marks does not
activate the external CNC emergency output.
They can be named by means of mark M4500-M4563 or by means of their associated
mnemonic ERR1 - ERR64:
Because the PLC program is not interrupted by these marks, it is advised to make it possible to
change their status via accessible external inputs; otherwise, the CNC will keep receiving the
same error at every PLC scan (cycle) thus preventing access to any PLC mode.
By activating one of the marks M4700-M4955 user pages 0-255 can be activated in the CNC.
They can be named by means of mark M4700-M4955 or by means of their associated
mnemonic PIC0 - PIC255:
4. Registers:
These are elements which store a numerical value in 32 bits, their value remaining
unalterable even when the power supply to the system is cut off. They do not have image
values and are represented by the letter R, followed by the register number it is desired to
reference, for example R1, R25, R102, etc.
The PLC has the following registers:
User registers R1 - R499
Registers for communication with the CNC R500 - R559
The PLC will consider each value stored in each register as an integer with a sign, and can be
within ±2147483647.
It is also possible to make reference to a BIT of the REGISTER by putting the letter B and the bit
number (0/31) in front of the selected register. For example:
B7R155 Refers to bit 7 of register 155.
The PLC considers bit 0 as being the one with least significance and bit 31 as being the one with
most significance.
The value stored in a register can be treated as being decimal, hexadecimal, binary or BCD for
example:
decimal 156
Hexadecimal $9C
Binary B0000 0000 0000 0000 0000 0000 1001 1100
5. TIMERS:
These are elements capable of maintaining their output at a determined logic level
during a preset time (time constant), after which the output changes status. They do not have
image values and are represented by the letter T, followed by the number of the timer it is
required to reference, for example, T1, T25, T102, etc. The time constant is stored in a 32-bit
variable, and so its value can be between 0 and 4294967295 milliseconds, which is equivalent
to 1193 hours (almost 50 days). The PLC has 256 timers, each of which has T status output and
TEN, TRS, TG1, TG2,
TG3 and TG4 inputs. It is also possible to consult at any moment the time which has elapsed
from the moment it was activated.
Enable Input (TEN):
This input allows the timing of the timer to be stopped. It is referred to by the letter TEN
followed by the number of the timer which is wished to reference, for example TEN 1, TEN 25,
TEN 102, etc.
So that the time elapses within the timer this input must be at level “1”. By default and
every time a timer is activated the PLC will assign this input a logic level of “1”. If, once the
timer is activated, TEN = 0 is selected, the PLC stops timing, and it is necessary to assign TEN = 1
for this timing to continue.
Reset Input (RES):
This input allows the timer to be initialized, by assigning the value 0 to its T status and by
cancelling its count (it initializes this to 0). It is referred to by the letters TRS followed by the
timer number it is wished to reference, for example TRS 1, TRS 25, TRS 102, etc.
This initialization of the timer will be made when a transition of logic level from “0” to “1”
(leading edge) is produced. By default and every time a timer is activated the PLC will assign this
input a logic level of “0”. If, once the timer is activated, a leading edge is produced at the TRS
input, the PLC initializes the timer, assigning value 0 to its T status and cancelling the count (it
initializes this to 0). Additionally, the timer is deactivated it being necessary to activate its
trigger input to activate it again.
Status Output (T):
This output indicates the logic status of the timer. It is referred to by the letter T followed
by the number of the timer which it is required to reference, for example T1, T25, T102, etc.
The logic status of the timer depends on the operating mode selected by means of the
trigger inputs TG1, TG2, TG3 and TG4, and so the activation or deactivation of this signal is
explained in each of the PLC operating modes.
Elapsed Time (t):
This output indicates the time elapsed in the timer since the moment it was activated. It is
referred to by the letter T followed by the number of the timer which it is required to reference,
for example T1, T25, T102, etc.
Although when written as T123 it coincides with the status output, both are different and they
are also used in different types of instruction.
Trigger Inputs (TG1, TG2, TG3, TG4):
These inputs allow the timer to be activated, and it begins to time. They are referred to
by the letters TG1, TG2, TG3, TG4 followed by the number of the timer it is required to
reference and the value which is required to start the count with (time constant).
The time constant value is defined in thousandths of a second, and it is possible to indicate this
by means of a numerical value or by assigning it the internal value of an R register.
Inputs TG1, TG2, TG3 and TG4 are used to activate the timer in four
different operating modes:
TG1 input in MONOSTABLE mode
TG2 input in DELAYED CONNECTION mode
TG3 input in DELAYED DISCONNECTION mode
TG4 input in SIGNAL LIMITING mode
This activation of the timer is made when a logic level transition of any of these inputs is
produced, either from “0” to “1” or from “1” to “0” (leading or trailing edge) depending on the
chosen input. By default and every time the timer is initialized by means of the reset input
(TRS), the PLC will assign logic level “0” to these inputs.
Monostable mode: TG1 Input
In this operational mode the timer status is kept at the high logic level (T=1) from the moment
the TG1 input is activated until the time indicated by the time constant elapses.
If the timer is initialized with values TEN=1 and TRS=0, the timer will be activated when a
leading edge is produced at input TG1. At that moment, the timer status output (T) changes
status (T=1) and timing t starts from a value of 0.
Once the time specified by the time constant has elapsed, timing will be considered as having
finished. The timer status output (T) changes status (T=0) and the elapsed time will be
maintained with the time value of the timer (T).
Any alteration which may be produced in input TG1 (leading or trailing edge) during the timing
operation will have no effect whatsoever.
If, once the timing is complete it is required to activate the timer again, another leading