S.NO. TOPIC PAGE NO.
1 INTRODUCTION 6
2 AUTOMATION 7
3 PLC(PROGRAMMABLE LOGIC
4 PROGRAMMING IN PLC 11
5 COMPONENTS OF PLC 12
6 MICROLOGIX 1000 15
7 COMMUNICATION OF PLC WITH PC 18
8 TIMERS AND COUNTERS 23
9 COMPARE FUNCTIONS 27
10 INTRODUCTION TO SCADA 31
11 SCADA PROGRAMMING 33
12 RELAYS 36
13 CONTACTORS 37
14 HMI 38
15 REFERENCES 40
Control engineering has evolved over time. In the past humans were the main method for
controlling a system. More recently electricity has been used for control and early electrical
control was based on relays. These relays allow power to be switched on and off without a
mechanical switch. It is common to use relays to make simple logical control decisions. The
development of low cost computer has brought the most recent revolution, the Programmable
Logic Controller (PLC). The advent of the PLC began in the 1970s, and has become the most
common choice for manufacturing 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.
• Cost effective for controlling complex systems.
• 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.
• Reliable components make these likely to operate for years before failure.
The term SCADA stands for Supervisory Control and Data Acquisition. A SCADA system is
a common process automation system which is used to gather data from sensors and
instruments located at remote sites and to transmit and display this data at a central site for
either control or monitoring purposes. The collected data is usually viewed on one or more
SCADA Host computers located at the central or master site.
Automation or automatic control is the use of various control systems for operating
equipment such as machinery, processes in factories, boilers and heat treating ovens,
switching in telephone networks, steering and stabilization of ships, aircraft and other
applications with minimal or reduced human intervention. Some processes have been
The biggest benefit of automation is that it saves labor however, it is also used to save energy
and materials and to improve quality, accuracy and precision.
The term automation, inspired by the earlier word automatic (coming from automaton), was
not widely used before 1947, when General Motors established the automation department. It
was during this time that industry was rapidly adopting feedback controllers, which were
introduced in the 1930s.
Automation has been achieved by various means including mechanical, hydraulic, pneumatic,
electrical, electronic and computers, usually in combination. Complicated systems, such as
modern factories, airplanes and ships typically use all these combined techniques
History of Automation:-In the ancient times people worked by hand. They made every
tasks, every works without any help. Later they began to do some simple (and later more
complicated ) machines, eg. water wheels for lifting water from channels, mills (water and
wind mills ) for milling corns, etc. They began to use animals to give their force, their power
to get work machines, vehicles, etc
In the XIXth century the machines were able to do many tasks. Steam engines gave the
mechanical energy to machines, but the man had to control every machine.
Control consists of some activities:
• observe the phenomena (speed of machine, pressure of steam, temperature of
• compute (decide) the needed activity (growing or reducing the amount of fuel ),
• set the appropriate device (modify the setting of fuel valves ).
Advantages of Automation:-
The main advantages of automation are:-
• Increased through output or productivity.
• Improved quality or increased predictability of quality.
• Improved robustness (consistency), of processes or product.
• Increased consistency of output.
• Reduced direct human labor costs and expenses.
Disadvantages of Automation:-
The main disadvantages of automation are:-
• Causing unemployment and poverty by replacing human labor.
• Security Threats/Vulnerability: An automated system may have a limited level of
intelligence, and is therefore more susceptible to committing errors outside of its
immediate scope of knowledge (e.g., it is typically unable to apply the rules of simple
logic to general propositions).
• Unpredictable/excessive development costs: The research and development cost of
automating a process may exceed the cost saved by the automation itself.
• High initial cost: The automation of a new product or plant typically requires a very
large initial investment in comparison with the unit cost of the product, although the cost
of automation may be spread among many products and over time.
Parts of Automation:-
1. Hardware Control-
2. Software Control-
3. Field Instruments-
PROGRAMMABLE LOGIC CONTROLLER (PLC):-
A Programmable Logic Controller is an industrial computer control system that continuously
monitors the state of input devices and makes decisions based upon a custom program to
control the state of output devices.
Almost any production line, machine function, or process can be greatly enhanced using this
type of control system. However, the biggest benefit in using a PLC is the ability to change
and replicate the operation or process while collecting and communicating vital information.
Another advantage of a PLC system is that it is modular. That is, you can mix and match the
types of Input and Output devices to best suit your application
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.
Interface between Input and Output to process the desired logic.
TYPES OF PLC:-
1. Compact type
2. Modular type
1. Compact type:-
a) Slots are not available
b) I/O cannot be varied
c) Also compact in its size
2. Modular type:-
a) Slots are available
b) I/O can be varied
PROGRAMMING LANGUAGE USED IN A PLC
The Ladder Logic is the most commonly used PLC programming language.
Ladder Diagram (LD) Traditional ladder logic is graphical programming language.
Initially programmed with simple contacts that simulated the opening and closing of relays,
Ladder Logic programming has been expanded to include such functions as counters, timers,
shift registers, and math operations.
ADDRESSING FOR INPUT AND OUTPUT:-
FILE TYPE: FILE NO.:SLOT NO. *WORD NO./BIT No.
i.e. For Input:-I:0.0/0,I:0.0/1 and so on….
For Output:-O0:0.0/0,O0:0.0/1 and so on…
SYMBOLS USED IN LADDER LOGIC PROGRAMMING:-
COMPONENTS OF A PLC:-
1. Power Supply:-
Provides the voltage needed to run the primary PLC components 24vDC, 220vAC, and 110ac
The wiring diagram shows the inputs and outputs connected irectly (hard wired)
to the PLC. The devices shown are on/off or digital in nature but the signal to the PLC is
analog. Many commonly used devices conform to a 4-20 mA standard whereby signals of
4mA and 20mA form respectively the minimum and maximum values of an analog signal.
With analog devices, a separate cable needs to be run between the end device and the control
system because only a single analog signal can be represented on the circuit. The 4-20 mA
standard is slowly being replaced by network or fieldbus communications. Fieldbus is a
multi-drop digital two-way communication link between intelligent devices. Fieldbus allows
the connection of a number of sensors all located in the same area to the same cable. Fieldbus
comes in many varieties depending on the manufacturer and application. Examples include
ASibus, Profibus, Devicenet and Modbus. A more recent trend is the development of
Industrial Ethernet which has the capacity to transport large quantities of data not only for
process control but also to integrate the process with management information systems.
3. Input Modules:-
a)Provides signal conversion and isolation between the internal logic-
b)level signals inside the PLC and the field’s high level signal.
c)The I/O interface section of a PLC connects it to external field devices.
d)The main purpose of the I/O interface is to condition the various signals received from or
sent to the external input and output devices.
e)Input modules converts’ signals from discrete or analog input devices to logic levels
acceptable to PLC’s processor.
3.1 Discrete Input:-
A discrete input also referred as digital input is an input that is either ON or OFF is
connected to the PLC digital input. In the ON condition it is referred to as logic 1 or logic
high and in the OFF condition may be referred to as logic o or logic low. It can be toggle
switch, push button etc.
An analog input is an input signal that has a continuous signal. Typical inputs may vary
from 0 to 20mA, 4 to 20mAor 0 to10V. Below, a level transmitter monitors the level of liquid
in the tank. Depending on the level Tx, the signal to the PLC can either increase or decrease
as the level increases or decreases. e.g. temperature and pressure related instruments etc.
Output modules converts signal from the processor to levels capable of driving the connected
discrete or analog output devices.
An analog output is an output signal that has a continuous signal. Typical outputs may vary
from 0 to 20mA, 4 to 20mAor 0 to10V.
A discrete output is either in an ON or OFF condition. Solenoids, contactors coils, lamps are
example of devices connected to the Discrete or digital outputs. Below, the lamp can be
turned ON or OFF by the PLC output it is connected to.
The processor module contains the PLC’s microprocessor, its supporting circuitry, and its
memory system.The main function of the microprocessor is to analyze data coming from
field sensors through input modules, make decisions based on the user’s defined control
program and return signal back through output modules to the field devices. Field sensors:
switches, flow, level, pressure, temp. transmitters, etc. Field output devices: motors, valves,
solenoids, lamps, or audible devices.
The MicroLogix 1000 programmable controller is a packaged controller containing
a power supply, input circuits, output circuits, and a processor. The controller is
available in 10 I/O, 16 I/O and 32 I/O configurations, as well as an analog version
with 20 discrete I/O and 5 analog I/O.
The catalog number for the controller is composed of the following:
• Compact design—
Let’s the MicroLogix 1000 controller thrive in limited panel space.
• Choice of communication networks—
An RS-232-C communication port is configurable for: DF1 protocol for direct connection
to a programming device or operator interface; DH-485 networking through a 1761-NET-
AIC converter; DeviceNet networking through a 1761-NET-DNI interface; EtherNet/IP
networking through a 1761-NET-ENI interface; or for half-duplex slave protocol in
• Simple programming with your choice of programming device—
You can program these controllers in familiar ladder logic with MicroLogix 1000 A.I.
, PLC 500 A. I. Series Programming Software, RSLogix 500™
Windows Programming Software, or the MicroLogix Hand-Held Programmer (1761-
HHP-B30). This symbolic programming language is based on relay ladder wiring
diagrams that simplify the creation and troubleshooting of your control program.
• Comprehensive instruction set—
Over 65 instructions including simple bit, timer, and counter instructions, as well as
instructions for powerful applications like sequencers, high-speed counter, and shift
Execution time for a typical 500-instruction program is only 1.56 ms.
• Choice of languages—
Software and documentation are available in 5 languages. The hand-held programmer has
6 languages built in.
PROGRAMMING OF PLC
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.
In Allen Bradley PLC’s the logic used for the programming is ladder logic. Ladder logic is a
programming language that represents a program by a graphical diagram based on the circuit
diagrams of relay-based logic hardware. It is primarily used to develop software for
Programmable Logic Controllers (PLCs) used in industrial control applications. The name is
based on the observation that programs in this language resemble ladders, with two vertical
rails and a series of horizontal rungs between them.
Ladder logic is widely used to program PLCs, where sequential control of a process or
manufacturing operation is required. Ladder logic is useful for simple but critical control
systems, or for reworking old hardwired relay circuits. As programmable logic controllers
became more sophisticated it has also been used in very complex automation systems.
Simple ladder logic
If a path can be traced between the left side of the rung and the output, through asserted (true
or "closed") contacts, the rung is true and the output coil storage bit is asserted (1) or true. If
no path can be traced, then the output is false (0) and the "coil" by analogy to
electromechanical relays is considered "de-energized.Ladder logic has contacts that make or
break circuits to control coils. Each coil or contact corresponds to the status of a single bit in
the programmable controller's memory. Unlike electromechanical relays, a ladder program
can refer any number of times to the status of a single bit, equivalent to a relay with an
indefinitely large number of contacts.
So-called "contacts" may refer to physical ("hard") inputs to the programmable controller
from physical devices such as pushbuttons and limit switches via an integrated or external
input module, or may represent the status of internal storage bits which may be generated
elsewhere in the program.
Each rung of ladder language typically has one coil at the far right. Some manufacturers may
allow more than one output coil on a rung.
--( )-- a regular coil, energized whenever its rung is closed
--()-- a "not" coil, energized whenever its rung is open
--[ ]-- A regular contact, closed whenever its corresponding coil is energized
---- A "not" contact, open whenever its corresponding coil is energized
The "coil" (output of a rung) may represent a physical output which operates some device
connected to the programmable controller, or may represent an internal storage bit for use els
------[ ]--------------[ ]----------------O---
Key Switch 1 Key Switch 2 Motor
“This is a logical AND.”
COMMUNICATION OF PLC WITH PC:-
To make communication of PLC with PC following steps are noted down:
1) Connect PC and PLC via RS232 comport or Ethernet.
2) Then click on RS Linx icon, a window will appear as shown in fig below
2) RS Linx classic window
3) In this window add drivers i.e. whether it is RS232 comport or Ethernet and configure the
drivers and closes the window.
4) Then click on icon RS who on the RS Linx classic window, another window will appear as
shown in fig 220.127.116.11.
5) After opening the RS who window click on AB DF1-1 DH-485, the PLC is running is
shown on the window. Then close this window and double click on RS Logix 500 starter.
Fig RS Who window
6) When we double click on RS Logix 500 starter a window will appear as shown in fig .
RS Logix 500 window
There are various instructions which are useful for making ladder logic for PLC
programming. These are as follows:
4.1) XIC (Examine if closed):
Use the XIC instruction in your ladder program to determine if a bit is ON. When the
instruction is executed, if the bit addressed is on (1), then the instruction is evaluated as true.
When the instruction is executed, if the bit addressed is off (0), then the instruction is
evaluated as false.
XIC (Examine if closed):
Examples of devices that turn on or off include:
• A push button wired to an input (addressed as I:0/4).
• An output wired to a pilot light (addressed as O:0/2).
• A timer controlling a light (addressed as T4:3/DN).
4.2) XIO (Examine if open):
Use the XIO instruction in your ladder program to determine if a bit is OFF. When the
instruction is executed, if the bit addressed is off (0), then the instruction is evaluated as true.
When the instruction is executed, if the bit addressed is on (1), then the instruction is
evaluated as false.
Examples of devices that turn on or off include:
• Motor overload normally closed (N.C.) wired to an input (I:0/10).
• An output wired to a pilot light (addressed as O:0/4).
• A timer controlling a light (addressed as T4:3/DN).
4.3) Output Energize (OTE):
Use the OTE instruction in your ladder program to turn on a bit when rung conditions are
evaluated as true. An example of a device that turns on or off is an output wired to a pilot
light (addressed as O:0/4).
OTE instructions are reset when:
• The SLC enters or returns to the REM Run or REM Test mode or
Power is restored.
• The OTE is programmed within an inactive or false Master Control
Reset (MCR) zone.
Timers are used to perform the timing operations. Time base is the minimum value of time in
second that can be taken by the timer. Preset value is the total number of the seconds for
which the timing operation has to be done Accumulator starts increasing the time in seconds
upto the preset value. Upto the preset value of the accumulator the enable bit of timer is high
& the timer runs. When accumulator reaches the preset value then the timer stops and the
done bit of the timer becomes high.
The timer has following bits and these bits are useful in the operation of timer:
EN- Enable- This bit will high when the input is given to the timer
TT - Timer timing bit - This bit will be high during the timing process. It remains high
till accumulator value becomes equal to preset value
DN – Done – This bit will be high when the timing process is ended. It set to high
when the accumulator value becomes equal to preset value.
In Micrologix 1000 and 1100 PLC there are three types of timers i.e.
TYPES OF TIMERS USED:-
4.5.1 TON Timer
4.5.2 T-OFF Timer
4.5.3 Retentive timer ON (RTO)
Use the TON instruction to turn an output on or off after the timer has been on for a preset
time interval. The TON instruction begins to count time-base intervals when rung conditions
become true. As long as rung conditions remain true, the timer adjusts its accumulated value
(ACC) each evaluation until it reaches the preset value (PRE). The accumulated value is reset
when rung conditions go false, regardless of whether the timer has timed out
Use the TOF instruction to turn an output on or off after its rung has been off for a preset time
interval. The TOF instruction begins to count timebase intervals when the rung makes a true-
to-false transition. As long as rung conditions remain false, the timer increments its
accumulated value (ACC) based on the timebase for each scan until it reaches the preset
value (PRE). The accumulated value is reset when rung conditions go true regardless of
whether the timer has timed out.
Retentive Timer (RTO):
Use the RTO instruction to turn an output on or off after its timer has been on for a preset
time interval. The RTO instruction is a retentive instruction that begins to count timebase
intervals when rung conditions become true.
The RTO instruction retains its accumulated value when any of the following occurs:
• Rung conditions become false.
• You change processor operation from the REM Run or REM Test
mode to the REM Program mode
• The processor loses power (provided that battery backup is maintained)
• A fault occurs
When you return the processor to the REM Run or REM Test mode and/or rung conditions
go true, timing continues from the retained accumulated value. By retaining its accumulated
value, retentive timers measure the cumulative period during which rung conditions are true.
A Retentive Timer (RTO)
Counters are used to count the number of operations. Its function is same as the timer accepts
that the timer counts the number of seconds and the counter counts the number of operations
or pulses. At each operation the value of the accumulator increases and when the value of the
accumulator comes to the preset value of the counter then the counter stops.
TT - Timer timing bit - This bit will be high during the counting process. It remains
high till accumulator value becomes equal to preset value
DN – Done – This bit will be high when the counting process is ended. It set to high
when the accumulator value becomes equal to preset value.
Counter UP (CTU):-
The CTU is an instruction that counts false-to-true rung transitions. Rung transitions can be
caused by events occurring in the program (from internal logic or by external field devices)
such as parts traveling past a detector or actuating a limit switch. When rung conditions for a
CTU instruction have made a false-to-true transition, the accumulated value is incremented
by one count, provided that the rung containing the CTU instruction is evaluated between
these transitions. The ability of the counter to detect false-to-true transitions depends on the
speed (frequency) of the incoming signal. The accumulated value is retained when the rung
conditions again become false. The accumulated count is retained until cleared by a reset
(RES) instruction that has the same address as the counter reset.
Counter UP (CTU)
Counter Down (CTD):-
The CTD is an instruction that counts false-to-true rung transitions. Rung transitions can be
caused by events occurring in the program such as parts traveling past a detector or actuating
a limit switch. When rung conditions for a CTD instruction have made a false-to-true
transition, the accumulated value is decremented by one count, provided that the rung
containing the CTD instruction is evaluated between these transitions. The accumulated
counts are retained when the rung conditions again become false. The accumulated count is
retained until cleared by a reset (RES) instruction that has the same address as the counter
Counter Down (CTU)
COMMANDS FOR COMPARISON:-
EQU (equal to):-
This input instruction is true when source A becomes equal to source B. The EQU instruction
compares two user specified values if values are equal, it allows rung continuity. The rung
goes true and output energies.
GEQ (greater than equal to)
Fig 4.8) Greater than Equal to
This instruction compares two values and will be high when the counted value becomes equal
to or greater than the fixed value and will energize everything that is connected next to it.
LEQ(less than equal to)
Fig 4.9) Less than Equal to
This instruction compares two values and will be high when the counted value becomes equal
to or less than the fixed value and will energize everything that is connected next to it.
GRT (greater than)
Fig 4.10) Greater Than
Use of the GRT instruction to test whether one value (source A) is greater than another
(source B). If the value at source A is greater than the value at source B, the instruction is
logically true. If the value at source A is less than or equal to the value at source B, the
instruction is logically false. Source A must be an address. Source B can either be a program
constant or an address. Negative integers are stored in two’s complement form.
4.11) LES (less than)
Fig 4.11) Less than
Use of the LES instruction is to test whether one value (source A) is less than another (source
B). If source A is less than the value at source B, the instruction is logically true. If the value
at source A is greater than or equal to the value at source B, the instruction is logically false.
Source A must be an address. Source B can either be a program constant or an address.
Negative integers are stored in two’s complement form.
4.12) LIM (Limit):-
Use the LIM instruction to test for values within or outside a specified range,
depending on how you set the limits.
4.14) RES (Reset):
Fig 4.14) Reset
Use a RES instruction to reset a timer or counter. When the RES instruction is enabled, it
resets the Timer ON Delay (TON), Retentive Timer (RTO), Count UP (CTU), or Count
Down (CTD) instruction having the same address as the RES instruction.
When resetting a counter, if the RES instruction is enabled and the counter rung is enabled,
the CU or CD bit is reset. If the counter preset value is negative, the RES instruction sets the
accumulated value to zero. This in turn causes the done bit to be set by a count down or count
SCADA stands for supervisory control and data acquisition. It generally refers to an
industrial control system a computer system monitoring and controlling a process. SCADA
stands for Supervisory Control And Data Acquisition. As the name indicates, it is not a full
control system, but rather focuses on the supervisory level. As such, it is a purely software
package that is positioned on top of hardware to which it is interfaced, in general via
Programmable Logic Controllers (PLCs), or other commercial hardware modules.
SCADA systems are used not only in industrial processes: e.g. steel making, power
generation (conventional and nuclear) and distribution, chemistry, but also in some
experimental facilities such as nuclear fusion. The size of such plants range from a few1000
to several 10 thousands input/output (I/O) channels. However, SCADA systems evolve
rapidly and are now penetrating the market of plants with a number of I/O Channels of
several 100 K: we know of two cases of near to 1 M I/O channels currently under
Leading SCADA companies
Invensys Wonder ware : In touch
Allen Bradley: RS View 32
Industrial process includes those of manufacturing production, power generation,
fabrication, and refining, and may run in continuous, batch, repetitive, or discrete modes.
Infrastructure processes may be public or private, and include water treatment and
distribution, wastewater collection and treatment, oil land gas pipelines, electrical power
transmission and distribution, and large communication system.
Facility processes occur both in public facilities an private ones, including building, airports,
ships, and space stations.
Types of SCADA
1. D+R+N ( Development +Run + Networking)
2. R+N ( Run +Networking )
3. Factory focus
Features of SCADA
1. Dynamic process Graphic
2. Alarm summery
3. Alarm history
4. Real time trend
5. Historical time trend
6. Security (Application Security)
7. Data base connectivity
8. Device connectivity
10. Recipe management
The term SCADA usually refers to centralized systems which monitor and control entire
sites, or complexes of systems spread out over large areas (anything between an industrial
plant and a country). Most control actions are performed automatically by remote terminal
units ("RTUs") or by programmable logic controllers ("PLCs"). Host control functions are
usually restricted to basic overriding or supervisory level intervention. For example, a PLC
may control the flow of cooling water through part of an industrial process, but the SCADA
system may allow operators to change the set points for the flow,and enable alarm conditions,
such as loss of flow and high temperature, to be displayed and recorded. The feedback
control loop passes through the RTU or PLC, while the SCADA system monitors the overall
performance of the loop.
Application of SCADA
Electric power generation, transmission an distribution.
The SCADA system used by us is SCADA Intouch Wonder. This SCADA system is created
by WonderWare. It has variety of commands, tool library and many other features required
for programming. It is an integrated, component-based software for monitoring and
controlling automation machines and processes.
• Open its graphic displays as OLE containers for ActiveX® controls — with thousands
of third-party ActiveX controls to choose from, you can drop ready-made solutions
right into your projects
• Develop an object model to expose portions of its core functionality, allowing it to
interoperate easily with other component-based software products
• Support OPC standards as both a server and a client for fast, reliable communications
with a wide variety of hardware devices
• Support interfacing with PLC ,excel and other tools also.
Benefits of Intouch
• Interact with other Rockwell Software products
• Share data with Microsoft products
• Enjoy preferred compatibility with Rockwell Automation products
• Maximize your hardware investments with OPC
• Update projects online
Programming with Intouch
1. Double click on “intouch” icon and a window will appear named Intouch
2. Create a ‘New’ application.
3. Then give a specific name to it.
4. Now open that application.
5. A window is appeared as:-
6. Select windows properties and click OK
7. At the right most corner of this software the project window will appear. In
this window there are all the options related to our project in the SCADA.
Like system, graphics, alarms,buttons , datalogs, logic & control etc.
A relay is an electrical switch that opens and closes under the control of another
electrical circuit. In the original form, the switch is operated by an electromagnet to
open or close one or many sets of contacts. It was invented by Joseph Henry in 1835
When a relay is used to switch a large amount of electrical power through its contacts, it
is designated by a special name: contactor. Contactors typically have multiple contacts,
and those contacts are usually (but not always) normally-open, so that power to the load is
shut off when the coil is de-energized. Perhaps the most common industrial use for
contactors is the control of electric motors. The top three contacts switch the respective
phases of the incoming 3-phase AC power, typically at least 480 Volts for motors 1
horsepower or greater. The lowest contact is an "auxiliary" contact which has a current
rating much lower than that of the large motor power contacts, but is actuated by the same
armature as the power contacts. The auxiliary contact is often used in a relay logic circuit,
or for some other part of the motor control scheme, typically switching 120 Volt AC
power instead of the motor voltage. One contactor may have several auxiliary contacts,
either normally-open or normally-closed, if required.
• A contactor is a large relay, usually used to switch current to an electric motor or
other high power load.
• Large electric motors can be protected from over current damage through the use of
overload heaters and overload contacts. If the series-connected heaters get too hot
from excessive current, the normally-closed overload contact will open, de-energizing
the contactor sending power to the motor.
HMI (HUMAN MACHINE INTERFACE)
The user interface (also known as human computer interface or man-machine
interface (MMI)) is the aggregate of means by which people—the users—interact
with the system—a particular machine, device, computer program or other complex
tool. The user interface provides means of:
• Input, allowing the users to manipulate a system
• Output, allowing the system to indicate the effects of the users' manipulation.
• Steps to interface HMI with PLC:-
• Create a new application
• Select the type of HMi(here we are using PV 300 Micro with DF1)
• Give application name and then click “OK”
• A window similar to the HMI(hardware) is displayed as:3
• Here on the top there are various tools available for the HMI programming.
The steps are:-
OPEN A NEW APPLICATION
Applications are created with default file names that you can change when saving the
application. The default file name is PVcApplication1. The number automatically increments
as you create new applications.
• Click the Create & Edit button in the Panel View Explorer Startup window
Review areas of screen. This is where you will spend most of your time
1. Navigation tabs Provides access to the different functional areas of an application
2. Application toolbar Provides common tools that are available to all views of the
application. Drag your mouse over each tool
3. Cursor controls Hides or shows the Controls or Properties panel to increase the
4. Screen list Contains a list of screens in the application including the alarm banner and
5. Screen workspace Contains objects that you drag to the screen from the object
6. Object palette Contains panels of objects that you can drag to the screen workspace.
Click the cursor on a tab to open or close a panel of objects. The palette can occupy 25, 50 or
75% of the Controls panel. Right-click on the object palette heading to resize it. The object
palette and screen list are resized accordingly
7. Properties panel Contains panels of properties to configure the appearance, navigation,
common properties, or connection tags of a selected object. Panels vary for each object. Click
the cursor on a tab to open orclose a panel You can also change the screen properties by
clicking a blank area of a screen. Screen properties include name, description, grid spacing.