4. CR1
CR1-1
Relays
• Original control elements
• Now used as auxiliary devices
• The PLC is not designed to switch high currents or voltages
5. Contactors
•Used for heavy-duty switching
•Provides isolation from high voltages and large currents
•Usefully for large inductive currents, such as motor starting
6. Motor Starters
•Contactors + Overload Relay
•Overload relays were usually heaters and bimetal strips
•The bimetal strip separates when heated
•Next steps:
•PLCs and motor starters
•Electronic overloads
•Intelligent starters
7. Manually Operated Switches
•Pushbuttons
•Normally open
•Normally closed
•Break-then-make
•Make-then-break
•Selector switches
•Maintained or spring return
10. Control Systems Types
Programmable Logic Controllers
Distributed Control System
PC-Based Controls
11. PLC Systems
•CPU
•Processor
•Memory
•One Module
•Power Supply
•Part of the chassis or a separate module
•Programming/ Monitoring Device
•I/0 Modules
13. Advantages of PLCs
•Lessandsimplerwiring.
•WiringbetweendevicesandrelaycontactsaredoneinthePLCprogram.
•Solid-state-nomovingparts.
•Easierandfastertomakechanges.(Flexible).
•Fasterresponsetime.
•Sophisticatedinstructionsetsavailable.
•Troubleshootingaidsmakeprogrammingeasierandreducedowntime.
•Reliablecomponentsmaketheselikelytooperateforyearsbeforefailure.
•Allowsfordiagnostics”easytotroubleshoot”.Easymaintenance.
•Lessexpensive
•Awiderangeofcontrolapplication
INTRODUCTION TO PLCS
14. Disadvantages of PLC :
PLC were Designed for Relay Logic Ladder and have Difficulty with some Smart Devices.
To maximize PLC performance and Flexibility, a number of Optional Modules must be added
15. PLC Origin
•-Developed to replace relays in the late 1960s
•-Costs dropped and became popular by 1980s
•-Now used in many industrial designs
16. 16
Historical Background
The Hydramatic Divisionof the General Motors Corporationspecified the design criteria for the first programmable controller in 1968
Their primary goal
To eliminate the high costs associated with inflexible, relay-controlled systems.
17. 17
Historical Background
•The controller had to be designed in modular form, so that sub- assemblies could be removed easily for replacement or repair.
•The control system needed the capability to pass data collection to a central system.
•The system had to be reusable.
•The method used to program the controller had to be simple, so that it could be easily understood by plant personnel.
18. PLC developments
1968Programmable controller concept developed.
1969Hardware CPU controller, with logic instruction, 1k of memory and 128 I/O points.
1974Use of several processors within a PLC –timers and counters, arithmetic operations, 12k of memory and 1024 I/O points.
1976Remote input/output systems introduced.
1977Microprocessor-based PLC introduced.
1980Intelligent I/O modules developed,
Enhanced communications facilities,
Enhanced software features,
Use of personal microcomputer as programming aids.
1983Low-cost small PLC introduced.
1985Networking of all levels of PLC, computer and Machine under standard specification
Distributed, hierarchical control of industrial plants.
20. 20
Programmable Logic Controllers
( Definition according to NEMA standard ICS3-1978)
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.
21. 21
Leading Brands Of PLC
AMERICAN1. Allen Bradley
2. Gould Modicon
3. Texas Instruments
4. General Electric
5. Westinghouse
6. Cutter Hammer
7. Square D
EUROPEAN1. Siemens
2. Klockner& Mouller
3. Festo
4. Telemechanique
JAPANESE1. Toshiba
2. Omron
3. Fanuc
4. Mitsubishi
26. 26
Areas of Application
Manufacturing /Machine controls
Food / Beverage, Packaging, Material handling,
Metals
Power
Mining
Petrochemical / Chemical
27. In Snack Foods Industries
◊Temperature Control ◊Pressure Control
◊Variable Speed Drive Systems Batching Systems
◊Continuous Mixing System Controls
◊Batch Mixing Systems Material Handling
◊Pneumatic Conveying Systems
◊Vacuum Conveying Systems
◊Product Conveying Systems Cooker Systems
◊Temperature Control
◊Level Control
◊PH Control Extrusion & Cutting Systems
◊Speed Control
◊Pressure Control
◊Cutting Control Slurry Mixing and Distribution
◊Pump Control Systems
◊Valve Control Systems
28.
29. Kiln Control Systems
◊Temperature Control
◊Humidity Control Material Handling
◊Pneumatic Conveying Systems
◊Vacuum Conveying Systems
◊Product Conveying Systems Cutting Control Systems Forming Systems
◊Variable Speed Drive Systems Gypsum Mixing and Distribution
◊Pump Control Systems
◊Valve Control Systems Batching Systems
◊Continuous Mixing System Controls
◊Inventory Control System
30. Tank Used to Mix Two Liquids
A
B
C
FS
MOTOR
TIMER
FLOAT SWITCH
SOLENOIDS
SOLENOID
1 -MINUTE
31. 31
Tank Used to Mix Two Liquids
A tank is used to mix two liquids. The control circuit operates as follows:
1. When the start button is pressed, solenoids A and B energize. This permits the two liquids to begin filling the tank.
2. When the tank is filled, the float switch trips. This de-energizes solenoids A and B and starts the motor used to mix the liquids together.
3. The motor is permitted to run for one minute. After one minute has elapsed, the motor turns off and solenoid C energizes to drain the tank.
32. 4. When the tank is empty, the float switch de-energizes solenoid C.
5. A stop button can be used to stop the process at any point.
6. If the motor becomes overloaded, the action of the entire circuit will stop.
7. Once the circuit has been energized it will continue to operate until it is manually stopped.
32
Tank Used to Mix Two Liquids
34. PLC Size
1.Nano (SMALL)-it covers units with up to 128 I/O’s and memories up to 2 Kbytes.
-these PLC’s are capable of providing simple to advance levels or machine controls.
2.Micro (MEDIUM)-have up to 2048 I/O’s and memories up to 32 Kbytes.
3. LARGE-the most sophisticated units of the PLC family. They have up to 8192 I/O’s and memories up to 750 Kbytes.
-can control individual production processes or entire plant.
35. Kinds of PLC
Monolithic construction
Monoprocessor
Fieldbus connection
Fixed casing
Fixed number of I/O (most of them binary)
No process computer capabilities (no MMC)
Typical product: Mitsubishi MELSEC F, ABB AC31, SIMATIC S7
Modular construction (backplane)
One-or multiprocessor system
Fieldbus and LAN connection
3U or 6U rack, sometimes DIN-rail
Large variety of input/output boards
Connection to serial bus
Small MMC function possible
Typical products: SIMATIC S5-115, Hitachi H-Serie, ABB AC110
(2)
(1)
Compact
Modular PLC
(3)
Soft-PLC
Windows NT or CE-based automation products
Direct use of CPU or co-processors
36. courtesy ABB
Modular PLC
RS232
CPU
CPU
Analog I/O
Binary I/O
backplane
parallel bus
•housed in a 19" (42 cm) rack (height 6U ( = 233 mm) or 3U (=100mm)
•concentration of a large number of I/O
Power Supply
•high processing power (several CPU)
•primitive or no HMI
•cost effective if the rack can be filled
•tailored to the needs of an application
•supply 115-230V~ , 24V= or 48V= (redundant)
fieldbus
LAN
•large choice of I/O boards
•interface boards to field busses
•requires marshalling of signals
fieldbus
development
environment
•cost ~ €10’000 for a filled crate
37. Small modular PLC
mounted on DIN-rail, 24V supply
cheaper (€5000)
not water-proof,
no ventilator
extensible by a parallel bus (flat cable or rail)
courtesy ABB
courtesy Backmann
38. Specific controller (railways)
data bus
special construction: no fans, large temperature range, vibrations
three PLCs networked by a data bus.
39. Compact or modular ?
€
# I/O modules
Limit of local I/O
compact PLC
(fixed number of I/Os)
modular PLC (variable number of I/Os
field bus
extension
40. Industry-PC
Wintel architecture
(but also: Motorola, PowerPC),
MMI offered (LCD..)
Limited modularity through mezzanine boards
(PC104, PC-Cards, IndustryPack)
Backplane-mounted versions with PCI or Compact-PCI
Competes with modular PLC
no local I/O,
fieldbus connection instead,
courtesy INOVA
courtesy MPI
costs: €2000.-
41. Soft-PLC (PC as PLC)
• PC as engineering workstation
• PC as human interface (Visual Basic, Intellution, Wonderware)
• PC as real-time processor (Soft-PLC)
• PC assisted by a Co-Processor (ISA-or PC104 board)
• PC as field bus gateway to a distributed I/O system
2
12
2
3
3
23
4
I/O modules
42. Compact PLC
Monolithic (one-piece) construction
Fixed casing
Fixed number of I/O (most of them binary)
No process computer capabilities (no MMC)
Can be extended and networked by an extension (field) bus
Sometimes LAN connection (Ethernet, Arcnet)
Monoprocessor
Typical product: Mitsubishi MELSEC F, ABB AC31, SIMATIC S7
costs: €2000
courtesy ABB
courtesy ABB
courtesy ABB
43. Specific Controller (example: Turbine)
Thermocouple
inputs
binary I/Os,
CAN field bus
RS232 to HMI
Relays and fuses
Programming port
cost: €1000.-
tailored for a specific application, produced in large series
courtesy Turbec
46. What is a PLC?
Inputs Outputs
The Basic Block
A PROGRAMMABLE LOGIC CONTROLLER is a solid state control system that
continuously monitors the status of devices connected as inputs. Based upon a user written
program, stored in memory, it controls the status of devices connected as outputs.
CPU
47. A PLC is simply a block / device use to MANIPULATE input signal by using certain
RULES
The manipulation process called Control The rules called Program
48. Basic criteria for PLC Types
Memory Capacity
I/O Range
Packaging and Cost per Point
49. PLC evolution
A
B
P2
P1
I1
Analog World
Binary World
C
continuous processes
Regulation, controllers
discrete processes
combinatorial
sequential
relay controls,
Relay control
pneumatic sequencer
Pneumatic and electromechanical
controllers
Programmable Logic Controllers
50.
51. PLC: Location in the control architecture
Enterprise Network
directly connected
I/O
Control Bus
(e.g. Ethernet)
Engineer
station
I/O
I/O
I/O
I/O
CPU
Sensor Bus (e.g. ASI)
Field Bus
gateway
Field Stations
Control Station
with Field Bus
direct I/O
I/O
Field Devices
FB
gateway
gateway
I/O
I/O
I/O
I/O
CPU
COM
I/O
I/O
I/O
COM
CPU
COM
COM
COM
I/O
Field Bus
CPU
COM 2
I/O
I/O
I/O
CPU
COM1
COM 2
I/O
CPU
Operator
station
large
PLCs
small PLC
PLC
PLC
COM1
COM1
Supervisor
Station
data concentrators, not programmable, but configurable
52. MAJOR COMPONENTS OF A PLC
PROCESSOR
POWER
SUPPLY
I M
N O
P D
U U
T L
E
O M
U O
T D
P U
U L
T E
PROGRAMMING DEVICE
From SENSORS
Pushbuttons,
contacts,
limit switches,
etc.
To
OUTPUT
Solenoids, contactors, alarms
etc.
53. GeneralPLC architecture
CPU
Real-TimeClock
flash
EPROM
ROM
buffers
signal conditioning
power amplifiers
relays
signalconditioning
serial port
controller
Ethernet
parallel bus
ethernet
controller
RS 232
analog-
digital
converters
digital-
analog
converters
Digital Output
Digital
Input
fieldbus
controller
external
I/Os
extension
bus
field bus
direct Inputs and Outputs
55. COMPUTERISED CONTROL SYSTEM
Reference signal
controller
Actuator
system
Output signal
COMPUTER
Measurement element
Block Diagram of Closed Loop System
56. The signal chain within a PLC
analogvariable
(e.g. 4..20mA)
filtering
&
scaling
analog- digital
converter
processing
digital- analogconverter
analogvariable
e.g. -10V..10V
time
y
time
y(i)
sampling
binaryvariable
(e.g. 0..24V)
filtering
sampling
time
y
transistororrelay
binaryvariable
amplifier
011011001111
counter
1
non-volatile
memory
0001111
time
y(i)
57.
A/D
CPU
U/I
Trip
Digital
filter
Sample and holdA/D conversion
Inputtransformer
Anti aliasing filter
Protectionalgorithm
Outputdriver
f = 1 MHz
f = 200 kHz
f = 100 kHz
f = 300 -1200 Hz
reaction < 10 ms
58. I/O Module
DC INPUT MODULE
OPTO-
ISOLATOR
IS NEEDED TO:
Prevent voltage transients from damaging the processor.
Helps reduce the effects of electrical noise
Current
Limiting
Resistor
FROM INPUT
DEVICE
USE TO DROP THE VOLTAGE TO LOGIC LEVEL
Buffer, Filter, hysteresis Circuits
TO
PROCESSOR
59. I/O Module
AC INPUT MODULE
OPTO-
ISOLATOR
IS NEEDED TO:
Prevent voltage transients from damaging the processor.
Helps reduce the effects of electrical noise
Rectifier,
Resistor
Network
FROM INPUT
DEVICE
CONVERTS THE ACINPUT TO DCAND DROPS THE VOLTAGE TO LOGIC LEVEL
Buffer, Filter, Hysteresis Circuits
TO
PROCESSOR
62. I/O Module
DC / AC OUTPUT MODULE
OPTO-
ISOLATOR
IS NEEDED TO:
Prevent voltage transients from damaging the processor.
Helps reduce the effects of electrical noise
FROM PROCESSOR
TTL
Circuits
Amplifier
RELAY
TRIAC
X’SISTOR
TO
OUTPUT
DEVICE
64. I/O Circuits
4. Analog I/O
Circuitsofthistypesenseordriveanalogsignals.
Analog inputs come from devices, such as thermocouples, strain gages, or pressure sensors, that provide a signal voltage or current that is derived from the process variable.
StandardAnalogInputsignals:4-20mA;0-10V
Analog outputs can be used to drive devices such as voltmeters, X-Y recorders, servomotor drives, and valves through the use of transducers.
Standard Analog Output signals: 4-20mA; 0-5V; 0-10V
66. L1
L2
P. B SWITCH
INPUT MODULE
WIRING DIAGRAM
LADDER PROGRAM
I:2
0
I= Input
Module
slot # in rack
Module
Terminal #
Allen-Bradley 1746-1A16
Address I:2.0/0
67. N.O
C
L2
L1
L1
L2
OUTPUT MODULE
WIRING
MOTOR
CONTACTOR
O:4
0
CONTACTOR
LADDER PROGRAM
L1
L2
FIELD WIRING
•SOLENOID
•VALVES
•LAMP
•BUZZER
68. Discrete Input
A discrete input also referred as digital input is an input that is either ON or OFF are connected to the PLC digital input. In the ON condition it is referred to as logic 1 or a logic high and in the OFF condition maybe referred to as logic o or logic low.
Normally Open Pushbutton
Normally Closed Pushbutton
Normally Open switch
Normally Closed switch
Normally Open contact
Normally closed contact
69. IN
PLC
Analog
Input
Module
Tank
Level Transmitter
An analog input is an input signal that has a continuous
signal. Typical inputs may vary from 0 to 20mA, 4 to 20mA
or 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.
Analog Input
70. Memory Map Organization
SYSTEM
•System memory includes an area called the EXECUTIVE, composed of permanently-stored programs that direct all system activities, such as execution of the users control program, communication with peripheral devices, and other system activities.
•The system memory also contains the routines that implement the PLC’s instruction set, which is composed of specific control functions such as logic, sequencing, timing, counting, and arithmetic.
•System memory is generally built from read-only memory devices.
APPLICATION
•The application memory is divided into the data table area and user program area.
•The data table stores any data associated with the user’s control program, such as system input and output status data, and any stored constants, variables, or preset values. The data table is where data is monitored, manipulated, and changed for control purposes.
•The user program area is where the programmed instructions entered by the user are stored as an application control program.
•Data Table
•User Program
71. Memory Designs
VOLATILE.
A volatile memory is one that loses its stored information when power is removed.
Even momentary losses of power will erase any information stored or programmed on a volatile memory chip.
Common Type of Volatile Memory
RAM.Random Access Memory(Read/Write)
Read/write indicates that the information stored in the memory can be retrieved or read, while write indicates that the user can program or write information into the memory.
72. Memory Designs
The words random accessrefer to the ability of any location (address) in the memory to be accessed or used. Ram memory is used for both the user memory (ladder diagrams) and storage memory in many PLC’s.
RAMmemory must have battery backupto retain or protect the stored program.
73. Memory Designs
Several Types of RAM Memory:
1.MOS
2.HMOS
3.CMOS
The CMOS-RAM (Complimentary Metal Oxide Semiconductor) is probably one of the most popular. CMOS- RAM is popular because it has a very low current drain when not being accessed (15microamps.), and the information stored in memory can be retained by as little as 2Vdc.
74. Memory Designs
NON-VOLATILE
Has the ability to retain stored information when power is removed, accidentally or intentionally. These memories do not require battery back-up.
Common Type of Non-Volatile Memory
ROM, Read Only Memory
Read only indicates that the information stored in memory can be read only and cannot be changed. Information in ROM is placed there by the manufacturer for the internal use and operation of the PLC.
75. Memory Designs
Other Types of Non-Volatile Memory
PROM,Programmable Read Only Memory
Allows initial and/or additional information to be written into the chip.
PROM may be written into only once after being received from the PLC manufacturer; programming is accomplish by pulses of current.
The current melts the fusible links in the device, preventing it from being reprogrammed. This type of memory is used to prevent unauthorized program changes.
76. Memory Designs
EPROM,Erasable Programmable Read Only Memory
Ideally suited when program storage is to be semi- permanent or additional security is needed to prevent unauthorized program changes.
The EPROM chip has a quartz window over a silicon material that contains the electronic integrated circuits. This window normally is covered by an opaque material, but when the opaque material is removed and the circuitry exposed to ultra violet light, the memory content can be erased.
The EPROM chip is also referred to as UVPROM.
77. Memory Designs
EEPROM, Electrically Erasable Programmable Read Only Memory
Also referred to as E2PROM, is a chip that can be programmed using a standard programming device and can be erased by the proper signal being applied to the erase pin.
EEPROM is used primarily as a non-volatilebackup for the normal RAM memory. If the program in RAM is lost or erased, a copy of the program stored on an EEPROM chip can be down loaded into the RAM.
78. Specifications
MEMORY CAPACITY
The amount of memory required for a particular application is related to the length of the program and the complexity of the control system. Simple applications having just a few relays do not require significant amount of memory. Program length tend to expand after the system have been used for a while It is advantageous to a acquire a controller that has more memory than is presently needed.
79. While the PLC is running, the scanning process includes the following four phases, which are repeated continuously as individual cycles of operation:
PHASE 2
Program
Execution
PHASE 3
Diagnostics/
Comm
PHASE 4
Output
Scan
PHASE 1
Read Inputs
Scan
80. PHASE 1 –Input Status scan
A PLC scan cycle begins with the CPU reading the status of its inputs.
PHASE 2–Logic Solve/Program Execution
The application program is executed using the status of the inputs
PHASE 3–Logic Solve/Program Execution
Once the program is executed, the CPU performs diagnostics and communication tasks
PHASE 4 -Output Status Scan
•An output status scan is then performed, whereby the stored output values are sent to actuators and other field output devices. The cycle ends by updating the outputs.
81. CHECK INPUT STATUS
First the PLC takes a look at each I/O to determine if it is on or off.
EXECUTE PROGRAM
Next the PLC executes the program
one instruction at a time.
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.
PLCOPERATION
84. PLC Programming Standards
The open, manufacturer-independent programming standard for automation is IEC 61131-3. You can thus choose what configuration interface you wish to use when writing your application :
Ladder Diagram
Instruction List
Function Block Diagram
Sequential Function Chart
Structured Text
85. 85
Ladder Diagram
•Ladder diagrams are specialized schematics commonly used to document industrial control logic systems.
•It is a language or a method to create a program. The first PLCs were programmed with a technique that was based on relay logic wiring schematics.
•Basic concept of this diagram is similar to the electrical wiring. However in ladder logic, the symbol has changed and been standardized.
86. Ladder Diagram cont..
•Type of graphic language automatic control systems.
•A drawing program of a switching circuit.
•Called "ladder"diagrams because they resemble a ladder, with two vertical linesrepresenting the power trails(supply power) and circuits are connected in horizontal linescalled rungs.Connection between the element in the rungcalled link.
87. Ladder logic is a programming language used to develop software for PLC used in industrial control applications.
RUNGES
RAIL
RAIL
PLCPROGRAMMING
88. Ladder Diagram Operational Principle
•Referring to figure below, between these two rails, a horizontal straight line was drawn with two symbols. These two symbols refer to the input and output devices, which are used in the actual process/system.
•On the left, we put all kinds of input. While on the right, we place all types of the outputs.
•Once we complete one line of the program it seems like a ladder. This horizontal line which places the input and output make one rung.
Input
Interface
Output
+24V
-0V
89. 90
PROGRAMMING
Normally Open
(NO)
Normally Closed
(NC)
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.
90. 91
Coils
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.
91. Ladder Diagram Symbols
•Ladder diagram uses standard symbols to represent the circuit components and functions found in a control system.
92. DEK 3113 94
Normally Open Schematics (NO)-Input Schematics
93. DEK 3113 95
Normally Closed Schematics (NC)-Input Schematics
107. Control Circuit
Start stop circuit
-PB is pressed, output IR is activated
-IR contact will closed
-When PB is depressed, the output IR is still
activated since current can go through contact IR unless is disturbed by stop button.
108.
109. Overload protection device
There are several overload protection device:
1) TOR: Thermal Overload Relay
-excess heat
2) CB: Circuit Breaker
-excess current
3) Fuse
-excess current
110. DEK 3113 112
Control circuit has Overload Protection Device
111. Control circuit in ladder diagram.
-When PB is pushed(forward/reverse),motor will move according to the command.
-But, when there is an overcurrent,CBwill stop the current flow by blow the fuse.
-Means, NC of CB will open and stop the current flow to the circuit.
-The circuit can be recovered by change the fuse.
-If there is thermal overload, TOR will cut the current flow.
-Lamp,L3 will turn on and TOR need to be reset.
112. 114
Two wire control
-only has one contact for switching device either ON or OFF state.
-When ON state, M will energize and activate three phase motor.
-Heater will heat if there is over current and open the circuit.
113. DEK 3113 115
Two-Wire Control Circuit
•Used in application of automatic system.
•Two wire used to provide voltage to load.
•Applications: pump, heater or compressor.
•Typically closed a disconnect switch or circuit breaker to energize the circuit.
•An overload coils is located to protect the circuit against over current.
114. Three wire control
-the connection almost the same as two wire circuit except has an extra set of contact connected in parallel as the pilot switch.
-this extra contact provide extra third wire.
-this auxiliary contact keep coil M energize even after start push button release.