PLC General
description
Transcript of PLC General
Sensors Placed in the field
Automation : Typical installation . . .Automation : Typical installation . . . .Automation : Typical installation . . .Automation : Typical installation . . . .
Junction Box
Field Cabling
Control Panel
Control Hardware
SCADA Software
Communication Cable
Field Cabling
Control Systems TypesControl Systems Types
Programmable Logic Controllers Distributed Control System PC- Based Controls
IntroductionIntroduction
The PLC is microprocessor based specialized computer that carries out control functions of many types and levels of complexity. Its purpose is to monitor crucial process parameters and adjust process operations accordingly. It can be programmed, controlled and operated.
Applications :
Machine controls, Packaging, Palletizing, Material handling, similar Sequential task as well as Process control
Advantages of PLCs Flexibility, Reliability Large quantity of contacts Online/ offline modifications In-house simulation & testing of project Speed in operation Ladder or Boolean programming methods Ease of maintenance / troubleshooting Simplicity of ordering control system components Documentation, Security
Programmable Logic Controllers Programmable Logic Controllers
PLC Types
Nano (Small) Micro (Medium) Large
Basic criteria for PLC Types
Memory Capacity I/O Range Packaging and Cost per Point
Programmable Logic Controllers Programmable Logic Controllers
Various Brands of PLCsVarious Brands of PLCs
Allen Bradley USA Siemens Germany Modicon France Mitshubishi Japan GE Fanuc USA Omron Japan
Ranges in Allen BradleyRanges in Allen Bradley
Programming Software: RS Logix 500 & Programming Software: RS Logix 500 & RS Logix 5000RS Logix 5000
PICO Mirco Logix SLC PLC Compact Logix Flex Logix Control Logix
Ranges in SiemensRanges in Siemens
PLC Programming Software
S5 Dos based S7-200 Microwin S7-300 Sematic Manager S7-400 Sematic Manager
Ranges in ModiconRanges in Modicon
PLC Programming S/W
Nano PL7 Pro Micro PL7 Pro Premium PL7 Pro Quantum Concept Atrium Concept
Types of PLCsTypes of PLCs
Compact Modular Distributed
Compact PLCsCompact PLCs
Modular PLCsModular PLCs
CPU
Power Supply I/O Modules
ATS05
STZ
10
Remote I/O 1 2 3 4
Distributed PLCs with Remote I/ODistributed PLCs with Remote I/O
ATS05ATS05 ATS05
Central Processing Unit (CPU) Input Output Modules Power Supply Bus system Programming Device
P L C Components P L C Components
CPU
PROGRAMDEVICE
IN OUT m
MODULEMODULE
It is a micro-controller based circuitry. The CPU consists of following blocks :
Arithmatic Logic Unit (ALU), Program memory Process image memory (Internal memory of CPU) Internal timers and counters, Flags CPU performs the task necessary to fulfill the PLC functions.
These tasks include Scanning, I/O bus traffic control, Program execution, Peripheral and External device communication, special functions or data handling execution and self diagnostics.
P L C : Central Processing Unit P L C : Central Processing Unit
How CPU FunctionsHow CPU Functions
Read InputsRead Inputs
Comn with NetworkComn with Network
Read User ProgramRead User Program
Up KeepUp Keep
Read RegistersRead Registers
Write to OutputWrite to OutputWrite to OutputWrite to Output
Scan Cycle of CPUScan Cycle of CPUScan Cycle Depends upon No of Scan Cycle Depends upon No of I/OsI/OsMore I/Os More scan timeMore I/Os More scan timeApplication Decides the Scan Application Decides the Scan time of a PLCtime of a PLCScan time in normal Scan time in normal applications is 1 ms to 2 ms & in applications is 1 ms to 2 ms & in bigger applications 100 ms to bigger applications 100 ms to 200 ms200 ms
Scan Cycle Depends upon No of Scan Cycle Depends upon No of I/OsI/OsMore I/Os More scan timeMore I/Os More scan timeApplication Decides the Scan Application Decides the Scan time of a PLCtime of a PLCScan time in normal Scan time in normal applications is 1 ms to 2 ms & in applications is 1 ms to 2 ms & in bigger applications 100 ms to bigger applications 100 ms to 200 ms200 ms
Features of CPUsFeatures of CPUs
Execution Speed .1 ms/1ms/10ms I/O Handling capacity Memory capacity Instruction sets (Normal, advance) Language support (FB, LD) Support for application specific module Integrated functionality
PLC Input ModulesPLC Input Modules These modules act as interface between real-
time status of process variable and the CPU Digital (Contacts, Switches, Limit switch,Push
buttons, Pressure switch, pump / valve on-off status)
Typical modules is 24 V DC, 115 V AC, 230 V AC (0 or 1, Closed or open, True or false)
Analog (Pressure, Flow, Level, Tx, RTD Thermocouple)
4-20ma, 0-10v, -10-+10v, 0-5v, 0-20ma, -20-+20ma.
Note: There are modules which can handle all are called universal modules
Digital Input ModuleDigital Input Module
No of channels: 4,8,16,32, 64 24vdc, 230v ac, 110dc Source, sink or both Isolated or un-isolated common
Digital Input Module- InternalDigital Input Module- Internal
StartStart
StopStop
S/WS/W
Current limiting resister
Current limiting resister
5v dc
5v dc
InverterInverter
O/P highO/P high
ComCom
Opto couplerOpto coupler
In case one diode is parallel to another diode in opposite polarity. It can act as source or sink both
In case one diode is parallel to another diode in opposite polarity. It can act as source or sink both
When diode conducts, infra red light falls on the base of the transistor, which conducts and inverter makes O/P high
Diode transistor pair is called optical isolation (produces 1.5kv isolation)
In case of higher voltages only card is damaged, functioning of the entire plant is saved.
NoteNoteNoteNote
120 V acL1 L2
L2
L1
1
2
3
4
PB
inputfield
device
Input moduleterminal board
Input statusindicator
Digital Input Module-External Digital Input Module-External
Digital Output ModuleDigital Output Module These modules act as link between the CPU and the
output devices in the field No of channels: 4,8,16,32, 64 24vdc, 230v ac, 110dc Solenoid Valves, lamps, Actuators, dampers, Pump/valve on
off control Isolated or un-isolated common Relay type (both ac & dc), TTL Type (only dc), Triac
type (only ac)
Note: contact life of a relay is generally 1 million operations, use of semiconductor switching in triac & TTL increases life and switching response is faster.
Note: contact life of a relay is generally 1 million operations, use of semiconductor switching in triac & TTL increases life and switching response is faster.
In Triac changing over is done at zero In Triac changing over is done at zero crossing. Advantage: Negative spikes crossing. Advantage: Negative spikes produced by inductive loads, which are produced by inductive loads, which are harmful for electronic ckts are reduced. harmful for electronic ckts are reduced. Amount of back emf is drastically Amount of back emf is drastically reducedreduced
In Triac changing over is done at zero In Triac changing over is done at zero crossing. Advantage: Negative spikes crossing. Advantage: Negative spikes produced by inductive loads, which are produced by inductive loads, which are harmful for electronic ckts are reduced. harmful for electronic ckts are reduced. Amount of back emf is drastically Amount of back emf is drastically reducedreduced
Transistor- Transistor Logic Transistor- Transistor Logic (TTL)(TTL)
Triac outputsTriac outputs
0 V0 V0 V0 V
24 V24 V24 V24 V
In dc modules a parallel In dc modules a parallel diode is placed to reduce diode is placed to reduce noise /back emfnoise /back emf
In dc modules a parallel In dc modules a parallel diode is placed to reduce diode is placed to reduce noise /back emfnoise /back emf
LoadLoad
ComCom
diodediode
ComCom
Isolated Com
Isolated Com LoadLoad
In isolated type modules In isolated type modules common is different for all common is different for all loadsloads
In isolated type modules In isolated type modules common is different for all common is different for all loadsloads
Digital Output ModuleDigital Output ModuleDigital Output ModuleDigital Output Module
Analog Input ModuleAnalog Input Module
No of channels: 2, 4,8,16 (rarely 16 channels)
Isolated or un-isolated common Type of input: Thermocouple, RTD, Voltage 2 wire, 4 wire Resolution
Analog Input ModuleAnalog Input Module
Ohm
TX
Ohm
TX
PT-100PT-100
TXTX
24V dc
24V dc
++
++
__
__
4-20 mA4-20 mA
4-20 mA4-20 mA
++
4 Wire TX
4 Wire TX
2 Wire TX
2 Wire TX
24v dc24v dc
A/D converte
r
A/D converte
r
Low pulse filter ckt
Low pulse filter ckt Scalin
g
Scaling
Note: A/D converter comes with 16, 14, 12, 18 bit resolution
Note: A/D converter comes with 16, 14, 12, 18 bit resolution
Example: Microscope’s resolution is good if we can see each part of an organism
Example: Microscope’s resolution is good if we can see each part of an organism
Analog Input ModuleAnalog Input Module
Resolution: Allen Bradley uses natural binary conversion.
Higher the resolution higher the cost & depends upon how minute data can be monitored
12 bit resolution = 4096 bits. Data to be measured will be divided into 4096 parts.
Most of Analog Input modules use 16 bit. Digital information is at bit level Analog information is at word level
Analog Output ModuleAnalog Output Module No of channels: 2, 4,8,16 (rarely 16 channels) Isolated or un-isolated common Current, Voltage Resolution 12 bit, 14 bit, 15 bit, 16 bit output is 4-20 mA, 0-10 V Ex : Control Valve, Speed, Vibration
Note: For Robotic operation you need finer control, hence needed high resolution. For Normal Control valve operation less resolution may be used
Note: For Robotic operation you need finer control, hence needed high resolution. For Normal Control valve operation less resolution may be used
Analog Output ModuleAnalog Output Module
I/P Converter
I/P Converter
++
__
D/A Converter
D/A Converter
Digital Form
Digital Form
PID Alogrithm
PID Alogrithm
Constant Current Source
Constant Current Source
50% Opening50% Opening
50% Opening50% Opening
0-327670-32767Constant current Constant current
source will give 12 source will give 12 mA for opening mA for opening
50%50%
Constant current Constant current source will give 12 source will give 12
mA for opening mA for opening 50%50%
120 V acL1 L2
L2
L1
1
2
3
4
Output statusindicator
Output field device
Module blown Fuse indicator
Output module Terminal board
Output module- Output module- connectionsconnections
Application Specific ModulesApplication Specific Modules
Stepper Control modules Servo Control modules Common modules
Modbus profibus Device Net ASi Bus (2 wire,Very high speed comn
carries power & signal both) DG Synchronization modules etc.
Sinking/SourcingSinking/Sourcing
The power supply gives the voltage required for electronics module (I/O Logic signals, CPU, memory unit and peripheral devices) of the PLC from the line supply.
The power supply provides isolation necessary to protect the solid state devices from most high voltage line spikes.
As I/O is expanded, some PLC may require additional power supplies in order to maintain proper power levels.
P L C : Power Supply P L C : Power Supply
It is path for the transmission of the signal . Bus system is responsible for the signal exchange between processor and I/O modules
The bus system comprise of several single line ie wires / tracks
P L C : Bus System P L C : Bus System
PLC CyclePLC Cycle
Outputs
Machineor
Process
Programmablecontroller
Inputs
Sense the Input Process the Logic Give Output
PLC Signal FlowPLC Signal Flow
Programming Terminal
O:0/7
O:0/7
O:1/5
Output Devices
Output ModulesProcessor MemoryInput Module
Input DevicesLadder Program
O:0/7
O:1/5
I:0/6
I:1/4
O:1/5
I:0/6
I:1/4
I:0/6
I:1/4
Data InputImage Table
OutputImage Table
PLC Architecture in 1970sPLC Architecture in 1970s
Discrete Machine Control
ProgrammingTerminal
PLC
I/O
Connection Point to Point
Programming Language :
- Relay ladder logic - Flexibility in altering - Control system operation
Connection Point to Point
Discrete and Process Control
PLC Architecture in 1980s
Reasonable ComputerRunning PLC
Programming Software
PLC
I/O
Programming Language :
- Ladder Program - PID - Data Storage
MS - DOS
PLC Architecture in 1990sPLC Architecture in 1990s
Discrete and Process Control
PC running PLC Programming Software
PLC
I/O
Connection in networked allowing Multiple PLC
PLC became a part of the developing enterprise resource system
Windows
PLC
Distributed I/O Modules
Distributed I/O modules
PLC
Distributed I/O scanner
Data Communication Bus
PLC Architecture TodayPLC Architecture Today
Remote I/O Network
SPLITTERS
FIBER OPTIC LINK
TAPS
Remote I/O
Hot Redundant System
PLC Architecture TodayPLC Architecture Today
Controller ControllerController
Controller
Workstation Workstation Workstation Workstation
Switched Hub
PLC Architecture todayPLC Architecture today
Ethernet Technology in PLCs
RemotePlatform
Wireless Modem
Wireless Modem
PLC
H M I Display
PC
PLC Architecture todayPLC Architecture today
Wireless communication
PLC
PLC Programming StandardsPLC 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 Statement List Instruction List Function Block Diagram Sequential Function Chart Structured Text
Ladder BasicsLadder Basics Ladder is widely used language & is
close to Electrical basics. In 50-60% places in a ladder: NO, NC
or (XIC, XIO in case of Allen Bradley) are used.
If s/w If s/w closedclosed at this add at this add CPU interprets it as CPU interprets it as TrueTrue
conditionconditionIf s/w If s/w OpenOpen at this add at this add CPU interprets it as CPU interprets it as FalseFalse conditioncondition
If s/w If s/w closedclosed at this add at this add CPU interprets it as CPU interprets it as TrueTrue
conditionconditionIf s/w If s/w OpenOpen at this add at this add CPU interprets it as CPU interprets it as FalseFalse conditioncondition
If s/w If s/w OpenOpen at this add at this add CPU interprets it as CPU interprets it as TrueTrue
conditionconditionIf s/w If s/w ClosedClosed at this add at this add CPU interprets it as CPU interprets it as FalseFalse conditioncondition
If s/w If s/w OpenOpen at this add at this add CPU interprets it as CPU interprets it as TrueTrue
conditionconditionIf s/w If s/w ClosedClosed at this add at this add CPU interprets it as CPU interprets it as FalseFalse conditioncondition
Comparison & use of XIO, Comparison & use of XIO, XICXIC
RelayRelayRelayRelay
StopStopStopStop
StartStartStartStart
MotorMotorMotorMotor
AuxiliarAuxiliaryy
AuxiliarAuxiliaryy
PPPP
NNNN
StartStartStartStart StopStopStopStop RelayRelayRelayRelay
AuxiliarAuxiliaryy
AuxiliarAuxiliaryy
StartStartStartStart StopStopStopStop RelayRelayRelayRelay
AuxiliarAuxiliaryy
AuxiliarAuxiliaryy
Basic Relay LogicBasic Relay Logic
Basic Start/ Stop circuit with Basic Start/ Stop circuit with latchlatch
AND Gate, Relay and PLC EquivalentAND Gate, Relay and PLC Equivalent
OR Gate, Relay and PLC OR Gate, Relay and PLC
EquivalentEquivalent
NOT Gate, Relay and PLC EquivalentNOT Gate, Relay and PLC Equivalent
PSUPSUPSUPSU
CPUCPUCPUCPU
DI 16
CH
DI 16
CH
DI 16
CH
DI 16
CH
DI 8 C
H
DI 8 C
H
DI 8 C
H
DI 8 C
H
DO 16
CH
DO 16
CH
DO 16
CH
DO 16
CHPSUPSUPSUPSU
DI 32
CH
DI 32
CH
DI 32
CH
DI 32
CH
AI 4 C
H
AI 4 C
H
AI 4 C
H
AI 4 C
H
AO 4 C
H
AO 4 C
H
AO 4 C
H
AO 4 C
H
AI/AO 4
CH
AI/AO 4
CH
AI/AO 4
CH
AI/AO 4
CH
Slot 0Slot 0Slot 0Slot 0 Slot 1Slot 1Slot 1Slot 1 Slot 2Slot 2Slot 2Slot 2 Slot 3Slot 3Slot 3Slot 3 Slot 4Slot 4Slot 4Slot 4 Slot 5Slot 5Slot 5Slot 5 Slot 6Slot 6Slot 6Slot 6 Slot 7Slot 7Slot 7Slot 7
Addressing Scheme in AB PLCAddressing Scheme in AB PLC
File type: slot add .word add /bit addCPU generally is in Slot 0Slot 1 - I :1.0/0 to I:1.0/15Slot 2 - I:2.0/0 to I:2.0/7Slot 3 - O:3.0/0 to O:3.0/15Slot 4 - I:4.0/0 to I:4.0/31Slot 5 - I:5.0 to I:5.3Slot 6 - O:6.0 to O:6.3Slot 7 - I:7.0 to I:7.1
O:7.0 to O:7.1