p l c general
TRANSCRIPT
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PROGRAMMABLE LOGIC
CONTROLLER
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Control Systems Control Systems TypesTypes
Programmable Logic ControllersDistributed Control SystemPC- Based Controls
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PLCPLC
The PLC is an assembly of solid state digital logic elements design to make logical decisions and provide outputs.
PLC is programmed interface between input sensor &output device.
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Programmable Logic Programmable Logic ControllersControllers
Sequential logic solverPID Calculations.Advanced SubroutinesBIT Operations.Data Transfer.Text Handling.
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Applications : Machine controls, Packaging, Material handling, similar
Sequential task as well as Process control
Advantages of PLC : They are fast and designed for the rugged industrial
environment. They are attractive on Cost-Per-Point Basis. These Devices are less Proprietary ( E.g.. Using Open Bus
Interface.) These Systems are upgraded more Capabilities with dedicated
PID and Ethernet Modules.
Disadvantages of PLC : PLC one time cost is high To maximize PLC performance a number of IO Modules to be
added. PLC hold only one copy of program.
Programmable Logic Programmable Logic Controllers Controllers
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Central Processing Unit (CPU) Input Modules Output Modules Power Supply Bus system Rack(Rail)
P L C P L C Components(Hardware)Components(Hardware)
CPU
POWER SUPPLY
I/Pmod
O/Pmod m
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It is a micro-controller based circuitry. The CPU consists of following blocks :
Arithmetic Logic Unit (ALU), Program memory Process image memory (Internal memory of CPU) Internal timers ,counters and Flags . CPU performs the task necessary to fulfill the PLC
functions. i.e. Scanning I/O bus traffic control, Program execution, Peripheral and External device communication, data handling and self diagnostics.
Central Processing UnitCentral Processing Unit
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These modules act as interface between real-time status of process variable and the CPU.
Analog input module : Typical input to these modules is 4-20 mA, 0-10 V Ex : Pressure, Flow, Level Tx, RTD (Ohm), Thermocouple
(mV) Digital input module : Typical input to these modules is 24 V DC,
115 V AC, 230 V AC Ex. : Switches, Pushbuttons, Relays, pump valve on off status
Input moduleInput module
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These modules act as link between the CPU and the output devices in the field.
Analog output module : Typical output from these modules is 4-20 mA, 0-10 V
Ex : Control Valve Digital output module : Typical output from these
modules is 24 V DC, 115 V AC, 230 V AC Ex. : Solenoid Valves, lamps, Actuators, Pump valve on
off control
Output module Output module
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I/O MODULE SPECIFICATIONI/O MODULE SPECIFICATION
COST INPUT VOLTAGE ON-STATE INPUT VOLTAGE RANGE AMBIENT TEMP RATING INPUT DELAY – NOMINAL OUTPUT VOLTAGE MAX O/P CURRENT ELECTRICAL ISOLATION –
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The power supply gives the voltage required for electronics module (I/O, CPU, memory unit) 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.
Power SupplyPower Supply
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It is path for the transmission of the signal between power supply module,processor and I/O modules.
The bus comprise of several single line i.e. wires /tracks
Bus SystemBus System
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Advantage of PLC Over Advantage of PLC Over RelayRelay
RELAY PLC 1-More wiring 1-Less wiring
2-Changes difficult 2-Changes easy
3-More power 3-Low power
4-More maintenance 4-Solid state reliability
5-Difficult to expand 5 -Easy to expand
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PLC CyclePLC Cycle
OutputsCPUInputs
Sense the Input Process the Logic Give Output
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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 I/pImage Table
OutputImage Table
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PLC Architecture EvolutionPLC Architecture Evolution
1970s : Discrete Machine Control
ProgrammingTerminal
PLC
I/O
Connection is Point to Point
Programming Language :
- Relay ladder logic - Flexibility in altering Control system operation
Connection is Point to Point
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1985 : Discrete and Process Control
PLC Architecture EvolutionPLC Architecture Evolution
Reasonable ComputerRunning PLC
Programming Software
PLC
I/O
Programming Language :
- Ladder Program - PID - Data Storage
MS - DOS
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PLC Architecture EvolutionPLC Architecture Evolution
1990’s : 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
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TodayToday : : Distributed I/O ModulesDistributed I/O Modules
Distributed I/O modules
PLC
Distributed I/O scanner
Data Communication Bus
PLC Architecture PLC Architecture EvolutionEvolution
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Remote I/O Network
SPLITTERS
FIBER OPTIC LINK
Remote I/O
Today : Today : Hot Redundant SystemHot Redundant System
PLC Architecture PLC Architecture EvolutionEvolution
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Controller ControllerController
Controller
Workstation Workstation Workstation Workstation
Switched Hub
PLC Architecture PLC Architecture EvolutionEvolutionToday : Today : Ethernet Technology in PLCsEthernet Technology in PLCs
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RemotePlatform
Wireless Modem
Wireless Modem
PLC
H M I Display
PC
PLC Architecture PLC Architecture EvolutionEvolution
Today : Today : Wireless communicationWireless communication
PLC
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PLC Systems of various vendors PLC Systems of various vendors
Siemens S5 -110U, 115U, 135U S7 - 200, 300, 400
Allen Bradley Micrologix 1000, 1200,
1500 SLC 5/01, 5/02, 5/03 LOGIX PLATFORM
Modicon Nano Micro Premium Quantum
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8 Analog Inputs 1 Analog Output
Up/Down Fast Counter
Up Counter
Programming Terminal PC Connection
Unitelway Port for connection of up to 5 Slaves
PCMCIA memory expansion port
PCMCIA communications port
TSX37-22
Built in display for I/O (in-rack, AS-i) and Diag
I/O Modules
Configuration of PLC : Configuration of PLC : ModiconModicon
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Configuration of PLC : Configuration of PLC : SiemensSiemens
CPU
External Power
Supply
I/O Modules
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Configuration of PLC : Allen Configuration of PLC : Allen BradleyBradley
CPU
Power Supply I/O Modules
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Configuration of PLC : GE FANUCConfiguration of PLC : GE FANUC
CPU
I/O Modules Back plane
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PLC Programming StandardsPLC Programming Standards
Ladder Diagram Function Block Diagram Sequential Function Chart Structured Text Language
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Scan RateScan Rate
The completion of one cycle of the sequence is called- SCAN
Time required for one cycle is called SCAN TIME
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Cost of hardware, I/O requirement CPU memory Spare parts& Maintenance, Reliability, Flexibility& Integration of High-level Application. Compatible Protocol
PLC Selection CriteriaPLC Selection Criteria
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Memory TypesMemory Types
ROM (Read Only Memory) RAM (Random Access Memory) PROM (Programmable ROM) EPROM (Erasable PROM) EAROM- Electrically alterable ROM EEPROM-Electrically erasable PROM
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Binary System Binary System
BIT – Each digit of a binary number i.e.0 or1
BYTE – Group of 8 bits WORD = Two bytes=16 bits DOUBLE WORD =Two word
=4bytes=32bits 1 0234567
8 BIT WORD
BYTE BYTE
16 BIT WORD
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PLC : Terminology PLC : Terminology
INPUT is referred by – I OUTPUT is referred by – Q or O TIMER is referred by – T FLAGS are referred by – M or B COUNTERS are referred by – C
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PLC : Protocol PLC : Protocol
It is a set of rules for data transmission when PLC is connected to network
RS-232 (Recommended standard) RS-485 MPI(Multi point Interface) Profibus DH(Data Highway) Ethernate Controlnet