P L C General
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Transcript of P L C General
PROGRAMMABLE LOGIC
CONTROLLER
Control Systems Control Systems TypesTypes
Programmable Logic ControllersDistributed Control SystemPC- Based Controls
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.
Programmable Logic Programmable Logic ControllersControllers
Sequential logic solverPID Calculations.Advanced SubroutinesBIT Operations.Data Transfer.Text Handling.
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
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
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
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
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
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 –
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
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
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
PLC CyclePLC Cycle
OutputsCPUInputs
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 I/pImage Table
OutputImage Table
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
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
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
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
Remote I/O Network
SPLITTERS
FIBER OPTIC LINK
Remote I/O
Today : Today : Hot Redundant SystemHot Redundant System
PLC Architecture PLC Architecture EvolutionEvolution
Controller ControllerController
Controller
Workstation Workstation Workstation Workstation
Switched Hub
PLC Architecture PLC Architecture EvolutionEvolutionToday : Today : Ethernet Technology in PLCsEthernet Technology in PLCs
RemotePlatform
Wireless Modem
Wireless Modem
PLC
H M I Display
PC
PLC Architecture PLC Architecture EvolutionEvolution
Today : Today : Wireless communicationWireless communication
PLC
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
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
Configuration of PLC : Configuration of PLC : SiemensSiemens
CPU
External Power
Supply
I/O Modules
Configuration of PLC : Allen Configuration of PLC : Allen BradleyBradley
CPU
Power Supply I/O Modules
Configuration of PLC : GE FANUCConfiguration of PLC : GE FANUC
CPU
I/O Modules Back plane
PLC Programming StandardsPLC Programming Standards
Ladder Diagram Function Block Diagram Sequential Function Chart Structured Text Language
Scan RateScan Rate
The completion of one cycle of the sequence is called- SCAN
Time required for one cycle is called SCAN TIME
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
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
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
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
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