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SUBMITTED BYMOHIT GUPTABTECH 4th YEAR ECE.

PLC(Programmable Logic Controller)Industrial Automationcomputers are used in factories...Robotic arm, CNC, injection molding

Industrial AutomationIce cream sandwich machines

Industrial AutomationToday this is usually accomplished with Programmable Logic Controllers (PLCs)

PLCs are the answer to a variety of needs: durability, reliability, flexibility, scalability, reprogrammability, etc...5Programmable 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.

HistoryMachines become autonomous.

Common method: relay logic

Relay LogicConditional logic can be represented in terms of contacts and coils.

Contact: A simple input switch. Coil: An output load, e.g., a relay or motor.Symbolic representation called ladder logic.currentRelay LogicTo clarify: Ladder Logic is a notation originally used to describe & document relay logic configurations.Later became the basis for PLC programming languagesLadder LogicPower supply rails drawn as parallel vertical lines on left and rightConnection of rails implies current will flowAn output is on when a connection is completed and current flows through the loads coilLadder LogicSimple always on load:

[Always_On = 1] note: sometimes illegal

Boring... Load controlled by a single contact:

[Switch_Con = Switch]

11Programmable Controller Development1968 Programmable concept developed1969 Hardware CPU controller, with logic instructions, 1 K of memory and 128 I/O points 1974 Use of several (multi) processors within a PLC - timers and counters; arithmetic operations; 12 K of memory and 1024 I/O points1976 Remote input/output systems introduced1977 Microprocessors - based PLC introduced12Programmable Controller Development1980 Intelligent I/O modules developedEnhanced communications facilitiesEnhanced software features (e.g. documentation)Use of personal microcomputers asprogramming aids1983 Low - cost small PLCs introduced1985 on Networking of all levels of PLC, computer and machine using SCADA software.

PLCThe first PLC was invented by Dick Morely in 1978.Morely designed a computer with three components: a processor, memory, and a logic solver.[The logic solver] allowed us to get the speed we needed in this application-specific computer to solve the perceptually simple problem of several cabinets full of relay wiring. -MorelyThe first commercial successful PLC, the 184, was introduced in 1973 which was designed by Michael Greenberg.

14Step7-1200

1.Power connector

2.Memory card slot under the top door

3.Removable user wiring connectors

4. Status LEDs for on board I/O

5.Profinet connectorS7-1200 PLC17Major Components of a Common PLCPROCESSOR POWERSUPPLYI MN O P D U UT L E

O M U OT DP UU LT E

PROGRAMMING DEVICEFrom SENSORS

Pushbuttons,contacts,limit switches,etc.ToOUTPUT

contactors, alarmsetc.18Major Components of a Common PLCPOWER SUPPLY

Provides the voltage needed to run the primary PLC components

I/O MODULES

Provides signal conversion and isolation between the internal logic- level signals inside the PLC and the fields high level signal.

19Major Components of a Common PLCPROCESSOR

Provides intelligence to command and govern the activities of the entire PLC systems.

PROGRAMMING DEVICE

used to enter the desired program that will determine the sequence of operation and control of process equipment or driven machine.

20While the PLC is running, the scanning process includes the following four phases, which are repeated continuously as individual cycles of operation:PHASE 2ProgramExecutionPHASE 3Diagnostics/ CommPHASE 4Output ScanPHASE 1Read InputsScan21PHASE 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 inputsPHASE 3 Logic Solve/Program Execution Once the program is executed, the CPU performs diagnostics and communication tasks22PHASE 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.

23PROGRAMMINGNormally 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.

24CoilsCoils represent relays that are energized when power flows tothem. When a coil is energized it causes a correspondingoutput to turn on by changing the state of the status bit controlling the output to 1. That same output status bit maybe used to controlnormally open or normally closed contact anywhere in the program.25BoxesBoxes represent various instructions or functions that areExecuted when power flows to the box. Some of these Functions are timers, counters and math operations.26AND OPERATIONEach rung or network on a ladder program representsa logic operation. In the rung above, both inputs A and Bmust be true (1) in order for the output C to be true (1).A BC27OR OPERATIONIn the rung above, it can be seen that either input A or Bis be true (1), or both are true, then the output C is true (1).inputA BC28NOT OPERATIONIn the rung above, it can be seen that if input A is be true (1),then the output C is true (0) or when A is (0), output C is 1.inputA CCRIsolationBarrierIsolationBarrierCentralProcessorUnit(CPU)MEMORYprogramdataHighVoltageHighVoltageLow VoltageAC Power SupplyOutputCircuitsDC Power Supply

orCommunicationsPortInputCircuitsInside a PLCPrimary components of virtually all PLCs, no matter what size are:Input CircuitryOutput CircuitryCentral ProcessorMemoryCommunications Port(s)Power SupplyPLCs are industrially hardened devices capable of operating in extreme environmentsWide Temp extremes 0-60 CHigh humidityHigh VibrationDirty Electrical PowerHigh Noise (electrical) environmentsPLCsWidely Applied in Every IndustryWere Developed to Simplify the Implementation of Control Automation Systems in Plants and Assembly LinesDesigned to Minimize the Number of Control Relays in a Process and Maximize the Ways Relays can be UsedFirst Applied to Automobile Industry in the Late 1960sFlexible, Reliable and Low CostPLC Components

I/O ModulesInput Modules: Input Signals can be AC or DC, Analog or Digital Output Modules: Outputs are either AC or DC Analog Signals (Although it is possible to Construct Digital Outputs)Modern PLCs have Expansion Ports to Increase the Number of Available Inputs and OutputsExamples of I/O SignalsInputs:Pushbutton (Energizing or Grounding an Input)Relay Contact OutputDC Voltage LevelDigital Logic Signal (+5V or 0 V, etc)Outputs:24 V ac120 V ac120 Vdcetcetera

RelaysIn General, Relays Transform a Control Signal into a Control ActionRelays Provide:Isolation Between Input and OutputLeverage (Small Signal Can Control Large Action)Automation (Minimize Human Interaction with a Control Process) Relay Components

Basic Relay Symbols

Relay ApplicationsRelays can be Designed to Perform Many FunctionsDetect Out of Limit Conditions on Voltages and CurrentsStart MotorsPrevent Motors from Over HeatingControl Assembly LinesAdjust Lighting

Advantages of PLCs Less wiring. Wiring between devices and relay contacts are done in the PLC program. Easier and faster to make changes. Trouble shooting aids make programming easier and reduce downtime. Reliable components make these likely to operate for years before failure.

INTRODUCTION TO PLCS3839Areas of Application Manufacturing / Machining

Food / Beverage

Metals

Power

Mining

Petrochemical / Chemical PLC Operating Cycle Four Steps in the PLC Operations Input Scan Scan the state of the Inputs Program Scan Processes the program logic Output Scan Energize/de-energize the outputs Housekeeping This step includes communications, Internal Diagnostics, etc. The steps are continually repeated - processed in a loopSTARTInput ScanProgramScanHousekeepingOutputScan