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Brands of PLC’c

A llen BradleyS iemens

M itsubishiT ata H oneywell

A BBA LS T O MFES T O

Fuj i E lectr ic

RelianceB & R

T oshibaCut ler H ammer

A nshumanS chneider

KoyoS igmatek

M essungO mronFanuc

M odicon

PLC - Definition-• Formal definition of a PLC by

NEMA – National Electrical Manufacturers Association -

A Programmable Controller is a digitally operated electronic system, designed for use in an Industrial Environment, which uses a Programmable Memory for the internal storage of user-oriented instructions for implementing specific functions such as Logic, Sequencing, Timing, Counting, and Arithmetic, to control, through Digital or Analog Inputs and Outputs, various types of machines or Processes. Both the PLC and its peripherals are designed so that they can be easily integrated into an industrial control system and easily used in all their intended functions.

P.L.C. Programmable Logic

Controller

• CPU - Decision Making Unit

• Inputs-Digital/Analog/High Speed

• Outputs - Digital / Analog

• Power Supply - 24 V DC/AC / 48 V DC/AC, 110 V DC/AC / 220 V DC/AC / +/- 10V

• Timers / Counters / Flags / Registers / Memory

• Communication - Serial - RS232C / Equivalent / DH-485

• Programming - Through PC / Hand held Terminal / Programmer

Why to use PLC’s ?

• COST :- PLC can scan Digital & Analog Inputs through relevant sensors. It can execute the Logic w.r.t. the Scanned Inputs, take necessary decision and send it to Digital / Analog Outputs. It can also perform PID control Functions. The cost of all this is much less than a conventional DATA Logger !!

• Versatility :- The ability to combine discrete (Digital) & Analog logic is a powerful tool for the Control Engineers. Control of critical start-up parameters, such as temperature and pressure, can be precisely pre-programmed for each start-up step.


• Expandability :- As a process matures, it is inevitable that enhancements will be needed.

These usually require more outputs.

For hard-wire Relays system this

usually necessitates extensive panel changes, which generally are problematic.

A PLC easily accommodates the

additional I/O’s without requiring changes in the existing wiring.

If a PID loop is to be added, no

panel rework is necessary; only the wiring of new points and some re-programming to incorporate them is required.


• Flexibility :- As a process goes ONLINE and Refined, the Control Equipment should be easily reconfigured to accommodate such modifications.

Bottling Plant Control, Traffic

Light Control, Process Control of Temp., Pressure, Level, Flow etc., Car Parking Control etc. are all within the Capabilities of PLC’s.

• As one common device (PLC) performs multiple functions in a Plant, fewer spare parts are needed .

• The Digital nature and self-Diagnostic capabilities are strong additional justification for the PLC.

Advantages of PLC over Electro-

mechanical Relays

• Ability to interface / communicate with Computers

• Simple Programming

• Field Programming possible (HHT)

• High Reliability (Better MTBF)

• Easy Maintenance• Rugged Construction - Can

operate in Extremely harsh field conditions

• Smaller Size• Easy Expandability (Due to

Modular Design)• Economical in Long Term

Relay O/P Switching

•Advantages – [1] Contacts forgiving to a temporary overload[2] Immune to false trips from elec

noise[3] Little voltage drop across contacts[4] No restrictions when connecting in

series or parallel configurations[5] Difinite ON / OFF state, with contacts physically open.[6] No Leakage[7] Contacts generate little heat[8] Inexpensive to purchase

•Disadvantages –[1] Mechanical switching is slow[2] Mechanical life is limited by demands

of

the load and the contacts.[3] Require 50mA or more to

energize[4] Subject to contact arcing or welding

[5] Subject to contact bounce[6] Cannot be completely sealed.

Solid State O/P Switching

•Advantages – [1] Fast Switching Speeds

[2] High Reliability & almost infinite life

[3] Low Power required to energize[4] No Contact Arcing[5] Little / nil Switching noise

[6] +ve switching, no contact bounce

[7] Can be hermetically sealed – good for hostile environments.

• Disadvantages –[1] May be destroyed by overload[2] Tend to fail in ON state[3] Heat dissipation[4] Expensive to purchase[5] Possibility of false trips from

electrical noise.

Differences between -PLC & PC / Computers

•Real Time Operation - PLC’s are designed to operate in a REAL-TIME control Environment. Most PLC’s have internal clocks and built-in “Watch-Dog Timers”.

PLC’s Vs PC’s•Environmental Conditions

PLC’s are designed to operate near the equipment they are meant to control. This means that they function in hot, humid, dirty, noisy and dusty industrial environments.

PLC’s can operate in 60 Deg C as well as 0 Deg C, with tolerable relative Humidity ranging from 0% to 95% non-condensing.

PLC Vs PC•Programming Languages & Techniques -

• PLC - Ladder Diagram format is read & understood world-wide by maintenance technicians as well as by engineers.

• Unlike Computer Programming, PLC Programming does not require extensive special training.

• Programmed operation are performed by the PLC in the order they were programmed . This allows easy programming of Shift Registers

PLC Vs PC• Maintenance & Trouble-

shooting

• As PLC is a Plant Floor Controller it has to be maintained / serviced by plant electrician or the Instrument Technician.

• It would be highly impractical to require computer type maintenance service.

• Most PLC Components are modular and simple to isolate, remove-and-place (system modules) diagnostic techniques are usually implemented.

Digital I/O Devices

• Digital Input Field Devices

• Pushbuttons (For Start / Stop )• Thumbwheel Switches• Limit Switches• Selector Switches• Proximity Switch• Photoelectric Sensors

• Digital Output Field Devices

• Discrete Outputs - Relays, Solenoids, Contactors, Motors starters, Annunciate Windows, Pilot Lights etc.

• Register Outputs - Displays, Panel Meters etc.

Various Types of Transmitters

T em perature T ransm itters

Pressure T ransm itters

Flow T ransm itters

Level T ransm itters

Transmitters

Analog I/O Devices

•Analog Output Devices : –

V.F.D’s - Variable Speed Drives or Variable Freq. Drives.

Proportional Control Valves – Hydraulic / Pneumatic.

•Analog Input Devices :-

• Transducers (Temp./Pres/Level /Flow)

• Thermocouples T/C / RTD’s• Flow Transmitters• Temperature Transmitters• Level Transmitters• Pressure Transmitters• Strain Guage

Analog Signals

• Analog Control is used in applications concerned with continuous-process control such as -

Temperature, Pressure, Flow, Humidity, Analog Valves, Load Cells, Sensing Tank Levels, Motor Drives, Meters, Actuators, Resolvers, Chart Recorders and Potentiometers.

• Analog input modules are used in applications where the input signal is in a continuous and varying form as compared to discrete, strictly ON-OFF signals.

Digital / Analog I/O’s

• Digital Inputs - 1-4096 / more• (Useful for sensing of entry of CAR)

• (To Sense COIN in vending machine)

• (To sense if Door Bell is pressed)

• Digital Outputs – 1-4096 / more • (To indicate Traffic Light Signals)• (To display Alarm indication)• (To display CAR is exiting

parking)

• Analog Inputs - 1-4096 or more• (To continuously Scan the Temp.)• (To continuously Scan Level /

Flow)

• Analog Outputs - 1-4096 / more• (To control Temp. / Pressure /

Level / Flow / Humidity etc. continuously.

Digital I/O Voltages

•DC Input Modules - 24 V DC

48 V DC 10-60 V DC

120 V DC 230 V DC 5-50 V DC Sink / Source 5 V DC TTL Level 5/12 V DC TTL Level

•AC Input Modules –

24 V AC 48 V AC

120 V AC / Isolated 240 V AC / Isolated 24 V AC / DC

Analog I/O Voltages

Voltage Range Decimal Equivalent

-10 V to + 10V - 32768 to + 32767

0 to + 10V 0 to + 32767

0 to +5V 0 to + 16384

1V to + 5V 3277 to + 16384

Current Range Decimal Equivalent

-20mA to +20mA -16384 to +16384

0 to +20mA 0 to +16384

4 to +20mA 3277 to +16384

PLC Terms

• Input / Output (I/O) Modules- I/O Modules are available as

either Input Only, Output Only or a combination of Inputs & Outputs e.g.– 16I/P ; 16 O/P;

8 I/P + 8 O/P; 16I/P + 16O/P

•Threshold Detection :- Threshold detection Circuitry detects if the incoming signal has reached or exceeded a predetermined value for a predetermined Time and whether it should be classified as a valid On or OFF signal.

PLC Programming Languages

• Ladder Diagram Programming

•Function Block Diagram

• Sequential Function Chart (SFC) or Continuous Flow Chart (CFC)

• Statement / Instruction List

•Structured Text

• ‘C’


•Ladder Diagram It is similar to Relay Ladder Logic.

•Function Block Diagram

It is based on a graphical language. Process flow applications can be shown graphically as function blocks that are wired together.Function blocks are controlled by external parameters and are standard blocks that execute algorithms.


•Instruction List – It is a low-level Assembly-type Language. In this case the instructions are organised in a list-like format. It allows one operation to be performed at a time. It is usually used in smaller applications.

•Structured Text :- It is an English-like programming language that resembles BASIC programming.


•Sequential Function Chart-

It is similar to Flow Chart Programming. It consists of steps and transtions. Each step is represented by a box that contains one or more major actions. When all actions in the box are satisfied, the box is excited. A transition step has to be true before moving on to the next step. Once leaving a particular step the processor executes the next step.Previous steps are no longer executed.

PLC Programming

[1] Edit / Write a Ladder Programme

[2] Simulate Programme using Simulator

[3] Change the Programme if necessary

[4] Download the Programme PC to PLC

[5] Execute the Programme in PLC

[6] Change Inputs to see effects on Outputs

[7] Modify the Programme for different

field conditions & repeat steps 4,5,6.

PLC Applications using Static Application Panels

• CAR PARKING• TRAFFIC LIGHT CONTROL• SOFT DRINK DISPENSER• WASHING MACHINE• REACTION VESSEL• PROCESS CONTROL • TANK LEVEL CONTROL• DOOR BELL DIGITAL LOCK• MICROWAVE OVEN• BOTTLING PLANT• SEQUENTIAL CONTROL

MOTORS• SWITCHING OF LIGHTS• MIXING OF 2 CHEMICALS• STARER CONTROL• STAR-DELTA STARTER

Other Applications of PLC’s

[1] Control of SPM’s (Special

Purpose Machines - Like Drilling M/c or Grinding M/c or Lathes etc.

[2] Packing Machines Like -

Capsule Packing Machines Tablet Packing Machines; Milk Pouches Packing M/c.

[3] Injection Moulding M/c’s (Windsor Plastic Injection Moulding Machines) etc.

While Chosing PLC for an Application, following points should be taken into consideration

•Maintenance•Spare Parts•Operation•Modifications•Losses (Production,

Equipment, Personnel)• Information Technology•Space & Weight•Flexibility•Expandability•Operability•Cost of Control &

Instrumentation

Aspects of Control & Instrumentation

•Standardisation•Speed of Response•Hardware Variety•Software Portability•User Interface•Memory•Compactness•Power Requirement•System Integrity

(Reliability, Availability, Security)

•Control & Logic Algorithms

A Control Unit Should have following capabilities as

Standard • Continuous Control• Batch Control• Logic• Advanced Control• Simulation• Neural Network &

Knowledge based Systems• A PC-Oriented

Programming Language• Dual or Triple Redundancy• High Scan rates (1 to 10

mS)• High Resolution Time

Stamping (1 mS)• A Communication

Processor that can handle popular protocols

A N D

O R

N A N D

N O R

NOT

E x-O R

E x-N O R

TIM E R

C A S C A D E TIM E R

S R F L IP -F lop

C O U N TE R

Logic Funct ions

Safety Considerations

• The most important safety feature, which is often neglected is PLC system design. This feature must be included whenever a hardwired device is used in order to ensure operator protection against the unwanted application of power.

• Emergency STOP function should be completely hardwired.

Software functions should

not be relied upon to shut-off the process or the machine.

NOISE• Electro-Magnetic Interference /

NOISE / Unwanted Electrical Signals can generate problems for all solid state circuits, particularly Micro-processors.

Each PLC manufacturer suggests methods for designing a noise-immune system.

• I/O system are isolated from the field, but voltage spikes can still appear within the low-voltage environment of the PLC if Proper Grounding practices are not followed.

Often it is necessary to keep AC and DC wiring bundles apart, particularly when high-voltage AC is used at the same time that low-level analog signals are present.

Temperature

Considerations

• Installing any solid state device requires paying attention to –

• Ambient Temperature • Radiant Heat Bombardment• And the Heat generated by

the Device itself.

• PLC’s are typically designed for operation over a broad range of Temperatures, usually from 0 to 60 Deg.C

• For Cooling, blowing filtered air through the enclosure can resolve minor difficulties.

Enclosures• Enclosure of PLC protects PLC’s

from moisture, Oil, Dust Particles and unwanted tampering.

• Most Manufaturers recommend NEMA 12 Enclosure for the Standard Industrial Environment.

• PLC’s are designed to be located close to the machine or the process under control. This keeps the wiring runs short and aids in the trouble-shooting procedure.

• It is not advisable to place a PLC near a Virating Machine, Electrical NOISE Interference or Excessive Heat Environment conditions.

KEY-WORDS of PLC

•PLC - Programmable Logic Controller

•PID – Proportional + Integral +

Derivative Control Function.

•DCS – Distributed Control System

•SCADA – Supervisory Control &

Data Acquisition System

•RTOS- Real Time Operating System

KEY-WORDS of PLC• RTC - Real Time Clock

• RTU – Remote Terminal Unit

• Timers – On-Delay Off-Delay Monoshot /

Monostable Pulse Flasher Astable

Bistable

• Counters – Up / Down

Timers •On-Delay Timer – (T-ON)

Counts Time interval when conditions preceding it in the rung are true. Produces an output when accumulated value (Count) reaches preset value. Resets when rung is false (when non-retentive)

•OFF-Delay Timer (T-OFF) Counts time intervals when conditions preceding it in the rung are false. Produces an output when accumulated value (Count) reaches preset value. Resets when rung is true (when non-retentive)

Timers

•Retentive Timer – (RTO)

This is an On-Delay Timer that retains its accumulated value when –

- rung conditions go false

- mode changes to program mode from run / test

mode.

- the processor loses power

- a fault occurs.

Counters• Up-Counter / Count-up

(CTU) Counts up for each false-to-

true transition of conditions preceding it in the rung. Produces an output when accumulated value (Count) reaches preset value.

• Down Counter / Count-Down (CTD)

Counts down for each false –to-true transition of conditions preceding it in the rung. Produces an output when accumulated value (count) reaches preset value.

Timers / Counters

•High Speed Counter (HSC) – Applies to 24 V DC fixed I/O controllers (In case of SLC 5/2) Counts high-speed pulses from high speed input. Maximum pulse rate of 8 KHz (In case of SLC 5/2)

•Reset (RES) –

Its used in Timers & Counters. When conditions preceding it in the rung are true, the RES instruction resets the accumulated value and controls bits of the timer or counter.

KEY-WORDS of PLC

• Flags / Registers / Latches / Memory Set-Reset / Retentive – Non-Retentive

• HHT – Hand Held Terminal• HHP – Hand Held Programmer

It is used for PLC Programming at

the Installation site.

• MMI – Man-Machine Interface• HMI – Human Machine Interface

Useful for ease of operation of PLC

by operator/s.

Dynamic Data Exchange-DDE

• Dynamic Data Exchange (DDE) and Object Linking and Embedding (OLE) are part of the Microsoft Windows Operating System. The software package that links the PLC to the PC is a Dynamic Data Exchange Server. This allows MS Windows DDE – Compliant applications to exchange data with PLC’s processor. Exchanging data from the plant floor to a supervisory computer allows data logging, data display, trending, downloading of recipes, setting of selected parameters and availability of general production data.

Functioning of Timers / Counters / Flags /

Registers

T IMERS 0 to 2 5 6 in A n sh u m an

M on os tab leA s tab le

COUNTERS 0 to 2 5 6 n os in A n sh u m an

U p C ou n terD own C ou n ter

FLAGS 0 to 2 5 6 n os in A n sh u m an

R eten tiveN on -R eten tive

REGISTERS0 to 2 5 6 n os in A n sh u m an

R eten tiveN on -R eten tive

PLC

H.H.T./ H.H.P.- Advantages• Easy transfer of PLC

Program to HHT / HHP for editing or troubleshooting.

• Easy transport of a program to the field to update a current machines program.

• Rugged and industrially hardened for the factory environment.

• Low cost, cheaper than a notebook computer.

• Easy to use & easy to learn, no software required.

• Compact Size (pocket size)• Easy storage of Program• Monitor resident PLC

Program for trouble shooting.

H.H.T./ H.H.P.– Disadvantages

• Not supported by some PLC’s.• An HHP can hold only one

program at a time – whereas a Laptop / PC can hold many programs on its HDD.

• HHP’s usually require more keystrokes to enter and get the same information as compared to a laptop / PC.

• Limited capability to display ladder rungs due to screen size

• Documentation not displayed

• Different HHPs are needed for different PLC manufacturers if more than 1 PLC’s are in field.

• If the Battery of the HHP discharges, a program stored in the memory will be lost.

KEY-WORDS of PLC

• Memory Cartridge / Module

Consists of either –

RAM ---- Random Access Memory.

(Volatile) ROM ---- Read Only Memory

EPROM -- Erasable Programmable Read Only Memory.

EEPROM -- Electrically Erasable Programmable Read

Only Memory.

FLASH --- Non-Volatile

Softwired Vs Harwired

components of PLC

•Soft-wired Components –

Timers Counters Logic Circuits

Latches

•Hard-wired Components -

24 V DC Lamps Relays Contactors

Solenoid Valves

Scan-Time / Scan-Cycle

•Scan Time of PLC – It is the time between an

Input being sensed & the corresponding output.

•Single Scan Cycle –

Single Scan Cycle function enables the circuit diagram to run for one processing cycle and then stop.

This is useful in analyzing the circuit diagram and observing how it works.

PLC Scan

•Input Scan – PLC scans the status of all the Inputs.

•Logic / Process Scan PLC goes through the ladder program / logic

•Output Scan – PLC sends Outputs as per various Inputs and the corresponding Ladder/Logic program.

Input Scan

•During the Input Scan the CPU scans each Input module for the ON / OFF states of each of the associated input points.

•The ON / OFF input states are stored in the input status file.

Program Scan• After the inputs are read and

stored in the input status file, the processor will use this information to solve the user ladder program.

• The processor scans the user program starting at rung zero at the left power rail, working left to right and evaluating one instruction at a time until the output instruction is reached.

• The Output status is the logical resultant of the solved input logic for that rung. The logical one or zero output status is placed in the output status file.

• After completing rung zero, the processor goes on to rung 1,2,3… and so on, sequentially, to the last rung except in case of Master Control Relay (MCR)

• At the end of the program, an END-Rung is automatically inserted which alerts the CPU the it has reached the END of the Ladder Program.

Input / Output Status File

•Input Status File – It is a group of words in memory that are organised to store input data. This data is processed by CPU when the program is executed.

•Output Status File It is a group of words in memory that are organised to store the ON-Off status of each Output. Once the user program is executed the ON-OFF status of each output is stored in the Output status File.

PLC – Concepts

PC – to - PLC or PLC – to – PLC

Communication can be done through - RS-232C (Serial Port) RS-422 DH-485 Data Highway Ports.

PLC Types – Fixed / Modular•Fixed PLC’s –

In these the number of I/O lines available are fixed. These cannot be expanded as per our requirement.

•Modular PLC’s –

In these, the number of Digital / Analog I/O’s can be further expanded depending upon our requirement.

I/O Addressing Format for

Expandable PLC’s

•e.g. – I :3/2 O:5/6 Input or Output : (Separator) Module Slot Number / (Slash) The Screw Terminal No.

PLC – Concepts•Online (Run) / Offline Mode of operation.

•Uploading/ Downloading

of Programmes from - PLC to PC & PC to PLC

•Display – LEDs / LCDs /VFD – Vacuum

Florescent Display.

PLC – Concepts

•MCR – Master Control Relay Function

•File Handling / Addressing System

•PLC Simulator Software

Key-Words of PLC

• WDT - Watch-Dog-Timer –

In case of PLC control loss due to EMI / NOISE, WDT brings back control of CPU to a Known State.

This Timer Circuit usually

resides on the CPU card itself.

It works like a MONOSHOT PULSE GENERATOR of width greater than MAXIMUM SCAN TIME.

WDT - Watch-Dog-Timer

• In order to insure system predictability a WDT is used to insure that the processor completes each scan in a timely manner.

• WDT is a hardware timer incorporated into the CPU’s circuitry that monitors the cyclical process / scan of the CPU.

• WDT is a safeguard that verifies the processor does not become stuck while scanning the user program or for some other reason, become unable to complete the current scan.

WDT - Watch-Dog-Timer

• The WDT is reset at the end os each Scan Cycle by the CPU when the scan time is less than WDT’s preset time.

• In case of one or more sub-routines, program scan time can exceed WDT time value. In some cases increasing the WDT’s preset value can solve the problem.

• Some PLC’s have WDT with fixed time intervals, while others are adjustable within specific limits.

• A typical default time of 100 / 200 mS is standard for many PLC’s with either fixed or variable WDT Timing Cycles.

SLC-500 - Processor

operating modes

•Program Mode•Run Mode•Remote Run Mode•Remote Program Mode•Test Mode•Single-Step Test Mode•Single – Scan Test Mode•Continuous Scan Test

Mode

•Test Mode – Test Program execution before allowing the PLC to operate the actual Hardware.

GE – 90-70 CPU - Processor operating

modes

•Run with Outputs Enabled

•Run with Outputs disabled

•Stop Mode

•Stop & I/O Scan Mode

•Run Mode Store Function.

Key-Words of PLC• CCU - Central Control Unit -

It consists of a CPU + PALS-GALS + RTOS + EPROM / RAM / EEPROM

• Process / Ladder Logic Memory It could be integrated with CPU or in a separate DATA / MEMORY CARTRIDGE / MODULE. Usually it is a replaceable Cartridge.

• Optoisolation - Analog I/O’s should be isolated otherwise induction / pickup can lead to malfunctioning of PLC

Digital Electronics

• Boolean Algebra• Binary / Hexadecimal nos.• Logic Gates & Truth Tables

•AND•OR •NAND•NOR•Ex-OR•Ex-NOR•NOT

PLC Programming AND OR NOT NAND NOR Ex-OR Ex- NOR

Timers Astable Monostable Bistable Counters Flags Retentive Non-Reten Registers Retentive

APPLI CATI ONS Traffi c Light Control Process Control Tank Level Control Bottling Plant Digital Lock Microwave Oven Washing Machine Door Bell & Alarm Sequential Control Silo Control

DCS / SCADA

•D.C.S. :- Distributed Control Systems

•S.C.A.D.A.:-

Supervisory Control And Data Acquisition System. (Through Network Data Acquisition, Data Display, Data Processing, Data Storage, Data Analysis etc.)

DCS Vs SCADA

• Generally supplied by a single Vendor with dedicated H/W & S/W.

• Costly due to redundent design

• Application Areas - Large Mfg. Facilities

• Comm’n - Confined to factory premises (LAN for H/W)

• Analog Processing - Large Analog I/O’s using PID’s

• Programming - by creating drawing like charts called as configuration diagram

• Suppliers - Honeywell, Foxboro I/A series, Bailey 90 etc.

• Normally supplied by Multiple / Competing Vendors

• Competitive cost due to Multi-Vendor products.

• Can be applied to very low cost applications

• Comm’n - Can cover larger geographical area by use of modems and T/p lines

• Small to medium Analog I/O’s with / without PID.

• Programming - PLC by relay Ladder Diagram or STL and SCADA using built-in graphics editor and drivers.

• Suppliers - PLC’s - Siemens, Allen Bradley, Omron etc. SCADA - Intellution, NI-Lookout / Labview

Following Displays are available in most Control Systems

•Overview•Area•Group•Details•Trends•Configuration•Diagnostics•Alarm Summary•System Status (LAN)•Scratch Pad

Comparison Instructions

(Conditional Input Instructions)

• Equal (EQU) – Instruction is true when source A = Source B

• Not Equal (NEQ) - Instruction is true when source A is Not Equal to Source B

• Less Than (LES) – Instruction is true when Source A < Source B

• Less Than or Equal (LEQ) - Instruction is true when

Source A <= Source B

Comparison Instructions

(Conditional Input Instructions)

• Greater Than (GRT) - Instruction is true when Source A > Source B

• Greater Than or Equal (GEQ) - Instruction is true when Source A >= Source B

• Masked Comparision for Equal –

MEQ – Compares 16 –bit data of a Source address to 16 Bit data at a reference address through a mask. If the values match the instruction is true.

• Limit Test - LIM – True / False instruction depends on how a test value compares to specified low and high limits.

Conditional Input / Output BIT Instructions

• Examine if Closed – XIC

• Examine if Open – XIO

• One-Shot Rising – OSR

• Output Energize – OTE

• Output Latch – OTL

• Output Unlatch – OTU

I/O Message & Communication

Instructions

• Immediate Input with mask (IIM)

• Immediate Output with Mask (IOM)

• Message Read / Write (MSG)

• Service Communications (SVC)

• I/O Interrupt Enable (IIE)

• I/O Interrupt Disable (IID)

• Reset Pending I/O Interrupt (RPI)

• I/O Refresh

Math Instructions

• Add - ADD

• Subtract – SUB

• Multiply – MUL

• Divide – DIV

• Double Divide – DDV

• Negate NEG

• Clear – CLR

• Convert to BCD – TOD

• Convert from BCD – FRD

• Decode – DCD

• Square Root – SQR

• Scale – SCL

Move & Logical Instructions

• Move – MOV

• Masked Move - MVM

• And – AND

• Inclusive Or – OR

• Exclusive Or – XOR

• Not - NOT

File Copy & File Fill Instructions

• File Copy – COP

• File Fill – FLL

Bit Shift, FIFO & LIFO Instructions

• Bit Shift Left (BSL)

• Bit Shift Right (BSR)

• First In First Out Load (FFL)

• First In First Out Unload (FFU)

• Last In First Out Load (LFL)

• Last In First Out Unload (LFU)

Sequencer Instructions

• Sequencer Output

• Sequencer Compare

• Sequencer Load

Control Instructions

• Jump to Lable – JMP

• Lable – LBL

• Jump to Subroutine (JSR)

• Subroutine (SBR)

• Return from Sub-Routine (RET)

• Master Control Reset (MCR)

• Temperory End (TND)

• Suspend (SUS)

• Selectable Timed Disable (STD)

• Selectable Timed Enable (STE)

• Selectable Timed Start (STS)

• Interrupt Subroutine (INT)

Other Terms related to Control Systems

• UCP - Unified Control Panel• UCS - Unified Control System• UCN - Universal Control

Network• UOC - Unit Operation Controller

• TDC - Totally Distributed • Control System

• SOE - Sequence Of Events• SP --- Set-Point• SFC - Sequential Function

Chart• SAT - Site Acceptance Test• SAS - Safety & Automation

Systems

Other Terms Used in Control Systems

RTU - Remote Terminal UnitROC - Rate of ChangePV --- Process VariablePS --- Process StationPSD - Process Shut-DownPIU - Plant Interface UnitPIN - Plant Interface NetworkPCS - Process Control SystemPFD - Process Flow Diagram PCN - Process Control Network

P&ID - Piping & Instru’t Diag.


OBT - Optical Bus TerminalOLE - Object Linking & EmbeddingOLM - Optical Link Module

NIU - Network Interface Unit

MC---- Multifunction ControllerMTU - Master Terminal UnitMCS - Master Control StationMAS - Manufacturing Automation System

MAP - Manufacturing Automation Proto’l

MTBF - Mean Time Between FailureMTTR - Mean Time To Repair


• LLPIU - Low-Level Process Control Station

• LCN --- Local Control Network• LCR --- Local Control Room• LAN --- Local Area Network

• ISA - Instrument Society of America

• ISO - International Standards Organization

• HSE ---- High Speed Ethernet

• HIPPS -- High Level Process Protection

System• HAZOP - Hazard & Operability

Study


• FAT- Factory Acceptance Test• EUC - Equipment Under Control• ESD - Emergency Shut-Down System

• EC --- Extended Controller

• DPS - Dynamic Positioning System

• AC --- Adaptive Control

• CFC - Continuous Function Chart

• C & I - Control & Instrumentation

• CCR -- Central Control Room

•Other Terms Used in Control Systems

• BCL -- Batch Control Language

• BC --- Basic Controller

• AEC - Advanced Extended Controller

• AMC - Advanced Multifunc’n Controller

• CAD - Computer Aided Design

• CADAS - Computer Aided Design Analysis &

Application

FF-Bus -Foundation Field Bus

• FF-Bus is a Digital Comm’n System

• A Summary of improvements, which FF-Bus will offer as it becomes more widely applied are – * Higher Communication Speed - 10 to 100 M Baud* Higher nos. of modes per

branch to reduce cabaling & termination effort

• More efficient Communication

• Better diagnostics & predictive maintenance in field Instrumentation.

FF-Bus

• More reliable Control System because of better maintenance & Higher distribution control.

• Faster Control System Response.

• Saving in Hardware (Cabling, I/O cards, Cabinets)

• Higher Accuracy because Process Parameters are Sampled Locally & Transmitted Digitally to local / remote Control Units.

• Major Improvements in System Commissioning saving Time & Costs.

FF-Bus

•Reduction in Documentation (No. of Loop Diagrams, Termination Schedules etc.)

•Possibilities od using Multifunction Instruments - Where one Transmitter measures multiple variables (e.g. A Corolis meter can measure - flow, Density & Temperature )

•A High Degree of Inter-operability among system Computers & Instruments from different Vendors.

• DPS - Dynamic Positioning System

•Availability = MTBF / (MTBF + MTTR)

• Categories of Consequences Definitions

• Catastrophic ---- Multiple Loss of Life

• Critical -------- Loss of a Single Life

• Marginal ------- Major injuries to one or more persons.

• Negligible ------ Minor injuries at worst

Catagories of Likelihood

Categories of Likelihood

Definition (in System Life)

Failures Per Year

Frequent Many Times > 10- 3

Probable Several Times 10- 4 to 10- 3

Occasional One Time 10- 5 to 10- 4

Remote Unlikely 10- 6 to 10- 5

Impossible Very Unlikely

10- 7 to 10- 6

I ncredible Cannot believe it could happen

< 10- 7

* Analog Input :- DC models of

Pico are provided with two

analog inputs I7 and I8. The

permissible input voltages are

between 0 V and 10 V. The

measured data is evaluated by

an integrated Analog Value

Comparator relay.

* Circuit Connection:

Each line in the circuit

diagram display is a circuit

connection.

Circuit Diagram Elements:

The circuit diagram is made

up of circuit diagram elements from conventional wiring practice. These include input, output and auxiliary relays as well as function relays and P buttons.

Contact/Coil Monitor:

The Contact/Coil Monitor is

a dialog for displaying and forcing the logic states of selected relays (contacts / coils).

Device Test :-

The device test shows in plain text the results of comparison between the selected Pico device and the circuit diagram. All contact/coil elements that are not available on the device used will be listed, and the number of circuit connections used will be checked. If the Pico device cannot properly process the circuit diagram, a device will be suggested on which the circuit diagram can be used successfully.

Function Relay :-

Function relays are used for complex switching tasks. Pico devices are provided with the following function relays: Timing relays (T), Time switches (H), Counters (C), Analog value comparators (A), Text relays (D).

Impulse Relay :-

An impulse relay is one that changes and then retains this state if a voltage is momentarily applied to it.

Input :-

External contacts are connected to the inputs of the device. Inputs are evaluated in the circuit diagram via the switching contacts I1 to I12 and R1 to R12. The 24 V DC Pico models can also receive additional analog data via inputs I7 and I8.

Input Debounce :-

Input signals can be evaluated by the device with a delay in order to compensate for the contact bounce of switches and pushbuttons.

Interface :-

The device interface allows circuit diagrams to be exchanged and stored on a memory card or PC. A memory card saves both the circuit diagram and device settings. PicoSoft PC software allows you to control the device from the PC. The PC is connected to Pico via the "1760-CBL-PM02" cable.

I/Q Window :-

The I/Q window contains the input simulator and the display for Q and S coils. The input simulator or I window is used as a central tool in circuit diagram simulation. It enables you to create dynamic input signal states for the simulated circuit diagram. For this you can also assign different functions to the I and R buttons.

I/R Function :-

The I/R Function determines the switching function of the elements I1 to I16 and R1 to R16. These can be latching make contacts, latching break contacts, momentary make contacts or momentary break contacts.

Operator Buttons :-

The device features 8 operator buttons by which you can select the menu functions and also enter the circuit diagram directly via the Pico display. The centrally arranged cursor buttons are used to move the cursor in the Pico display. DEL, ALT, ESC and OK are also provided with additional functions.

Output :-

The outputs are used to switch loads such as contactors, lamps or motors. The outputs are controlled in the circuit diagram via the output relay coils Q1 to Q8 and S1 to S8.

Parameters :-

Function relays are assigned particular parameters by the user. Set values may include, for example, switching times or counter setpoints. These are set in the Contact/Coil dialog.

P Buttons :-

The P buttons allow you four additional inputs that are switched via the cursor buttons on Pico instead of external contacts. The switching contacts of the P buttons are wired in the circuit diagram.

Retention :-

This function allows data to be retained in the device even after its power supply has been switched off. Retentive data consists of: Device circuit diagram, parameters, setpoints, text, system settings, password, actual values of auxiliary relays (markers), timing relays, counters.

Signal Diagram :-The Signal Diagram allows you to display the behavior up to eight selected relays along a time axis. The diagram produced can also be printed out for documentation purposes.

Single Cycle :-The Single Cycle function enables your circuit diagram to run for one processing cycle and then stop. This helps you in analysing the circuit diagram and observing how it works. This function is only available during Simulation.

Startup Behavior :-

The startup behavior is an important help during commissioning. The circuit diagram may not be completely wired when it is transferred to Pico, or the system/machine to be controlled is in a state in which it cannot be controlled by Pico. If Pico is then switched on, it may therefore be desirable for the outputs to remain inactive. For this set the startup behavior to STOP. If the startup behavior is set to RUN, Pico will start processing the circuit diagram as soon as it is switched on.

Stop Point :-

In order to analyse your circuit diagram effectively, you need a tool to interrupt processing selectively, evaluate the state of selected contacts or coils and continue processing. The Stop Point function makes this possible. It is only available during Simulation.

Wiring via the Keyboard

PicoSoft also enables you to wire up your circuit diagram via keyboard commands.

Selecting Make/Break Contact Behavior :-

Entering letters in lower case selects make contacts, and entering letters in upper case selects break contacts.

Adding / Deleting Contacts :-Position the cursor on the contact field required and enter the contact via the keyboard. Use the following shortcuts for contacts & f’n relays:

i, I Controller Inputs

p, P Soft Inputs - Keypad

q, Q Controller Outputs

m, M Internal Marker Bits

c, C Counters

t, T Timers

h, H Time Switch Relay

a, A Analog Setpoint Compare

d, D Text Display

r, R Expansion Inputs

s, S Expansion Outputs or Internal Marker BitsTo delete the contact, press the Del key

Adding / Deleting Coils

Position the cursor on the coil field required and enter the coil via the keyboard. Use the following shortcuts for coils and coil functions:

q Controller Outputs

m Internal Marker Bits

t Timer "Trigger" coil

c Counter "Trigger" coil

d Text Display "contactor" function

s Internal Marker "contactor" function

To select the coil function required, press the Shift key and select the appropriate coil function letter below:

Shift + E Impulse relay

Shift + S Latching (Set)

Shift + R Unlatching (Reset)

Shift + D Direction coil for counter

The default setting is for the contactor function. To revert to the simple contactor function of the coil, press the letter for the coil concerned.

To delete the coil,

press the Del key.

Connecting Inputs and Outputs

Use Shift+Cursor key to make the connection between the individual contacts and coils.

Adding Empty Lines

Position the cursor on the circuit connection in front of which you wish to add the empty circuit connection. Press Ctrl+I to add the empty circuit connection.

Deleting Circuit ConnectionsPosition the cursor on the circuit connection you wish to delete. Press Ctrl+D to delete the entire circuit connection.

Deleting ConnectionsPosition the cursor on the connection you wish to delete.

To delete the connection,

press the Del key.

If the circuit connection contains branches, the selected connection will only be deleted up to the next node.

P.I.D.• When you select Position, the

PID object calculates the output as follows:

• MV = Kc (en + integral sumn – Td / dT (Pv n – Pv n-1)) =

• where:• dT = time increment between

current and previous calc.• MV = controller output

(manipulated variable)• Kc = controller gain (units: %

output / % error)• en = error at sample n (error =

SP – Pv n )• integral sumn = integral sum

n–1 + dT / Ti (en – en–1 ) also called bias

• Td = rate, or derivative time• Pvn – Pvn–1 = change in PV from

previous to current calculation

P.I.D.• The output of the velocity form of

the PID equation is the velocity or rate of change of the output signal. The velocity form of the PID equation is the first derivative of the position form of the PID equation with respect to time, so the result is the rate of change of the controller position.

• When you select Velocity, the object calculates the output as follows:

• dMV = MVn – MVn–1 = Kc ((en – en–1) + Tsen / Ti + Td / Ts (Pvn – 2PVn–1 + PVn–2)

• where:• MV = controller output position

(manipulated variable)• dMV = contoller output velocity• Kc = controller gain (units: % output

/ % error)• en = error at sample n (error = SP–

Pvn )• Td = rate, or derivative time• PV = process variable

P.I.D.• The PID object compares a Process Variable to a Setpoint. If there is a difference, it calculates the error and adjusts its output to compensate until the

Process Variable is equal to the Setpoint.

• PID stands for Proportional-Integral-Derivative. These are three factors in the equation that can be applied against the calculated error. • You specify Gain which is the proportional factor, Reset (the integral factor), and Rate (the derivative factor) to define how the object responds to the error.

• NOTE: The way in which the PID object responds to your process can vary greatly according to the parameters you enter and the process you are controlling. Any discussion regarding tuning of a PID loop falls outside of the topics addressed in this manual.

• Type selects either positional control or velocity control .

• Process Variable (PV) is typically the numeric signal from the field that you want to control. The PID loop equation does not expect this value to be normalized; rather the PID object performs the scaling of loop input and output values from engineering units.

• Setpoint (SP) is typically the value of a Pot object, a constant numeric value, or the output signal from another PID object in a cascaded loop. Like the process variable, the setpoint is also scaled internally by the PID object.

• Setpoint Min and Max are numeric constants that specify the range of SP and PV in engineering units.

• Manual Output is a numeric parameter that specifies the output of the object when it is in manual mode; that is, when the Automatic Enable expression is FALSE. Users typically enter either a constant, or the name of a Pot object in this field.

• Output Min and Max are numeric constants that specify the range of the object output signal. The output is often referred to as the manipulated variable (MV).

• Sample Pulse indicates the frequency at which the PID object executes. This parameter field can contain either a numeric constant or a logical variable. If you use a numeric constant (like 0:01 for one second), the object calculates a new output value at the defined frequency. If you use a logical variable, then the variable should pulse at some desired frequency. Any time the pulse transitions from FALSE to TRUE, the object calculates a new output value. It is very important not to over-sample your data. Start with a slow sample rate.

• Gain (Kc) is a numeric parameter that determines the overall sensitivity of the PID loop to changes in error. A gain value of 1.00 changes the proportional increment of the PID equation by 50 percent when there is a 50 percent change in error. A gain value of 0.25 changes the proportional increment by 12.5 percent with a 50 percent change in error.

• Reset (Ti) also referred to as integral time, is a numeric parameter that specifies the amount of time it takes for the integral sum increment of the PID loop equation to react to a given change in error. For example, if the error suddenly changes by 20% and reset = 0:10 (10 seconds), the integral increment of the PID loop increases at a rate of 0.5 percent per second until it has changed by 20 percent after 40 seconds. This 20 percent contribution is multiplied by the gain, so if the gain is 2.0, the integral term contributes 40% to the loop output in this example. In other words, the shorter the reset time, the faster the object output responds to a change in either PV or SP.

• Rate (Td) also referred to as derivative time, is a numeric parameter that dampens loop response. It is calculated based upon the rate of change of PV and adds an increment to the output that attempts to anticipate and slow the change in PV. As an example, if PV is increasing by 10 percent per minute, and rate is 0:30 (0.5 minutes), the derivative increment is calculated as –(10%/min. x 0.5 minutes)= –5% (or –0.05). So the derivative term would contribute –5% to the output if the gain is 1.0.

• Automatic Enable specifies whether the loop controller is operating in automatic mode or manual mode. When it is ON, controller is operating in automatic mode and the output signal is being calculated using the PID algorithm. In manual mode, the output signal is equal to the Manual Output input signal.

• The PID object provides bumpless transfer from manual to automatic operation—• when the controller is switched from manual to automatic, its output begins changing from the current manual output setting. Contrast this with a loop

controller without bumpless transfer. When such a controller is in manual, the integral term continues to accumulate. When the controller is switched to automatic, the loop controller would immediately go to a high or low output.

• Add proportional increment specifies whether the loop equation adds the proportional increment of the PID equation to MV. This value is typically ON.

• Freeze Enable specifies whether the loop bias should be frozen or actively back-calculated when the controller output signal goes out of range. In either case, the loop controller is protected from integral wind-up, but if Freeze Enable is OFF (recommended setting), the bias is actively back-calculated to prevent controller overshoot when PV comes back into range.

• The PID object protects against integral windup in one of two selectable ways: It either freezes the bias term when the controller output goes out of range, or it actively back-calculates the bias so the controller responds smoothly with less chance of overshoot when its output returns to range.

• Output Time is a numeric constant that specifies the time domain of the controller output when operating in velocity mode. For example, if the object output controls a value with dimensions of inches per minute, output time would be 1:00 (one minute).

• Low Limit Enable is used in velocity control mode. It is an optional logical signal that clips the PID output to a value grater than or equal to zero when TRUE. This input can be used to signal the controller that the low limit switch on the controlled device has been activated.

• High Limit Enable is used in velocity control mode. It is an optional logical signal that clips the PID output to a value less than or equal to zero when TRUE. This input can be used to signal the controller that the high limit switch on the controlled device has been activated.

• Comments The proportional term of the PID equation contributes an amount to the output equal to the error multiplied by the Gain. This provides an immediate output compensation when the error value changes.

• The integral term of the PID equation calculates a running total of the error summed (or integrated) over time—think of this increment as adding the area under the curve of a plot of error versus time. While SP is greater than PV, the integral term is increasing, and while PV is greater than SP, the integral term is decreasing. The sensitivity of the integral output is set by the gain and the reset variables. Integral action can be eliminated by setting Reset to a higher number. At least some Integral action is required, however, for the loop controller to operate properly with bias adjustment. If you do not use any Integral, you may experience offset, a condition in which the output is adjusted to compensate for the error, but not enough to correct the error.

• The derivative term of the PID equation acts to dampen the change in PV by adding a negative value for a positive-going PV and a positive value for a negative-going PV

• . Because PV is subject to sudden small changes and signal noise in many process loops, derivative action can cause a loop to respond erratically. Rate can be set to 0, especially when initially tuning the loop, to eliminate derivative action. Derivative action dampens process loops that tend to oscillate around the setpoint and thus provide better loop response. Rapidly changing loops such as liquid flow control in a pipe may not benefit from derivative action, but more sluggish loops that tend to build momentum, such as temperature control, benefit from derivative action by preventing overshoot and dampening oscillatory action.

• PID Positional Control• PID Velocity Control• PID Data Members

P.I.D.• NOTE: The way in which the PID object responds to your process can vary greatly according to the parameters you enter and the process you

are controlling.

• Type selects either positional control or velocity control .

• Process Variable (PV) is typically the numeric signal from the field that you want to control. The PID loop equation does not expect this value to be normalized; rather the PID object performs the scaling of loop input and output values from engineering units.

• Setpoint (SP) is typically the value of a Pot object, a constant numeric value, or the output signal from another PID object in a cascaded loop. Like the process variable, the setpoint is also scaled internally by the PID object.









• The PID object provides bumpless transfer from manual to automatic operation—• when the controller is switched from manual to automatic, its output begins changing from the current manual output setting. Contrast this

with a loop controller without bumpless transfer. When such a controller is in manual, the integral term continues to accumulate. When the controller is switched to automatic, the loop controller would immediately go to a high or low output.












P.I.D.• Setpoint (SP) is typically the value of a Pot object, a constant numeric value, or the output signal from another PID object in a

cascaded loop. Like the process variable, the setpoint is also scaled internally by the PID object.









• The PID object provides bumpless transfer from manual to automatic operation—• when the controller is switched from manual to automatic, its output begins changing from the current manual output setting.

Contrast this with a loop controller without bumpless transfer. When such a controller is in manual, the integral term continues to accumulate. When the controller is switched to automatic, the loop controller would immediately go to a high or low output.












P.I.D.• Output Min and Max are numeric constants that specify the range of the object output signal. The output is often referred to

as the manipulated variable (MV).• Sample Pulse indicates the frequency at which the PID object executes. This parameter field can contain either a numeric

constant or a logical variable. If you use a numeric constant (like 0:01 for one second), the object calculates a new output value at the defined frequency. If you use a logical variable, then the variable should pulse at some desired frequency. Any time the pulse transitions from FALSE to TRUE, the object calculates a new output value. It is very important not to over-sample your data. Start with a slow sample rate.





• The PID object provides bumpless transfer from manual to automatic operation—• when the controller is switched from manual to automatic, its output begins changing from the current manual output

setting. Contrast this with a loop controller without bumpless transfer. When such a controller is in manual, the integral term continues to accumulate. When the controller is switched to automatic, the loop controller would immediately go to a high or low output.












P.I.D.• Gain (Kc) is a numeric parameter that determines the overall sensitivity of the PID loop to changes in error.

A gain value of 1.00 changes the proportional increment of the PID equation by 50 percent when there is a 50 percent change in error.

A gain value of 0.25 changes the proportional increment by 12.5 percent with a 50 percent change in error.




• The PID object provides bumpless transfer from manual to automatic operation—• when the controller is switched from manual to automatic, its output begins changing from the current manual output

setting. Contrast this with a loop controller without bumpless transfer. When such a controller is in manual, the integral term continues to accumulate. When the controller is switched to automatic, the loop controller would immediately go to a high or low output.












P.I.D.• Reset (Ti) also referred to as integral time, is a numeric parameter that specifies the amount of time it takes

for the integral sum increment of the PID loop equation to react to a given change in error. • For example, if the error suddenly changes by 20% and reset = 0:10 (10 seconds), the integral increment of

the PID loop increases at a rate of 0.5 percent per second until it has changed by 20 percent after 40 seconds. This 20 percent contribution is multiplied by the gain, so if the gain is 2.0, the integral term contributes 40% to the loop output in this example. In other words, the shorter the reset time, the faster the object output responds to a change in either PV or SP.



• The PID object provides bumpless transfer from manual to automatic operation—• when the controller is switched from manual to automatic, its output begins changing from the current

manual output setting. Contrast this with a loop controller without bumpless transfer. When such a controller is in manual, the integral term continues to accumulate. When the controller is switched to automatic, the loop controller would immediately go to a high or low output.












P.I.D.• Rate (Td) also referred to as derivative time, is a numeric parameter that dampens loop response.

• It is calculated based upon the rate of change of PV and adds an increment to the output that attempts to anticipate and slow the change in PV.

• As an example, if PV is increasing by 10 percent per minute, and rate is 0:30 (0.5 minutes),

the derivative increment is calculated as –(10%/min. x 0.5 minutes)= –5% (or –0.05).

So the derivative term would contribute –5% to the output if the gain is 1.0.


• The PID object provides bumpless transfer from manual to automatic operation—• when the controller is switched from manual to automatic, its output begins changing from the current

manual output setting. Contrast this with a loop controller without bumpless transfer. When such a controller is in manual, the integral term continues to accumulate. When the controller is switched to automatic, the loop controller would immediately go to a high or low output.












P.I.D.• Automatic Enable specifies whether the loop controller is operating in automatic mode or manual mode. When it

is ON, controller is operating in automatic mode and the output signal is being calculated using the PID algorithm. In manual mode, the output signal is equal to the Manual Output input signal.

• The PID object provides bumpless transfer from manual to automatic operation— when the controller is switched from manual to automatic, its output begins changing from the current manual output setting.

Contrast this with a loop controller without bumpless transfer. When such a controller is in manual, the integral term continues to accumulate.

When the controller is switched to automatic, the loop controller would immediately go to a high or low output.












P.I.D.• Add proportional increment specifies whether the loop equation adds the

proportional increment of the PID equation to MV. This value is typically ON.

• Freeze Enable specifies whether the loop bias should be frozen or actively back-calculated when the controller output signal goes out of range.

In either case, the loop controller is protected from integral wind-up, but if Freeze Enable is OFF (recommended setting), the bias is actively back-calculated to prevent controller overshoot when PV comes back into range.










P.I.D.• The PID object protects against integral windup in one of two selectable ways:

It either freezes the bias term when the controller output goes out of range, or it actively back-calculates the bias so the controller responds smoothly with less chance of overshoot when its output returns to range.

• Output Time is a numeric constant that specifies the time domain of the controller output when operating in velocity mode.

• For example, if the object output controls a value with dimensions of inches per minute, output time would be 1:00 (one minute).








P.I.D.• Low Limit Enable is used in velocity control mode. It is an optional

logical signal that clips the PID output to a value grater than or equal to zero when TRUE. This input can be used to signal the controller that the low limit switch on the controlled device has been activated.


• Comments -The proportional term of the PID equation contributes an amount to the output equal to the error multiplied by the Gain. This provides an immediate output compensation when the error value changes.





P.I.D.• Comments -The proportional term of the PID equation

contributes an amount to the output equal to the error multiplied by the Gain. This provides an immediate output compensation when the error value changes.

• The integral term of the PID equation calculates a running total of the error summed (or integrated) over time—think of this increment as adding the area under the curve of a plot of error versus time. While SP is greater than PV, the integral term is increasing, and while PV is greater than SP, the integral term is decreasing.The sensitivity of the integral output is set by the gain and the reset variables.Integral action can be eliminated by setting Reset to a higher number. At least some Integral action is required, however, for the loop controller to operate properly with bias adjustment. If you do not use any Integral, you may experience offset, a condition in which the output is adjusted to compensate for the error, but not enough to correct the error.




P.I.D.• The derivative term of the PID

equation acts to dampen the change in PV by adding a negative value for a positive-going PV and a positive value for a negative-going PV

• Because PV is subject to sudden small changes and signal noise in many process loops, derivative action can cause a loop to respond erratically. Rate can be set to 0, especially when initially tuning the loop, to eliminate derivative action. Derivative action dampens process loops that tend to oscillate around the setpoint and thus provide better loop response. Rapidly changing loops such as liquid flow control in a pipe may not benefit from derivative action, but more sluggish loops that tend to build momentum, such as temperature control, benefit from derivative action by preventing overshoot and dampening oscillatory action.

Step-by-Step PICO Programming

• Step-by-Step Procedure (For operating Allen Bradley’s (Rockwell Automation) – PLC - PICO Model, using PICOSOFT Software Package –

• [1] Install PICOSOFT Software by • double-clicking option • PICOSOFT-WEB-6L.

• [2] After Installing, double-click on

• “ PICOSOFT ” ICON • on the Desk-top of your PC.

• [3] A Screen will appear on the • monitor of your PC. Close the • existing program, which

appears • on the screen


• [4] Go to option VIEW and Tick • option - Grid Lines – so that grid • lines appear on the Screen of • your PC.

• [5] Go to option VIEW and Tick • options – Status Bar, • Toolbar and Simulation Toolbar.

• [6] Go to option View and Tick option

• – DISPLAY FORMAT • – ANSI / CSA.

• [7] Go to option CIRCUIT DIAGRAM • and select NEW program for • editing / writing a new Ladder • Program


• NOW YOU ARE IN A POSITION TO EDIT / WRITE NEW LADDER PROGRAM USING PICOSOFT SOFTWARE PACKAGE.

• [8] There are 7 columns on the • screen – You can write / Edit • CONTACTS (INPUTS) in • Column nos. 1,3 & 5.

• Column nos. 2, 4 & 6 are for • wiring / connection.

• Column no. 7 is for COIL’s • (OUTPUTS).


• [9] In Ist ROW, Click the Cursor of the Mouse

• in Column 1. A vertical rectangle will appear.

• Double-Click the Mouse button, • a table with different options • will appear on the screen.

• Select - ‘I’ and then ‘1’ - I1 • contact will appear on screen.

• Click the button once in the • Last Column of Ist ROW.

• Double-Click the mouse button; • a table with different options • will appear on the screen

• Select – ‘Q’ and then ‘1’ - Q1 • (Coil) will appear on the screen.

• Take the mouse cursor near right hand of • I1 - then Click the mouse button, keep it • pressed and drag the cursor to join I1 • and Q1.


• [10] Go to SIMULATION Option – • Click I/Q window; a table with • different Inputs and Outputs • will appear on the Screen• • [11] Again go to SIMULATION

window and select option – RUN

• A small red line will appear on

• left side of all the rungs.

• Click I1 in the table to see • the effect on Q1.

• When you make I1 – ON, Q1 • becomes ON. • When you make I1 – OFF, Q1 • also becomes OFF.


• [12] NOTE – For successful operation

• of Step – 11, ensure the • following –

• Go to SIMULATION window, • select option I/R - • A table will appear on the • screen – with I1 to I16 • (INPUTS – can be available • Externally.) and R1 to R16 • (Internal INPUTS – not • available externally) •

• These can be selected as – • Closed Pushbutton• Or Open Push-Button• Or Closed Switch • Or Open Switch

respectively.


• [13]• I – Inputs (Contacts)• Q – Outputs (Coils)• R – Internal Inputs (Not available • externally for connections)• S – Internal Outputs (Not

available • externally for connections)• M- Marker Bits (Memory)• P - Internal Push-buttons (Not • available externally)• T - Timers – On-Delay / Off- • Delay / Single Pulse / Flashing • / Random• C - Counters – Up/Down

Counters. D - Display – 4 Line Message

• A – Analog Inputs ( I-7 or I-8)• H – Real Time Clock• : - Jump


• [14] For Outputs / Coils – Q, S, M

• & D - you can select 4 different • Options – VIZ.-

• [Q or QS or QR or _|Q

• In case of [Q – • If I1 is connected to [Q1,

• When I1 is ON, [Q1 becomes ON.

• When I1 is OFF, [Q1 becomes OFF.

• In case of QS – • If I2 is connected to Q2S (SET)

• When I2 is ON, Q2 becomes ON (set).

• When I2 is OFF, Q2 remains ON • (Latched / SET)


• In case of QR – • If I3 is connected to Q2R (RESET)

• When I3 is ON, Q2 becomes OFF.• (i.e. Q2 is Unlatched / RESET)

• In case of _|Q – • If I4 is connected to _|Q4,

• When I4 is operated like a push-button, • Q4 becomes ON.

• When I4 is operated again like a push-button,

• Q4 is OFF


• Q4 is ON


• Q4 is OFF• • i.e. Q4 operates like – Push-to-ON, • Push-to-OFF output.


• [15] For using ‘M’ i.e. internal • marker bit (memory) :-

• If Q1 is to be made ON, Only • after All Inputs i.e. I1, I2, I3, • I4 & I5 are ON, it can be • achieved using internal

marker • bit i.e. M.

• Write I1 & I2 & I3 in series • and connect it to M1 in Rung –1• • Note :- Only 3 Inputs / Contacts • are allowed in a ROW in • case of PICOSOFT. • Whereas any number of • contacts can be made • parallel.


• [16] For using ‘P’ i.e. Push-Buttons :-

• Double-click in 1st Column of Rung-1,

• Select Option – P-1, connect it to

• Output Q1.

• When you Simulate the program,

• When you press P1, Q1 will glow• When you release P1, Q1 will • become OFF.

• Note :- To Activate Push-Buttons, Click

• Options, then Select ‘ System • Setting via circuit diagram, and

• Tick – P-Buttons.


• [17-A] For Using Timers –

• ON-Delay Timer –

• Double-click in 1st Column of Rung-1, Select Option – I-1, connect it to Timer TT-1,

• Select Option ‘X’ i.e. ON-DELAY Timer, Enter the number of Seconds in Time Base window and click Accept option at the end of the Window.

• In Rung-2, Ist – Column, Select Timer T-1 as a Contact and then Connect it to Output ‘Q-1’.

• When you Simulate the program, When you press I1, Q1 will glow after a Delay of -- Seconds and will remain ON -- till either the Input I1 is switched OFF or the Timer T1 is RESET using one more Input Viz.- (I2).

• This can written in Ring-3 – as – Select I2 in Ist Column and Select Timer Option – then select RT-1 Option and Press Accept option and connect I2 & RT1


• [17-B] For Using Timers – OFF-Delay Timer –•

• Double-click in 1st Column of Rung-1, Select Option – I-1, connect it to Timer TT-1,

• Select Option ‘Fully Filled Square - i.e. • OFF-DELAY Timer, • • Enter the number of Seconds in Time Base

window and click Accept option at the end of the Window.

• In Rung-2, Ist – Column, Select Timer T-1 • as a Contact and then Connect it to Output

Q1

• When you Simulate the program, When you

• press I1, Q1 will glow immediately but will • not become Off. Only When I1 is made OFF,

after a Delay of --Seconds Q1 will be Off.• or the Timer T1 is RESET using one more

Input Viz.- (I2).

• This can written in Ring-3 – as – Select I2 in Ist Column and Select Timer Option – then select RT-1 Option and Press Accept option and connect I2 & RT1


• [17-C] For Using Timers –

– Single Pulse Timer (Edge Triggered Timer) •

• Double-click in 1st Column of Rung-1, • Select Option– I-1, connect it to Timer TT-1, • Select Option ‘Pulse – symbol i.e. Single

Pulse • / Mono-shot Timer. • Enter the number of Seconds in Time Base • window and click Accept option at the end of • the Window.


• When you Simulate the program, When you press I1, Q1 will become ON and will remain ON for – Sec. Q1 will become OFF nd will remain ON -- till either – Sec are over

• or the Timer T1 is RESET using one more Input Viz.- (I2).

• This can written in Ring-3 – as – • Select I2 in Ist Column and Select Timer

Option – then select RT-1 Option and Press Accept option and connect I2 & RT1


• [17-D] For Using Timers – • Flashing ON-OFF-ON-OFF (Asynchronous) –• • Double-click in 1st Column of Rung-1, • Select Option – I-1, connect it to Timer TT-1, • Select Option ‘ Up-side-down i.e.

FLASHING Timer, Enter the number of Seconds in Time Base window and click Accept option at the end of the Window.


• When you Simulate the program, • When you press I1, Q1 will become OFF-ON-

OFF-ON for every – Seconds Q1 will become OFF only if – Either I1 is switched OFF

• or the Timer T1 is RESET using one more Input Viz.- (I2).

• This can written in Ring-3 – as – • Select I2 in Ist Column and Select Timer

Option – then select RT-1 Option and Press Accept option and connect I2 & RT1.


• [18] For using Counters –

• Double-click in 1st Column of Rung-1, • Select Option– I1, connect it to Counter CC-

1, • Enter – Set-point – (Count value For e.g. –

‘5’) in the Window and Click – Accept option• • In Rung-2, Ist – Column, Select Counter C-1

as a Contact and then Connect it to Output ‘Q-1’.

• When you Simulate the program, • Only When you Click I-1 for 5 times, • Q1 will become ON & will remain ON • It will reset only when –

• In Rung – 3, Ist Column, Select option – I-2, Then in last Column, select option ‘C’, in that select Option ‘RC-1’ and connect I-2 to RC-1.

• During simulation, when I-2 is pressed, the ‘ ACTUAL VALUE ‘ in the Counter will RESET. (This can be observed by – Double-Clicking the Counter option in the Last Column When Simulation is in RUN Mode.


• [19] When using Text Message Display (D) -

• Double-click in 1st Column of Rung-1, • Select Option – I-1, connect it to D-1 i.e.

Text Message Display, • Enter the Message in – TEXT Window –

and click Accept option.• • When you Simulate the program, • When you Click I-1, D1 will become ON i.e

the Message will be displayed

• The Message / Display will reset only when either –

• I-1 is switched OFF • Or - In Rung – 2, Ist Column, • Select option – I-2, • Then in last Column, select option ‘RD-1’,

and connect I-2 to RD-1. During simulation, when I-2 is pressed, the Message/Display resets.


• [20] When using Analog Inputs I-7 / I-8

• Double-click in 1st Column of Rung-1, • Select Option – A-1, connect it to Q-1, • If you double-click on A-1, you can • select 6 different options – VIZ. –•

• I-7 <= I-8 (Value of I7 is Less than • or Equal to the value of I8 Input)• I-7 >= I-8 (Value of I7 is Greater • than or Equal to the value of I8

Input)• I-7 <= VALUE (I7 is Less than or Equal • to some VALUE defined by you.)• I-7 >= VALUE (I7 is Greater than or • Equal to some VALUE defined by

you.)

• I-8 <= VALUE (I8 is Less than or Equal • to some VALUE defined by you.)• I-8 >= VALUE (I8 is Greater than or

Equal to some VALUE defined by you.)


• For e.g. – If you want to give an indication – Output Q1 when Value of I7 is Less than or Equal to the value of I8 - When you double-click on A-1, Select option – I7 <= I8,

• When you Simulate – and select RUN option – Initially both I7 & I8 value are ‘0 – ZERO’. Slowly increase the value of I7 by selecting the vertical POT in the Simulation– I/Q Window on the Right hand side to a value of @ 2.0.Then slowly increase the value of I8 by selecting the relevant POT.

• You can notice that - Upto a condition of I7<=I8, Q1 is OFF. As soon as I7 value becomes equal to or Less than I8 value, Q1 becomes ON.

• NOTE :- Similarly one can select the other 5 options and Simulate the corresponding conditions for various values.

• When Options like I7 <= VALUE are selected, A Value can be entered in the WINDOW which will be accepted as valid value ONLY when ACCEPT option is selected by clicking the mouse on that option.


• [21] When using ‘ CLOCK – REAL TIME CLOCK

• Double-click in 1st Column of Rung-1, • Select Option – H (Clock- as contact) -1,

connect it to Q-1, Double-click H-1,

• Enter the DAY option for e.g. From Monday To Monday Enter the Time option for e.g. From 14 01 to 14 02 (i.e. 2 O’ Clock

• One minute to 2 O’ Clock 2 minutes) • and select ACCEPT option.

• NOTE :- Enter a time as per the current Time of the PC on which you are working. Enter a Value of Time which will occur after 5 minutes of your writing the program, which will give you sufficient Time for going to Simulation mode.

• During Simulation, Q1 will become ON exactly at 14 01 (TIME SET by you) And Q1 will become OFF exactly at 14 02.

• In this way PLC can be programmed to operate a specific Output on a specific DAY for a specific TIME duration.

PLC - Sizes

Micro-PLC’s

Small Sized PLC’s

Medium Sized PLC’s

Large Sized PLC’s

Very large sized

PLC’s

1 to 32 I/O Lines

32 to 128 I/O Lines

128 to 256 I/O Lines

256 to 1024 I/O Lines

I/O Lines more than 1024

AB – PICO

Picosoft

AB

H/W-

S/W-

uLogix

RS-Logix

1000

1200

1500

AB-

SLC-500

5/2/3/4

Siemens

LOGO

Logosoft

Siemens

H/W --

S/W ---

S-7-200

Step-7

S-7-300

Step-7

S-7-400

Step-7

PLC – Brands – (Foreign)

USA-UK Germany Japan Other parts of Europe

Allen Bradley

Rockwell

Automa-tion

Siemens Fanuc

Hitachi

ABB

Honeywell

BOSCH Mitsubishi Alsthom

B & R Automa-tion

Toshiba Schneider

Korea –

L.G.

Cutler - Hammer

PLC – Brands – ( Indian )

• Messung.

• Asia Automation.

• Micro-Verse Automation.

( PLC / DCS )

PLC Programming LanguagesLadder Diagram Programming

Similar to Wiring Diagram

Understood by ALL Brands of PLC’s.

Function Block Diagram

Similar to Boolean Algebra

Understood by Siemens, Fanuc PLc’s

Statement List or Instruction List

Similar to uP Assembly Language

Understood by Siemens PLC’s

Structured Text Similar to BASIC

Understood by Siemens

Sequential Function Chart – SFC

Similar to Flow Charts

Understood by Siemens, Schneider,

Continuous Flow Chart – CFC

Similar to Flow Charts

Fanuc, Mitsubishi PLC’s.

‘C’ Similar to C , C++, VC ++

Siemens, B&R Automation PLC’s

Timers• ON - Delay Timer :-

( Similar to Indian Workers mentality )

• It will become ON –

After _ Time of Input becoming ON.

• It will remain ON –

Only till Input is ON.

• It will become OFF –

[a] As soon as Input becomes OFFOr [b] Immediately in case of Reset Input (Emergency condition).

Timers• OFF - Delay Timer :-

( Similar to Japanese Workers mentality )


As soon as Input becomes ON.


Till Input is ON + ____ additional Time.


[a] After _Time of Input becoming OFF

Or [b] Immediately in case of Reset

Input (Emergency condition).

Timers• Single Pulse or

Edge –Triggered Timer :-

( Similar to Professional American Worker )


As soon as Input becomes ON.


Only for ___ Time, even if Input remains ON or becomes off after triggering it.


[a] Automatically after __ Time (Irrespective of Input condition )Or [b] Immediately in case of Reset Input (Emergency condition).

Timers• Flashing /

Asynchronous Timer :-

( Similar to Local Bus Driver / Conductor mentality )


After ___ Time of Input becoming ON.

• It will continuously become ON & OFF –

But Only till Input is ON.


[a] As soon as Input becomes OFF. Or [b] Immediately in case of Reset Input (Emergency condition).

Counters• Up / Down Counters :-

• Cnt :- Counter Triggering Input (Input to this terminal gives trigger / counting 157 gives a Reset Pulse to the Counter.

• Dir.:- (Direction Input Terminal) If Input to this direction terminal is Off, the Counter Counts in UP Direction Viz.- 1,2,3,4…. And if input to this direction terminal if ON, the Counter Counts in DOWN Direction Viz. – 4,3,2,1.

PLC Basics

* H.M.I. / M.M.I. :-

• H.M.I. – Human Machine Interface• M.M.I. – Man Machine Interface

• It consists of a Display (16*1 / 16*2 / 20*1 / 20*2 / 20*4 Line Alpha-Numeric LCD / LED Display & a User definable Key-Pad with arrow Keys & 4 / 8 / 16 / 32 keys keypad.

• It is used to change the variable in a Control Program.

• It is not used for changing the PLC Program itself. (The Program inside the PLC is normally changed using HHT / HHP / Laptop or a PC.

PLC Basics

•Force / Un-Force :-

• Inputs / Outputs / Timers / Counters / Flags / Registers in a PLC can be either forced to become ON (even when Input is not ON) or can be Unforced to see the effect on Outputs, while checking program after transferring the Program from PC to PLC.

PLC Basics• Retentive / Non-Retentive :-• Inputs / Outputs / Timers / Counters / Flags /

Registers in a PLC can be either Retentive / Non-Retentive.

• If the event is important, retentive functions are to be used.

• If the event is not important, Non-Retentive functions may be used.

• Retentive Functions RETAIN ONLY their OWN STATUS even after Mal-functioning / Power Loss of the PLC.

• Generally out of 100% Inputs / O / T / C / F / R, Only 25% functions are Retentive and the others are Non-Retentive.

• Retentive functions retain their status using Battery-Back-up Memory hence if all the functions are provided as retentive it will result in fast discharge of the Battery used for memory back-up.

PLC Basics

• Up-Loading / Down-Loading

• Generally speaking transfer of Program / DATA from a MASTER (PLC) to a SLAVE (PC) can be called DOWNLOADING.

and transferring the Program / DATA from a SLAVE (PC) to a MASTER (PLC) can be called as UP-LOADING.

PLC Basics

• Sink – Source Concept.

PS – Switch – Lamp – PS

•Source – (To Give)

•Sink – ( To Take away)

Source Sink• w.r.t. Swt. – P.S. Lamp• w.r.t. Lamp - Swt. P.S.

PLC Basics

•OFF-Line Mode

of Operation of a PLC :- During Off-Line Mode, the PLC Scans the status of all the Inputs but it does not send the corresponding Outputs.

•ON-Line Mode

of Operation of a PLC :- During ON-Line Mode, the PLC Scans the status of all the Inputs as well as sends the corresponding Outputs.

• Generally a PLC Program is not changed when the PLC is in ON-Line Mode of Operation to avoid accidents.

PLC Basics

• Memory Cartridges :-

• Normally if the Program in a PLC is required to be changed very often, it is stored in a RAM (Read & Write - Volatile Memory) - Cartridge with Battery-Back-up facility.

• If the Program is not supposed to be changed very often it may be stored in an EPROM Cartridge (Non-Volatile and more reliable than RAM in case of power failures. It can be erased using UV eraser and can be programmed using an EPROM Programmer).

• A combination of RAM + EPROM Cartridge is also available.

PLC Basics

• Text Message Display :-

• In PICO model of AB PLC’s if a message is to be given in case of a certain event, function ‘D’ can be activated to display a 4 Line Message in case of occurrence of an event. For e.g. – In case of an Alarm Condition.

PLC Programming Rules

• Rule – 1 :- (Writing)

• When Writing Programme from the Truth Table, always write the program ONLY for + Ve (1) Output conditions.

• Mark the Input conditions for the +Ve (1) Outputs.

• For +Ve (1) Output –

• If the Input is ‘ 0 ‘ –

take NC contact

• If the Input is ‘ 1 ‘ –

take NO contact


• Rule – 2 :- (Checking)• When Checking Programme

from the Truth Table –

• If the Input is ‘ 0 ‘ – don’t operate the Input, keep it as it is. i.e.

If it is initially NO - Keep it NO. If it is initially NC - Keep it NC. And then give voltage to see the

effect on the Output.

• If the Input is ‘ 1 ‘ – Operate the Input, i.e. Make it Opposite –

If it is initially NO - Make it NC. If it is initially NC - Make it NO.

And then give voltage to see the effect on the Output.


• Rule – 3 :-

• When the Output is same but the Inputs are different – make the Inputs Parallel and then connect them to the corresponding Output.

• ‘n’ numbers of Inputs can be connected in Series ( limited only by the Model of PLC being used ).

• Similarly ‘n’ numbers of Inputs can be connected in Parallel ( without any limitation. )


• Rule – 4 :-

• With the same Input if two or more Outputs are to be made ON, the Outputs cannot be connected either in Series or in Parallel.

Separate lines have to be written for driving different Outputs through same Input.


• Rule – 5 :-

•If NC contact is used in a rung, one can use a Hold-ON contact in that rung, but Set / Reset cannot be used in that rung for the Output / Coil.


•Rule – 6 :-

• If Set / Reset is to be used fro an Output, in a rung, ‘NC’ contact cannot be used in that rung. Only ‘NO’ contact can be used for Output Set / Reset.

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