PLCProgrammable Logic Controller

Prepared by

Tahmid Rongon and Ahad hossain

CONTENT History What is PLC ? Why PLC ? Architecture of a PLC  Components Programing Language

Of PLC Ladder Logic Programming Example Block Diagram

Our Project Circuit Project video Advantage Disadvantage Area of Applications Conclusion Summery References

HISTORY PLC was introduced in late 1960’s. First commercial and successful programmable

logic controllers was designed and developed by modicon as a relay replacer for General Motors.

Earlier , it was a machine with thousand of electronic parts.

Later in late 1970’s the microprocessor became and greatly enhanced the role of PLC permitting it to evolve from simply relay to the sophisticated system as it is today.

WHAT IS PLC?

The automation of many different processes , such as controlling machines or factory assembly lines, is done through

the use of small computers called a programmable logic controllers(PLCs).

Programmable Logic Controller (PLC) is an industrial computer that monitors inputs, makes decisions based on its program and controls outputs to automate a process or machine.

WHY PLC? To reduce human efforts . To get maximum efficiency

from machine and control them with human logic .

To reduce complex circuitry of entire system .

To eliminate the high costs associated with inflexible, relay-controlled systems.

ARCHITECTURE OF A PLC 

INPUT

Power Supply

PLC OUTPUT

MEMORY INTERFACE

COMPONENTS

COMPONENTS INPUT MODULES accepts and converts signals from sensors

into a logic signal Ex. : Switches, Pushbuttons. OUTPUT MODULES that convert control instructions a signal

that can be used by actuators. Ex. : lamps, alarm.

INPUT (PUSH BUTTON ) PLC OUTPUT (INDICATOR LIGHT)

PROGRAMING LANGUAGE OF PLC Most common languages

encountered in PLC programming are:

1) Ladder Logic. 2) Functional Block Diagram. 3) Sequential Function Chart. 4) Boolean mnemonics.

LADDER LOGIC The ladder logic is the oldest programming

language for PLC. It is well suited to express Combinational logic. The main ladder logic symbols represent the

elements :

PROGRAMMING EXAMPLE:Ladder Logic Program for Start/Stop of Motor :

BLOCK DIAGRAM OF OUR PROJECTLiquid-1 Liquid-2

MixtureTank

DumpTank

OUR PROJECT Automatic liquid mixing machine for industrial use.

CIRCUITNeutral Mood

CIRCUITLiquid Coming Mood

CIRCUITMotor Starting Mood

CIRCUITDump Mood

AREA OF APPLICATION Machine controls

AREA OF APPLICATION Machine controls Food/Beverage processing

AREA OF APPLICATION Machine controls Food/Beverage processing Car park & Train station control system.

AREA OF APPLICATION Machine controls Food/Beverage processing Car park & Train station

control system. Manufacturing, Packaging,

Palletizing

AREA OF APPLICATION Machine controls Food/Beverage processing Car park & Train station

control system. Manufacturing, Packaging,

Palletizing Material handling

AREA OF APPLICATION Machine controls Food/Beverage processing Car park & Train station

control system. Manufacturing Packaging, Palletizing Material handling Textile,Travel,printing Industry similar Sequential task as well as

Process control etc.

ADVANTAGES very Fast , High speed of operation. Small physical size, shorter project time Reduced space. inputs and outputs already inside the controller. Low power consumption designed to withstand vibrations,temperature,humidity,noise

etc. Easy maintenance due to modular assembly and flexibility Improves Productivity Improves Quality

DISADVANTAGESInitial Costs Are HighPLC hold only one copy of programmesPLC Devices Are ProprietaryUnemployment Rate IncreasesThere's difficulty with changes or replacements.When a problem occurs, hold-up time is

indefinite, usually long, It's always difficult to find errors.

CONCLUSIONThe PLC have in recent years experienced an

unprecedented growth as universal element in industrial automation .

It can be effectively used in applications ranging from simple control like replacing a small number of relays to complex automation problems.

Today the PLCs are used for control & automation job in a single machine & it increases up to full automation of manufacturing / testing process in a factory.

SUMMARY In this presentation we have discussed about:What is PLC.Why we use PLC.Description of PLC.A project over PLC.Area of application.Advantages & disadvantages

REFERENCESWikipediaIndustrial Control Handbook, Industrial Press Inc.W. Bolton, Programmable Logic Controllers, Fifth

Edition. Maher, Michael J. Real-Time Control and

Communications.

ANY QUESTION