PROGRAMMABLE LOGICAL CONTROLLER

(PLC)

PRESENTED BY:-

Mrs. Bindu ThakralAnd

Jaidev Singh

INDEX Introduction PLC Basics PLC and Controls History Advantages of PLCs PLC Operation Comparison to Relay Logic Applications Conclusion

INTRODUCTION

Programmable Logic Control, or PLC as it is universally called, is the ‘work horse’ of industrial automation.

A PLC is used to control, time and regulate the sequence.

Many production processes are controlled using PLCs like – metal machining sequences, product assembly lines and batch chemical processes.

PLC BASICS Programmable Logic Controllers (PLCs), also

referred to as programmable controllers, are in the computer family. They are used in commercial and industrial applications

BASIC PLC OPERATION PLCs consist of input modules or points, a Central

Processing Unit (CPU), and output modules or points.

BASIC PLC OPERATION (CONT..) Pushbuttons (sensors), in this simple example,

connected to PLC inputs, can be used to start and stop a motor connected to a PLC through a motor starter (actuator).

PLC AND CONTROLS HISTORY Large amount of work required connecting

wires

Difficulty with changes or replacements Difficulty in finding errors; requiring

skillful/experienced work force

When a problem occurs, hold-up time is indefinite, usually long

o Too many moving parts

ADVANTAGES OF PLCS Number of wires reduced

by approximately 80%

Fast and easy error detection.

No change in wiring to change program

Needs fewer spare parts Cheaper when large

number of I/O instruments are needed

Less moving parts Compact Cost effective for

installation/maintenance

COMPONENTS

CPU

Memory Areas

Circuits to input oroutput data

Basically, a big box of math

SPECIFIC COMPONENTS

•Input Relays (contacts)

•Output Relays (coils)

•Data Storage

•Internal Utility Relays

•Counters

•Timers

PLC OPERATION

Continually scans ladder diagram

Consists of 3 important steps

PLC SCAN:-

LADDER LOGIC

•Definition

•Comparison to RelayLogic

DEFINITION One form of drawing

electrical logic schematics

Very popular for PLCs

Originally invented for use with relays

COMPARISON TO RELAY LOGIC

First used for technicians,electricians &engineers

Still first choice for most technicians, electricians, etc.

RELAY LOGIC

LADDER LOGIC

•“Jog” function added to previous relay circuit

•1 component added

•3 wires added

•Two status indicators added •6 additional wires

PROGRAMMING

Basics – NO/NC Contacts/Coils AND & OR Gates Timers and Counters Building a PLC Ladder Logic

Programming

BASICS NO Contact

NO Coil (Output)

NC Contact

NC Coil (Output)

AND GATE

OR GATE

TIMERS

Very simple concept, it times

2 basic types, on- delay and off-delay

Still sends logic as its output

COUNTERS Counts number of

times a lever ispulled, a button ispushed, etc.

3 types Up Counter Down Counter Up-Down Counter

BUILDING A PLC/LADDER LOGIC PROGRAM

To illustrate, will start in relay logic, convert to ladder logic at end

Will need to remove/replace some components

Relay Logic converted to Ladder Logic Diagram Much fewer hard wired components Double Pole Pushbutton for Jog switched to

Single Pole Instead of motor relays, PLC just checks state of

motor output

APPLICATIONS:- Manufacturing Industry

Food Industry

Textile Industry

Plastics Industry

And many other……

CONCLUSION :- We can conclude that

A lot of wiring work have been reduced

Error detection has became fast and easy

Size has been reduced

Cost effective for installation/maintenance

THANKSQ&A