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