Having Information Regarding "PLC"

1. (Programmable Logic Controllers)
PLC

2.  Contents
Introduction
Historical Background
PLC function
PLC vs Computer
Basic components of PLC
Ladder logic diagram
Advantages
Conclusion
References

3.  Introduction
A digitally operating electronic device which uses a
programmable 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 input/output
modules, various types of machines or processes.
PLC (Programmable Logic Controller)

4. Historical Background
1968  Programmable concept developed
1969  Hardware CPU controller, with logic
instructions.
1974  Use of several (multi) processors within a
PLC - timers and counters; arithmetic
operations.
1976  Remote input/output systems introduced
1977  Microprocessors - based PLC introduced

5. 1980  Intelligent I/O modules developed
Enhanced communications facilities
Enhanced software features.
1983  Low - cost small PLC’s introduced.
1985 on  Networking of all levels of PLC, computer
and machine using SCADA software.

6.  Birth of PLC
Problem faced before the emergence of PLC:-
Lack of flexibility in operation.
Problem inTroubleshooting.
 PLC Function
 A PLC performs the functions of
conventional relays, timers, counters.

7. V/S
Computer
PLC

8.  Basic Components
 There are six basic components in a PLC
system:
A PLC processor, or controller
I/O (Input /Output) modules
Chassis or backplane
Power supply
Programming software
A network interface

9.  Processor or Controller
Stores the control program and data in its
memory.
Reads the status of connected input and
output devices.
Executes the control program.
Commands connected outputs to change
state based on program execution.

10.  Input Modules
Physically connect to field devices
• Input modules convert electrical signals
coming from input field devices to electrical
signals that the processor can understand.
 Input modules interface directly to devices
such as switches and temperature sensors.

11.  Output Modules
Output modules interface directly to output
devices such as motor starters and lights.
Output modules take digital signals from the
Processor and convert them to electrical
signals.
Output modules take a signal from processor
and convert it to a signal that a field device
needs to operate.

12. All PLCs need some method of
communication between the controller, I/O
and communications modules.
 Chassis/Backplane

13.  Power supply
A power supply is needed to provide power to the
PLC and any other modules.
 Programming Software
Software that runs on a PC is required to configure
and program PLCs.

14.  Network Interface
Most PLCs have the ability to communicate
with other devices, it lets an operator to enter
commands into the PLC, or I/O devices that is
located in a remote location from the PLC.

15. Input contacts(switches, relays))
Output loads(alarms, lights)
Logical inversion(NOT)
Logical AND operation
Logical OR operation
 Ladder logic diagram

16.  Advantages
 More flexibility
Less space, more compact
Higher reliability (less mechanical parts)
Modular, can be easily connected to
computer systems and to hardware

17.  CONCLUSION
Now a days PLC’s are used in large scale
in the industries due to it’s compact size,
higher reliability and faster response.

18.  References
Wikipedia.
Books:-
Programmable logic controller (William Bolton)
Programmable Logic Controller (Gleen j. sartori)

19. Thank you…