Before PLCs, control systems used relay logic which lacked flexibility for process changes and expansion. The first commercial and successful PLC was designed and developed by Modicon in the late 1960s as a relay replacement for General Motors. A PLC is an industrial solid-state computer that performs logic functions to control machines and processes. It reads input signals from sensors, processes the data, and provides output signals to control devices like motors, valves, and relays. PLCs were developed to replace mechanical relay-based systems and offer more flexibility through reprogramming compared to hardwired relay panels.

1. History of PLC

2. Before the Programmable controller
• Control system implemented using relay controller.
• Lack of flexibilty for process changes or expansion
• Troubleshooting: Five hours to find and five minutes to fix,it.

3. History of PLC
• Before The days of the PLC The only way to control mahinery was
through the use of relays.
• PLC was Introduction in late 1960's
• First Commorercial and successful programmable logic controllers
was designed and devloped by modicon as a relay replacer for
general motors.
• Earlier it was a machine with thousands of electronic
parts.

4. What is a PLC ?

5. Why PLC Use ?
PLC
OUTPUT
PUSH
BUTTON
INPUT
Motor
A PLC is a solid state/Computerized industrial computer that
performs discrete( 0 , 1 ) or sequential logic in a factory
environment its called PLC
PLC:- Programmable Logic control

6. What Is PLC..
What is Sequential:- it means when you press a switch
then start light one by one.
What is Discrete:- It means when you press a switch then
start all light.
It was originally developed to replace mechanical
relay,Timer,Counters.PLC are used successfully to
execute complicated control operations in a plant.

7. Application
Process Automation Plants (e.g. mining, oil &gas)

8. Application
Glass Industry

9. Application
 Paper Industry

10. Application
 Cement Manufacturing

11. Application
 In boilers – Thermal Power Plants

12.  Car Manufacturing Plants..

13. Advantages
 Reliability
 Flexibility in programming and reprogramming
 Cost effective for controlling complex systems.
 Small Physical size, shorter project time.
 High Speed of operation.
 Ability to communicate With computer systems in the plant.
 Ease of maintenance / troubleshooting.
 Reduced space.
 Energy Saving

14. Disadvantages
 PLC device are proprietor it means that part or software of one
manufacturer can't be used in combination with parts of
another manufacturer.
 Limited design and cost option.
 Fixed Circuit operations.
 PLCs manufacturers offer only closed architectures.

15. Block Diagram of PLC
&
Components of PLC

16. Block Diagram of PLC
Programming
Communication
Device
Central
Processing
Unit (CPU)
Memory
Program
Power Supply
INPUT
Circuit
(Field Area)
OUTPUT
Circuit
(Field Area)
Optical
Isolation
Optical
Isolation

17. Components of PLC
 CPU(Central Processing unit)
 INPUT Module
 OUTPUT Module
 Power Supply
 Programming Device

18. Components of PLC
 CUP(Central Processing unit):-
• CPU module has a central processor, ROM & RAM memory.
• ROM memory includes operating system, driver and application
program. RAM memory is used to store programs and data.
• CPU is the brain of PLC with an octal or hexagonal
microprocessor. Being a microprocessor based CPU, it replaces
timers, relays, and counters.
• Two types of processors as a single bit or word processor can be
incorporated with a PLC.
• CPU reads the input data from sensors, process it and finally the
command to controlling devices.

19. Components of PLC
CPU consist of following blocks
• ALU(Arithmetic Logic Unit)
• Programming memory.
• Process image memory.
• Internal timer and counter.
• Flags or status bit filter.
• CPU required 5v.

20. Components of PLC
INPUT MODULE:-
• Input module act as an interface between the field control input and the CPU
voltage/current generated by the sensors,transducer,limit switch,push
button,etc.
• Input module converts the field signal into standard control signal for processing
by the PLC
• The input module of PLC does four main functions.
1. Input module interface receives the signal from process devices at 220 V AC
2. Converts the input signal to 5 V DC that can be used by PLC
3. Isolator block is used to isolate/prevent PLC from undergoing fluctuation
4. After which the signal is sent to the output end i.e the PLC

21. Components of PLC
OUTPUT Module:-
 Output Module acts as link between the CPU and the output devices located in
the field devices could be relays,contaector,lamps,motorized actuators, solenoid
valves,etc.These device actually control the process.

22. Power Supply:-
 This module is used to provide the required power to the whole
PLC system.
 It converts the available AC power to DC power which is required
by the CPU and I/O module. PLC generally works on 24V DC
supply and Rack type PLC work on 230/220Vac. Few PLC uses
an isolated power supply.

23. Components of PLC
Programming Device:-
 A personal computer(PC) is the
most commonly used programming
device.The software allows users to
create,edit,store and troubleshoot
programs.
 This is show pitchure id
programming cable Rs-232 and
Ethernet cabl for Programming
cable
RS-232 Cable
Ethernet Cable

24. Next Video Topic
 Types of PLC.

25. Types OF PLC

26. Types of PLC
Types of PLC
Moduler
PLC
Compact
PLC

27. Moduler Type PLC
• This type of PLC permits
multiple expansion through
“modules”, hence referred to
as Modular PLC.
• I/O components can be
increased.
• It is easier to use because
each component is
independent of each other.
A Moduler TypePLC

28. Compact Type PLC
Within a single case, there would be many modules.
It has a fixed number of I/O modules and external I/O cards.
So, it does not have the capability to expand the modules.
Every input and output would be decided by the manufacturer.
PLC are divided into three types based on output namely Relay
output, Transistor output, and Triac Output PLC.
The relay output type is best suited for both AC and DC output
devices. Transistor output type PLC uses switching operations
and used inside microprocessors.

29. PLC
INPUTs and OUTPUTs
Module

30. Here Is Two Types Of Input / Output Module.
1. Analog Module:- Analog Input and out module work it's shoud
be 0v ~ 10v , 4ma ~ 20ma , -20ma ~ 20ma.
2. Digital Module:- Digital Input and output module work it's
should be '0' and '1'.
Digtal
Module
Analog
Module

31. Signal of Inputs ans Outputs module
Digital Type Analog Type
Input Output
• Push Buttons
• Switch
• Limit Switch
• Proximity sensor
• Photo Sensors
• Relay
• Contactors
• Lamps
• Alarm Hotters
• LED
• Solinoid Valved
• Coils
Input Output
• RTD
(Temp Sensor)
• Thermocouple
• Transducers
• Transmitter
• Drive
(Analog
Port)
• Actuator
• Valve Position

32. PLC Programming
Languages

33. PLC Programming Languages
Ladder Diagram (LD)
Structured Text (ST)
Sequential Function
Chart (SFC)
Function Block
Diagram (FBD)
Instruction List (IL)

34. Ladder Diagram (LD)
Ladder Logic
 Ladder logic is the simplest from of PLC programming It is also known as
“Relay logic”.
 The Relay contacts used in relay controlled systems are represented using
ladder logic.we check example.
In the mentioned example, two
pushbuttons are used to control the same
lamp load. When any one of the switches
is closed, the lamp will glow.
The two horizontal lines are called rungs
and two vertical lines are called rails.
Every rung forms the electrical
connectivity between Positive rail (P) and
Negative rail (N). This allows the current
to flow between input and output devices.

35. Function Block Diagram
 Functional Block Diagram (FBD) is a simple and
graphical method to program multiple functions in
PLC.
 PLC Open has described using FBD in the
standard IEC 61131-3.
A function block is a program instruction unit that,
when executed, yields one or more output values.It
is represented by a block as shown fig.
It is represented as a rectangular block with inputs
entering on left and output lines leaving at the
right.
It gives a relation between the state of input and
output

36. PLC SCAN TIME

37. PLC SCAN TIME BASICS CONCEPT
PLC SCAN CYCLE
INPUT SIGNAL LOGIC SOLVE OUTPUT SIGNAL
Input Read NO,NC,OUTPUT
COIL,TMR,CNT
Output Write
PLC Scan Time
LOOP
LOOP
INPUT Signal
Read +
LOGIC
SOLVE +
OUTPUT
Write =
PLC SCAN
TIME

38. PLC SCAN TIME
Read
Input
Logic Solve
Update
Output
PLC Scan Cycle
• What is a ScanTime:- It is
the time taken PLC to read
INPUT process the logic
Solve and update OUTPUT
in one cycle its called Scan
Time.
• PLC SCAN Time Depends on
No.of inputs,length of
logic,and No.of Outputs.
• This Process in LOOP
• PLC Scan time very between
0.1ms to 50ms.

39. PLC SCAN TIME
NO.of Inputs
Length of Logic
 Analog module each channel taken 3ms.
 PLC Scan Time Depands in below three parts
No.of Outputs
Scan time depands
on this three parts

40. PLC Fundamental
wiring
and Sink/Source

41. PLC Fundamantel
• What Is PLC ?????
Programmable Logic Controller
Hardware
- Ladder Logic
- FBD
- SFC
Reprogramming
• Let's come next page how to use thsi systemparcticaly

42. PLC Fundamantel
• Example:- Water Level Control
INPUT OUTPUT
Processor
PLC
80%
60%
40%
20%
0%
NO/OFF
Valve
Automatic
Manualy
Valve
Tank
• This System INPUT is User level
requirment like 50% ,80% ,20%.
• And Output is solenoid valve
• This All system runing in
processor means this work on
PLC.so this is functioning of PLC.
• This Fundamantel of PLC...

43. PLC INPUT Wiring
What is Sink and Source:-Sink and source refer to the direction
of current flow between an I/O point on an I/O module and the connected
device. It is only relevant for DC circuits with positive and negative
polarities since current flows both directions in an AC circuit.more
explain..
S/S
X0
X1
X2
X3
INPUT
S/S
X0
0V
24V
24V
0V
_
+
_
+
This Circuit Call Opto
couplor
• If input 24v
then we gives
S/S 0V so it will
be depand on
INPUT

44. PLC INPUT Wiring
S/S
X0
X1
X2
X3
INPUT
24V
0V
 If your are gives 24v in
S/S pin and it should be
gives in X0 pin 0V.

45. PLC INPUT Wirnig
Here Is Three types of INPUT sensor.
PNP Sensor
NPN Sensor
Universal Sensor
24V
0V
24V or 0V
Explain Each Sensor Details

46. PLC INPUT Wiring
NPN Proximatary Sensor.
24V
0V
S/S
X1
24V
3 Wire NPN
Sensor

47. PLC INPUT Wiring
PNP Proximatary Sensor.
24V
0V
S/S
X1
0V
3 Wire PNP
Sensor

48. PLC INPUT Wiring
Universal Proximatary Sensor.
24v
0v
24v
0v

49. PLC OUTPUT Wiring
Hear Is Two Types Of PLC output.
Transistor Type
Output
Relay Type
Output
 Transistor type PLC output capcity 0.1A as per PLC
configuration so we can not use havy load out put.
 If you want to use havy load output in transistor type
plc you can use external rely then we use havy load
output.
 Transistor type PLC mostly use in high speed
application.e.g Servo motor,steppar motor etc.
 Relay Type PLC have 1A to 10A capacity so wecan
directly use havy load output.
 its was used in genral purpos
motor,contector,solenoid valve application

50. PLC OUTPUT Wiring
0V
LAMP 24V
0v
This Lap taks 0.1amp
Transister Type PLC OUTPUT.
C0
Y0
C1
Y1
0V
This load 4Amp
This relay 10Amp
24V

51. PLC OUTPUT Wiring
0V
LAMP 24V
0v
This Lap taks 0.1amp
Relay Type PLC OUTPUT.
C0
Y0
C1
Y1
0V
24V
This load 4Amp

52. PLC Wiring
and
Programming

53. PLC Wirning and Programming
From PLC Wiring to pogramming !!

54. From PLC Wiring to pogramming
S/S
X0
X1
X2
C
Y0
Y1
Y2
INPUT OUTPUT
24V
0V
0V
24V
This is Software Part
This Is a Hardware Part
X0
X1
Y0
Y1
This Is Normally
Open Contact
Output
Coil

55. PLC Relay Latching
and Unlatching

56. PLC Relay Lathing and Unlatching
Relay
 Relay Configuration.
IEC255
5A 250VAC~
5A 240VAC
5A 28Vdc
This Relay Have a 10Amps
capacity.

57. PLC Relay Lathing and Unlatching
24V 0V
Relay
NO Switch
NO Contact
This is Latching
13 14
5 6
Relay Common
Relay NO

58. 24V 0V
Relay
NO Switch
NO Contact
PLC Relay Lathing and Unlatching
This is UnLatching
NC Switch
5 6
13 14

59. `
PLC Relay Lathing and Unlatching
Relay Important.
1. Check Coil rating:- 5 Vdc
12 Vdc
24 Vdc
110 Vac
240 Vac
2. Contact rating:-10Amp
Let's We can chacke example why we alwasy chacke contact
rating.

60. PLC Relay Lathing and Unlatching
• Example:-
L
N
MOTOR
220v
Motor
5Amp
singal
pahse
motor
10Amps
relay
NO
C

61. PLC Relay Lathing and Unlatching
Motor
Object
• Example:-Latch motor using switch Unlatch its using
sensor.
Sensor
ON OFF
ON / OFF
Switch
Conveyor
Let's See we chcek on circuit

62. PLC Relay Lathing and Unlatching
24V 0V
R2
Relay
NO Switch
13 14
5 6
PNP
Sensor
24V 0V
24V
R2
Relay
R2