PROGRAMMABLE LOGIC CONTROLLERS

Workshop on
“PLC Basics & Programming”
Prepared by- Rahul N Deshmukh
Asst Professor
E&TC Dept

Content-
• History
• Basics of Programmable Logic Controller (PLC)
• PLC hardware & software
• Inputs/Outputs
• PLC Programming Languages
• What is an Automation?
• Supervisory Control & Data Acquisition System (SCADA)
Rahul N Deshmukh E&TC Dept
SSBT's COET Bambhori Jalgaon

History-
In 1968, a group of engineers from General Motors developed the
concept of PLC with an initial specification. The PLC must be:
i . Easy to program.
ii. Not need rewiring the control system if change
the program.
iii. Smaller in size, cheaper and high reliability.
iv. simple construction and low maintenance
v. Cost- competitive

Development -
• Manual
• Contactor & relay based
• Logic gates
• Microcontroller based
• Programmable Logic Controllers
• Touchscreen & Wireless PLC’s

Advantages of PLC-
• Less wiring.
• Wiring between devices and relay contacts are done in the
PLC program.
• Easier and faster to make changes.
• Trouble shooting aids make programming easier and reduce
downtime.
• Reliable components make these likely to operate for years
before failure.

PLC Size-
• 1. SMALL - it covers units with up to 128 I/O’s and
memories up to 2 Kbytes.
- these PLC’s are capable of providing simple to
advance levels or machine controls.
• 2. MEDIUM - have up to 2048 I/O’s and memories up to 32
Kbytes.
• 3. LARGE - the most sophisticated units of the PLC family.
They have up to 8192 I/O’s and memories up to
750 Kbytes.
- can control individual production processes or
entire plant.

Applications-
• Manufacturing / Machining
• Food / Beverage
• Metals
• Power
• Mining
• Petrochemical / Chemical

CPU
The Basic Block
Inputs Outputs
What is PLC?

What is PLC?

PLC Construction-
Compact PLC Modular PLC

Some PLC’s-
• 80% market is covered by
Siemens PLC
• Modicon is a first PLC
invented in france
• Messung & Delta are India
made PLC’s
Allen
Bradley
Siemens
Modicon Mitsubishi
Schneider
Electric
Messung

Block Diagram of PLC-
PROCESSOR
POWER
SUPPLY
I M
N O
P D
U U
T L
E
O M
U O
T D
P U
U L
T E
PROGRAMMING
DEVICE
From
SENSORS
Pushbuttons,
contacts,
limit switches,
etc.
To
OUTPUT
Solenoids,
contactors,
alarms
etc.

Functional Interaction of PLC system-

Rack & Rail System in PLC-

What is PLC?
network
digital
inputs
digital
outputs
analog inputs /
outputs

Siemens S7-200 PLC Configuration-

Siemens S7-200 CPU-

Siemens PLC expansion Module-

Siemens PLC Status Indicator-

Siemens PLC CPU Internal Circuitry-

Digital Input Circuitry-

Physical Wiring Input Side-
AC input module
DC input module

DC Inputs (Source/Sink)-
Sinking input module/sourcing input device
Sourcing input module/sinking input device

Digital Outputs-

Digital Output Logic-
Rahul N Deshmukh E&TC Dept SSBT's COET Bambhori Jalgaon

Physical wiring Output Side-
Rahul N Deshmukh E&TC Dept SSBT's
COET Bambhori Jalgaon

Analog Input-

Physical Wiring PLC analog Input-

Analog Input example-

Analog Output-

Physical Wiring PLC analog Output-

Analog Output example-

• Switches and Pushbuttons
• Sensing Devices
• Limit Switches
• Photoelectric Sensors
• Proximity Sensors
• Condition Sensors
• Pressure Switches
• Level Switches
• Temperature Switches
• Vacuum Switches
• Float Switches
• Encoders
What are inputs?

• Valves
• Motor Starters
• Solenoids
• Actuators
• Control Relays
• Horns & Alarms
• Stack Lights
• Fans
• Counter/Totalizer
• Pumps
• Printers
What are outputs?

Contactor & Relay-
Contactor Relay

Input Connection-

Output Connection-

PLC Scan Cycle-

Allen Bradley PLC
(America)
Siemens PLC
(Germany)

Modicon PLC
(France)
Crouzet PLC
GE Fanuc (Japan
& America)

• Delta PLC
(India)
• Messung
PLC (India)
• Mitsubishi
(Japan)

S1
S2
K1
S1 S2
PLC
K1
Hardwire PLC
0 V
24 VDC
K1
L
N

S7-300 PLC Wiring Diagram

Types of Programming Software Languages
• Ladder Logic (LL)
• IEC Format
• Function Block Diagram (FBD)
• Structured Text (ST)
• Instruction List (IL)
• Ladder Diagram (LD)
• Sequential Function Chart (SFC) - also known as “Grafcet”

Ladder Logic
Read / Conditional
Instructions
Write / Control
Instructions
| | |/|
| | |/|
| |
| | |/| ( )
| |
| |
Start (Rung #1)
End (Rung #4)
( )
( )
( )
Inputs Outputs

Siemens S7-200 I/O Configuration-

Addressing System Input & Output-
Input-
Output-

Function Block Diagram (FBD)

Structured Text (ST)

Instruction List (IL)

Ladder Diagram (LD)

Sequential Function Chart (SFC)

PLC Software View

PLC Program example-
eg- Lamp Glows when input switch is activated

eg- to start & stop the motor

eg- to stat the motor

Latching Condition-

PLC Programming
(Siemens S7-300)

Hardware-Siemens S7-300
Software-Simatic Manager
-80% market occupied by Siemens
-STEP-5 & STEP-7 available with Siemens
-I/O Capacity (S7-200 )-32 analog & 256 digital
(S7-300)-256 analog & 1024 digital
(S7-400)-1500 analog & 128000 digital

Hardware-Siemens S7-300
Software-Simatic Manager
Steps for creating programming window (OB-Organization
Block)
-Install Simatic Manager V-5.5 Software
-for (Simulation) install PLCSim v-5.1

Addressing System for S7-300

• Automation is a delegation of human control to the machine
• For e.g-

PLC Implementation-

PROGRAMMABLE LOGIC CONTROLLERS

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