This document summarizes a presentation on programmable logic controllers (PLCs). It defines a PLC as a type of computer used in commercial and industrial control that monitors inputs, makes decisions based on a stored program, and controls outputs to automate processes. It outlines the main advantages of PLCs, describes the different types and basic architecture of PLCs including the processor, memory, I/O, and programming devices. It also explains the PLC scan process and use of ladder logic diagrams for programming. Finally, it lists some common PLC applications in manufacturing and major PLC manufacturers.

1. a
Summer Training
presentation
on
PLC: ProgrammableLogic Controller
undertaken
at
M.S.M.E
(Ministry of Micro Small & Medium Enterprises)
By: Ankit kaim
(ECE-II)

2. Contents
1) Introduction
2) Advantages of PLCs
3) Types of PLCs
4) PLC Architecture
5) PLC Scan
6) Ladder Logic Diagram
7) PLCs Applications & Manufacturers

3. Introduction
A Programmable Logic Controller (PLC), also
referred to as programmable controller, is the name
given to a type of computer commonly used in
commercial and industrial control applications. PLCs
differ from office computers in the types of tasks that
they perform and the hardware and software they
require to perform these tasks. While the specific
applications vary widely, all PLCs monitor inputs and
other variable values, make decisions based on a stored
program, and control outputs to automate a process or
machine.

4. advantages of plc
 The program can be entered by anyone who has
some basic knowledge of PLC.
 Designed for an electrically noisy environment no
extra filtering is required.
 They are smaller, faster and more reliable than
hardwired systems.
 Drum switches, timers, counters all are
implemented using software programs.
 Easier and faster to make changes.
 Applications can be duplicated faster and less
expensively.

5. Types of PLC
Programming logic controller (PLCs) has several types: Based on the size of the
module and it can be classified according to is working as :
(I) Micro PLCs
(II) Medium PLCs
(III) Large PLCs

6. PLCArchitecture
It contains:
(I) A processor
(II) Memory chip
(III) Inputs and Outputs
(IV) Programming devices
Outputs to Plant
(Bulbs, Motor Starters, Solenoids, Valves etc)
Inputs from Plant
(Push Buttons, Sensors, Toggle Switches etc)
PLC
Output Interface
Processor Memory
Input Interface
Programmer
Keypad &
Display

7. The PLC program is executed as part of a
repetitive process referred to as a scan. A
PLC scan starts with the CPU reading the
status of inputs. The application program
is executed using the status of the inputs.
Once the program is completed, the CPU
performs internal diagnostics and
communication tasks. The scan cycle ends
by updating the outputs, then starts over.
The cycle time depends on the size of the
program, the number of I/O, and the
amount of communication required.
PLCScan

8. Ladder logic (LAD) is one programming
language used with PLCs. Ladder logic uses
components that resemble elements used in a
line diagram format to describe hard-wired
control. The left vertical line of a ladder logic
diagram represents the power or energized
conductor. The output element or instruction
represents the neutral or return path of the
circuit. The right vertical line, which represents
the return path on a hard-wired control line
diagram, is omitted. Ladder logic diagrams are
read from left-to-right, top-to-bottom.
Ladder Logic Diagram

9. PLCAPPLICATIONS & MANUFACTURERS
Applications
 CNC machines
 Conveyors
 Heat treatment
 Welding & Painting
 Assembly machines
 Packaging
Manufacturers
 Allen Bradley
 Siemens
 Saticon
 Square D
 Mitsubishi
 Modicon