Automation ll

UNIVERSIDAD AUTONOMA DE TAMAULIPAS
PINTOR CASTILLO SALVADOR
MARCELO MARTINEZ RAUL
FAZ TORRES HILARIO
PEREZ MUÑOZ JOSÉ
JORGE GUSTAVO SILVA DE LA CRUZ
INGENIERO.

INTRODUCTION
THROUGHOUT THE HISTORY OF THE HUMAN BEING, MAN HAS
BEEN CREATING TOOLS AND DEVICES THAT HELP HIM PERFORM
TASKS THAT MAY BE COMPLICATED AND / OR DANGEROUS FOR
HIM; AND THUS, GREAT INVENTIONS OF MACHINES WERE
REACHED THAT HAVE SEVERAL ADVANTAGES AMONG THEM:
MAXIMIZING COSTS, REDUCING RISKS FOR WORKERS,
REDUCING OPERATING TIMES, SERIAL PRODUCTION, ETC.

What is
a PLC?
A PROGRAMMABLE LOGIC CONTROLLER
(PLC) is an industrial computer control
system that continuously monitors the state
of input devices and makes decisions based
upon a custom program to control the state
of output devices.
Almost any production line, machine
function, or process can be greatly enhanced
using this type of control system. However,
the biggest benefit in using a PLC is the
ability to change and replicate the operation
or process while collecting and
communicating vital information.
Another advantage of a PLC system is that it
is modular. That is, you can mix and match
the types of Input and Output devices to
best suit your application.
HISTORY OF PLCS
The first Programmable Logic Controllers
were designed and developed by Modicon
as a relay re-placer for GM and Landis.
These controllers eliminated the need
for rewiring and adding additional
hardware for each new configuration of
logic.
The new system drastically increased the
functionality of the controls while
reducing the cabinet space that housed
the logic.
The first PLC, model 084, was invented
by Dick Morley in 1969
The first commercial successful PLC, the
184, was introduced in 1973 and was
designed by Michael Greenberg.
WHAT IS INSIDE A PLC?
The Central Processing Unit, the
CPU, contains an internal program
that tells the PLC how to perform
the following functions:
Execute the Control Instructions
contained in the User's Programs.
This program is stored in
"nonvolatile" memory, meaning
that the program will not be lost
if power is removed
Communicate with other devices,
which can include I/O Devices,
Programming Devices, Networks,
and even other PLCs.
Perform Housekeeping activities
such as Communications, Internal
Diagnostics, etc.
HOW DOES A PLC OPERATE?
There are four basic steps in the
operation of all PLCs; Input Scan,
Program Scan, Output Scan, and
Housekeeping. These steps
continually take place in a repeating
loop.
Four Steps In The PLC Operations
WHAT PROGRAMMING LANGUAGE IS USED TO PROGRAM A PLC?
While Ladder Logic is the most commonly used PLC programming language, it is not
the only one. The following table lists of some of languages that are used to program
a PLC.
Ladder Diagram (LD) Traditional ladder logic is graphical programming language.
Initially programmed with simple contacts that simulated the opening and closing of
relays, Ladder Logic programming has been expanded to include such functions as
counters, timers, shift registers, and math operation.
1.) Input Scan
Detects the state of all input
devices that are connected to
the PLC
2.) Program Scan
Executes the user created
program logic
3.) Output Scan
Energizes or de-energize all
output devices that are
connected to the PLC.
4.) Housekeeping
This step includes
communications with
programming terminals,
internal diagnostics, etc...
Pintor Castillo Salvador Page 03

DICIEMBRE DE 2016
Architecture of PLC
ARCHITECTURE OF PLC
CPU (Central Processing Unit):
PLC system contains of the following parts
Power supply
CPU
Input modules
Output modules
Programming Device
Power Supply :
This module supplies power to the CPU,
input and output modules. It can be built
into the PLC or be an external unit.
Common voltage levels required by the PLC
(with and without the power supply) are
24Vdc, 110Vac, 220Vac.
This module is considered as the brain of
the PLC system and where
ladder logic is stored and processed.
•The memory contains the data and the
ladder program.
It contains an “Executive” program that tells
the PLC how to:
• Execute the control Instructions
• User’s Program
• Communicate with other devices
• Other PLCs, Programming devices, I/O
devices, etc.
• Perform Housekeeping activities
• Diagnostics, etc
This program is stored in “nonvolatile”
memory
• Meaning that the program will not be lost
if power is removed.
I/O MODULES:
Ø The I/O interface section of a PLC
connects it to external field devices.
Ø The main purpose of the I/O
interface is to condition the various
signals received from or sent to the
external input and output devices
Ø Inputs to, and outputs from, a PLC
are necessary to monitor and control a
process. Both inputs and outputs can
be categorized into two basic types:
logical or continuous.
Perez Muñoz Jose Page 04

PLC PROGRAMMING BASICS
The User Program
CPU of the PLC executes two different
programs:
1. The Operating System
2. The User Program
The Operating System
The operating system organizes all the
functions, operations and sequences of the
CPU that are not associated with a control
task. The OS tasks include
Handling a hot restart and warm restart
Updating and outputting the process
image tables of input and outputs
Executing the user program
Detecting and calling the interrupts
Managing the memory areas
Establishing communication with
programmable devices
It is a combination of various functions
which are required to process an
automated task. This must be created by
the users and need to be downloaded to
the CPU of the PLC. Some of the tasks of
the user program include:
Initiating all the conditions for starting the
specified task
Reading and evaluating all binary and
analog input signals
Specifying output signals to all binary and
analog output signals
Executing interrupts and handling errors
1.Textual language
Instructions List (IL)
Structured Text (ST)
2. Graphical language
Ladder Diagrams (LD)
Function Block Diagram (FBD)
Sequential Function Chart (SFC)
PLC Programming Devices
Various types of programming devices are
used to enter, modify and troubleshoot a
PLC program. These programming terminal
devices include handheld and PC based
devices. In the handheld programming
device method, a proprietary device is
connected to PLC through a connecting
cable. This device consists of a set of keys
that allows to enter, edit and dump the
code into the PLC. These handheld devices
consist of small display to make the
instruction that has been programmed
visible. These are compact and easy to use
devices, but these handheld devices have
limited capabilities.
Most popularly a Personal Computer (PC) is used for programming the PLC in conjunction with the software given by the
manufacturer. By using this PC we can run the program in either online or offline mode, and can also edit, monitor,
diagnose and troubleshoot the program of the PLC. The way of transferring the program to the PLC is shown in the
above figure wherein the PC consists of program code corresponding to control application which is transferred to the
PLC CPU via programming cable.
Marcelo Martinez Raul Page 05

LADDER LOGIC PLC PROGRAMMING
Step-By-Step Procedure for Programming
Among several programming languages
ladder logic diagram is the most basic and
simplest form of programming the PLC.
Before going to program the PLC with this
language, one should know some basic
information about it. The below figure
shows the hardwired-ladder diagram
wherein the same lamp load is controlled
by two push button switches, In case if any
one of the switches gets closed, the lamp
glows. Here two horizontal lines are called
rungs which are connected between two
vertical lines called rails. Each rung
establishes the electrical continuity
between positive (L) and negative rails (N)
so that the current flows from the input to
output devices. Some of the symbols used
in ladder logic programming are shown in
the figure.
PLC Using Ladder Logic
The procedure for programming a PLC for a
certain application depends on the type of
standard manufacturer software tool and
the type of control application. But in order
to give a basic guidance to the students,
this atrticle provides a simple approach of
designing control application in PLC
programming software, as given below But
this way of programming doesn’t exactly fit
into all the types of programming tools and
control applications.
The primary step to program the PLC is to
get the idea for which you are going to
develop an application-based program. If
you are driving a line follower robot by the
use of DC motor when the push button is
pressed. This status must be displayed by
the LED light when the motor gets turn on.
The motor is also attached with a sensor
(Here it is considered as another switch)
that detects obstacles, so when this turned
on, the motor should be turned off. And
correspondingly, if the motor switched off,
the buzzer should be turned on.
Faz Torres Hilario Page 06

UNIT
2

GENERAL SPECIFICATIONS
(1) Use this Conductor
Category information for
planning conductor
routing. Refer to
Indistrial Autimation
Wiring and Grounding
Guidelines, publication
1770-4.1
6
Specifications for imputs
Page 11
HILARIO FAZ TORRES