The document provides an introduction to programmable logic controllers (PLCs), explaining manual and automatic control systems, as well as differentiating between PLCs and microcontrollers. It covers types of controllers, basic PLC operation, and outlines the main components and applications of PLCs, with a focus on the Siemens Logo! PLC. Key objectives include programming a PLC, identifying parts, and selecting suitable controllers for various applications.

1. PLC Fundamentals
Module 1: Introduction to PLC

2. Module Objectives
• Upon successful completion of this module, students
will be able to:
• Differentiate between MANUAL and AUTOMATIC control.
• Define a ‘control system’ and draw its block diagram.
• Differentiate between DIGITAL and ANALOG control.
• Mention the different types of controllers and give examples.
• Differentiate between a MICTOCONTROLLER and a PLC.
• Mention the main parts of a PLC.
• Give examples of PLC applications and list the PLC
manufacturers.
• Select the most suitable controller for a given problem.
• Identify the main parts of the Siemens LOGO! PLC Module.
• Program the Siemens LOGO! PLC Module through its Basic
Control Unit using simple commands.

3. 1.1 Introduction
• Give Examples of the physical quantities that we need
to control :
• In everyday operations or industrial processes, we come
across situations where there is a need to control some
device or a physical quantity such as time, temperature,
sound, light and so on, to get the required result or output.
• Give an Example of a control system:
• i.e, do you think an airplane would be useful to a pilot, if he
cannot make it go where he wants it to go? Or would an air-
conditioner be useful, if the temperature in a room cannot
be controlled? In both the examples, there is a need to
control a process.

4. 1.1.1 Manual & Automatic Control
• Electrical control:
• using electrical signals such as “current or voltage” to enable or disable or
direct a certain process.
• Control is either manual or automatic.

5. Manual Control
• Its when a user performs an action for the system
to function.
• For example, the user might flip the switch of a
manual starter to start and stop a motor.

6. Automatic Control
• When the action is
performed automatically
in response to a set of
conditions.
• Usually, there is a
combination of manual
and automatic control.
For example, a process
that is started manually
may stop automatically
when certain conditions
are met.

7. Control System
• A Control System: is a system that can direct,
command and regulate itself or another system.
• The control system starts with input signals that
activate the process to control output devices
• A block diagram of a control system:
Input Process Output

8. In terms of Output Value, a control system can be classified:
• Discrete (digital) control: The value to be controlled
can be either ON or OFF. Example: Turning a light ON
and OFF.
• Continuous (analog) Control: The value to be
controlled varies smoothly. Example: Motor speed.

9. 1.2 Types of controllers
• Different types of controllers could be used based
on the requirements of the application. Some
examples are included below:
• 1. Relays and Contactors
• Simple electromechanical devices like relays and
contactors are most widely used for controlling a
discrete manufacturing process.

10. 2. Programmable Logic Controllers (PLCs)
• A Programmable Logic Controller (or PLC) is a
specialized digital controller that can control
machines and processes. it monitors inputs, makes
decisions, and controls outputs in order to automate
machines and processes. demonstrates its function.

11. 3. Microcontrollers (μCs)
• Microcontroller is a special purpose computer
that can do one job, for example, the one that is
used in an automatic washing machine and in a
microwave.

12. 1.3 PLC vs. Microcontroller
• Usually PLCs are used in an industrial environment, where as the
microcontrollers are smaller and well suited for embedded situations.
• PLCs are programmed with ready made blocks or programming
elements, whereas in Microcontrollers a programming language must
be used to write a programing code.
• The price of the µC could vary from 5 Dirhams to 50 Dirhams. Some
of the cheapest PLC's could cost AED 400 for the basic frame (with
digital inputs and outputs).

13. PLC Advantages
• They are highly reliable, fast and flexible.
• They can handle severe conditions such as dust,
humidity etc.
• They can communicate with other controllers.
• They are easy to program and troubleshoot.
• They include display units.

14. 1.4 Basic PLC Operation
• In the example shown in fig 1.12, pushbuttons are
connected to the PLC’s inputs and a motor is
connected to the PLC’s output. Here the pushbuttons
are used to start and stop the motor.

15. PLC Basic Parts
• A PLC consists of the following basic parts:
• Inputs
• Central Processing Unit (CPU)
• Outputs
•
• Examples of PLC input devices are sensors, switches,
pushbuttons etc
• Examples of PLC output devices are valves, motors, solenoids
etc

16. 1.5 PLC Applications
• A PLC can be used in a wide range of applications,
some of which are shown below:

17. 1.6 PLC Manufacturers
• The PLC that will be introduced in this course is
the LOGO! PLC from Siemens. The table below
shows a list of other PLC Manufacturers.

18. SIMATIC S7 1200
Programming Level 1

19. Basics of PLCs