Author
seema-vishwakarma
View
6.270
Download
4
Embed Size (px)
DESCRIPTION
Learn about Programmable Logic Controller and Ladder Logic Programming from the very basic level
Introduction to Programmable
Logic Controllersand Ladder Logic
Welcome
The purpose of this Presentation is to give you a very simple look Programmable Logic Controllers and its programming using Ladder Logic.
There is no need for you to be familiar in any way with this field. The only requirement is that you
enter with an open mind.
To begin with..
What is
automation?
You may have come across the word “automated” very usually!
Automation is the use of machines, control systems and information technologies to monitor and control the production.
In other words, an automated system is any system that require minimum or no human intervention.
Automation has made our life extremely simple.
Earlier, processes were carried out by operator, hence were much prone to human errors.
So we can imply that with Industrial control, factory automation, and PLC (if are done well), we can save a lot of time, materials, energy, and money.
Where do we begin?
Let’s recall the story of an explorer in Africa who asked the native tribesman,
How does one eat a huge animal like an elephant?"
The tribesman looked at the explorer in astonishment and replied, "We eat it just like
everything else, one bite at a time."
Simple as it is, industrial control is comprised of many smaller circuits. By exploring and learning simple smaller circuits, you can learn to build a complete automated system.
Programmable logic controllers
Lets Start With…
What is
a small computer with a built-in operating system which monitor inputs and other variable values, make decisions based on a stored program, and control outputs to automate a process or machine.
Programmable logic controllersWhat is
Well, that was simple isn’t it ?
Lets put it in another way..
A PLC is similar to a computer which is designed to be programmed once, and run repeatedly as needed.
Elements of PLC
Let’s have al look at..
Input ModulesSenses the input signal, isolates it and converts it to DC level.
Central Processor Unit (CPU)
microprocessor system that contains the system memory and its decision making unit very similar to that of a computer’s CPU.
Input ModulesSenses the input signal, isolates it and converts it to DC level.
Output Modulereceives the convert control signals from the CPU and them converts them into digital or analog values that can be used to control various output devices.
Central Processor Unit (CPU)
microprocessor system that contains the system memory and its decision making unit very similar to that of a computer’s CPU.
Input ModulesSenses the input signal, isolates it and converts it to DC level.
Programming Device Personal computer or a Laptop
And Communication Cable
Output Modulereceives the convert control signals from the CPU and them converts them into digital or analog values that can be used to control various output devices.
Central Processor Unit (CPU)
microprocessor system that contains the system memory and its decision making unit very similar to that of a computer’s CPU.
Input ModulesSenses the input signal, isolates it and converts it to DC level.
PLC scanWhat is a
Reads Inputs
Execute Programs
Diagnostics & Communication
Updates Outputs
PLC scan
PLC scan
Programming PLC
The first and still most popular programming language used with PLC is Ladder Logic Programming (LAD).
They are called "ladder" diagrams because they resemble a ladder,
with two vertical rails (supply power) and as many "rungs"
(horizontal lines).
The first and still most popular programming language used with PLC is Ladder Logic Programming (LAD).
Basic Ladder Logic Symbols
Normally Open (NO) contactPasses power (on) when coil driving the contact is on.
Contacts
Normally Closed (NC) contactPasses power (on) when coil driving the contact is off.
Basic Ladder Logic Symbols
Normally Open (NO) contactPasses power (on) when coil driving the contact is on.
Contacts
Output or CoilWhen power flows through the Coils via contacts they are energized.
Basic Ladder Logic Symbols
Schematic of ladder diagram
Selecting a PLC
Criteria
• Number of logical inputs and outputs.• Memory• Number of special I/O modules• Scan Time• Communications• Software
Functional Operation
AND OperationOR Operation
NOT Operation
Lets have a look at their truth table and Ladder Logic diagram
35
AND Operation
Both inputs S4 and S5 must be true (1) in order for the output L3 to be true (1).
Ladder diagram
OR Operation
Ladder diagram
Either input S1 or S2 is true (1), or both are true, then the output L2 is true (1).
37
NOT Operation
If input S1 is be true (1), then the output L1 is true (0) or when A is (0), output C is 1.
Ladder diagram
Programming Functions
TimersCounters
Timers
On-Delay Timer (TON)Off-Delay Timer (TOF)Retentive On-Delay Timer (TONR)
Counters
Count UP Counter (CTU)Count DOWN Counter (CDU)Count UP/DOWN Counter (CTUD)
Programming Examples
Lets start with simple examples…
Programming Examples
D = (A AND B) OR C
Programming Examples
Triggering the Relay Coil
Ladder Diagram for Triggering the Relay Coil
Learn the Basics of Programming Logic Controller & Ladder Logic by Downloading this E-book
This E-book contains
Programmable logic controllersPLC ScanBasic Ladder Logic SymbolsFunctional Operation Programming Functions Programming To PLC (Practical Examples)Illustration of PLC Scan
DOWNLOAD OUR EBOOK
For Further Reading
Introduction to Programmable Logic Controller and Ladder Logic