[PPT]PROGRAMMABLE LOGIC CONTROLLER
Control Systems Types
Programmable Logic Controllers
Distributed Control System
PC- Based Controls
Programmable Logic Controllers
Sequential logic solver
PID Calculations.
Advanced Subroutines
BIT Operations.
Data Transfer.
Text Handling.
Applications :
Machine controls, Packaging, Palletizing, Material handling, similar Sequential task as well as Process control
Advantages of PLC :
They are fast and designed for the rugged industrial environment.
They are attractive on Cost-Per-Point Basis.
These Devices are less Proprietary ( E.g.. Using Open Bus Interface.)
These Systems are upgraded to add more Intelligence and Capabilities with dedicated PID and Ethernet Modules.
Disadvantages of PLC :
PLC were Designed for Relay Logic Ladder and have Difficulty with some Smart Devices.
To maximize PLC performance and Flexibility, a number of Optional Modules must be added
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[PPT]Programming PLCs using LADDER Logic
Review of Ladder Programming
Keyence PLC Ladder Builder
Example 1: Motor Control
Example 2: Drill Control
Example 3: Traffic Light
Ladder Logic Diagrams
Diagrams
Sequential Function Charts
Instruction ListFunction Block
Structured Text
High-Level Language
[PPT]Introduction to IEC1131-3 Ladder Diagram
Origins of Ladder Diagram
The Ladder Diagram (LD) programming language originated from the graphical representation used to design an electrical control system
Control decisions were made using relays
After a while Relays were replaced by logic circuits
Logic gates used to make control decisions
Finally CPUs were added to take over the function of the logic circuits
I/O Devices wired to buffer transistors
Control decisions accomplished through programming
Relay Logic representation (or LD) was developed to make program creation and maintenance easier
Computer based graphical representation of wiring diagrams that was easy to understand
Reduced training and support cost
What is a Rung?
A rung of ladder diagram code can contain both input and output instructions
Input instructions perform a comparison or test and set the rung state based on the outcome
Normally left justified on the rung
Output instructions examine the rung state and execute some operation or function
In some cases output instructions can set the rung state
Normally right justified on the rung
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