08-11-2012, 04:00 PM
Basic PLC
Basic PLC.ppt (Size: 1.15 MB / Downloads: 223)
Description
This training introduces the basic hardware and software components of a Programmable Controller (PLC). It details the architecture and basic instruction set common to all PLC’s. Basic programming techniques and logic designs are covered. This training describes the operating features of the PLC, the advantages of the PLC over hard-wired control systems, practical applications, troubleshooting and maintenance of PLC’s.
Objectives
At the end of the training the participants should be able to:
Describe the major components of a common PLC.
Interpret PLC specifications.
Apply troubleshooting techniques.
Convert conventional relay logic to a PLC language.
Operate and program a PLC for a given application.
Course Contents
History of Programmable Controllers
Relay Ladder Logic
Central Processing Unit
Input/Output System
Programming and Peripheral Devices
Programming Concepts
Applications
Troubleshooting and Maintenance
INTRODUCTION TO PLCS
Less wiring.
Wiring between devices and relay contacts are done in the PLC program.
Easier and faster to make changes.
Trouble shooting aids make programming easier and reduce downtime.
Reliable components make these likely to operate for years before failure.
Historical Background
The Hydramatic Division of the General Motors Corporation specified the design criteria for the first programmable controller in 1968
Their primary goal
To eliminate the high costs associated with inflexible, relay-controlled systems.
The controller had to be designed in modular form, so that sub-assemblies could be removed easily for replacement or repair.
The control system needed the capability to pass data collection to a central system.
The system had to be reusable.
The method used to program the controller had to be simple, so that it could be easily understood by plant personnel.
Programmable Logic Controllers
A digitally operating electronic apparatus which uses a programming memory for the internal storage of instructions for implementing specific functions such as logic, sequencing, timing, counting and arithmetic to control through digital or analog modules, various types of machines or process.
Tank Used to Mix Two Liquids
A tank is used to mix two liquids. The control circuit operates as follows:
1. When the start button is pressed, solenoids A and B energize. This permits the two liquids to begin filling the tank.
2. When the tank is filled, the float switch trips. This de-energizes solenoids A and B and starts the motor used to mix the liquids together.
3. The motor is permitted to run for one minute. After one minute has elapsed, the motor turns off and solenoid C energizes to drain the tank.
4. When the tank is empty, the float switch de-energizes solenoid C.
5. A stop button can be used to stop the process at any point.
6. If the motor becomes overloaded, the action of the entire circuit will stop.
7. Once the circuit has been energized it will continue to operate until it is manually stopped.
Major Components of a Common PLC
PROCESSOR
Provides intelligence to command and govern the activities of the entire PLC systems.
PROGRAMMING DEVICE
used to enter the desired program that will determine the sequence of operation and control of process equipment or driven machine.