Article Content
• Background
• PLC definition
• PLC manufacturers
• PLC Programming software
• How it works
• Advantages & Disadvantages of PLC
• Application of PLC
• Ladder logic
• Conclusions and Recommendations
Introduction
Background
See Also: HOW TO BUILD IOT DEVICES AND APPLICATIONS USING ARDUINO AND PYTHON
See Also: LONG TERM EVOLUTION TECHNOLOGIES, 3G AND 4G
Click the link to download the PDF copy of this article for free: INDUSTRIAL AUTOMATION USING PROGRAMMABLE LOGIC CONTROLLER (PLC)
GM Hydra-Matic Mandate

PLC Pioneers
• Dick Morley’s company Bedford Associates in Massachusetts proposed something called a Modular Digital Controller (MODICON).• The MODICON 084 brought the world’s first PLC into commercial production.
The picture below shows some PLC Pioneers posing with the MODICON 084.

What is a PLC?
A Programmable Logic Controller (PLC) is an electronic device with a Programmable memory, multiple input and output terminals that is used to logically control various industrial machines and processes.Below is the picture of a Programmable Logic Controller (PLC).

Major Components of a PLC
• POWER SUPPLY– Provides the voltage needed to run the primary PLC components.
• I/O MODULES
– Provides signal conversion and isolation between the internal logic-level signals inside the PLC and the field’s high level signal.
• 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.

Leading Brands of PLC
AMERICAN
1. Allen Bradley2. Modicon
3. Texas Instruments
4. General Electric
EUROPEAN
1. Siemens2. Festo
3. Telemechanique
JAPANESE
1. Toshiba2. Omron
3. Mitsubishi
PLC Programming Software
• Allen-Bradley – Rockwell RSLogix500/5000
• Omron – CX-ONE


How does the PLC Software Work?
• Self scan: Testing of its own hardware and software for faults.• Input scan: A PLC scan cycle begins with the CPU reading the status of its inputs.
• Logic scan: The application program is executed using the status of the inputs.
• Output scan: The cycle ends by updating the outputs.
The diagram below illustrates better how the PLC software works.

Concept of Ladder logic

On Delay Timers (TON)

EN: This is the timer Enable
bit that comes on once the timer is energised
DN: This is the timer Done
bit that only comes on once the time is done counting
TT: This is the Timer Timing
bit which comes on and stays on as long as the timer is counting and goes
off once the timer is done counting.
Coils

AND OPERATION

OR OPERATION

NOT OPERATION

Tank Used to Mix Two Liquids

• When the start button is pressed, solenoids A and B energize. This permits the two liquids to begin filling the tank.
• 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.
• 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.
• When the tank is empty, the float switch de-energizes solenoid C.
• A stop button can be used to stop the process at any point.
• Once the circuit has been energized it will continue to operate until it is manually stopped.
A Sample Program for the Mixing of Two Liquids

Advantages of Programmable Logic Controller (PLC)
• Cost Effective
• Ease of maintenance/ troubleshooting
• Rugged and reliable
• Easier and faster to make changes
• High Speed of Operation
• Diagnosis can be centrally available
Disadvantage of PLC
Real Life or Business Applications of PLC
• Factory/Process automation
• Warehouse Automation
• Traffic management controls
• Power systems
• Water treatment systems
Conclusions & Recommendations
Click the link to download the PDF copy of this article for free: INDUSTRIAL AUTOMATION USING PROGRAMMABLE LOGIC CONTROLLER (PLC)
See Also: HOW TO BUILD IOT DEVICES AND APPLICATIONS USING ARDUINO AND PYTHON
See Also: LONG TERM EVOLUTION TECHNOLOGIES, 3G AND 4G
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