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TOPIC 2: INTRODUCTION TO PLC

2.1 Define PLC

What is Programmable LogicController?

❖ Definition: National Electrical manufacturers Association US (NEMA) A PLC is

digital operating electronic apparatus which uses a programmable memory

for internal storage of instruction for implementing specific function such as

logic, sequencing, timing, countingand arithmetic to control through analog

or digital input/output modules various types of machines orprocess.

❖ The first Programmable Logic Controller (PLC) was developed by a group of

engineer at General Motor in1968.

❖ An electronic system working digitally forthe use in industrial environment

with a programmable memory for the internal storage of user-orientated

control instructions for the implementation of specific functions.

❖ For example: logic operation control, process control, timer, counting and

arithmetic function, in order to controlvarious machines and processes

through digital or analog input and output variable

❖ The logic programmable controls as wellas the peripheral installations (PLC-

system) are designed so that they can beeasily integrated in an industrial

control system and be implemented in all their desired functions.

2.1.1 PLC Function

❖ PLC performs the function of conventional relay, timers, counters.

❖ Capable of storing instructions, suchas sequencing, timing, counting,

arithmetic, data manipulation and communication, to control industrial

machines and processes.

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