Rockwell-automation 1772-LV Mini-PLC - 2/15 Programmable Controller (S Uživatelský manuál stáhnout pdf (Strana 12)

An Introduction to Programmable

Controllers

Chapter 2

25

In addition, the output section of modules with fuses has blown fuse indicators.

Typically, each output circuit is fused in the output section. Groups of these

fuses will have a blown fuse indicator associated with them. When one of the

fuses in the group opens, the blown fuse indicator will be lit.

Conditioning

The output section conditions the programmable controller’s signals for the

machine. that is, it converts the low-level DC voltages of the programmable

controller to the type of electrical power used by the output devices at the

machine.

Isolation

The output section isolates the more sensitive electronic circuitry of the

programmable controller from unwanted and dangerous voltages that

occasionally occur at the machine or the plant’s wiring system. There are

situations where additional external protection may be required.

Processor

Section

The four major section of a programmable controller is the processor. The

processor section might be called the “brains” of the programmable controller

because it is divided into halves that serve functions similar to your brain. One

half is the Central Processing Unit (CPU), the other is memory.

Central Processing Unit

The Central Processing Unit (CPU) is divided into two sections:

Decision area - makes decisions about what the machine is to do.

Memory - storage area.

Memory

The programmable controller’s memory serves three functions:

Stores important information (or data) that the CPU may need to make its

decisions.

Stores sets of instructions called a program.

Stores messages.

Processor

Section

CPU

Data

Table

Program

Storage

Memory

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Rockwell-automation 1772-LV Mini-PLC - 2/15 Programmable Controller (S Uživatelský manuál Strana 12