Rockwell Automation 1772-LS_LSP,D17726.8.6 PROG/OPER MANUAL-MINI PLC-2/05 - Manual (Page 16)

An Introduction to
Programmable Controllers
Chapter 2
2Ć2
Programmable controllers can perform many of the functions of traditional
controls. Sensing devices report to the processors. The output devices at the
machine operate the same as they would with traditional controls.
Control Panel Programmable
Machine
Sensing
Devices
Output
Devices
11592
Conditons
Controller
Action
Command
The field wiring between the machine and the control panel provides electrical
paths from the sensing devices to the control panel, and from the control panel
to the output devices.
However, inside the control panel you’ll find a programmable controller rather
than relays or discrete solid state devices. Instead of wiring those devices and
relays together to produce a desired response, you simply tell your
programmable controller by means of a program how you want it to respond to
the same conditions.
Programming is telling your programmable controller what you want it to do.
A program is nothing more than a set of instructions you give the programmable
controller telling it how to react to different conditions within the machine.
Let’s take a closer look at a typical programmable controller. It usually consists
of four major sections:
processor
input
output
power
supply
Programmable Controls
The Four Major Sections