The Programmable Logic Controller (The PLC)

Section Objectives:
Before the invention of the Programmable Logic Controller
(PLC), most industrial control was done using relay control
panels.
Switches and relays can be arranged in circuits to make
logical decisions. Output from these circuits can be used to
drive “loads” such as motors, heaters, or electromagnetic
coils. A relay control panel is comprised of a single to
thousands of these circuits.
In this Section, relay control panels will be presented.
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