Programmable Controller

Introduction

Programmable controllers were originally designed to replacerelay-based control systems and solid-state, hard-wired logiccontrol panels. However, the modern programmable controllers systemis far more complex and powerful.

The most basic function performed by programmable controllers isto examine the status of inputs and in response, control someprocess or machine through outputs. The logical combinations ofinputs to produce an output or outputs are called control logic.Several logic combinations are usually required to carry out acontrol plan or program. This control plan is stored in memoryusing a programming device to input the program into the system.The processor, usually a high-speed microprocessor, in apredetermined sequential order, periodically scans the control planin memory. The period required to examine the inputs and outputs,perform the control logic, and execute the outputs is called the”scan time.”

Edition:

4

Published:

01/01/2005

Number of Pages:

386

File Size:

1 file , 7 MB