Guide to Programmable Logic Controllers

By: Hugh Wright

Abstract: This tutorial offers an in-depth introduction into programmable logic controllers (PLCs). The article starts with an overview of the history and the role PLCs in factory automation. The basic principles of PLC operation are discussed. The core modules of an industrial-control system are examined: the analog input function, analog output functions, the distributed control (fieldbus) interface, digital inputs and outputs (I/Os), the CPU, and isolated power. Functional block diagrams and recommended devices are included for each function.