A J Wright

Ladder Logic Programming Fundamentals A J Wright

This book, "Ladder Logic Programming Fundamentals" is the second edition of the book and is updated with more useful information on the latest Allen Bradley PLCs. It teaches you step by step the fundamentals of ladder logic diagrams, their basics and variables, including how ladder logic diagrams can be derived from traditional schematic circuit diagrams, and the general rules governing their use.




Ladder logic is the primary programming language for Programmable Logic Controlers (PLCs). It has following advantages:

It is the primary language used in industrial applications, especially for programming PLCs.

It is a graphical and visual language, unlike textual high-level languages, such as C, C]+, Java and so on.

It can be derived from traditional schematic diagrams which can be cumbersome for complicated circuits (for example, relay logic diagrams).

It makes use of primitive logic operations like AND, OR and NOT.

It can be used where the primary reasons are safety, ease and isolation. For example, for electrical isolation of high-power industrial motors.

It has a control behavior. For example, it can be used to control motors, transformers, contactor coils and overload relays in an electrical control system, for example, to make a light bulb come on when either switch A is ON (closed) or when switch B is ON (closed).




In this edition, I explore the Allen-Bradley controllers in chapters where PLCs are treated in great details.




The Studio 5000 software discussed in this book includes the Logix Designer application for the programming and configuration of Allen-Bradley ControlLogix 5570 and CompactLogix 5370 programmable automation controllers.




I also give you the link to download a 90 day trial version of the RSLogix 5000 software which you can use to learn how to program Logix5000 controllers. Logix Designer will continue to be the package you use to program Logix5000 controllers for discrete, process, batch, motion, safety, and drive-based systems.




Logix Designer offers an easy-to-use, IEC61131-3 compliant interface, symbolic programming with structures and arrays and a comprehensive instruction set that serves many types of applications. It provides ladder logic, structured text, function block diagram and sequential function chart editors for program development as well as support for the S88 equipment phase state model for batch and machine control applications.