Control engineering has evolved over time. In the past humans were the main method for controlling a system. More recently electricity has been used for control and early electrical control was based on relays. These relays allow power to be switched on and off without a mechanical switch. It is common to use relays to make simple logical control decisions. The development of low cost computer has brought the most recent revolution, the Programmable Logic Controller (PLC). The advent of the PLC began in the 1970s, and has become the most common choice for manufacturing controls | page i Copyright c 1993-2003 Hugh Jack jackh@ . Permission is granted to copy distribute and or modify this document under the terms of the GNU Free Documentation License Version or any later version published by the Free Software Foundation with no Invariant Sections no Front-Cover Texts and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License . This document is provided as-is with no warranty implied or otherwise. There have been attempts to eliminate errors from this document but there is no doubt that errors remain. As a result the author does not assume any responsibility for errors and omissions or damages resulting from the use of the information provided. Additional materials and updates for this work will be available at http clay-more. engineer. gvsu. edu jackh books. html page il TODO LIST 2. PROGRAMMABLE LOGIC CONTROLLERS . INTRODUCTION Ladder Logic Programming PLC Connections Ladder Logic Inputs Ladder Logic Outputs A CASE STUDY SUMMARY PRACTICE PROBLEMS PRACTICE PROBLEM SOLUTIONS ASSIGNMENT PROBLEMS 3. PLC INTRODUCTION INPUTS AND OUTPUTS Inputs Output Modules RELAYS A CASE STUDY ELECTRICAL WIRING DIAGRAMS JIC Wiring Symbols SUMMARY PRACTICE PROBLEMS PRACTICE PROBLEM SOLUTIONS ASSIGNMENT PROBLEMS 4. LOGICAL SENSORS . INTRODUCTION SENSOR WIRING Switches Transistor Transistor Logic TTL Sinking Sourcing Solid State Relays PRESENCE DETECTION Contact Switches Reed Switches Optical Photoelectric Sensors Capacitive Sensors Inductive Sensors Ultrasonic Hall Effect .
