Instrumentation and Control Systems, 3rd Edition

Chapter 7

PLC Systems

Abstract

This chapter introduces the programmable logic controller and its programming using ladder diagrams. The functions of logic gates are also considered. Case studies of ladder programs are included.

Keywords

Programmable logic controller; ladder programs; logic gates

Outline

• 7.1 Introduction 165
• 7.2 Logic Gates 166
  • 7.2.1 Field-Programmable Gate Arrays 169
• 7.3 PLC System 170
• 7.4 PLC Programming 171
  • 7.4.1 Logic Gates 173
  • 7.4.2 Latching 174
  • 7.4.3 Internal Relays 174
  • 7.4.4 Timers 175
  • 7.4.5 Counters 176
• 7.5 Testing and Debugging 178
• 7.6 Case Studies 179
  • 7.6.1 Signal Lamp to Monitor Operations 179
  • 7.6.2 Cyclic Movement of a Piston 179
  • 7.6.3 Sequential Movement of Pistons 179
  • 7.6.4 Central Heating System 181
• Problems