Hooper, Jay F.

Introduction to Plcs

Preface ix Foreword xi Overview 3(10) An Origin Story 3(2) The Four Parts of a PLC 5(2) PLC Symbols 7(1) PLC Terminal Numbers 7(1) PLC Logic Symbols 8(5) Hardware 13(10) Input Rack 13(2) Output Rack 15(1) Different Voltage Levels 15(1) Current Drains 16(1) Terminal Diagrams 16(2) Seven General Rules 18(5) General Rule #1 18(1) General Rule #2 19(4) Programming Basics 23(6) Inputs and Outputs 23(1) The IO Scan 24(2) General Rule #3 25(1) Branching 26(1) General Rule #4 27(1) Gates 27(1) Symbols on Terminal Diagrams 28(1) Basic Logic 29(8) And and Or 29(2) Not 31(1) Out 31(1) Nand and Nor 31(1) Logic in Everyday Speech and in the PLC 32(5) General Rule #5 33(4) Ladder Logic 37(8) Control Relays 37(1) Contactors and Motor Starters 38(1) Two-Wire (Automatic) Control Circuits 38(1) Three-Wire (No-Voltage Protection) Control Circuits 39(1) Open vs. NO and Closed vs. NC 40(2) Photo Eyes and Proximity Detectors 42(1) Mechanically Interconnected Switches 43(2) Counters 45(10) Count Up and Count Down Counters 45(1) General Rule #6 45(1) Preset, Reset, and Accumulated Values 45(2) Enable and Done Bits 47(1) Example of a Light Chaser Circuit 48(7) Timers 55(6) Timer On Delay (TON) 55(1) Timer Off Delay (TOF) 55(1) One-Shot Timer 56(2) Preset, Reset, Accumulated Values, and Time Units 58(2) One-Shot Timed Contact 60(1) Sequencers 61(10) Sequencer Symbol (SQO) 61(1) Sequencer Output Table 62(2) File, Mask, Destination, Control, Length, and Position Values 64(2) Example of a Light Chasing Circuit 66(5) Math Functions and Analog Inputs and Outputs 71(8) Addition, Subtraction, Multiplication, and Division Functions 71(1) Less Than, Greater Than, and Equal To Functions 72(1) Analog Inputs and A-to-D Conversion 72(1) Analog Outputs and D-to-A Conversion 73(1) Example of a Deadband Circuit 73(6) General Rule #7 76(3) Appendix A 79(16) Symbols in the Electrician World 79(11) Symbols in the Electronic World 90(2) Logic 92(3) Appendix B 95(4) Exercises 99(4) Selected Solutions 103