1. Chapter 14
Understanding Relay Instructions and the Programmable Controller Input Modules

2. Objectives (1 of 2)
Explain proper programming of normal closed and normally open PLC input signals.
Describe hardware relay operation and its correlation to proper PLC interface and programming.
Convert a conventional start-stop schematic to a PLC ladder rung diagram.

3. Objectives (2 of 2)
Explain why PLC ladder logic for motor starter interface has an additional contact in comparison to a conventional schematic.
Hook up a start-stop station to a PLC input module.
Hook up and develop a PLC program to correctly control a motor starter.

4. Typical Hard-Wired Start-Stop Latching Circuit

5. Incorrect Conversion of Conventional Start-Stop Schematic to PLC Control

6. Normally Open Pushbutton and Non-energized Relay

7. Normally Open Pushbutton Energizing Relay Coil and Pilot Light B

8. Normally Closed Pushbutton Energizing Relay Coil and Pilot Light B

9. Normally Closed Stop Pushbutton Depressed

10. Relay Status in Conjunction with Input Pushbuttons

11. Input and Output Separation

12. Separated Inputs Connected to PLC Input Screw Terminals

13. Start Push-Button Status Reflected in the Input Status Table

14. Start-Stop Input Bit Status from Input Hardware in a Non-energized State

15. Normally Open Pushbutton Not Activated

16. Normally Open Pushbutton Input Pressed

17. Normally Closed Input Pushbutton

18. Normally Closed Pushbutton Input to PLC

19. Pushbutton Released Output Latched through CR 1-1

20. Conventional Schematic Start-Stop Logic

21. Conventional Motor Starter Schematic Diagram

22. Conventional Motor Starter Circuit Converted for PLC System Management