This module is intended to provide an introduction to relay logic and relay logic diagrams. The basic operating principles of relays are presented as well as detailed information regarding sizing and rating of electromagnetic contactors. Seal-in circuits and their application in control systems is discussed as well as an introduction to timing circuits. In addition, the module covers I/O devices and their application in PLC systems.

Learning Outcomes:

Upon completion of this module the student will be able to:

• Name three types of mechanical switches and three types of proximity switches.
• Define inductive arcing and explain how it can be prevented.
• Describe the basic operating principle of a control relay.
• Explain the purpose of overload relays.
• Define the term holding contact.
• Differentiate between a control relay and a solenoid.
• List three applications of rotary actuators.
• Name three types of time-delay relays.
• Define the term relay logic.