Page 117 - Programmable Logic Controllers, Fifth Edition

6

Developing Fundamental

PLC Wiring Diagrams and

Ladder Logic Programs

Courtesy of Siemens
Chapter Objectives

For ease of understanding, ladder logic pro- After completing this chapter, you will be able to:
grams can be compared to relay schematics. • Identify the functions of electromagnetic control relays,
This chapter gives examples of how traditional contactors, and motor starters
relay schematics are converted into PLC ladder • Identify switches commonly found in PLC installations
logic programs. You will learn more about the • Explain the operation of sensors commonly found in
wide variety of field devices commonly used in PLC installations
connection with the I/O modules. • Explain the operation of output control devices
commonly found in PLC installations
• Describe the operation of an electromagnetic latching relay
and the PLC-programmed LATCH/UNLATCH instruction
• Compare sequential and combination control processes
• Convert fundamental relay ladder diagrams to PLC
ladder logic programs
• Write PLC programs directly from a narrative description

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