Page 14 - Programmable Logic Controllers, Fifth Edition

Programming Timers
Timer number
File number
EN TT DN
Word 0
4
Word 1
Preset value
Word 2
Accumulated value
rogrammable Logic Controllers makes it
Image Used with Permission of Rockwell Automation, Inc.
easy to learn PLCs from the ground up! Up- 7 Timers File type T4:2 15 14 13
P to-the-minute revisions include all the new- Chapter Objectives
est developments in programming, installing, and
maintaining processes. Clearly developed chapters After completing this chapter, you will be able to:
deliver the organizing objectives, explanatory con-
tent with helpful diagrams and illustrations, and • Describe the operation of pneumatic on-delay and The most commonly used PLC instruction, after
closing review problems that evaluate retention of off-delay timers coils and contacts, is the timer. This chapter
the chapter objectives. • Describe PLC timer instruction and differentiate deals with how timers time intervals and the way
between a nonretentive and retentive timer in which they can control outputs. We discuss
• Convert fundamental timer relay schematic diagrams to the basic PLC on-delay timer function, as well as
PLC ladder logic programs other timing functions derived from it, and typical
CHAPTER OBJECTIVES overview the chapter, letting stu-
dents and instructors focus on the main points to better grasp • Analyze and interpret typical PLC timer ladder logic industrial timing tasks.
concepts and retain information. programs
• Program the control of outputs using the timer
instruction control bits
Chapter content includes rich illustrative detail and extensive visual
aids, allowing students to grasp concepts more quickly and understand
practical applications

Inputs Ladder logic program Outputs
L1 L2
S1
MOV
S1 MOVE Heater
Source Thermocouple
Destination LED
B3:0/1 LED
Thermocouple LEQ 131
LESS THAN OR EQUAL Here, drawings and photos of real-world input
Source A Thermocouple (Internal)
LED Display and output devices have been included
Source B 597
59 5
GEQ B3:0/2
GREATER THAN OR EQUAL
Source A Thermocouple (Internal)
Source B 603
High temp. Low temp.
S1 B3:0/2 B3:0/1 Heater

Heater

HMI Package PLC
Tag Database

I/O
Server
In Chapter 02, students not only read about but can also see how
HMIs fit into an overall PLC system, giving them a practical Communication
introduction to the topics ports
Start Stop Graphic
Screen

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