Page 148 - Programmable Logic Controllers, Fifth Edition

CHAPTER 6 PROBLEMS

1. Design and draw the schematic for a conventional L1 L2
hardwired relay circuit that will perform each of Run
the following circuit functions when a normally Stop OL
closed pushbutton is pressed: M
• Switch a pilot light on Jog M
• De-energize a solenoid
• Start a motor running
• Sound a horn Figure 6-78 Hardwired control circuit for Problem 4.
2. Design and draw the schematic for a conventional
hardwired circuit that will perform the following will correctly execute the hardwired control circuit
circuit functions using two break-make pushbuttons: in Figure 6-78.
• Turn on light L1 when pushbutton PB1 is pressed. Assume: Stop pushbutton used is an NO type.
• Turn on light L2 when pushbutton PB2 is pressed. Run pushbutton used is an NO type.
• Electrically interlock the pushbuttons so that L1 Jog pushbutton used has one set of NO
and L2 cannot both be turned on at the same time. contacts.
3. Study the ladder logic program in Figure 6-77, and OL contact is hardwired.
answer the questions that follow: 5. Design a PLC program and prepare a typical I/O
a. Under what condition will the latch rung 1 be true? connection diagram and ladder logic program that
b. Under what conditions will the unlatch rung 2 be true? will correctly execute the hardwired control circuit
c. Under what condition will rung 3 be true? in Figure 6-79.
d. When PL1 is on, the relay is in what state Assume: PB1 pushbutton used is an NO type.
(latched or unlatched)? PB2 pushbutton used is an NC type.
e. When PL2 is on, the relay is in what state PS1 pressure switch used is an NO type.
(latched or unlatched)? LS1 limit switch used has only one set of
f. If AC power is removed and then restored to the NC contacts.
circuit, what pilot light will automatically come L1 L 2
on when the power is restored? Start PB 1 Stop
g. Assume the relay is in its latched state and all three PB 2
inputs are false. What input change(s) must occur CR1
for the relay to switch into its unlatched state?
h. If the examine if closed instructions at addresses PL1
I/1, I/2, and I/3 are all true, what state will the CR1-1
relay remain in (latched or unlatched)?
CR1-2
4. Design a PLC program and prepare a typical I/O SOL 1
connection diagram and ladder logic program that
PS1
Inputs Ladder logic program Outputs CR2
L1 L2
I/1 I/1 I/2 O/9 LS1 CR2-1 SOL 2
Rung 1 L O/9 PL1
SS1
I/2 I/3 O/9 CR2-2 SOL 3
Rung 2 U
O/10 PL2
I/3 O/9 O/10
Rung 3 PL2

Figure 6-77 Ladder logic program for Problem 3. Figure 6-79 Hardwired control circuit for Problem 5.

Developing Fundamental PLC Wiring Diagrams and Ladder Logic Programs Chapter 6 129

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