Page 298 - Programmable Logic Controllers, Fifth Edition - Mobile version

c. What is the address of the sequencer file that sets
the states for the outputs? 5. Using whatever PLC sequencer output instruction
you are most familiar with, develop a program that
d. What is the address of the sequencer file that con- will operate the cylinders in the desired sequence.
tains the preset timer values? The time between each step is to be 3 seconds.
e. For what length of time is the red light The desired sequence of operation will be as
programmed to be on? follows:
f. For what length of time is the green light • All cylinders to retract.
programmed to be on? • Cylinder 1 advance.
g. For what length of time is the yellow light • Cylinder 1 retract and cylinder 3 advance.
programmed to be on? • Cylinder 2 advance and cylinder 5 advance.
h. What is the time required for one complete cycle • Cylinder 4 advance and cylinder 2 retract.
of the sequencer? • Cylinder 3 retract and cylinder 5 retract.
i. Assume that the decimal value stored in N7:13 is • Cylinder 6 advance and cylinder 4 retract.
changed to 35. Outline the changes that this new • Cylinder 6 retract.
value will have on the timing of the traffic lights. • Sequence to repeat.
4. Answer each of the following with reference to 6. Using whatever PLC sequencer output instruction
the event-driven sequencer program shown in you are most familiar with, develop a program to
Figure 12-43: implement an automatic car-wash process. The pro-
a. When does the sequencer advance to the next step? cess is to be event-driven by the vehicle, which acti-
b. Assume that the sequencer is at position 2, as vates various limit switches (LS1 through LS6) as it
shown; what bit outputs will be on? is pulled by a conveyor chain through the car-wash
c. Assume that the sequencer is stepped to position bay. Design the program to operate the car wash in
8; what bit outputs will be on? the following manner:
d. Assume that the sequencer is at position 8 and a • The vehicle is connected to the conveyor chain and
true-to-false transition of one of the inputs occurs. pulled inside the car-wash bay.
What happens as a result? • LS1 turns on the water input valve.

Inputs Ladder logic program Output
L1 module O:2 L2
SQO 0
S1 SEQUENCER OUTPUT
S1 1
File #B3:0 EN 2
Mask F0FF DN 3
S2 Dest O:2 4
Control R6:0
S2 5
Length 8
Position 2 6
7
8
15 11 10 98 0 Destination
0 000 0000 11 11 O:2 9
10
11
12
0 1111 0 000 11111111 Mask
13
14
Pos File 15
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 #B3:0
1 0 0 1 1 0 0 0 0 0 0 1 1 0 0 1 1 Current Pos 2
Pos 2 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 step
3 1 1 0 0 0 0 0 0 1 1 0 0 1 1 0 0
4 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
5 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0
6 0 0 1 1 0 0 0 0 1 1 1 1 1 1 1 1
7 0 0 0 1 0 0 0 0 0 0 0 1 1 1 1 1
8 0 1 0 1 0 0 0 0 0 1 0 1 0 1 0 1
Figure 12-43 Event-driven sequencer program for Problem 4.

Sequencer and Shift Register Instructions Chapter 12 279

pet73842_ch12_252-280.indd 279 03/11/15 7:20 PM