my lesson about counters in terms of up and down as well up/down counters

1. 1

2. IBRAHIM AL-ZUGHAIBI
COUNTERS
2

3. Counters
Common applications of counters include keeping track
of the number of items moving past a given point, and
determining the number of times a given action occurs.
A preset counter can control
an external circuit when its
counted total matches the
user-entered preset limits.
3

4. Electronic Counters
Electronic counters can count up, count down, or be combined
to count up and down. They are dependent on external
sources, such as parts traveling past a sensor or actuating a
limit switch for counting.
Counter
Applications
4

5. Block-Formatted Counter Instruction
Type of
counter
Preset value
Accumulated
value
Count line
Reset line
Output
line
5

6. The up-counter is incremented by 1 each time the rung
containing the counter is energized.
Counter Counting Sequence
The counter will increment until the accumulated value is
equal to or greater than the preset value, at which time an
output will be produced.
6

7. The down-counter decrements by 1 each time the rung
containing the counter is energized.
Counter Counting Sequence
7

8. Simple Up-counter Program
7
8

9. Up-counter Program Timing Diagram
9

10. 10

11. 1. One common application for a counter is
keeping track of the number of items moving
past a given point. (True/False)
2. Timers, like counters, are not dependent on
external sources for counting. (True/False)
3. The down-counter increments by 1 each time
the rung containing the counter is energized.
(True/False)
10 points
10 points
10 points
11

12. 4. Normally, when power to your PLC
system is lost, when power is restored the
counter accumulated value will be:
a. zero
b. whatever it was preset for
c. maximum
d. Unchanged
10 points
12

13. 5. The output of a PLC counter is switch from “off”
to “on” any time the count input rung is "true".
(True/False)
6. A PLC up-counter normally counts true-to-false
transitions. (True/False)
7. In order for the PLC counter to reset, the
counter reset rung must be “false”.
(True/False)
10 points
10 points
10 points
13

14. 8. The done bit of a counter is true whenever:
a. the accumulated value is equal to the preset
value
b. the counter instruction is true
c. the accumulated value is greater than the
preset value.
d. both a and c
10 points
14

15. 9. The _________ value of a PLC counter
is the current count based on the number
of times the rung goes from false-to-true.
a. preset c. accumulated
b. overflow d. underflow
10 points
15

16. 10. Count rung transitions can be caused by
actuating:
a. a limit switch c. a pressure switch
b. a sensor d. any of these
10 points
16

17. 17

18. Down-Counter
Normally the down-counter is used in conjunction with
the up counter to form an up/down counter.
18

19. Up/Down Counter Timing diagram
Preset Value = 3
19

20. Parking Garage Counter Program
20

21. Parking Garage Counter Program
50
50
38
38
150
150
21

22. Partner Work
22