Presentation on the AB ControlLogix counters; CTU and CTD. Also includes a brief introduction to IEC 61131-3 standard counters using Siemens and AB CCW as examples.

1. Chapter 05 - Counters
Covered in class

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

3. Mechanical Counters
 Programmed counters
can serve the same
functions as mechanical
counters
 Every time the actuating
lever is moved or rotated,
the counter adds one or
subtracts one number.
The actuating lever then
returns automatically to
its original position.
Resetting the counter to
zero is usually done with
a pushbutton located on
the unit.

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.
 PLC/PAC counters function in a very
similar manner.

5. PLC/PAC Counters
 PLC/PAC counters are usually ‘retentive’.
 Whatever count was contained in the counter
at the time of a processor shutdown will be
restored to the counter on power-up.
 A counter(s) can be reset on power-up if
the reset condition is activated at the time
of power restoration; the first scan.
 PLC/PAC counters can be designed to
count up to a preset value or to count
down to a preset value.

6. Counter Instructions –
Ladder Programming
 Allen Bradley ControlLogix has two instructions
available:
 CTU – Count UP
 CTD – Count DOWN
 Allen Bradley CCW has three counter instructions
available: (IEC 61131-3)
 CTU – Count UP
 CTD – Count DOWN
 CTUD – Count UP-DOWN
 Siemens has three counter instruction available:
(IEC 61131-3)
 CTU – Count UP
 CTD – Count DOWN
 CTUD – Count UP-DOWN

7. ControlLogix CTU
Counter tag name:
Ex. cartonCount
Preset – Number of items or
events to count before an
output occurs
Accumulator – The
current number of
counts on the counter
 ControlLogix CTU counter has three parameters.

8. ControlLogix Counter
Parameters
 Counter
 The tag name of the counter. Example:
cartonCount. The tag is created as a Counter
Data Type.
 Preset Value (PRE)
 The Preset value is the number of counts that
should occur before the counting event is done.
The valid range is:
 -2,147,483,648 to 2,147,483,647
 Accumulator Value (ACC)
 Stores the current count value of the counter. The
value range is the same as the preset parameter.

9. ControlLogix Counter
Memory
 Counters use a counter data type called a
Structure. Structures are data types that
consist of more than one word.
 The Counter structure consists of three,
32-bit words where:
 Word 0 of the structure stores the Status bits
of the counter.
 Word 1 of the structure stores the Preset
value.
 Word 2 of the structure stores the
Accumulator value.

10. ControlLogix Counter
Memory
 There are five counter status bits:
 CU – Count UP (CTU only)
 CD – Count DOWN (CTD only)
 DN – Done (CTU & CTD)
 OV – Overflow (CTU only)
 UN – Underflow (CTD only)
Structure
members
The plus (+) sign is
used to drill into the
structure. The minus
(-) is used to collapse
a structure
Data types of the
members of the
structure.

11. Counter Status Bits
 Count UP (CU) (CTU only)
 Sets to a logic ‘1’ when the rung containing the
Count UP (CTU) counter is true, otherwise it is a
logic ‘0’.
 Count DOWN (CD) (CTD only)
 Sets to a logic ‘1’ when the rung containing the
Count DOWN (CTD) counter is true, otherwise it
is a logic ‘0’.
 Done (DN)
 Sets to a logic ‘1’ when the Accumulator value is
greater than or equal to the preset value
(ACC  PRE), other wise it is a logic ‘0’.

12. Counter Status Bits
 Overflow (OV) (CTU only)
 Used with the Count UP (CTU) counter. If the
accumulator has reached a maximum positive
value of +2,147,483,647 and the counter is
incremented up again, the accumulator will wrap
around to -2,147,483,648. When this wrap around
occurs, the Overflow (OV) bit will set to a logic ‘1’.
If the Done (DN) bit is set to a ‘1’ and the counter
overflows, the Done (DN) bit will remain a ‘1’,
even if the accumulator is less than the preset
(ACC < PRE). The counter must be reset with the
RES instruction to reset the Overflow (OV) bit to a
logic ‘0’ and to clear the Done (DN) bit.

13. Counter Status Bits
 Underflow (UN) (CTD only)
 Used with the Count DOWN (CTD) counter. If the
accumulator has reached a minimum negative
value of -2,147,483,648 and the counter is
decremented down again, the accumulator will
wrap around to +2,147,483,647. When this wrap
around occurs, the Underflow (UN) bit will set to a
logic ‘1’. If the Done (DN) bit is set to a ‘1’ and the
counter underflows, the Done (DN) bit will remain
a ‘1’, even if the accumulator is less than the
preset (ACC < PRE). The counter must be reset
with the RES instruction to reset the underflow
(UN) bit to a logic ‘0’ and to clear the Done (DN)
bit.

14. CTU Functionality
 Count UP counters count false to
true rung transitions. Each false to
true transition generates one count
on the CTU counter.
 When the rung is true, the Count
UP (CU) bit is set to a ‘1’. When
the rung is false, the Count UP
(CU) is reset to a ‘0’.
 When the ACC  PRE, the Done
(DN) bit is set to a ‘1’. An RES
instruction is required to reset the
accumulator to zero.
Rung CU OV DN ACC
0 0 1
0 0 2
0 0 500
0 1 1000
0 1 1050
0 1 Max+
1 1 Min-

15. Accessing Counter Data
 The ‘dot’ notation is used to access the data
of a counter structure.
 To access the status bits of the cartonCount:
 The Done (DN) bit would be the, counter tag,
‘dot’, the bit designator
 cartonCount.DN
 The other status bits are accessed in a
similar manner:
 cartonCount.CU for the Counter Count UP Bit
 cartonCount.OV for the Counter Overflow Bit

16. Accessing Counter Data
 The ‘dot’ notation is used to access the data
of a counter structure.
 To access the value of the preset or the
accumulator words:
 cartonCount.PRE for the Preset value
 cartonCount.ACC for the Accumulator value
 All words can also be referenced to bit level,
therefore:
 cartonCount.ACC.5 would be bit 5 of the
Accumulator word of the cartonCount counter.
 cartonCount.PRE.12 would be bit 12 of the
Preset word of the cartonCount counter.

17. ControlLogix CTU
Counter

18. ControlLogix CTD
 ControlLogix CTD counter has three
parameters.
Counter tag name:
Ex. bottleExiting
Preset – Number of events to
count before an output occurs
Accumulator – The
current number of
counts on the counter

19. ControlLogix Counter
Parameters
 Counter
 The tag name of the counter. Example:
bottleExiting. The tag is created as a Counter
Data Type.
 Preset Value (PRE)
 The Preset value is the number of counts that
should occur before the counting event is done.
The valid range is:
 -2,147,483,648 to 2,147,483,647
 Accumulator Value (ACC)
 Stores the current count value of the counter. The
value range is the same as the preset parameter.

20. ControlLogix Counter
Memory
 Counters use a counter data type called a
Structure. Structures are data types that
consist of more than one word.
 The Counter structure consists of three,
32-bit words where:
 Word 0 of the structure stores the Status bits
of the counter.
 Word 1 of the structure stores the Preset
value.
 Word 2 of the structure stores the
Accumulator value.

21. ControlLogix Counter
Memory
 There are five counter status bits:
 CU – Count UP (CTU only)
 CD – Count DOWN (CTD only)
 DN – Done (CTU & CTD)
 OV – Overflow (CTU only)
 UN – Underflow (CTD only)
Structure
members
The plus (+) sign is
used to drill into the
structure. The minus
(-) is used to collapse
a structure
Data types of the
members of the
structure.

22. Counter Status Bits
 Count UP (CU) (CTU only)
 Sets to a logic ‘1’ when the rung containing the
Count UP (CTU) counter is true, otherwise it is a
logic ‘0’.
 Count DOWN (CD) (CTD only)
 Sets to a logic ‘1’ when the rung containing the
Count DOWN (CTD) counter is true, otherwise it
is a logic ‘0’.
 Done (DN)
 Sets to a logic ‘1’ when the Accumulator value is
greater than or equal to the preset value
(ACC  PRE), other wise it is a logic ‘0’.

23. Counter Status Bits
 Overflow (OV) (CTU only)
 Used with the Count UP (CTU) counter. If the
accumulator has reached a maximum positive
value of +2,147,483,647 and the counter is
incremented up again, the accumulator will wrap
around to -2,147,483,648. When this wrap around
occurs, the Overflow (OV) bit will set to a logic ‘1’.
If the Done (DN) bit is set to a ‘1’ and the counter
overflows, the Done (DN) bit will remain a ‘1’,
even if the accumulator is less than the preset
(ACC < PRE). The counter must be reset with the
RES instruction to reset the Overflow (OV) bit to a
logic ‘0’ and to clear the Done (DN) bit.

24. Counter Status Bits
 Underflow (UN) (CTD only)
 Used with the Count DOWN (CTD) counter. If the
accumulator has reached a minimum negative
value of -2,147,483,648 and the counter is
decremented down again, the accumulator will
wrap around to +2,147,483,647. When this wrap
around occurs, the Underflow (UN) bit will set to a
logic ‘1’. If the Done (DN) bit is set to a ‘1’ and the
counter underflows, the Done (DN) bit will remain
a ‘1’, even if the accumulator is less than the
preset (ACC < PRE). The counter must be reset
with the RES instruction to reset the underflow
(UN) bit to a logic ‘0’ and to clear the Done (DN)
bit.

25. CTD Status Bit
Functionality
 Count DOWN counters count false to
true rung transitions. Each false to true
decrements one count on the CTD
counter.
 When the rung is true, the Count
DOWN (CD) bit is set to a ‘1’. When the
rung is false, the Count DOWN (CD) is
reset to a ‘0’.
 When the ACC  PRE, the Done (DN)
bit is set to a ‘1’. An RES instruction is
required to reset the accumulator to
zero.
Rung CD UN DN ACC
0 1 -1
0 1 -36
0 1 -50
0 0 -51
0 0 -53
0 0 Min -
1 0 Max +

26. Accessing Counter Data
 The ‘dot’ notation is used to access the data
of a counter structure.
 To access the status bits of the bottleExiting:
 The Done (DN) bit would be the counter tag, ‘dot’,
the bit designator
 bottleExiting.DN
 The other status bits are accessed in a
similar manner:
 bottleExiting.CD for the Count DOWN Bit
 bottleExiting.UN for the Underflow Bit

27. Accessing Counter Data
 The ‘dot’ notation is used to access the data
of a counter structure.
 To access the value of the preset or the
accumulator words:
 bottleExiting.PRE for the Preset value
 bottleExiting.ACC for the Accumulator value
 All words can also be referenced to bit level,
therefore:
 bottleExiting.ACC.5 would be bit 5 of the
Accumulator word of the bottleExiting counter.
 bottleExiting.PRE.12 would be bit 12 of the
Preset word of the bottleExiting counter.

28. ControlLogix CTD
Counter

29. COUNTER EXAMPLES

30. Parts Counting
 Counter totalNumOfParts
counts the total number of
parts coming off an assembly
line for final packaging.
 Each package must contain
10-parts.
 When 10-parts are detected,
counter numberOfParts sets bit
intBoxClosSeq to initiate the
box closing sequence.
 Counter totalPackages counts
the total number of packages
filled per day.
 A push button is used to restart
the total part and package
count to zero, daily.
http://www.keyence.com/img/products/series/il_ws_sr48219_device_count.gif

31. Parts Counting
Program continued on next slide

32. Parts Counting

33. Conveyor Motor
 This circuit will use a oneshot
for reset and another oneshot
to prevent the PLC from
seeing chatter from the
sensor.
 Sequential task:
 The VFD is used to start the
conveyor motor.
 Parts pass the sensor and
increment a counter
accumulator.
 After 50-counts, the conveyor
motor automatically stops and
the counter accumulator is reset.
 The conveyor motor can be
stopped or started manually at
any time without loss of
accumulator counts.
http://www.keyence.com/img/products/series/il_ws_sr48219_device_count.gif

34. Conveyor Motor

35. Alarm Monitor
 The alarm is triggered by the closing of liquid level
switch LS1.
 The alarm light will flash whenever the alarm
condition is triggered and has not been
acknowledged, even if the alarm condition clears
in the meantime.
 The alarm is acknowledged by closing selector
switch SS1.
 The alarm light will operate in the steady mode
when the alarm trigger condition exits but has
been acknowledged.

36. Alarm Monitor

37. Parking Garage Counter
 As a car enters the parking garage it triggers an up
counter and increments the accumulator by one count.
 As a car leaves the parking garage it triggers a down
counter and decrements the accumulator by one count.
 The up and down counters will use the same tag name.
Since the counters have the same tag name, the
accumulated value is the same for both counters.
 Whenever the accumulator value is equal to the preset
value, the counter output is energized to light the “Lot
Full” sign.

38. Parking Garage Counter

39. IEC Counters
 The IEC 31161-3 standard specifies three
counters:
 Count UP – CTU
 Count DOWN – CTD
 Count UP/DOWN – CTUD
 The functionality of the CTU and CTD are
basically the same as the ControlLogix
counters.
 Siemens and Allen Bradley CCW use the
IEC standard counters.

40. IEC 31161-3 CTU
 The IEC 31161-3 CTU has three inputs and two
outputs:
 IN – Data type BOOL ≡ Count UP (CU)
 R – Data type BOOL (Reset the counter)
 PV – Data type DINT ≡ Preset (PRE)
 Q – Data type BOOL ≡ Done Bit (DN)
 CV – Data type DINT ≡ Accumulator (ACC)
Siemens counter shown

41. IEC 31161-3 CTD
 The IEC 31161-3 CTD has two inputs and two
outputs:
 CD – Data type BOOL ≡ Count DOWN (CD)
 LD – Data type BOOL – Load (CV = PV when LD is True)
 PV – Data type DINT ≡ Preset (PRE)
 Q – Data type BOOL ≡ Done Bit (DN)
 CV – Data type DINT ≡ Accumulator (ACC)
Siemens counter shown

42. IEC 31161-3 CTUD
 The IEC 31161-3 CTD has five inputs and three
outputs:
 CU – Data type BOOL ≡ Count UP (CU)
 CD – Data type BOOL ≡ Count DOWN (CD)
 R – Data type BOOL (Reset the counter)
 LD – Data type BOOL – Load (CV = PV when LD is
True)
 PV – Data type DINT ≡ Preset (PRE)
 QU – Data type BOOL ≡ Overflow (OV)
True when CV  PV
 QD – Data type BOOL ≡ Underflow (UN)
True when CV  PV
 CV – Data type DINT ≡ Accumulator (ACC)

43. IEC 31161-3 CTD
Siemens counter shown

44. IEC 31161-3 Counters -
CCW
 The Allen Bradley CCW software uses the same
type of counter with the same functionality.

45. IEC 31161-3 Counters -
CCW
 The Allen Bradley CCW software uses the same
type of counters with the same functionality.

46. References
Dagget, R. (n.d.). 3 Options for Starting and Stopping an AC Motor. Retrieved October 28,
2016, from Bastian Solutions:
https://www.bastiansolutions.com/blog/index.php/2014/03/17/3-options-for-starting-and-
stopping-ac-motor/#.WBO20y0rLiw
Direct Industry. (n.d). Digital Up-Down Counters. Retrieved October 2016, 2016, from Direct
Industry: http://www.directindustry.com/industrial-manufacturer/digital-up-down-counter-
159777.html
Direct Industry. (n.d.). Line Seike. Retrieved October 25, 2016, from Direct Industry:
http://www.directindustry.com/prod/line-seiki/product-23163-633672.html
Find Icons. (n.d.). Reset. Retrieved October 28, 2016, from Find Icons:
http://findicons.com/search/reset
Keyence America. (n.d.). An Even Wider Range of Applications. Retrieved October 28, 2016,
from Keyence America: http://www.keyence.com/products/measure/laser-
1d/il/applications/index.jsp
Newark element14. (n.d.). Veeder Root 0166726-006 Mechanical Counter, Ratchet Drive.
Retrieved October 25, 2016, from Newark element 14: http://www.newark.com/veeder-
root/0166726-006/mechanical-counter-ratchet-drive/dp/88C9906