Counter preset and reset in PLC Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to preset the counter value to 10.

PLC Programming

COUNTER [1] PRESET 10;

Drag options to blanks, or click blank then click option'

AC4

BC1

CC3

DC2

Attempts:

3 left

💡 Hint

Common Mistakes

Using a counter name that is not defined.

Forgetting to specify the counter name.

The counter named C1 is preset to 10 using the PRESET instruction.

2fill in blank

medium

Complete the code to reset the counter named C2.

PLC Programming

COUNTER [1] RESET;

Drag options to blanks, or click blank then click option'

AC1

BC3

CC2

DC4

Attempts:

3 left

💡 Hint

Common Mistakes

Resetting the wrong counter.

Omitting the counter name.

The RESET instruction is applied to counter C2 to reset its count.

3fill in blank

hard

Fix the error in the code to correctly preset counter C3 to 5.

PLC Programming

COUNTER [1] PRESET 5;

Drag options to blanks, or click blank then click option'

AC1

BC2

CC4

DC3

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different counter name than C3.

Syntax errors in the instruction.

The counter C3 is correctly specified for presetting to 5.

4fill in blank

hard

Fill both blanks to preset counter C4 to 7 and then reset it.

PLC Programming

COUNTER [1] PRESET 7;
COUNTER [2] RESET;

Drag options to blanks, or click blank then click option'

AC4

BC1

CC2

DC3

Attempts:

3 left

💡 Hint

Common Mistakes

Using different counters for preset and reset.

Forgetting to specify the counter name in one of the instructions.

Both preset and reset instructions apply to counter C4.

5fill in blank

hard

Fill all three blanks to preset counter C1 to 12, reset counter C2, and preset counter C3 to 8.

PLC Programming

COUNTER [1] PRESET 12;
COUNTER [2] RESET;
COUNTER [3] PRESET 8;

Drag options to blanks, or click blank then click option'

AC1

BC2

CC3

DC4

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up counter names for preset and reset.

Omitting a counter name.

The instructions apply preset to C1 and C3, and reset to C2 as required.

Practice

1. What does the preset value in a PLC counter do?

easy

A. It sets the target count the counter must reach.

B. It resets the counter to zero.

C. It increments the counter by one.

D. It pauses the counter from counting.

Solution

1. Step 1: Understand the role of preset in counters

   The preset value defines the goal number the counter counts up to before triggering an action.

2. Step 2: Differentiate preset from reset and increment

   Reset clears the count, increment adds to count, but preset sets the target number.

3. Final Answer:

   It sets the target count the counter must reach. -> Option A

4. Quick Check:

   Preset = target count [OK]

Hint: Preset is the goal number, reset clears count [OK]

Common Mistakes:

• Confusing preset with reset
• Thinking preset increments count
• Assuming preset pauses counting

2. Which of the following is the correct way to reset a counter named CNT1 in ladder logic?

easy

A. Use RES CNT1 instruction.

B. Use PRE CNT1 instruction.

C. Use INC CNT1 instruction.

D. Use SET CNT1 instruction.

Solution

1. Step 1: Identify reset instruction syntax

   In PLC ladder logic, RES is the standard instruction to reset a counter.

2. Step 2: Confirm other instructions meanings

   PRE sets preset, INC increments, SET sets bits, not reset counter.

3. Final Answer:

   Use RES CNT1 instruction. -> Option A

4. Quick Check:

   Reset = RES instruction [OK]

Hint: Reset uses RES instruction, not PRE or INC [OK]

Common Mistakes:

• Using PRE instead of RES to reset
• Confusing increment with reset
• Using SET which is for bits, not counters

3. Given a counter with preset 5 and current count 3, what will be the count after two increments?

medium

A. 4

B. 5

C. 3

D. 6

Solution

1. Step 1: Calculate count after increments

   Starting count is 3, two increments add 2, so 3 + 2 = 5.

2. Step 2: Compare count to preset

   The count reaches the preset value 5 after two increments.

3. Final Answer:

   5 -> Option B

4. Quick Check:

   3 + 2 = 5 [OK]

Hint: Add increments to current count, compare to preset [OK]

Common Mistakes:

• Not adding increments correctly
• Confusing preset with current count
• Assuming count resets automatically

4. A PLC counter is not resetting when the reset button is pressed. Which of these is the most likely cause?

medium

A. The preset value is set too high.

B. The increment instruction is used instead of reset.

C. The counter is already at zero.

D. The reset instruction is missing or not connected to the reset button.

Solution

1. Step 1: Check reset wiring and instruction

   If the reset button does not trigger reset, likely the reset instruction is missing or not linked to the button.

2. Step 2: Eliminate other causes

   Preset value or current count does not prevent reset; increment instruction wrong but would not cause no reset on button press.

3. Final Answer:

   The reset instruction is missing or not connected to the reset button. -> Option D

4. Quick Check:

   Reset fails if instruction missing or unlinked [OK]

Hint: Reset needs instruction linked to button [OK]

Common Mistakes:

• Blaming preset for reset failure
• Ignoring wiring or logic connection
• Confusing increment with reset

5. You want a counter to count up to 10, then reset automatically and start counting again from zero. Which ladder logic setup achieves this?

hard

A. Set preset to 0, increment counter indefinitely.

B. Set preset to 10, reset counter manually with a button.

C. Set preset to 10, use counter done bit to trigger reset instruction.

D. Use reset instruction before counting starts only.

Solution

1. Step 1: Understand automatic reset logic

   To reset automatically, use the counter's done bit (which is true when count reaches preset) to trigger the reset instruction.

2. Step 2: Evaluate other options

   Manual reset requires user action, preset 0 is invalid for counting, resetting only before counting won't loop.

3. Final Answer:

   Set preset to 10, use counter done bit to trigger reset instruction. -> Option C

4. Quick Check:

   Done bit triggers reset for auto count loop [OK]

Hint: Use done bit to auto reset counter [OK]

Common Mistakes:

• Relying on manual reset for auto counting
• Setting preset to zero
• Resetting only once before counting