Timer preset and accumulated values in PLC Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the timer preset value to 5000 milliseconds.

PLC Programming

Timer1.PRE = [1]

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

A5000

B1000

C0

DTimer1.ACC

Attempts:

3 left

💡 Hint

Common Mistakes

Using the accumulated value (ACC) instead of a fixed number.

Setting the preset to zero, which means no delay.

The preset value (PRE) sets the timer duration in milliseconds. Here, 5000 means 5 seconds.

2fill in blank

medium

Complete the code to reset the timer accumulated value to zero.

PLC Programming

Timer2.ACC = [1]

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

A0

BTimer2.PRE

CTimer2.EN

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting ACC to the preset value instead of zero.

Using the enable bit (EN) instead of a number.

Resetting the accumulated value (ACC) to zero clears the timer count.

3fill in blank

hard

Fix the error in the code to correctly compare the accumulated value with the preset.

PLC Programming

IF Timer3.ACC [1] Timer3.PRE THEN
  // Timer done
END_IF

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

A=

B!=

C>=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' which only checks exact equality.

Using '<' which checks if ACC is less than PRE.

The timer is done when the accumulated value is greater than or equal to the preset.

4fill in blank

hard

Fill both blanks to create a dictionary of timers with their preset and accumulated values.

PLC Programming

timers = {"T1": [1], "T2": [2]

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

ATimer1.PRE

BTimer2.ACC

CTimer1.ACC

DTimer2.PRE

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up preset and accumulated values.

Using the same value for both timers.

The dictionary maps timer names to their preset and accumulated values respectively.

5fill in blank

hard

Fill all three blanks to create a conditional that resets the timer if accumulated value exceeds preset.

PLC Programming

IF Timer4.ACC [1] Timer4.PRE THEN
  Timer4.ACC = [2]
  Timer4.EN = [3]
END_IF

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

A>

B0

CFalse

DTrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' in the condition.

Setting EN to True instead of False when resetting.

If accumulated value is greater than preset, reset ACC to zero and disable the timer.

Practice

1. What does the preset value of a timer represent in PLC programming?

easy

A. The number of times the timer has been reset

B. The current time counted by the timer

C. The total time the timer should count before activating

D. The delay before the timer starts counting

Solution

1. Step 1: Understand timer preset meaning

   The preset value is the target time set for the timer to reach before it triggers.

2. Step 2: Differentiate from accumulated value

   The accumulated value shows elapsed time, not the target time.

3. Final Answer:

   The total time the timer should count before activating -> Option C

4. Quick Check:

   Preset = target time [OK]

Hint: Preset is the goal time, accumulated is progress [OK]

Common Mistakes:

• Confusing preset with accumulated value
• Thinking preset changes during timing
• Assuming preset is a delay before start

2. Which of the following is the correct way to set a timer's preset value to 5000 milliseconds in a typical PLC timer instruction?

easy

A. TIMER.PRESET = 5000

B. TIMER.ACC = 5000

C. TIMER.SET = 5000

D. TIMER.TIME = 5000

Solution

1. Step 1: Identify correct property for preset

   In PLC timers, the preset value is usually set with the property named 'PRESET'.

2. Step 2: Check other options

   'ACC' is for accumulated time, 'SET' and 'TIME' are not standard properties for preset.

3. Final Answer:

   TIMER.PRESET = 5000 -> Option A

4. Quick Check:

   Preset set with .PRESET property [OK]

Hint: Preset uses .PRESET, accumulated uses .ACC [OK]

Common Mistakes:

• Using .ACC to set preset
• Using non-standard property names
• Confusing preset with timer start command

3. Given the following timer status after running:
TIMER.PRESET = 10000
TIMER.ACC = 7500
What is the timer's current state?

medium

A. Timer has finished counting and is done

B. Timer is paused at 7500 milliseconds

C. Timer is reset and not started

D. Timer is still counting and not done

Solution

1. Step 1: Compare accumulated and preset values

   The accumulated value (7500) is less than the preset (10000), so the timer has not reached its target.

2. Step 2: Determine timer state

   Since accumulated is less than preset, the timer is still counting and not done.

3. Final Answer:

   Timer is still counting and not done -> Option D

4. Quick Check:

   ACC < PRESET means timer running [OK]

Hint: If ACC < PRESET, timer is running [OK]

Common Mistakes:

• Assuming timer is done when ACC < PRESET
• Confusing paused with running
• Thinking reset means ACC is non-zero

4. A timer's accumulated value never increases even though the timer is enabled. Which is the most likely cause?

medium

A. The preset value is set to zero

B. The timer is not enabled or triggered properly

C. The accumulated value is manually reset continuously

D. The timer's accumulated value is greater than preset

Solution

1. Step 1: Understand timer behavior when enabled

   The accumulated value increases only when the timer is enabled and counting.

2. Step 2: Analyze causes for no increase

   If the timer is not enabled or triggered, the accumulated value stays the same.

3. Final Answer:

   The timer is not enabled or triggered properly -> Option B

4. Quick Check:

   Timer must be enabled to accumulate time [OK]

Hint: Timer must be enabled to increase ACC [OK]

Common Mistakes:

• Assuming preset zero stops accumulation
• Ignoring timer enable condition
• Thinking ACC resets automatically

5. You want a process to run exactly 15 seconds after a start signal. Which timer setup ensures the process starts only after 15 seconds have fully elapsed?

hard

A. Set TIMER.PRESET = 15000 and start process when TIMER.ACC >= TIMER.PRESET

B. Set TIMER.PRESET = 15000 and start process immediately when timer starts

C. Set TIMER.PRESET = 15000 and start process when TIMER.ACC = 0

D. Set TIMER.PRESET = 15000 and start process when TIMER.ACC < TIMER.PRESET

Solution

1. Step 1: Understand timing requirement

   The process must start only after 15 seconds have fully passed.

2. Step 2: Use timer values to control start

   Starting the process when accumulated time is equal or greater than preset ensures 15 seconds elapsed.

3. Final Answer:

   Set TIMER.PRESET = 15000 and start process when TIMER.ACC >= TIMER.PRESET -> Option A

4. Quick Check:

   Start after ACC >= PRESET for exact delay [OK]

Hint: Start process only when ACC reaches preset [OK]

Common Mistakes:

• Starting process immediately on timer start
• Starting before accumulated time reaches preset
• Using ACC = 0 as start condition