Parts counter with conveyor in PLC Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start the conveyor motor when the start button is pressed.

PLC Programming

IF StartButton = TRUE THEN
    ConveyorMotor := [1];
END_IF;

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

ASTOP

BOFF

CON

DRESET

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the motor to OFF instead of ON.

Using RESET or STOP which do not start the motor.

The conveyor motor should be turned ON when the start button is pressed.

2fill in blank

medium

Complete the code to increment the parts counter when the sensor detects a part.

PLC Programming

IF Sensor = TRUE THEN
    PartsCounter := PartsCounter [1] 1;
END_IF;

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

A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-' which decreases the counter.

Using '*' or '/' which are not for incrementing.

The parts counter should increase by 1 when a part is detected, so use the '+' operator.

3fill in blank

hard

Fix the error in the code to reset the parts counter when the reset button is pressed.

PLC Programming

IF ResetButton = TRUE THEN
    PartsCounter := [1];
END_IF;

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

A0

BPartsCounter

C1

DNULL

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning PartsCounter to itself does not reset it.

Using 1 or NULL which do not reset the counter properly.

To reset the counter, set PartsCounter to 0.

4fill in blank

hard

Fill both blanks to stop the conveyor motor when the stop button is pressed and reset the parts counter.

PLC Programming

IF StopButton = TRUE THEN
    ConveyorMotor := [1];
    PartsCounter := [2];
END_IF;

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

AOFF

BON

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Turning motor ON instead of OFF.

Resetting counter to 1 instead of 0.

When stopping, the motor should be OFF and the parts counter reset to 0.

5fill in blank

hard

Fill all three blanks to create a condition that starts the conveyor only if the start button is pressed, the stop button is not pressed, and the parts counter is less than 100.

PLC Programming

IF StartButton = TRUE AND StopButton = FALSE AND PartsCounter [1] [2] THEN
    ConveyorMotor := [3];
END_IF;

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

A<

B100

CON

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' for the counter check.

Turning motor OFF instead of ON.

The conveyor starts if PartsCounter is less than 100, so use '<' and 100, and turn motor ON.

Practice

1. What is the main purpose of a parts counter in a conveyor system?

easy

A. To count the number of parts passing a sensor and stop the conveyor after a set count

B. To increase the speed of the conveyor belt automatically

C. To sort parts by size on the conveyor

D. To clean the conveyor belt during operation

Solution

1. Step 1: Understand the role of the parts counter

   The parts counter uses a sensor to detect each part passing on the conveyor.

2. Step 2: Identify the action after counting

   Once the set number of parts is reached, the conveyor stops to control production.

3. Final Answer:

   To count the number of parts passing a sensor and stop the conveyor after a set count -> Option A

4. Quick Check:

   Parts counter purpose = Count and stop conveyor [OK]

Hint: Focus on counting and stopping conveyor after set parts [OK]

Common Mistakes:

• Confusing counting with sorting
• Thinking the counter speeds up conveyor
• Assuming it cleans the conveyor

2. Which of the following is the correct way to reset a parts counter in a PLC program?

easy

A. Disconnect the sensor from the PLC

B. Increase the counter value by one

C. Stop the conveyor without changing the counter

D. Set the counter value to zero using a reset instruction

Solution

1. Step 1: Identify how counters reset in PLCs

   Counters are reset by setting their value back to zero using a reset instruction.

2. Step 2: Eliminate incorrect options

   Increasing the counter or stopping conveyor does not reset the count; disconnecting sensor stops detection but not reset.

3. Final Answer:

   Set the counter value to zero using a reset instruction -> Option D

4. Quick Check:

   Reset counter = set to zero [OK]

Hint: Reset means setting count back to zero, not stopping conveyor [OK]

Common Mistakes:

• Confusing reset with increment
• Stopping conveyor does not reset count
• Disconnecting sensor is not a reset

3. Given this PLC ladder logic snippet for a parts counter:

IF Sensor = TRUE THEN
  Counter = Counter + 1
END IF
IF Counter >= 10 THEN
  Conveyor = OFF
END IF

What will be the state of the conveyor after 10 parts pass the sensor?

medium

A. Conveyor remains ON

B. Sensor stops detecting parts

C. Conveyor turns OFF

D. Counter resets to zero

Solution

1. Step 1: Analyze the counter increment

   Each time the sensor is TRUE, the counter increases by 1 until it reaches 10.

2. Step 2: Check conveyor control condition

   When counter is 10 or more, the conveyor is turned OFF.

3. Final Answer:

   Conveyor turns OFF -> Option C

4. Quick Check:

   Counter >= 10 stops conveyor [OK]

Hint: Conveyor stops when count reaches or exceeds limit [OK]

Common Mistakes:

• Thinking conveyor stays ON after 10 parts
• Assuming counter resets automatically
• Believing sensor stops detecting

4. Identify the error in this PLC code snippet for counting parts:

IF Sensor = TRUE THEN
  Counter = Counter + 1
END IF
IF Counter = 10 THEN
  Conveyor = OFF
  Counter = 0
END IF

What problem might occur?

medium

A. Counter resets before conveyor stops, so conveyor never stops

B. Counter never increments because sensor is not checked

C. Conveyor never turns OFF because condition uses '=' instead of '>='

D. Sensor input is not used in the code

Solution

1. Step 1: Review counter reset timing

   The counter resets to zero immediately after reaching 10, possibly before conveyor stops.

2. Step 2: Understand effect on conveyor

   If counter resets too soon, the conveyor OFF condition may not hold, causing conveyor to continue running.

3. Final Answer:

   Counter resets before conveyor stops, so conveyor never stops -> Option A

4. Quick Check:

   Resetting counter too early breaks stop logic [OK]

Hint: Reset counter after conveyor stops, not before [OK]

Common Mistakes:

• Resetting counter immediately after reaching target
• Using '=' instead of '>=' causing missed conditions
• Ignoring sensor input usage

5. You want to modify a parts counter program so the conveyor stops only after counting 50 parts, but also resets the counter automatically after stopping. Which sequence of actions in the PLC program is correct?

hard

A. Reset counter, then check if counter >= 50, then stop conveyor

B. Check if counter >= 50, then stop conveyor, then reset counter

C. Stop conveyor first, then check counter, then reset counter

D. Increment counter only after conveyor stops

Solution

1. Step 1: Set condition to check counter value

   The program must check if the counter has reached or exceeded 50 parts.

2. Step 2: Stop conveyor and then reset counter

   After stopping the conveyor, reset the counter to zero to prepare for next batch.

3. Final Answer:

   Check if counter >= 50, then stop conveyor, then reset counter -> Option B

4. Quick Check:

   Stop then reset after count reached [OK]

Hint: Stop conveyor first, then reset counter after count reached [OK]

Common Mistakes:

• Resetting counter before checking count
• Stopping conveyor without checking count
• Incrementing counter only after stopping conveyor