Numeric displays and indicators in PLC Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to display the numeric value on the indicator.

PLC Programming

DisplayValue := [1];

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

ASensorInput

BSetPoint

COutputSignal

DTimerValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using SetPoint instead of SensorInput.

Assigning OutputSignal which is an output, not a display value.

The variable SensorInput holds the numeric value to be shown on the display.

2fill in blank

medium

Complete the code to convert the integer value to a string for the display.

PLC Programming

DisplayString := [1](SensorValue);

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ATO_BOOL

BTO_STRING

CTO_INT

DTO_REAL

Attempts:

3 left

💡 Hint

Common Mistakes

Using TO_REAL which converts to real number, not string.

Using TO_BOOL which converts to boolean.

The function TO_STRING converts numeric values to text for display.

3fill in blank

hard

Fix the error in the code to correctly update the numeric display.

PLC Programming

IF SensorValue [1] 100 THEN
  DisplayValue := SensorValue;
END_IF

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

A==

B<

C=>

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=>' which is invalid.

Using '==' which is not standard in PLC languages.

The operator >= means 'greater than or equal to', which is correct syntax.

4fill in blank

hard

Fill both blanks to create a dictionary mapping sensor names to their display values.

PLC Programming

DisplayMap = {"TempSensor": [1], "PressureSensor": [2];

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ATempValue

BPressureValue

CSensorValue

DDisplayValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same variable for both sensors.

Using DisplayValue which is generic.

The dictionary keys map to the correct sensor values: TempValue and PressureValue.

5fill in blank

hard

Fill all three blanks to filter and display sensor values above threshold.

PLC Programming

FilteredDisplay = {k: v for k, v in SensorData.items() if v [1] [2];
DisplayValue = FilteredDisplay.get([3], 0);

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

A>

B50

C"TempSensor"

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' for filtering.

Using wrong sensor key in get().

The code filters values greater than 50 and gets the value for 'TempSensor'.

Practice

1. What is the main purpose of numeric displays in PLC programming?

easy

A. To control the power supply

B. To store data in memory

C. To show numbers clearly on control panels

D. To connect different devices

Solution

1. Step 1: Understand numeric displays

   Numeric displays are designed to show numbers clearly so operators can read values easily.

2. Step 2: Identify the correct purpose

   Among the options, only showing numbers clearly matches the function of numeric displays.

3. Final Answer:

   To show numbers clearly on control panels -> Option C

4. Quick Check:

   Numeric displays = show numbers clearly [OK]

Hint: Numeric displays always show numbers, not control or storage [OK]

Common Mistakes:

• Confusing numeric displays with data storage
• Thinking numeric displays control power
• Mixing numeric displays with device connections

2. Which of the following is the correct syntax to display a numeric value on a PLC numeric display using a function called DisplayNumber with input value?

easy

A. DisplayNumber(value);

B. DisplayNumber = value;

C. DisplayNumber:value;

D. DisplayNumber->value;

Solution

1. Step 1: Identify function call syntax

   In PLC programming, calling a function with an argument uses parentheses, like DisplayNumber(value);

2. Step 2: Check other options

   Options A, B, and C use incorrect assignment or symbol syntax not valid for function calls.

3. Final Answer:

   DisplayNumber(value); -> Option A

4. Quick Check:

   Function call syntax uses parentheses [OK]

Hint: Function calls use parentheses with arguments [OK]

Common Mistakes:

• Using assignment instead of function call
• Using colon or arrow symbols incorrectly
• Missing parentheses for function arguments

3. Given the following PLC code snippet, what will be the displayed output on the numeric display?

int temperature = 25;
DisplayNumber(temperature + 5);

medium

A. Error

B. 25

C. 5

D. 30

Solution

1. Step 1: Calculate the expression inside DisplayNumber

   The code adds 5 to the variable temperature (25 + 5), resulting in 30.

2. Step 2: Understand DisplayNumber output

   The function displays the calculated value, so the numeric display shows 30.

3. Final Answer:

   30 -> Option D

4. Quick Check:

   25 + 5 = 30 displayed [OK]

Hint: Add values before display function call [OK]

Common Mistakes:

• Ignoring the addition operation
• Assuming the display shows the variable only
• Thinking the code causes an error

4. Identify the error in this PLC code snippet intended to display a numeric value:

int speed = 100
DisplayNumber(speed);

medium

A. Incorrect function name

B. Missing semicolon after variable declaration

C. Variable type is wrong

D. DisplayNumber cannot take variables

Solution

1. Step 1: Check syntax of variable declaration

   The line int speed = 100 is missing a semicolon at the end, which is required.

2. Step 2: Verify function call correctness

   The function call DisplayNumber(speed); is correct and uses the variable properly.

3. Final Answer:

   Missing semicolon after variable declaration -> Option B

4. Quick Check:

   Semicolon missing after int declaration [OK]

Hint: Always end statements with semicolon [OK]

Common Mistakes:

• Forgetting semicolon after declarations
• Assuming function name is wrong
• Thinking variables can't be passed to functions

5. You want to display a temperature value with one decimal place on a numeric display in a PLC program. Which approach correctly formats the number before display?

float temp = 23.456;
// Choose the correct formatting method
DisplayNumber(____);

hard

A. round(temp, 1)

B. int(temp)

C. temp + 0.1

D. floor(temp)

Solution

1. Step 1: Understand formatting for decimals

   To show one decimal place, rounding the float to 1 decimal is needed.

2. Step 2: Evaluate options

   Only round(temp, 1) correctly rounds to one decimal place. temp + 0.1 (temp + 0.1) changes the value, B (int(temp)) removes decimals, D (floor(temp)) truncates down.

3. Final Answer:

   round(temp, 1) -> Option A

4. Quick Check:

   Rounding to 1 decimal = round(temp, 1) [OK]

Hint: Use round(value, decimals) to format numbers [OK]

Common Mistakes:

• Using int() which removes decimals
• Adding small values instead of rounding
• Using floor() which truncates without rounding