HMI screen design basics in PLC Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the screen title in an HMI project.

PLC Programming

screen.title = "[1]"

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

AMain Screen

BSensor Value

CStart Button

DAlarm Status

Attempts:

3 left

💡 Hint

Common Mistakes

Using control names like 'Start Button' as the screen title.

Leaving the title blank or generic.

The screen title should describe the screen purpose, such as 'Main Screen'.

2fill in blank

medium

Complete the code to create a button that starts a motor when pressed.

PLC Programming

button.action = "[1]"

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

Aopen_valve()

Bstop_motor()

Cstart_motor()

Dreset_alarm()

Attempts:

3 left

💡 Hint

Common Mistakes

Using stop_motor() which stops the motor instead of starting it.

Using unrelated functions like reset_alarm().

The button should trigger the start_motor() function to start the motor.

3fill in blank

hard

Fix the error in the code to display the temperature value on the HMI screen.

PLC Programming

display.text = sensor.[1]

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

Astatus

Bvalue

Cname

Dtype

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'status' which might be a string like 'OK' or 'Error'.

Using 'name' or 'type' which are descriptive, not numeric values.

The 'value' property holds the current temperature reading from the sensor.

4fill in blank

hard

Fill both blanks to create a conditional color change for a warning light on the HMI.

PLC Programming

if temperature [1] [2]:
    warning_light.color = "red"

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

A>

B<

C75

D50

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' which would trigger the warning for low temperature.

Using 50 which is a lower threshold than intended.

The warning light should turn red if temperature is greater than 75 degrees.

5fill in blank

hard

Fill all three blanks to create a dictionary mapping sensor names to their values, filtering only active sensors.

PLC Programming

sensor_data = { [1]: [2] for [3] in sensors if [3].status == 'active' }

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

Asensor.name

Bsensor.value

Csensor

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent variable names in the comprehension.

Not filtering by sensor.status == 'active'.

We use 'sensor' as the variable name, map sensor.name to sensor.value, and filter by sensor.status.

Practice

1. What is the main purpose of an HMI screen in PLC programming?

easy

A. To store machine data permanently

B. To write complex PLC code

C. To replace the PLC hardware

D. To allow users to control and monitor machines easily

Solution

1. Step 1: Understand HMI function

   An HMI (Human-Machine Interface) screen is designed to help users interact with machines.

2. Step 2: Identify main purpose

   The main goal is to make control and monitoring simple and clear for users.

3. Final Answer:

   To allow users to control and monitor machines easily -> Option D

4. Quick Check:

   HMI = control and monitor [OK]

Hint: HMI means user interface for machine control [OK]

Common Mistakes:

• Confusing HMI with PLC programming itself
• Thinking HMI stores data permanently
• Assuming HMI replaces hardware

2. Which of the following is the correct way to label a button on an HMI screen?

easy

A. Use only icons without text

B. Use vague text like 'Click Here'

C. Use clear text like 'Start Motor'

D. Use very long sentences explaining the button

Solution

1. Step 1: Understand button labeling

   Buttons should have clear, simple labels so users know their function immediately.

2. Step 2: Evaluate options

   'Start Motor' clearly tells the user what the button does, unlike vague or overly long labels.

3. Final Answer:

   Use clear text like 'Start Motor' -> Option C

4. Quick Check:

   Clear labels = better usability [OK]

Hint: Label buttons with clear, simple text [OK]

Common Mistakes:

• Using unclear or vague labels
• Relying only on icons without text
• Writing long explanations on buttons

3. Consider this HMI screen design rule: "Use consistent colors for similar controls." What is the likely result if this rule is ignored?

medium

A. Users may get confused about control functions

B. The PLC program will stop working

C. The screen will load faster

D. The machine will run automatically

Solution

1. Step 1: Understand color consistency

   Consistent colors help users recognize similar controls easily.

2. Step 2: Predict effect of ignoring rule

   If colors vary randomly, users may not know which controls do similar things, causing confusion.

3. Final Answer:

   Users may get confused about control functions -> Option A

4. Quick Check:

   Consistent colors = less confusion [OK]

Hint: Consistent colors help users understand controls [OK]

Common Mistakes:

• Thinking color affects PLC operation
• Assuming color changes speed up screen
• Believing color affects machine automation

4. You designed an HMI screen but users report they can't find the navigation buttons easily. What is the most likely design mistake?

medium

A. Navigation buttons are hidden or placed inconsistently

B. Buttons have clear labels and consistent colors

C. Screen title is too large and clear

D. Screen uses standard navigation layout

Solution

1. Step 1: Analyze user feedback

   Users can't find navigation buttons easily means buttons are not visible or confusingly placed.

2. Step 2: Identify design mistake

   Hidden or inconsistent placement of navigation buttons causes difficulty in finding them.

3. Final Answer:

   Navigation buttons are hidden or placed inconsistently -> Option A

4. Quick Check:

   Visible, consistent navigation = easy to find [OK]

Hint: Place navigation buttons clearly and consistently [OK]

Common Mistakes:

• Ignoring button placement importance
• Assuming large titles improve navigation
• Using non-standard layouts without testing

5. You want to design an HMI screen for a machine with multiple steps. Which approach best helps users navigate smoothly between steps?

hard

A. Place all controls on one screen without navigation

B. Use a clear menu with buttons labeled for each step

C. Use random colors for each step's controls

D. Hide navigation buttons to save screen space

Solution

1. Step 1: Understand multi-step navigation needs

   Users need to move easily between steps without confusion.

2. Step 2: Evaluate navigation methods

   A clear menu with labeled buttons helps users know where to go next and jump between steps.

3. Step 3: Reject poor options

   Putting all controls on one screen can overwhelm users; random colors confuse; hiding buttons blocks navigation.

4. Final Answer:

   Use a clear menu with buttons labeled for each step -> Option B

5. Quick Check:

   Clear menus = smooth navigation [OK]

Hint: Label navigation buttons clearly for each step [OK]

Common Mistakes:

• Overloading one screen with all controls
• Using inconsistent colors that confuse users
• Hiding navigation buttons to save space