An automation system is only as good as its interface. In this lesson, we transition from internal logic to the Human-Machine Interface (HMI). We will focus on how to display process data and how to build a multi-screen menu system that remains intuitive for plant operators.
1. Adding Variables to the Display
To show data on the screen (like the pressure value from Lesson 6), you must use the Display tab in ALP. Drag a “Float” or “Integer” object onto the screen area and link it to your internal variable. Pro Tip: Always set the “Decimal Places” parameter to prevent the screen from looking cluttered with unnecessary digits.
2. Multi-Screen Navigation Logic
Industrial controllers like the SMI200 or PR200 have limited screen real estate. To manage complex systems, you must create multiple screens (e.g., Dashboard, Manual Control, Settings). Navigation is handled by linking a Button Press to a “Change Screen” command in the property panel.
⚙️ Technical Insight: The “Home” Rule
Every sub-screen in your HMI should have a dedicated “Esc” or “Home” function. In an industrial emergency, an operator should never be more than two clicks away from the main dashboard or the Manual Override screen.
3. Visual Hierarchy & Status Colors
Use visual indicators wisely. A blinking text object should only be used for Critical Alarms. For standard operation, use static text. In akYtec ALP, you can use a boolean variable to toggle the visibility of an object—perfect for showing a “Motor Running” icon only when the output is active.