HMI PROGRAMMING
HMI Programming Training: How to Design Industrial Operator Screens
What an HMI is, how an HMI project is built, the high-performance design rules that make screens readable, and the common mistakes that cause trouble on site.
HMI programming is building the touchscreen application operators use to run a machine: screens linked to PLC tags, buttons and setpoint fields, alarms, trends, recipes and user logins. Good HMI training teaches the software and the design rules, such as ISA-101, that keep a screen readable when something goes wrong. You can learn it free using simulated panels.
In this lesson by RealPars, you get an introduction to what an HMI is. It is used in the "What an HMI Is and How to Choose One" module of the free HMI Design course, which places the HMI next to the PLC and SCADA and introduces high-performance design. Its practice task is to sketch an overview screen for a pump station. Watch it, then use the rest of this guide.
What an HMI is
An HMI (human-machine interface) is the operator's window onto a machine. It can be a panel mounted in the machine's door, an industrial PC, or a web client on a tablet. It reads and writes PLC tags over a network such as PROFINET, EtherNet/IP or Modbus TCP, and shows them as graphics, numbers, trends and alarms.
The HMI shows and requests. The PLC decides. A button on the screen asks the PLC to start a motor; the PLC checks its interlocks and starts it or not. Keeping that boundary clear is the most important rule in HMI work.
Platforms you will meet
- Siemens WinCC in TIA Portal: Basic and Comfort panels, and the newer WinCC Unified.
- Rockwell FactoryTalk View ME on PanelView Plus terminals, and FactoryTalk Optix for newer projects.
- Weintek [EasyBuilder Pro](https://www.weintek.com/globalw/Software/EasyBuilderPro.aspx) and Pro-face GP-Pro EX, which connect to many PLC brands.
If you are starting in TIA Portal, your first WinCC HMI screen walks from adding a panel to running it in simulation. Our guide to free HMI software for learning lists which of these you can use free and on what terms.
How an HMI project is built
The order is similar in every package:
A few details make a big difference. Group tags so the panel reads them efficiently rather than polling hundreds of scattered addresses. Build a template (header, alarm banner, navigation) once and use it on every screen. Use faceplates, reusable pop-ups for a motor or valve, linked to a PLC data type, so fifty motors share one design.
Design rules: the high-performance HMI
[ISA-101](https://www.isa.org/standards-and-publications/isa-standards/isa-101-standards) (ANSI/ISA-101.01) is the standard for HMI design in process automation, and its ideas suit machine HMIs as well:
- Muted graphics. A grey background and grey equipment, with strong colour reserved for abnormal conditions, so a problem stands out immediately.
- Values in context. A number alone does not tell an operator whether it is good. Show units, a range, and a simple indicator of where the value sits against its limits.
- A display hierarchy. An overview of the whole machine or area, then unit screens, then detail screens and diagnostics. Operators should always know where they are and how to get back.
- Consistency. The same symbol, colour and position mean the same thing on every screen.
Bright 3D pumps and animated pipes look impressive in a demonstration and make real problems harder to spot.
Alarms
HMIs usually have two kinds of alarm: discrete alarms triggered by a bit (motor tripped, door open), and analog alarms triggered by a value crossing a limit (tank level high). Every alarm should need an operator action, have a priority, and say what to do. The alarm management standard is ISA-18.2, part of the ISA-18 series and published internationally as IEC 62682. The SCADA training guide covers alarms at plant scale. Do not alarm on normal states such as a machine being stopped at the end of a shift.
Recipes, users and languages
Recipes store sets of setpoints for different products, so changing over a line means choosing a recipe rather than typing ten values. User administration restricts who can change setpoints or enter maintenance screens. Regulated industries such as pharmaceuticals add audit trails and electronic signatures (21 CFR Part 11 in the United States); see pharmaceutical automation for what that means for screens. Language switching lets one project serve operators in several countries.
Mistakes that cause trouble on site
- Putting logic in the HMI. Interlocks and sequences belong in the PLC. If the panel restarts, the machine must still be safe.
- Momentary buttons and lost communication. If a jog button sets a bit and the panel loses communication while it is pressed, the bit can stay set. Have the PLC reset command bits, or watch a heartbeat.
- Writing directly to outputs. The HMI should request, not switch an output directly.
- Unlimited setpoints. Limit entry on the screen and clamp again in the PLC.
- Showing the command instead of the result. A motor shown green because Start was pressed, not because the contactor closed, misleads operators.
Before handing over any screen, review it against this list:
Test before you hand over
An HMI is finished when it has been tested against the machine, not when the last screen is drawn. A short test plan catches most problems:
- Every button: press it and confirm the PLC receives the request and the right output responds, or the interlock that blocks it is shown.
- Every value: force or simulate the PLC tag across its range and check units, scaling and limits on screen.
- Every alarm: trigger it, check its text, priority and time stamp, acknowledge it and clear it.
- Lost communication: unplug the network and see what the screen shows. Stale values must look stale.
- Users: log in at each access level and confirm what each one can and cannot change.
Keep the results with the project. When someone asks later whether a screen was tested, you can show them.
Free HMI programming training
- HMI Design and Programming: Siemens WinCC and FactoryTalk View ME (beginner): high-performance design, then full projects in both tools.
- Siemens TIA Portal HMI: KTP and Comfort Panels (beginner): tags, screens, templates, trends, alarms, recipes and faceplates.
- Weintek HMI with EasyBuilder Pro (beginner): a brand-neutral panel with PLC links, logging, recipes and macros.
- FactoryTalk Optix HMI and Edge (beginner): Rockwell's newer, object-oriented HMI.
The HMI courses page lists the others, including WinCC Unified and Pro-face. Learning is free in full: credited video lessons from independent YouTube creators, written notes, a practice task per module and a 15-question final assessment (60% to pass, three attempts, then a 24-hour wait). Create a free account so progress is saved.
The optional EDWartens Certificate of Completion for these beginner courses is a small one-off fee, US$8.99. It can be checked at edwartens.com/verification. It is not a Siemens, Rockwell or Weintek certification and is not accredited.
Take the free course
Questions
What is the difference between an HMI and SCADA?
An HMI is usually a panel or single application for one machine, linked to one or a few PLCs. SCADA supervises a whole plant or many sites, with servers, historians and many clients. The screen design skills are the same.
Which HMI software should I learn first?
Match the PLC you are learning: WinCC in TIA Portal with Siemens, FactoryTalk View ME or Optix with Rockwell. Weintek EasyBuilder Pro is a good brand-neutral choice because it connects to many PLC families.
Do I need a real HMI panel to learn?
No. WinCC, FactoryTalk View, EasyBuilder Pro and Optix all include runtime simulation, and you can connect the simulated screen to a simulated PLC. A panel is only needed for download and hardware settings.
What is a high-performance HMI?
A style of screen design, described in ISA-101, that uses muted grey graphics and saves strong colour for abnormal conditions, shows values in context with ranges, and organises screens in a hierarchy from overview to detail.
Is the EDWartens HMI certificate a Siemens or Rockwell certificate?
No. It is an EDWartens Certificate of Completion, issued after you pass the final assessment and checkable at edwartens.com/verification. It is not a vendor certification.
Sources
- ISA: ISA-101 series of standards (HMI design)
- ISA: ISA-18 series of standards (alarm management)
- Weintek: EasyBuilder Pro HMI software
Written by the EDWartens engineering team for general education. Product names are trademarks of their owners; mentioning them does not imply endorsement. Prices and terms of other providers were checked on the date shown and can change.
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