A Key Button object set to System Key Code, Panel Setting, Call to System Screen opens the HMI system screen with one touch, so nobody needs the 3-second corner press-and-hold. Build it, size it for gloved hands at 20 mm or more, put it behind the maintenance password, and test it on the panel.
Operators and night-shift techs who were never shown the gesture cannot find the panel's system screen at all. The documented way in on many panels is a press-and-hold on the upper left corner held for 3 seconds. There is a better path, and it is a standard object: a Key Button set to a system key code opens the built-in system screen with one touch. The selections, in order, are System Key Code, the Panel Setting group, and Call to System Screen. No bit tag, no macro, no extra hardware; the call is handled by the panel itself. Build the button, put it on a password-protected maintenance screen, size it for gloved hands, and test it on the panel. This page walks through the build, the placement, a worked example and the checks, plus the fixes for the four mistakes that leave the button dead.
What you need
- The panel's HMI programming software with the project open for editing.
- A transfer path to the panel, network or cable, however that panel takes downloads.
- The panel powered and running the project, so you can test at the end.
- Agreement with the line owner about when it is safe to work on a panel that sits on a producing line.
No PLC connection is involved. The system screen call is a panel function, not a tag write, so nothing in the PLC program changes.
Build the one-touch button
- Open the project and go to the screen that will hold the button.
- Create a Key Button object on that screen. A bit button or a screen-change button cannot call the system screen; a bit button only writes a tag that stays on for a few PLC scans, which is a different mechanism from a key code.
- In the object's key settings, select System Key Code.
- Select Panel Setting as the key code group.
- Select Call to System Screen as the function.
- Label the button so the purpose is obvious, System or Panel Setup, and size it at least 20 mm across, so a gloved fingertip lands inside the target every time.
- Leave it on the maintenance or setup screen and place it away from buttons that write to the machine.
- Transfer the project to the panel and let it come back up in run mode.
If your software words these selections differently, look inside the button object for a system key group. Panel documentation for this class of hardware takes the same line: where the hardware RUN/STOP switch is not reachable, a key button object on a project screen opens the system screens.
Place it where the right people can reach it
A visible system button hands every operator a path to the RUN/STOP switch, network settings and the rest of the panel setup. Decide before you download:
- Maintenance only: put the button on a screen behind the project's password. If that gate is not built yet, start with password-protecting the HMI setup menu.
- Operator facing: if operators are meant to reach panel settings themselves, a labeled one-touch button beats a gesture nobody was taught.
- Fallback: keep the 3-second corner hold in the maintenance notes, because it stays available when the button screen is unreachable. If taps on the corner sometimes fail to open the hidden screen, why taps never open a hidden setup screen covers the causes and fixes.
Example: a packaging line panel
A line tech on a packaging machine opens the system screen about 4 times a shift to check settings between changeovers. Each access with the gesture means a 3-second hold, so 4 accesses a shift add 4 x 3 = 12 seconds of holding per shift. That total leaves out the minutes lost when an operator tries to help and cannot find the gesture at all. Maintenance adds a Key Button labeled System on the password-protected maintenance screen, 20 mm square, set to System Key Code, Panel Setting, Call to System Screen, and transfers the project. After the download, each access is one touch, so the 12 seconds of holding per shift becomes 4 short touches, and only the people holding the maintenance password see the button. The corner hold stays in the maintenance notes, so the tech still has a way in when the maintenance screen is not reachable.
Check it worked
- Transfer the edited project and let the panel start in run mode.
- Navigate to the screen holding the button and touch it once. The system screen should appear.
- Leave the system screen with its own exit function, then confirm the project screens and navigation come back normal.
- Test the corner hold too, so you know both access paths on this panel.
- Run the test on the panel itself. The software preview or offline simulation does not exercise firmware-level panel functions, so a button that looks dead in preview is a preview limitation, not a failed configuration.
- If the system screen lets the user write to the machine, test with the line in a safe state, the same discipline as testing operator-panel writes before motion.
One safety rule covers the whole job: agree with the line owner what a safe state is before you touch anything inside the system screen, because it holds the RUN/STOP switch and settings that move the process.
When the button does nothing
| Symptom | Check |
|---|---|
| Button does nothing on touch | Reopen the object and confirm all three selections: System Key Code, Panel Setting, Call to System Screen. A default key code or a different Panel Setting function is the usual miss. |
| Button missing on the panel | The edited project was never transferred. Download again and confirm the panel is running the new project. |
| Button works but you cannot get back | Use the exit function inside the system screen. Power-cycle the panel only if it is truly locked up. |
| You wired a bit tag and nothing happens | The system screen is not a tag and never shows up in the tag list. Delete the bit button and build a Key Button with the three selections above. |
The decision
Recommendation: On any panel whose system settings matter to the line, build a Key Button object with System Key Code, Panel Setting and Call to System Screen, size it 20 mm or larger, and put it on the password-protected maintenance screen, keeping the 3-second corner hold in the maintenance notes as the fallback. Put the button on the main operator screen only where operators are meant to reach panel settings themselves.
Questions
Do all HMI panels use these exact key code names?
No. The names System Key Code, Panel Setting and Call to System Screen are the selections this class of panel uses. Other vendors put the same function in the button object's key or system settings under different labels. Look for a system key group inside the button object's settings, and check the panel's own manual for the exact wording before you build.
Can I remove the 3-second corner press-and-hold from a panel?
The gesture belongs to the panel, not to your project screens, so adding or deleting buttons leaves it in place. Whether a panel lets you switch the gesture off is a configuration question to settle from that panel's documentation. Gate what matters instead: keep sensitive settings behind password-protected screens so a curious operator who does reach the system screen stops at a password.
Can the system screen button go on the main operator screen?
It can, and for some lines that is the right call: if operators are allowed to reach panel settings themselves, a labeled one-touch button beats a gesture nobody was ever taught. If only maintenance should change panel settings, keep the button on the password-protected maintenance screen and leave the corner hold in the maintenance notes as the hidden fallback.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.