Yes: map the Screensaver tag in the panel's PLC to Panel setup and have the PLC write 7 into that word when the idle condition is true. Combine each machine's idle bit into one PLC tag first, and clear any P001 PLC COM Time Out before you test the blank. A touch wakes the screen; the tag blanks the display, it does not switch power.
A PLC can blank an HMI screen. In the panel project's PLC to Panel setup there is a Screensaver tag location; when the controller writes the value 7 into the word that tag points at, the screen goes blank, and the first touch brings it back. That is the mechanism to use. A black background page hides the graphics, and switching the panel's power from the controller is a separate job with different hardware, so neither is the first choice. This article maps the tag, builds the idle signal that triggers the write, combines several machines into one tag, and clears the P001 communication error that stops the whole scheme.
What the screensaver tag does
In the PLC to Panel setup page, point the Screensaver tag location at a data word the controller can write. Writing 7 to that word drops the panel to a blank screen; 7 is the blanking value for this mapping. The wake needs no second write. The screensaver clears when an operator touches the screen, and the project then shows whatever screen its navigation selects next.
The tag blanks what the screen shows; it is not a power switch. Nothing here opens the panel's supply circuit. The material behind this mapping does not say whether the backlight itself turns off, so treat the blank as a visual change and size any heat or power saving from a measurement on the panel. One safety rule goes with the design: gate the write so it can never cover an active alarm screen. The controller already knows its alarm bits, so add them to the blank condition and let a fault always paint through.
What you need
- The panel project open in its editing software, with the PLC to Panel setup reachable.
- One data word the controller can write and the panel can read, mapped in the Screensaver tag location. In the working setup that word was V-memory.
- An idle condition: a timer per machine, or a bit each machine already sets after a quiet period.
- A healthy link between panel and controller. If P001: PLC COM Time Out flashes at the top of the panel, fix that first; the write never reaches the tag while it is up.
Steps
- Map the tag. In PLC to Panel setup, enter the Screensaver tag location and point it at the word you will write. Note the address; the project editor and the PLC program must agree on it.
- Confirm the blanking value. 7 blanks the screen in this mapping. Confirm it against your own project's screensaver mapping before the write goes live, especially if the project was built by someone else.
- Build one idle bit per machine. A 10-minute idle timer is a working default: 10 min x 60 s/min = 600 s per timer preset. The bit sets when no operator input has reached the machine for 10 minutes. If the screen should return to a home screen on idle instead of blanking, returning an HMI screen to home after 10 minutes idle covers that timer separately.
- Combine the bits in the PLC. AND them when the blank should wait for every machine to idle; OR them when any idle machine should blank the panel. Keep this logic in the controller and send one combined tag. The event manager can watch tags as an alternative, but it polls its tags on every screen, so three idle tags watched across a project slow overall polling; one combined tag keeps that traffic at a single word.
- Write the value. While the combined bit is high, the rung moves 7 into the screensaver word. With the alarm gate added, the rung reads: combined idle AND no active alarms.
- Leave the wake to touch. The screensaver clears on the first touch and the project navigates on from there. Decide which screen the wake should land on and set the navigation to match. If a touch fails to wake a blanked panel, the two checks in HMI screen won't wake from screensaver come first.
- Test with the cell in a safe state. Watch the blank appear, touch it back, and prove a forced alarm still shows while the idle condition is true.
Example: three machines, one blank command
A cell runs a press, a weld station and a packer, all watched by one panel. Each machine gets the 10-minute idle timer, so each preset is 600 s. The three idle bits feed one AND rung:
press_idle AND weld_idle AND pack_idle = all_idle
While all_idle is high and no alarm is active, the rung writes 7 to the screensaver word. The panel blanks 10 minutes after the last machine goes idle: if the welder stops at 14:00 and nobody returns, the blank lands at 14:10.
Swap the gate to an OR and the timing moves to the first machine: the blank arrives 10 minutes after the press, the welder or the packer idles, whichever comes first. The AND suits a cell an operator walks back into. The OR suits a shared notice panel that only needs to go dark once the area is quiet. Either way the panel sees one tag, so polling the idle state costs one word per scan instead of three.
Clear P001: PLC COM Time Out first
P001: PLC COM Time Out flashing at the top of the screen means the panel is not getting answers from the controller. The screensaver write dies with every other exchange. In the working setup the cause was the protocol selection, not the wiring: the controller's serial port mode was set to Modbus RTU Client while the panel's driver spoke the controller's native protocol, listed in that serial port mode menu as Programming. Selecting Programming restored communication, with the link running 38400 baud, 8 data bits, no parity, 1 stop bit (N-8-1).
Run the checks in this order:
- Protocol mode. Match the panel driver's protocol to the controller serial port mode. The Programming and Modbus RTU Client pair in that menu is the pair behind this fix.
- Serial settings. Same baud, parity and stop bits both ends; the working link used 38400 baud, N-8-1.
- Cable. Wire it the way the panel manual specifies for the port in use.
- Then the tag. With communication healthy, monitor the screensaver word: if the PLC writes 7 and the screen stays on, the tag address or the value mapping is the remaining suspect.
A step-by-step P001 time-out walkthrough for an Ethernet link covers the same error on a panel-to-controller Ethernet setup.
How to check it worked
- The panel's own communication test passes, and P001: PLC COM Time Out stays gone.
- With every machine idle past its timer, the screensaver word reads 7 and the screen goes blank within one poll cycle.
- A touch wakes the panel and lands on the screen you chose in step 6.
- A screen that went dark because it lost power looks like a blank from across the room. The power checks in HMI screen goes blank and freezes tell the two apart when your blank fails to appear.
The blank-page fallback
Panels whose project cannot map a screensaver tag can still go visually dark. Build a blank screen whose only object is a full-screen button with no visible graphics; pressing it navigates to the operating screen, so the same touch that hits the blank page brings the display back. That design ran on a 3-inch micro panel. Two checks decide whether it survives production: the touch has to register across the whole activation area from the operator's normal working position, and the wake has to land on the right screen. If operators cannot find the invisible button, add a small visible hint to the page or move the wake to a physical button wired through the controller. Write the activation area into the project notes, because the next person to edit the project has no other way to know it is there.
Recommendation: use the PLC to Panel screensaver tag with the value 7 as the blank, combine the machines' idle bits into one PLC tag behind an AND rung, and write it while all machines are idle and no alarm is active; keep the invisible-button blank page only for panels whose project cannot map a screensaver tag, and clear P001: PLC COM Time Out before you test any of it.
Questions
Can the panel be blanked at a fixed time instead of after idle time?
Yes. Replace the idle timer with a time-of-day comparison in the PLC: while the clock reads past your blank time and no wake condition is present, the same rung writes 7 into the screensaver word. The wake is still an operator touch, so the first person at the panel brings the display back by touching it.
Will the screen come back by itself when a machine starts?
The wake the working setup shows is an operator touch on the panel. If you want a machine start to do it, gate the write so 7 is present only while every machine is idle, then test on your panel whether the screen leaves the blank once the write stops. That exit behavior is not covered by the material behind this article.
What if there are four machines instead of three?
The same pattern scales. Give each machine its own idle timer and bit, then extend the AND rung to four inputs. The panel still sees a single combined tag, so its polling cost stays at one word however many machines feed the logic; only the PLC rung grows.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.