Alternate two pages on an HMI HDMI monitor output

How the window sequence behaves

The panel runs one window sequence, and everything displaying it follows the same order: the HDMI output and a cMTViewer session alike. Every session enters the sequence at the startup window, page 10 by default, and system parameters is where a different entry page is set. That shared entry point is the whole story. A cycle built into pages 10 and 11 rotates the monitor because the timer objects live in the pages, and it rotates the remote picture for the same reason: there is one sequence and both viewers are watching it. Nothing on the viewer side moves its start page; the startup window is the entry point for everyone.

What you need

• A cMT-series panel with HDMI output driving a monitor, such as the cMT-FHDX-820. If the monitor itself is still an open choice, the trade-offs are the ones in using a PC monitor as a shop-floor HMI display.
• An EasyBuilder Pro project with three pages built: 10 and 11 as the rotating pair, and 20 as the hub outside the cycle.
• An Action Trigger (Per-Page) object on each rotating page.
• A change-window button on each rotating page, pointing at page 20.
• cMTViewer on the remote PC, if remote viewing is part of the job.

Setting up the cycle

1. Set the startup window in system parameters so the sequence begins on the cycle's first page.
2. On page 10, add an Action Trigger (Per-Page) object, set it to trigger on page open, give it a delay of 15 s, and set its action to change window to page 11.
3. On page 11, add the same object: trigger on page open, the same delay, change window to page 10.
4. On both rotating pages, add a button whose action changes the window to page 20. Page 20 carries no timer object, so it stays where it is put.
5. Build page 20 as the hub, with navigation to the rest of the project, so a viewer can reach any page from it.
6. Download the project to the panel and open page 10, by restart or by selection from page 20.

Keep the rotation presentational. A page that swaps itself out on the timer is a bad home for machine controls; interlocks belong in the PLC and the hardwired circuit, where a page change cannot touch them.

What a cMTViewer session sees

The client side has choices of its own; choosing the remote-access client first sorts those out before the pages. Once connected, the viewer lands on the startup window and cycles with the monitor. Click the page-20 button, and the sequence moves to page 20 for everyone watching it; from there the viewer navigates the project freely, because pages outside the cycle carry no Action Trigger. When someone opens page 10 again, the per-page timers take over and the pair resumes 10, 11, 10. What the construction removes is the trap: without the exit button, a remote viewer sits in the full cycle loop with no way out except the panel's own screen. What it cannot do is show the viewer a page the monitor is not showing, because there is only one sequence.

Example: pages 10 and 11 cycling on the timer through an 8-hour shift

Inputs, and where each comes from:

• Delay on each rotating page: 15 s, entered in the Action Trigger (Per-Page) object on pages 10 and 11. The field takes a delay in seconds on page open; 15 s is this example's choice.
• Shift length: 8 h, the plant's day shift.
• Page 10 carries the alarm summary, about 20 words.

The rule in words: cycle time is the sum of the per-page delays, each cycle visits both pages once, and window changes per shift equal shift seconds divided by cycle seconds, times two.

The arithmetic:

• 15 s + 15 s = 30 s per cycle
• 3600 s per hour / 30 s per cycle = 120 cycles per hour
• 120 cycles per hour x 8 h = 960 cycles per shift
• 960 cycles x 2 changes per cycle = 1,920 window changes per shift

The reading check: average silent reading runs at about 200 to 250 words per minute, so a 20-word summary takes roughly 5 to 6 s to read. The chosen delay clears that with margin.

Result: a 30 s cycle, 1,920 window changes per shift, and every page long enough on screen to be read.

Decision: keep each per-page delay at least twice the reading time of the slower page. For this board that means 12 s or more, which the example meets. If operators copy values by hand, raise both delays together, because cycle time is always the sum of the delays: 25 s and 25 s give a 50 s cycle and 576 cycles per shift (28,800 s divided by 50 s).

When to let the PLC drive the page

A fixed cycle suits a shift board. When the page must follow production state instead of a clock, use a PLC Control object of type Change window and reference a PLC word: the value in the word selects the page, so the PLC can pull up the alarm summary the moment it raises a fault. Writing the page number from the PLC and taking control back afterwards are covered in change HMI screens from the PLC and give control back. The third route, terminal-side and PLC-free, is an internal LW word plus a macro that runs on a timed interval and performs the change. For a plain two-page cycle the per-page objects are still the least machinery. Timed rotation is a pattern across HMI lines; a walkthrough that configures pages to rotate every 30 seconds shows the same idea built with another timer object.

How to check it worked

• Leave the panel on page 10 for one delay period: the monitor changes to page 11, and back to page 10 after another delay period.
• Time a full round trip with a stopwatch; landing within about a second of 30 s confirms both delays downloaded.
• Open a cMTViewer session: it enters on the startup window and cycles with the monitor.
• Press the page-20 button from the viewer: page 20 holds on both displays past the timer's mark.
• Select page 10 from page 20: the cycle resumes on both.
• If the HDMI cable comes out mid-cycle, window behavior becomes its own subject; when a window opens on a disconnected monitor walks through that case.

Recommendation

Recommendation: Build the two-page cycle with an Action Trigger (Per-Page) object on each rotating page, set to trigger on page open with a delay that clears the reading-time rule, 15 s in the worked example above. Put a change-window button to the hub page on every rotating page, so a cMTViewer session leaves the loop in one click. Reserve the PLC Control Change window object for pages the PLC must select, and keep machine interlocks out of the rotating pages entirely.

Questions