Log the trend to the panel's internal card and treat the USB stick as a copy target. An indicator on the USB Ready tag, one pushbutton on SYSCopyLogtoUSB and one on EjectUSB move the data off the panel while the trend keeps writing. The stop button leaves the retrieval path for good.
You can pull the historical data off the panel without ever touching that Stop button. The stop control is the wrong retrieval tool because it couples the export to the logging: stop the trend, pull the device, restart the trend, and hope the restart takes. Split the two jobs instead. Send the trend's log files to the panel's internal card, and treat the USB stick as a copy target only. Three objects on one screen then do the whole handoff: an indicator driven by the USB Ready system tag, a pushbutton that switches SYSCopyLogtoUSB, and a pushbutton that switches EjectUSB. The trend keeps writing to the internal card through the entire export.
Why the stop button is the wrong tool
When the trend logs straight to the stick, every retrieval stops the collection, and the restart becomes a manual step somebody forgets at the end of a shift. Point the log destination at the panel's internal card and the coupling breaks: the card is the recorder, the stick is a visitor. Log files land on the internal CompactFlash storage, which is also the short answer to whether an HMI panel can store PLC data for later retrieval. When that card reaches end of life, replacing a proprietary HMI CompactFlash card is its own planned job.
What you need
The whole export path is three objects pointed at system tags the panel already carries:
| Object on the screen | System tag | What it gives you |
|---|---|---|
| Ready indicator | USB Ready | On when the panel has recognized the inserted stick |
| Copy pushbutton | SYSCopyLogtoUSB | Saves all log files on the panel to the stick |
| Eject pushbutton | EjectUSB | Releases the stick so it comes out without corrupting the copy |
The tag documentation for this panel family describes the copy tag as saving all log files when it is switched on, and prints it with a trailing device number after the tag name. All three are system tags: you point screen objects at them, you do not create them. A USB Write indicator is worth keeping beside the ready light, but it shows activity, and activity and readiness are different states.
Point the log destination at the internal card
- Open the project in the panel's programming software on a PC.
- In the trend setup, set the log storage destination to the internal card.
- Keep the Stop control on the trend screen only if the process needs it; take it out of the retrieval path.
- Download the project at a planned stop. A download changes what the operator sees on a running machine, so pick a moment the cell can spare the panel.
- Let the trend run through a few sampling periods and confirm the log on the internal card is growing.
Build the three controls
- Add an indicator, point it at USB Ready, and label it in words an operator reads at a glance, such as "USB ready".
- Add a pushbutton that switches SYSCopyLogtoUSB and label it "Copy logs".
- Add a pushbutton that switches EjectUSB and label it "Eject USB". Space it away from the copy button so a gloved press cannot land on the wrong one.
- If a USB Write indicator is already on the screen, keep it next to the ready light.
- Download at the same planned stop as the destination change.
If a copy starts and then stops partway, the button's trigger behavior is the first thing to check: why a USB log copy stops after one day.
Run the export
- Insert the stick.
- Wait for the ready indicator. Recognition takes a moment; if the light never comes on, read how long to wait on USB ready before calling a fault before you blame the stick.
- Press copy. Every log file on the panel goes to the stick.
- Wait for write activity to finish; the write indicator goes dark when the panel is done.
- Press eject, then pull the stick. Removing a USB data-log stick safely covers why the eject press belongs ahead of the pull.
- At the computer, open one log file end to end before you trust the batch.
Size the ready text for the distance it is read from
Operators read the ready state from where they stand while the machine runs, not from arm's length. Size the text for that spot. The planning figures: 30 ft of viewing distance per inch of capital height is the base legibility figure (FHWA), 20 ft per inch is the safer choice for fast reading, and line spacing runs at 1.7 times the capital height. The same figures size text on any shop-floor screen, from an HMI in a cabinet door to a status board across the aisle.
Example: sizing the USB Ready text at 6 ft
Inputs: the operator reads the export screen from 6 ft away, past the front of the machine. The figures come from the planning numbers above: 30 ft per inch base, 20 ft per inch for fast reading, spacing at 1.7 times capital height.
Rule in words: divide the viewing distance by the feet-per-inch figure to get the minimum capital height, then multiply that height by 1.7 for the gap between lines.
Arithmetic:
- Fast reading: 6 ft ÷ 20 ft per inch = 0.3 in of capital height.
- Base figure: 6 ft ÷ 30 ft per inch = 0.2 in, the absolute floor.
- Build size: round up to 0.4 in so the state reads at a glance.
- Spacing: 1.7 × 0.4 in = 0.68 in, so set the gap between the label line and the state line to 0.7 in.
Result: 0.4 in capitals with 0.7 in line spacing on the ready indicator.
Decision: any ready text below 0.3 in fails the fast-reading figure at 6 ft, and 0.2 in only meets the base figure. Print the two states, "READY" and "NO STICK", at 0.4 in.
Check the whole handoff
Run one full cycle at commissioning:
- With the stick out, the ready indicator stays dark.
- With the stick in, the indicator lights before anyone presses copy.
- After the copy, the files open on the computer.
- During and after all of it, the log on the internal card keeps growing.
If something fails, the symptom points at the layer:
| Symptom | Likely cause | Fix |
|---|---|---|
| Ready never comes on | The panel has not recognized the stick, or the indicator points at the wrong tag | Try a second stick, then re-check the tag mapping |
| Files missing or unreadable on the computer | The stick came out before writing finished, or the copy press never landed | Re-run the sequence and wait for the write indicator to go dark |
| The trend stops during retrieval | The log destination is still the stick, or someone pressed Stop | Point the destination at the internal card and start the trend with its own control |
When the panel sits on the plant network, collecting HMI trend logs over FTP removes the walk to the machine entirely; keep the stick workflow for isolated machine networks and one-off pulls.
Recommendation: log every trend to the panel's internal card and keep the stick as a copy target whenever the data matters enough to retrieve; log straight to a removable device only on a machine whose trend you are willing to stop and restart at every retrieval.
Questions
Does the copy take alarm and event logs as well as the trend?
Yes. The copy tag saves all log files on the panel, so alarm and event logs ride along with the trend samples. Sort out what the historian keeps on the computer afterwards.
Does inserting the USB stick start the copy?
No. Insertion only makes the device ready; the copy runs when the pushbutton tied to the copy tag is pressed. Wait for the ready indication first, press copy, then wait for the write to finish before ejecting.
Will the eject button restart a stopped trend?
No. EjectUSB acts on the storage device. Use the trend's own start control to resume logging, then check that fresh samples appear in the log before walking away.
Can the log files be reached over FTP instead of carrying a stick?
Yes, when the panel sits on the plant network and its file access is configured. FTP suits fixed polling into a historian; the stick suits isolated machines and one-off pulls.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.