Guide · 8 min read

Build an HMI screen for your machine.
No HMI software. No integrator.

A production manager, a maintenance mechanic, a young engineer — anyone who can install an app can put live values on a machine screen — and, once the right tags are identified, start/stop buttons and alarms. No FactoryTalk, no WinCC, no project file, no licenses. And when the machine needs a physical screen, you put this one on it.

Show me the steps →

The short answer: you can build a working HMI screen with the free LineKeeper app and nothing else — get the phone on the machine's network, let a scan find the PLC, and drag-and-drop the dashboard and operator panel from the controller's own tags. On an Allen-Bradley Logix it takes about 15 minutes; on Siemens S7 and Modbus you name the points once. No FactoryTalk, no WinCC, no integrator. The steps are below — first, why it usually isn't this easy.

Why machine screens became gate-kept

Every factory HMI panel is the output of specialized engineering software — FactoryTalk View for Allen-Bradley panels, WinCC inside TIA Portal for Siemens. The licenses cost thousands, the project file usually lives with the OEM or the integrator who built the machine, and changing so much as a button label means finding the person with both. (If you can get that project export, the free in-browser HMI converter rebuilds the old screens' buttons, indicators and values for the app — no redrawing. Graphics and alarm logic aren't carried over.)

Which is why so many machines run half-blind: the panel shows what someone chose to show in 2014, the interesting values are buried three menus deep, and adding a screen for the new fault everyone keeps chasing is "a project".

The PLC doesn't care. It answers the same protocols for anyone on the network — an HMI panel, a laptop, or a phone. That's the whole trick.

What you need

  • The free LineKeeper app on an iPhone or iPad.
  • A connection to the machine's network — plant Wi-Fi that routes to the PLC, or a USB-C Ethernet adapter. If a laptop there can ping the PLC, the app can connect.
  • Nothing else. No accounts, no cloud, no changes to the PLC logic — the app talks the same protocols an HMI uses: EtherNet/IP for Allen-Bradley CompactLogix and ControlLogix, S7comm for Siemens S7-300/400/1200/1500, Modbus TCP for everything else — drives, meters, Schneider and Click PLCs.

Want to try before you're at the machine? The app ships with a built-in demo line — two virtual PLCs with moving values, a packager that jams and wants its reset, start/stop/jog that actually work. Every step below can be rehearsed from the couch.

Building the screen, step by step

  1. Add the machine, scan the network. Create a piece of equipment — a line, a filler, a press. One scan sweeps the subnet and fingerprints every EtherNet/IP, S7 and Modbus device on it; tap a card and the connection form is prefilled. A machine with several PLCs — even mixed brands — lives in the app as one thing.
  2. Let the tags come to you. On Allen-Bradley Logix the app reads the controller's own tag list — controller- and program-scoped, with types and live values, searchable. Nothing to export, nothing to configure.
  3. No tag names? Name your points once. On Siemens and Modbus, add the points you care about by address — DB1.DBD4, M0.0, 40001 — with type and scaling. The live preview shows the value as you type, so a wrong address is obvious before you save it.
  4. No documentation either? Let the machine show you. The patent-pending Find by action wizard finds a tag by pressing the machine's real pushbutton in the rhythm the app dictates — down to one bit inside an I/O word, on a running machine. Parameter mode finds a setpoint the same way: nudge it one step on the machine's own controls and the app spots the tag that changed — scales included.
  5. Lay out the dashboard. Drop tags onto number, gauge, LED and trend tiles, organized into pages. Tiles from every PLC of the machine share one screen, each labeled with the controller it reads.
  6. Add the operator panel. Start/stop pulse buttons, hold-to-run jog, latching switches, setpoints with limits, status lamps. This is the part that turns "a monitoring app" into "the machine's screen".
  7. Map the alarms. Alarm words become operator texts — every bit of an INT or DINT one message. Active alarms show as a red banner over every tab, in an alarm list tile, and in a journal of appeared and cleared. When an unnamed bit fires, name it on the spot — the dictionary grows as the machine talks.
  8. Write values — deliberately. Every write asks for confirmation and is validated against the point's type and limits; hold-to-run releases the moment the app loses focus. Reading is free forever; writing is a one-time unlock, no subscription — the price of a coffee run, not a SCADA license.
  9. Share the result. The whole thing — PLCs, named points, dashboard, panel, alarm texts — is one machine profile. Export it as a file, send it to a colleague, and their phone has your exact screens. The screen you built once now belongs to the shift, not to a contractor.
Tag browser in the LineKeeper app: every tag of an Allen-Bradley controller with live values and search, read straight from the PLC with no export files
Step 2: the controller hands over its own tag list — live, searchable
Dashboard built in the LineKeeper app without HMI software: line speed gauge, part counter, motor current trend and temperature tiles from two PLCs
Step 5: the dashboard — gauges, counters and trends from both PLCs
Operator panel built in the LineKeeper app: start and stop push buttons, hold-to-run jog, speed setpoint and status lamps on an iPhone
Step 6: the operator panel — what turns an app into the machine's screen

When the machine needs a physical screen

A screen in your pocket is the troubleshooting tool. A screen on the machine is what the operator actually watches all shift. Two ways to get there:

  • Mount a tablet. Full-screen panel mode keeps the display awake, and on an iPad the same panel gets buttons big enough for gloves. A $30 wall mount and a spare iPad turn the screen you just built into the machine's screen — many plants stop here.
  • Go permanent. For Allen-Bradley lines there's the LineKeeper device — a self-contained 7″ or 10″ industrial touchscreen that lives on the machine, built the same drag-and-drop way, and adds what a phone shouldn't carry: years of tag history, downtime statistics, machine health reports.
The operator panel full-screen on an iPad: large start, stop and hold-to-run jog buttons, a speed setpoint and status lamps — a mounted tablet as the machine's physical screen
A mounted iPad in panel mode: buttons big enough for gloves
LineKeeper 10.1-inch industrial touchscreen device standing next to a machine as its permanent backup HMI panel
The permanent option: the LineKeeper device on the machine
The plug-in LineKeeper device — a 7″ or 10″ touchscreen version of the same idea, with 24/7 logging — is in development ($1,290 planned, one-time). No preorders, no deposits; details on the pricing page. The app is how we fund it: every install brings the backup panel closer to your machine.

What this doesn't replace

Honesty corner: the app is not a safety device, and it doesn't replace certified operator stations where your regulations require them. Safety logic lives in the PLC and stays there. What the app replaces is the waiting — for the integrator's slot, for the license budget, for the panel that shows the wrong things to finally get updated.

Free app · iPhone & iPad

Build your first screen tonight

Install free, open the demo line, and have a working dashboard before your coffee cools. Tomorrow, point it at a real machine.

Download on theApp Store
QR code — LineKeeper on the App StoreOn a desktop? Scan with your iPhone or iPad to get the free app.
See the full app tour →
FAQ

Fair questions

Do I need PLC programming skills to build a screen in the app?

No. On Allen-Bradley Logix controllers the app reads the tag list straight from the controller — you search and pick. On Siemens S7 and Modbus you enter addresses from the machine's documentation, or skip the documentation entirely: the patent-pending Find by action wizard locates a tag by pressing the machine's real button, and a parameter mode finds a setpoint from the value on the machine's own display.

Can the phone screen replace the machine's physical panel?

As a temporary or supplementary screen, yes: full-screen panel mode keeps the display awake, and a mounted iPad gives operators large glove-friendly buttons. It doesn't replace safety devices or certified operator stations where regulations require them. For a permanent panel on an Allen-Bradley line there is the LineKeeper device (in development, 7″ and 10″ sizes planned) — a self-contained industrial touchscreen built the same drag-and-drop way.

Is it safe to let a phone app write to a production machine?

Reading is the same polling load as one extra HMI screen. Writing is always deliberate: every write asks for confirmation and is validated against the point's type and limits, hold-to-run buttons release the moment the app loses focus, and the first write shows a one-time responsibility notice. Reading is free; writing is a one-time unlock.

What if my machine has several PLCs of different brands?

One piece of equipment in the app can hold several PLCs — an Allen-Bradley line controller next to a Siemens packager next to a Modbus drive. They share one dashboard and one operator panel; every tile is labeled with the PLC it reads, and each PLC reconnects independently.

The panel died and I found this article in a panic — where do I start?

With the 10-minute triage guide — a share of "dead" panels are a $40 power supply. If the panel is truly gone, come back here: the screen you build in the app is exactly the bridge that keeps the line producing while the repair or replacement is on its way. Brand-specific guides: PanelView Plus 7, PanelView Plus 1000, Siemens KTP / Comfort Panel.