Fair questions
We never made a copy and the panel is already dead. Too late?
No. A copy made in advance restores in minutes; without one, recovery is about an
hour of work. Connect LK Go to the PLC, get your programmer on the phone, and pick the
tags that matter together: on Allen-Bradley Logix the controller hands over its whole
tag list, so you search by names and addresses. Have the panel's project export? Drop
it into the free converter and the controls come back
with their tags. Find by action needs the panel alive, so it's the tool for the
copy you make today, not for tomorrow's rescue.
Our line is down right now. Can you help faster?
Two things, both free: install LK Go (it puts live values on a phone in about 15
minutes, and start/stop buttons once the right tags are identified) and
tell us the line is down. The remote triage call is free, and
often the panel failure has a workaround (or a repairable cause) that gets you producing
before any hardware arrives. Start with the
10-minute triage guide.
Which PLCs does it support?
Three protocols. Allen-Bradley CompactLogix and ControlLogix — the tag-based
Logix 5000 family — over EtherNet/IP, with the tag list read straight from the
controller. Siemens S7-300/400 and S7-1200/1500 (with PUT/GET enabled and
non-optimized DBs) over S7comm. And anything speaking Modbus TCP — Schneider,
AutomationDirect and Click PLCs, VFDs, energy meters, gateways. Micro800, SLC-500
and PLC-5 are not supported.
My S7-1200/1500 refuses to connect — why?
Almost always one of Siemens' two factory defaults: PUT/GET communication is
disabled, or the data blocks are "optimized" and have no absolute addresses. The app
detects the refusal and shows the exact TIA Portal steps for each case — enable
PUT/GET in the CPU's Protection settings and untick optimized block access on the
DBs you want to read — instead of a silent timeout.
Modbus devices have no tag names — how does that work?
A Modbus point is a register address plus a data type and scaling. Enter it once,
give it a name, and watch the live value preview as you type. The named register map
is saved in the machine profile — share the profile as a file and a colleague gets
the whole map on their phone.
What is "Find by action"?
A patent-pending way to find a tag without knowing the PLC program. Press the
machine's real pushbutton in the rhythm the app dictates: a baseline pass on the
running machine first sets aside counters, timers and drifting analogs, then lock-in
windows eliminate out-of-rhythm coincidences, and the app returns the tag that
followed your presses — down to a single bit inside an I/O word. A parameter mode
does the same for setpoints: nudge it one step on the machine's own controls, and the app finds the register that changed — scale factors included.
It works on all three protocols, not just Allen-Bradley. On Logix the app sweeps
the controller's whole tag list and hands back the real tag name. On Modbus it
sweeps the coil and holding-register ranges; on Siemens, the flag area plus one data
block whose number you enter — S7comm can't enumerate DBs. There the answer is an
address (MB4.3, co34), and you
give it a name once.
Do I need to change the PLC program or install a gateway?
No. The app speaks the same protocols an HMI uses — EtherNet/IP, S7comm, Modbus
TCP — directly to the controller. Nothing is installed on the PLC, no program
changes, no OPC server, no cloud account. Values go from the controller straight to
your phone. On Siemens S7-1200/1500 classic S7 communication needs PUT/GET enabled and non-optimized DBs: a CPU access setting your Siemens person changes in TIA Portal, not a change to the program.
Is it safe on a production network?
Browsing and dashboards only read values — the same polling load as one extra HMI
screen. Writing a value is always deliberate: every write asks for confirmation,
values are validated against the point's type and limits, and the first write shows a
one-time responsibility notice.
Will our IT department allow this?
That's genuinely IT's decision, so here is what they will want to know. There
is no cloud at all: traffic goes phone-to-controller on the local segment and
stops there — no account, no server, nothing leaves the plant. Reads are the same
standard requests any HMI already makes, on the same ports — EtherNet/IP
TCP 44818, S7comm TCP 102, Modbus TCP 502 — with no PLC program change and no
inbound ports opened on the phone. And the free version is read-only by design,
so IT can allow it as a view-only tool and treat writing as a separate
decision.
The phone doesn't have to join OT Wi-Fi either: a USB-C Ethernet adapter into
a spare machine-switch port puts it on the wire with the network config
untouched. Where personal devices are banned outright, the standard practice is a
company tablet under MDM, mounted as a panel. If IT still says no, that's their
call to make — but let them make it on facts: send them the
one-page summary below.
My machine runs several PLCs — do I need several dashboards?
No. A piece of equipment in the app can hold several PLCs — even a mix of brands,
an Allen-Bradley line PLC next to a Siemens packager. They share one dashboard and
one operator panel; every tile shows which PLC it reads, and each PLC reconnects
independently if it drops.
How does the phone reach the PLC?
The phone must be on the same network as the controller — plant Wi-Fi that routes
to the PLC VLAN, or a wired connection through a USB-C Ethernet adapter. There is no
cloud relay: if you can ping the PLC, the app can connect to it.
Can it show alarms like the factory panel?
Yes. Alarm words and status values map to operator texts — every bit of an INT or
DINT can be one alarm message. Active alarms show in a red banner over every tab, in
an alarm list tile on the dashboard, and on an Alarms screen with a session journal
of appeared and cleared events. When an unnamed bit fires, you can name it on the
spot.
What is machine history?
The first time the app connects to a PLC it records a parameter snapshot — a
searchable list of the values as they were that day — and from then on keeps a
timestamped change log of every dashboard tag while the app is connected, with a
marker whenever the link dropped. Take a fresh snapshot manually any time, for
example right after a good changeover. Everything stays on the phone; nothing goes
to a cloud.
Honest limit: it records only while the app is connected — a technician's
notebook, not a 24/7 plant historian. On real controllers machine history is part
of Pro; on the built-in demo line it's free.
Does LK Go work with LK On?
Yes. The Devices screen finds LK On devices on the local network — or add
one by IP — and after signing in with the device's own role and password, dashboards
and operator panels copy both ways: pull the device's screens onto your phone, or
build a layout in the app and send it to the device as a new named dashboard.
Existing dashboards on the device are never wiped, and widgets with no web
equivalent are skipped and listed — never dropped silently.
Does it work on iPad?
Yes — LK Go is a universal app, so the same tag browser, dashboard and
operator panel run on both iPhone and iPad from one free download. The larger iPad
screen just fits more dashboard tiles and bigger panel buttons, which makes it a
handy portable operator station on the machine.
How much does it cost?
LK Go is a free download. Browsing, dashboards, alarms, the network scan and
Find by action are free. Pro — a one-time $59.99 in-app purchase, no
subscription — unlocks writing values and machine history on real controllers.
In the App Store the purchase is listed as “Write Unlock”: that is Pro.
Is it on the App Store?
Yes — LK Go is live
on the App Store, listed there under the company name “LineKeeper”: a free install for iPhone and iPad. Browsing, dashboards and
alarms are free; Pro is a one-time $59.99 in-app purchase, listed there as “Write Unlock”.
