Free HMI and SCADA builder, in the browser

Draw an operator screen and run it against real ladder logic, with no account, no download and no tag limit. The runtime is the same scan engine the PLC simulator uses, so a start button on the glass starts the motor in the program.

The tag limit, which is usually the catch

Most free SCADA is free up to a number of tags, and the number is chosen carefully: high enough to build a demonstration, low enough that a real machine needs the paid tier. You find out at the point where the screen is nearly finished.

There is no tag count here, because nothing is being licensed. What an account adds is a project to file the application against, so the screens sit with the program, the drawings and the documents, and screen generation from a description, which needs a model and therefore a key that belongs to somebody.

It exports a panel that actually runs

One HTML file, holding the screens, the ladder program, the scan engine and the renderer. Open it and the screen is running: no install, no server, and no network, so it works from a USB stick on a machine that has never been online, which is the normal condition of the machine it ends up on.

Being exact about what that is, because "deploy to a panel" means something specific. It is not a TP1500 project or a PanelView application; those are closed vendor formats and writing one without their tooling is not something to claim. It is a panel for the other kind of hardware, which is most of the new kind: an industrial PC, a thin client, a tablet on the line, a small board beside the machine. All of those run a browser.

The runtime inside the file is the same code the builder runs, not a port of it. A second implementation is faithful on the day it is written and drifts from then on, and the entire value of exporting a screen somebody signed off is that it is the screen they signed off. The process behind it is still the simulator, and the file says so in its own source.

The run is recorded, and the spike survives

A trend on the screen shows the last few minutes, because that is what an operator needs. The question afterwards is different: what was it doing at the moment it tripped, and that moment has usually scrolled off the end. So every trend also records, and the recording survives pressing Stop, which is the exact moment somebody wants to look at it.

Older samples are compacted, and how they are compacted is the part that matters. An average per interval quietly removes the excursion, and the excursion is the reason anybody opened the recording; a one second spike inside a five minute average leaves a flat line through the failure. Each interval keeps its minimum and its maximum instead, so the chart draws a band and the spike is still there. Export is CSV with the low and the high in separate columns and timestamps in UTC.

What it will not do

• It does not talk to plant equipment. The runtime is the simulator, which is what makes a screen testable at a desk.
• It does not produce a vendor panel project. There is no download to a TP1500 or a PanelView, because those are closed formats; what it exports is a panel that runs in a browser.
• It is not a plant historian. A run can be recorded, reviewed and exported as CSV, but that is a record of a simulated test held in the browser, not months of instrument data you can query next year.
• Scripting is a small expression language over tags, deliberately not a programming language.

Questions

Is this SCADA software really free?

The builder is, with no account, no download, no trial period and no tag limit. That last one matters: most free SCADA is free up to a tag count, and the count is chosen to be just below what a real machine needs. There is no count here because nothing is being licensed.

Can I run the HMI without a PLC?

Yes, and that is the point of it. Draw a rung in the free ladder editor, come here, and the screen binds to that program's tags and runs against the same scan engine. A start button on glass starts the motor in the logic, the trend fills and the alarms evaluate, with no controller and no panel present.

How many alarms and tags can I have?

No imposed limit. Alarms follow the ISA-18.2 state machine with deadband, on delay and shelving that expires, and can be generated in bulk from an analogue tag table as a percentage of engineering span rather than defined one at a time.

Can I deploy this to a Siemens or Allen Bradley panel?

No. It designs, proves and documents the screens, and the connection settings are recorded for handover rather than dialled. Export to a panel runtime is the next substantial thing on its list, and it is worth knowing that before you build a plant on it.

What symbols are included?

Eighty seven across twelve categories: vessels, pumps and fans, valves, conveying, heat transfer, instruments, switchgear and pipework, in a flat ISA-101 style or a shaded realistic one. Any of them can be replaced with your own SVG or a photograph of the actual machine.

Does it talk to real plant equipment?

No, and it is not going to. The runtime is the ladder simulator, which is what makes a screen testable at a desk. The driver settings for OPC UA, Modbus TCP, EtherNet/IP or S7 are configured and exported so the design can be handed over, not so that this opens a socket to a machine.