OPC UA vs Modbus TCP vs MQTT — choosing a protocol for a retrofit
The three protocols solve different problems and are usually used together. A practical decision guide for brownfield plants.
Insights
Engineering notes, not thought leadership
Each of these answers one question properly — the kind an automation engineer actually searches for at eleven at night. Written by the people who do the work, and published whether or not it leads to an enquiry.
In the pipeline
Coming next
We would rather show the plan than pad this page with posts that were not written by an engineer. Two per month. If one of these is a question you need answered now, ask us directly and we will answer it before it is published.
How to connect an existing PLC to a cloud dashboard without changing the control program
The non-intrusive path from an installed PLC to a live dashboard: which protocols to read, how to size poll rates, and where the genuine limits are.
PlannedIndustrial IoTWhat OEE actually measures, and why most factory OEE numbers are wrong
Availability, performance and quality — where the assumptions hide, and how to produce an OEE figure that survives a review meeting.
PlannedMachine MonitoringRetrofitting machine monitoring onto equipment with no PLC
Current transformers, proximity counters and remote I/O: getting real state and real counts from machines that expose nothing.
PlannedMachine MonitoringMQTT Sparkplug B explained for automation engineers
Why plain MQTT is not enough, what birth and death certificates give you, and how state awareness changes alarm design.
PlannedEdge Computing & GatewaysEdge vs cloud: what should be computed at the plant
A decision framework based on latency, bandwidth, availability and cost — with worked examples from vibration and OEE.
PlannedEdge Computing & GatewaysA realistic architecture for monitoring 20 machines across two plants
A full worked architecture: gateways, protocols, tag model, storage, retention and what it costs to run.
PlannedIndustrial IoTWhy your SCADA data never reaches your ERP
The boundary problem, the person in the middle with a spreadsheet, and how to design the interface properly.
PlannedSystem IntegrationReading energy consumption per machine without rewiring the panel
Clamp-on CTs, meter selection, where to install, and how to attribute consumption to machine, shift and product.
PlannedIndustrial IoTDowntime reason codes: designing a system operators will actually use
Why most reason-code systems are abandoned within a month, and the design constraints that prevent it.
PlannedMachine MonitoringMigrating a legacy PLC without a full line shutdown
Proving functional equivalence, pre-testing off-line, staged cut-over, and keeping a real way back.
PlannedPLC ProgrammingIndustrial network segmentation basics — the Purdue model in practice
What the levels mean on a real shop floor, where the boundary device sits, and what your IT team will ask for.
PlannedSystem Integration
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