Vishal Tyagi
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Case Study·shipped

Bridging Isolated PLC Networks to a Cloud Dashboard

An ESP/NodeMCU bridge, then OPC UA/Node-RED on top, so factory-floor telemetry reaches a secured remote dashboard

Case study of bridging Siemens/Delta PLC telemetry — isolated on the factory network — into a Node-RED/OPC UA pipeline and a secured remote dashboard, starting from an ESP/NodeMCU bridge designed from scratch.

Date Shipped2025-05
Estimated Reading2 min read
Lifecycle Statusshipped
Primary Tech Stack
N/A

One manufacturing site

Deployment

ESP/NodeMCU, initial version

Bridge hardware

Secured tunnel to a live dashboard

Remote access

Companion write-up for Manufacturing Inventory Platform Rebuild.

Problem

Machine state lived entirely inside the plant’s isolated OT network. Siemens and Delta PLCs spoke OPC UA / Modbus to each other and to floor-local panels, but nothing about that state reached the inventory platform, and nothing about it reached anyone off the factory floor. A plant manager who wanted to check machine status, or toggle equipment like the PLC-driven AC unit, had to be physically on-site.

Constraints

  • Factory OT network is isolated by design — no direct exposure to the internet
  • Siemens/Delta gear speaks OPC UA / Modbus, not anything web-native
  • One site, real production line — no tolerance for downtime while building the bridge
  • Remote access has to be secured, not just “open a port”

Approach

The first version of the bridge was built from scratch on ESP/NodeMCU hardware: the actual mechanism that gets a signal off the isolated PLC network and into anything IoT-reachable. Node-RED and an OPC UA adapter sit on top of that bridge, translating controller events into a stream the Express API can consume alongside inventory data.

Diagram
Secured tunnelSwitch on/offSiemens / Delta PLCs —isolated OT networkESP/NodeMCU BridgeNode-RED + OPC UAAdapterExpress APIMongoDBRemote DashboardPlant manager, anywhere

Pieces that matter

  1. ESP/NodeMCU bridge — the actual first hop off an isolated PLC network, designed and built as the initial version before anything else in the pipeline existed
  2. Node-RED + OPC UA adapter — keeps industrial protocol handling out of core business logic in the Express API
  3. Secured tunnel — the remote dashboard isn’t just port-forwarded; access is tunneled and authenticated
  4. Two-way channel — the dashboard isn’t read-only telemetry; it can switch equipment (the PLC-driven AC unit) on or off remotely

Tradeoff

Rejected alternative: wait for a proper industrial IoT gateway product and integrate against it. Faster to ship, no vendor lock-in risk from a bridge nobody else maintains — but it means the bridge is bespoke, and its ESP/NodeMCU origin is closer to a hobbyist-hardware pattern than an enterprise OT gateway. That’s a real tradeoff, not hidden: it shipped and works at the one site it’s deployed to, but it hasn’t been proven at a second site or against gear beyond Siemens/Delta.

Evidence

  • Machine telemetry that was previously invisible off the plant floor now reaches the inventory platform
  • A plant manager can view machine status and switch the PLC-driven AC unit on or off from anywhere, through a secured tunnel, not from the plant floor only
  • Deployed and running at one manufacturing site — no claim of multi-site rollout

See the project page for the full inventory-platform rebuild this bridge feeds into.