Open source PLC: 5 case studies of machines that run on it
There's a question every engineer asks before their first project with an open source PLC: "does anyone actually use this for real work?"
It's a good question, and it deserves a substantial answer. Arduino and Raspberry Pi were born for education and prototyping, not for the plant floor — just like Linux was born in a university dorm room and today runs the planet's infrastructure. The question is never where a technology was born, but who hardened it for the environment it's going to work in: optocoupled I/O, protections, DIN rail, industrial temperature range and CE marking.
In this article we go through five real cases — all five published as case studies on our website, each with its own link — running on open source PLCs inside, across five different sectors: industry, energy, livestock, smart city and water. For each one: the project, the architecture, and why open source was the winning decision, so you can copy whichever one looks most like your project.
Case 1 — Industrial machinery retrofit: the packaging line that got back up to date
The project. The most common case of all: a food packaging line with sound mechanics and obsolete control. Replacing the machine made no economic sense; the retrofit modernized the control with an industrial PLC that integrates the line's sensors, actuators and control devices.
The architecture.
- Controller: ESP32 PLC — a deterministic dual-core microcontroller, no operating system, programmed with the Arduino IDE.
- Field: the PLC integrates the machine's existing sensors and actuators through its optocoupled inputs and industrial outputs.
- Connectivity: the platform comes with Ethernet, WiFi and BLE, and RS-485 built in — the modernized machine is now ready to report data, not just run.
Why open source. The retrofit's firmware belongs to the integrator, not to the control supplier: every adjustment gets deployed from their own code, with no per-unit licenses and no captive toolchain. Full case study: https://www.industrialshields.com/case-study-industrial-machinery-retrofit-with-esp32-plc
Case 2 — Energy: automation and monitoring of a biogas plant
The project. A biogas plant needed centralized control and supervision of its process: fermenters, agitators and meters, with a local management screen for the operator.
The architecture.
- Controller: industrial Arduino PLC. Deterministic logic, no operating system: millisecond startup and predictable cycle time — exactly what you want governing a biological process that never stops.
- Field: reading process meters and driving the agitators and fermenter equipment from the PLC's industrial I/O.
- Supervision: a local management screen to operate the plant, with control and supervision centralized in one place.
Why open source. A biogas plant is a multi-year project: independence from the control supplier — no recurring licenses, code in the hands of whoever operates it — is a long-term maintainability policy. Full case study: https://www.industrialshields.com/case-study-biogas-plant-automation-gr
Case 3 — Livestock: the automated pig farm that reports to a server
The project. A pig farm needed to automate control and monitoring of the facility — a harsh environment, with dust, humidity and ammonia — and also collect data on a server for later analysis. Modern intensive livestock farming is managed with data, not inspection rounds.
The architecture.
- Controller: industrial Arduino PLC governing the farm's control and monitoring, with autonomous local logic.
- Interface: Raspberry Pi-based panel PC with Wi-Fi connectivity as the local operator station.
- Data: facility data collected to a server, where it's analyzed — the farm keeps a history, not just live operation.
Why open source. The agricultural/livestock sector's economics don't support premium automation architectures, but the reliability requirement is industrial-grade: DIN-rail-hardened hardware at contained platform cost, and full freedom to adapt the logic to each installation. Full case study: https://www.industrialshields.com/case-study-arduino-plc-automated-pig-farm
Case 4 — Smart city: the public lighting controller that saves up to 60%
The project. Public lighting managed intelligently: full control of the luminaires, electrical monitoring of the installation, and alarms — with a measurable goal: cutting the municipality's energy bill.
The architecture.
- Controller: industrial Arduino PLC as a Smart Light Controller.
- Field: luminaire control via DALI and 12-24 V signals; power, voltage and current monitoring of the installation.
- Supervision: active alarms when something goes out of range — a burnt-out luminaire gets reported, not discovered.
Why open source. A lighting rollout means many repeated control points: with no per-unit licenses, the cost per point stays flat, and the dimming logic adapts to each street from proprietary code. The published result: energy savings of up to 60%. Full case study: https://www.industrialshields.com/smart-light-controller-solucion-industrial-para-alumbrado-publico
Case 5 — Water and environment: the hydrometeorological station on the Ucayali River (Peru)
The project. Real-time monitoring of the Ucayali River basin, in the Peruvian Amazon: measuring level and flow of the river, plus water quality — temperature, electrical conductivity, dissolved oxygen and pH — with automated hourly logging. A remote, demanding environment where nobody is going to stop by to "reset the unit."
The architecture.
- Controller: industrial Arduino PLC as an autonomous measuring station.
- Field: hydrometric and physicochemical probes (level, flow, temperature, EC, dissolved O2, pH) integrated into the PLC's inputs.
- Data: automated hourly logging of all measurements — the basin gets documented data point by data point, with no operator.
Why open source. In a remote environmental deployment, every measuring point competes for budget: the open source platform puts industrial reliability into each station with no per-point license cost, and the logging logic adapts from code to whatever the basin needs. Full case study: https://www.industrialshields.com/estacion-hidrometereologica-y-calidad-de-agua-automatica-en-la-cuenca-del-rio-ucayali
The pattern that repeats across all five cases
If these five stories have sounded similar to you in some way, it's because they are. In all five cases, the winning decision was the same: ownership of your own technology.
- No per-I/O-point or per-unit-manufactured licenses.
- No captive programming tool: Arduino IDE, Node-RED, or whatever language the team already knows.
- No waiting on the manufacturer's quote to change one line of logic.
- Knowledge of the machine — code, schematics, data — belongs to whoever builds or operates it, not to the control supplier.
Open source, in industrial settings, means exactly that. It's not a philosophy: it's a clause of technological independence that shows up in the margin on every machine sold and in the speed of every modification.
Which one looks like your project?
A quick table to help you place yourself:
| Your project looks like… | Family used in the case | Architecture highlights |
|---|---|---|
| Retrofit of an existing machine (case 1) | ESP32 PLC | Integrate existing sensors and actuators; built-in connectivity |
| Continuous process plant (case 2) | Arduino PLC | Deterministic control + local management screen |
| Agro-livestock installation with data (case 3) | Arduino PLC + Raspberry Pi panel PC | Local control + data to server for analysis |
| Deployment with many repeated points (case 4) | Arduino PLC | DALI and 12-24 V, electrical monitoring, alarms |
| Remote measuring station (case 5) | Arduino PLC | Multi-parameter probes + automated logging |
And the cross-cutting principle you already know if you're coming from the newsletter: a prototype running today on an Arduino, ESP32 or Raspberry Pi board migrates to its industrial PLC version without rewriting the code — same platform, same environment, hardened hardware.
📥 Download the checklist: "From Arduino Prototype to Industrial Installation"
Is your machine still a prototype? These five cases started the same way. The 12-step checklist maps out the complete path to the plant floor, in a printable PDF.
Download the free checklist →
Manufacturing machines in series? Check out the full catalog of open source industrial PLCs — Arduino, ESP32 and Raspberry Pi PLC — at https://www.industrialshields.com/shop, and the complete index of case studies by sector at https://www.industrialshields.com/arduino-plc-summary-case-studies-monitoring-control-and-automation-20211007-lp. And if your machine needs a controller the standard catalog doesn't cover, there's a custom product design service: https://www.industrialshields.com/industrial-open-source-hardware-custom-solutions