Arduino PLC vs ESP32 PLC vs Raspberry Pi PLC: Which to Choose

Arduino PLC vs ESP32 PLC vs Raspberry Pi PLC: Which to Choose

Choosing between an Arduino-based PLC, an ESP32 PLC, and a Raspberry Pi PLC looks simple. Three families, three datasheets, one decision.

But get it wrong and there are only two possible endings: either you overpay on every panel you build for years, or you save a few euros per unit and lose it many times over in debugging, redesign, and site visits nobody's going to pay you for.

At Industrial Shields we've been building industrial PLCs on these three platforms since 2012, and most of the selection mistakes we see in technical support boil down to one sentence: the choice was made by familiarity ("I already know Arduino") instead of the installation's real requirements. This guide exists so your decision gets made on requirements instead. At the end you'll also find the criterion almost nobody checks — one that disqualifies one of the three families in half the projects we analyze — plus the three costliest selection mistakes we've seen come through support.

The three families in one table

The table gives you the lay of the land, but the real decision comes from understanding each family's philosophy. Let's go through them one by one.

Arduino PLC (M-Duino family): the deterministic workhorse

An M-Duino has an Arduino-family microcontroller inside (ATmega2560 in most models). That means: no operating system, millisecond boot, predictable cycle time, and zero surprises after a power cut. The program you flashed is exactly what runs, cycle after cycle, for years.

When it's the right choice

When the job is pure control: read inputs, run logic, drive outputs, talk Modbus RTU/TCP to drives and sensors. Process machines, dosing, pumping, simple lines. On that turf, the simplicity of an 8-bit microcontroller isn't a limitation — it's the guarantee of reliability. Fewer layers between your code and the hardware means fewer things that can fail at 3 a.m.

The family covers everything from compact units to models with dozens of digital and analog I/O — models are named after their total I/O count: M-Duino 21+, 42+, and 58+. The 21+, for example, offers 13 inputs (6 analog-digital and 7 isolated digital, 2 of them interrupt-capable) and 8 outputs (5 isolated digital and 3 configurable as digital/PWM/0-10V analog) — all DIN-rail mounted, with optocoupled, protected I/O.

Where it falls short

If you need an embedded HMI, local databases, or on-device data processing, an 8-bit microcontroller isn't the place for it. You can force it — we've seen heroic attempts — but you'll be fighting the platform instead of working with it.

ESP32 PLC: control plus wireless connectivity out of the box

The ESP32 PLC keeps the microcontroller philosophy (deterministic, no operating system) but adds what the ATmega doesn't have: built-in WiFi and Bluetooth, two cores at 240 MHz, and a lot more RAM.

When it's the right choice

It's the natural choice for IIoT: publishing telemetry over MQTT to a broker, remote nodes where running Ethernet cable is expensive or flat-out impossible, retrofitting older machines you want to pull data from without touching their original control. Also when the control logic needs more compute muscle than an ATmega gives you, but without crossing into a full operating system.

Where it falls short

WiFi on the plant floor is a telemetry link, not a control bus. If your process safety depends on a frame traveling over WiFi between motors and drives, that's a design problem, not a product problem. Industrial radio suffers interference, roaming, spectrum congestion — and none of those variables are under your control. Telemetry over WiFi: yes. Interlocks over WiFi: never.

Raspberry Pi PLC: the edge computer with industrial I/O

Here the philosophy changes completely: Linux, gigabytes of RAM, and the door open to Node-RED, Python, local databases, OPC-UA gateways, and dashboards served straight from the PLC itself.

When it's the right choice

When the PLC not only has to control but also has to think: data concentrator for several machines, Modbus→MQTT/OPC-UA gateway, local historian, lightweight machine vision, web HMI served to the operator's tablet. One DIN-rail unit doing the job that used to require a PLC plus an industrial PC.

Where it falls short

A system running an operating system demands discipline: orderly shutdowns, disk-write management, application and system watchdogs. And for hard safety logic and guaranteed cycle times, a microcontroller is still simpler to justify — to yourself, to your customer, and to whoever signs off on the risk assessment.

The quick decision table

• Deterministic control, no data → Arduino PLC.
• Control + wireless telemetry / MQTT → ESP32 PLC.
• Data, gateways, HMI, historian, edge → Raspberry Pi PLC.

That resolves 80% of cases. The remaining 20% — and the projects that end badly — come down to the next criterion.

The criterion almost nobody checks: what happens when the power cuts out

Here's the promised criterion, the one that disqualifies one of the three families in half the projects we analyze: how the device behaves under uncontrolled power loss.

A microcontroller (Arduino PLC, ESP32 PLC) is inherently tolerant of power cuts: there's no filesystem to corrupt, no orderly shutdown to respect. Power comes back, it boots in milliseconds, and the program is exactly where the design says it should be.

A Linux device booting from an SD card is a different story. A power cut mid-write can corrupt the filesystem, and the symptom is the worst possible one: the device doesn't come back up, weeks or months after the cut that caused the damage. And boot time, even when everything goes fine, takes tens of seconds — during which your outputs sit in whatever state the hardware decides, not what your logic decides.

Does that mean the Raspberry Pi PLC isn't fit for the plant floor? No — it means it requires design work. Read-only filesystem (overlay) for the system partition, industrial SD card, backed-up power (DIN-rail UPS) or a voltage supervisor that triggers an orderly shutdown, and important logs sent to a server, not to the card.

The disqualifying question is this: does the installation have frequent power cuts, and is nobody going to budget for a UPS or shutdown design? If the answer is yes — and in half the projects we analyze, it is — the controller role has to fall to a microcontroller. The Raspberry Pi PLC can still be part of the architecture, but as the data layer: if it reboots, the machine doesn't even notice.

The 3 costliest selection mistakes we've seen in support

Mistake 1 — Overspeccing "just in case"

Choosing a Raspberry Pi PLC for pure machine control "because it's more powerful, so we're covered." The result: all the complexity of maintaining a Linux system (images, updates, SD cards, shutdowns) to run logic an M-Duino would have run for ten years without anyone giving it a second thought. Power you don't need isn't margin — it's failure surface and maintenance cost.

Mistake 2 — Underspeccing out of familiarity

The reverse, and the most common one: choosing an Arduino PLC "because I already know Arduino" and discovering at commissioning that the customer wanted a data historian, a screen, and reports. What follows is a festival of patches — external SD cards, a "temporary" desktop PC that sticks around for five years — or a redesign with the machine already sold. Data requirements get asked before picking a platform, not after.

Mistake 3 — Trusting control to WiFi

Choosing an ESP32 PLC and using the wireless link as the control bus between the PLC and the actuators. It works in the demo. On the plant floor, with twenty overlapping networks and a fleet of metal forklifts moving between antenna and device, link drops show up — and with them, stoppages. The rule is simple: data that can arrive late travels over WiFi; anything whose absence stops or damages the machine travels over cable.

How to decide in 5 questions

1. Does the device need to store or process data locally (historian, HMI, gateway)? → Yes: Raspberry Pi PLC. No: keep going.
2. Do you need built-in wireless connectivity (MQTT, remote nodes)? → Yes: ESP32 PLC. No: keep going.
3. Is the job pure control with Modbus/I/O? → Arduino PLC.
4. Are there frequent power cuts with no UPS budgeted? → Rule Linux out of the controller role.
5. Who will maintain the device in 5 years, and what do they know how to program? → If two families tie technically, the human team breaks the tie.

And one last note that simplifies everything above: all three families share an open-source philosophy, DIN-rail form factor, and industrial protections. Picking the wrong family within the catalog is fixed by migrating; picking the wrong philosophy — installing a bare prototype board in the panel — is paid for in full.

📥 Download the checklist: "From Arduino prototype to industrial installation"
The complete 12-step process for taking your project from the workbench to the electrical panel, in printable PDF.
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Already clear on which family fits your project? Explore the full range of open-source industrial PLCs — Arduino, ESP32, and Raspberry Pi, all DIN-rail mounted with protected I/O: https://www.industrialshields.com/shop (use the Configurable Finder to filter by CPU, number of I/O, communications, and price). And if you're still torn between two families, write to us with your I/O, communications, and environment — an engineer will tell you which one fits, and also if none of them do.