Arduino Opta: Industrial PLC Programming Guide

The industrial automation world has long been dominated by established players like Siemens, Allen-Bradley, and Schneider. Now Arduino Opta enters this space with a compelling proposition: bringing the accessible Arduino ecosystem to professional PLC applications without sacrificing industrial-grade reliability.

Having worked with traditional PLCs for years, I was initially skeptical about Arduino entering the industrial automation space. After extensive testing with the Opta, I’ve found it occupies a unique position—powerful enough for serious automation tasks while maintaining the programming flexibility that makes Arduino attractive. This guide covers everything you need to know about programming the Arduino Opta for industrial applications.

What is Arduino Opta?

The Arduino Opta is a micro PLC (Programmable Logic Controller) designed in partnership with Finder, a leading Italian manufacturer of relays and industrial components. Unlike hobbyist Arduino boards, the Opta is built specifically for industrial and building automation with proper certifications, robust I/O, and professional connectivity options.

What makes the Opta unique is its dual programming capability. You can program it using the familiar Arduino IDE with C/C++ sketches, or use the Arduino PLC IDE with all five IEC 61131-3 standard programming languages that traditional PLC engineers know: Ladder Diagram (LD), Function Block Diagram (FBD), Structured Text (ST), Sequential Function Chart (SFC), and Instruction List (IL).

The Opta runs on an STM32H747XI dual-core processor—the same chip powering Arduino’s professional Portenta line—providing serious computational horsepower for real-time control, predictive maintenance, and even edge AI applications.

Arduino Opta Technical Specifications

Understanding the specifications helps you evaluate whether the Opta fits your automation requirements:

Specification	Value
Processor	STM32H747XI dual-core ARM Cortex-M7 + M4
Clock Speed	M7: 480 MHz, M4: 240 MHz
Flash Memory	2 MB
RAM	1 MB
Digital/Analog Inputs	8 programmable (0-24V digital or 0-10V analog)
Relay Outputs	4 × 10A/250VAC (Normally Open)
Operating Voltage	12-24V DC
Operating Temperature	-20°C to +50°C
Certifications	CE, cULus, FCC, ENEC
Form Factor	DIN rail mountable
Dimensions	90.5mm × 42mm × 68.5mm

The 10A relay outputs are particularly notable—they can directly switch substantial loads without external relays, a genuine advantage for many control applications.

Arduino Opta Variants Comparison

Arduino offers three Opta variants to match different connectivity requirements:

Feature	Opta Lite	Opta RS485	Opta WiFi
Price (approx.)	$146	$175	$200
Ethernet	Yes	Yes	Yes
USB-C	Yes	Yes	Yes
RS-485	No	Yes	Yes
Modbus RTU	No	Yes	Yes
Wi-Fi	No	No	Yes
Bluetooth LE	No	No	Yes
Arduino Cloud	Yes	Yes	Yes

Choosing the Right Variant

Opta Lite: Suitable for standalone applications or those requiring only Ethernet/Modbus TCP connectivity. Ideal for basic automation tasks without fieldbus requirements.

Opta RS485: The choice for industrial environments requiring Modbus RTU communication with existing devices like VFDs, sensors, and energy meters. RS-485 enables reliable long-distance communication in electrically noisy environments.

Opta WiFi: Maximum flexibility with wireless connectivity for IoT applications, remote monitoring, and locations where wiring is impractical. Bluetooth LE enables local device communication and configuration.

Arduino Opta Input and Output Configuration

The Opta’s I/O system provides flexibility for various sensing and control requirements.

Input Specifications

Parameter	Digital Mode	Analog Mode
Voltage Range	0-24V DC	0-10V DC
Resolution	N/A	12-16 bit configurable
Input Protection	Anti-polarity, overvoltage	Anti-polarity, overvoltage
Number of Inputs	8	8

All eight inputs can be individually configured as digital or analog through software, providing deployment flexibility without hardware changes.

Relay Output Specifications

Parameter	Value
Type	Normally Open (NO)
Rated Load	10A/250VAC
Maximum Switching Voltage	400VAC
Maximum Peak Current	15A (≤0.5s, ≤10% duty cycle)
Response Time	6ms close, 4ms open
Number of Outputs	4

The electromechanical relays provide galvanic isolation between control and load circuits—essential for industrial safety.

Programming Arduino Opta with Arduino IDE

Programming the Opta using the Arduino IDE follows familiar patterns for anyone with Arduino experience.

IDE Setup

1. Install Arduino IDE (version 2.x recommended)
2. Navigate to Tools > Board > Boards Manager
3. Search for “Arduino Mbed OS Opta Boards”
4. Install the core package
5. Select your Opta variant under Tools > Board
6. Connect via USB-C and select the correct port

Basic Sketch Example

Here’s a simple example demonstrating digital input reading and relay control:

#include <Arduino.h>

void setup() {

  // Configure inputs

  pinMode(A0, INPUT);  // Digital input

  // Configure relay outputs

  pinMode(D0, OUTPUT); // Relay 1

  pinMode(D1, OUTPUT); // Relay 2

}

void loop() {

  // Read input state

  int inputState = digitalRead(A0);

  // Control relay based on input

  if (inputState == HIGH) {

    digitalWrite(D0, HIGH);  // Relay ON

  } else {

    digitalWrite(D0, LOW);   // Relay OFF

  }

  delay(100);

}

The Arduino IDE approach works well for developers comfortable with C/C++ and for applications requiring custom logic, sensor integration, or communication protocols not covered by standard PLC function blocks.

Programming Arduino Opta with PLC IDE

For engineers with traditional PLC backgrounds, the Arduino PLC IDE provides the familiar IEC 61131-3 programming environment.

PLC IDE Setup

1. Download Arduino PLC IDE from Arduino’s website
2. Install the PLC IDE Tools package
3. Create a new project selecting “Opta 1.0” as target
4. Download initial firmware to the Opta (required on first use)
5. Activate the PLC runtime license (included with hardware)

IEC 61131-3 Programming Languages

Language	Abbreviation	Best For
Ladder Diagram	LD	Relay logic, discrete control
Function Block Diagram	FBD	Process control, analog operations
Structured Text	ST	Complex algorithms, calculations
Sequential Function Chart	SFC	State machines, sequential processes
Instruction List	IL	Low-level operations (legacy)

Task Configuration

The PLC IDE offers two cyclical task types:

Task Type	Execution Period	Use Case
Fast	10ms, 20ms, or 50ms	Time-critical control loops
Slow	100ms	Non-critical monitoring, logging

The Fast task default of 10ms provides adequate response time for most industrial control applications.

Combining PLC and Arduino Code

A powerful feature of the PLC IDE is the ability to integrate Arduino sketches with IEC 61131-3 programs through shared variables. This enables:

• Using PLC languages for control logic
• Adding C++ code for advanced features (cloud connectivity, custom protocols)
• Leveraging existing Arduino libraries within PLC projects

Industrial Communication Protocols

The Arduino Opta supports standard industrial protocols for integration with existing systems.

Modbus Support

Protocol	Variant Support	Physical Layer
Modbus TCP	All variants	Ethernet
Modbus RTU	RS485 and WiFi	RS-485

The Opta can function as either Modbus master or slave, enabling communication with sensors, VFDs, energy meters, HMIs, and other Modbus devices.

OPC UA Support

Recent firmware updates enable OPC UA communication, allowing the Opta to integrate with modern industrial systems, SCADA platforms, and Industry 4.0 architectures. The Arduino_OPC_UA library exposes inputs, outputs, and custom variables as OPC UA objects accessible over Ethernet.

Arduino Opta Expansion Modules

For applications requiring more I/O, Arduino offers expansion modules that connect directly to the Opta base unit.

Module	Inputs	Outputs	Max Per System
Ext D1608E	16 digital/analog	8 electromechanical relays (250VAC 6A)	5
Ext D1608S	16 digital/analog	8 solid-state relays (24VDC 2A)	5
Ext A0602	6 analog (including 2× PT100)	2 analog + 4 PWM	5

With maximum expansion, a single Opta system can manage up to 88 inputs and 44 outputs—sufficient for substantial automation projects.

Arduino Cloud Integration

One of the Opta’s strongest differentiators is its native Arduino Cloud integration, enabling remote monitoring and control without complex configuration.

Cloud Features

Feature	Description
Real-time Dashboards	Visualize process variables, I/O states, and trends
Remote Control	Modify setpoints and trigger outputs from anywhere
Alerts and Notifications	Receive alerts when conditions exceed thresholds
Data Logging	Historical data storage for analysis and compliance
OTA Updates	Deploy firmware updates remotely
Device Management	Monitor fleet status and health

The cloud integration transforms the Opta from a standalone controller into a connected IIoT device, enabling predictive maintenance, energy monitoring, and remote troubleshooting that would require significant additional hardware and software with traditional PLCs.

Security Considerations

Arduino Opta includes hardware-level security features:

• Onboard secure element for cryptographic operations
• X.509 certificate compliance for authenticated connections
• Encrypted OTA updates
• Secure boot capabilities

These features address legitimate concerns about connecting industrial equipment to cloud services.

Arduino Opta vs Traditional PLCs

How does the Opta compare to established industrial controllers?

Feature	Arduino Opta	Siemens LOGO!	Allen-Bradley Micro800
Programming	Arduino IDE + IEC 61131-3	Proprietary (LOGO! Soft)	Proprietary (CCW)
Cloud Integration	Native (Arduino Cloud)	Limited	Limited
Open Source	Yes	No	No
Wireless Options	Wi-Fi, BLE	Web Server only	Optional modules
Entry Price	~$146	~$200	~$250
Relay Current	10A	10A	5A (typically)

Arduino Opta Advantages

• Dual programming environments (Arduino + PLC IDE)
• Native cloud connectivity and IoT features
• Open ecosystem with extensive libraries
• Strong relay outputs (10A direct switching)
• Lower entry cost
• Active development community

Arduino Opta Limitations

• Newer platform with developing ecosystem
• Fewer I/O on base unit than some competitors
• Limited simulation capabilities in PLC IDE
• Smaller installed base for troubleshooting references

Arduino Opta Applications

The Opta suits various industrial and building automation scenarios:

Industrial Applications

Application	Key Features Used
Conveyor Control	Digital I/O, relay outputs, Modbus
Pump Management	Analog inputs, timers, cloud monitoring
Process Monitoring	Sensors, data logging, predictive maintenance
Machine Retrofitting	Modbus gateway, legacy equipment integration

Building Automation

Application	Key Features Used
HVAC Control	Temperature sensing, relay control, scheduling
Lighting Automation	Digital I/O, time-based control, energy monitoring
Access Control	Input monitoring, relay actuation, logging
Energy Management	Analog inputs, Modbus meters, cloud dashboards

Useful Arduino Opta Resources

Resource	Description
Arduino Opta Documentation	docs.arduino.cc/hardware/opta
Arduino PLC IDE Download	arduino.cc/en/software
Opta User Manual PDF	Official datasheet with specifications
Arduino Cloud	cloud.arduino.cc
PLC IDE Programming Guide	Arduino Docs tutorials
Finder Opta Tutorials	opta.findernet.com
Arduino Forum (Opta section)	Community troubleshooting

Troubleshooting Common Issues

PLC IDE Connection Problems

If the PLC IDE fails to connect:

1. Ensure the initial firmware download completed successfully
2. Verify correct COM port selection
3. Try resetting the Opta before connecting
4. Check that no other software is accessing the port

Modbus Communication Failures

For RS-485 Modbus issues:

1. Verify wiring polarity (A/B connections may need swapping)
2. Add termination resistors if required (Opta has none internally)
3. Check baud rate and parity settings match all devices
4. Ensure proper grounding to reduce electrical noise

Relay Output Issues

If relays don’t switch as expected:

1. Verify output voltage and current within specifications
2. Check for inductive load kickback (add suppression if needed)
3. Confirm the software logic correctly addresses the output pins

Frequently Asked Questions

What programming languages does Arduino Opta support?

Arduino Opta supports two programming environments. The Arduino IDE allows programming in C/C++ using familiar sketches and libraries. The Arduino PLC IDE supports all five IEC 61131-3 standard languages: Ladder Diagram (LD), Function Block Diagram (FBD), Structured Text (ST), Sequential Function Chart (SFC), and Instruction List (IL). You can even combine both approaches using shared variables.

Can Arduino Opta replace traditional industrial PLCs?

Arduino Opta is suitable for many small to medium automation tasks, competing directly with products like Siemens LOGO! and Schneider Zelio. For mission-critical, high-reliability applications or those requiring extensive I/O counts, traditional PLCs from established manufacturers may still be preferred. The Opta excels in applications requiring IoT connectivity, cloud integration, or where programming flexibility is valued.

How many expansion modules can connect to Arduino Opta?

Arduino Opta supports up to five expansion modules connected via the integrated expansion bus. This enables scaling from the base unit’s 8 inputs and 4 outputs to a maximum of 88 inputs and 44 outputs depending on the expansion module combination selected.

Does Arduino Opta support Over-The-Air updates?

Yes, all Arduino Opta variants support OTA (Over-The-Air) firmware updates when configured through Arduino Cloud. This enables remote program updates without physical access to the device—valuable for distributed installations. Note that OTA updates are currently available through Arduino Cloud but not through the PLC IDE.

What certifications does Arduino Opta have for industrial use?

Arduino Opta holds CE, cULus (UL/CSA), FCC, and ENEC certifications, making it suitable for industrial and building automation applications in North America, Europe, and other regions recognizing these standards. The operating temperature range of -20°C to +50°C meets typical industrial environment requirements.

Getting Started Checklist

Before deploying Arduino Opta in your project, verify these requirements:

Requirement	Details
Power Supply	12-24V DC, adequate current for relays
Programming Cable	USB-C data cable (not charge-only)
Software	Arduino IDE and/or PLC IDE installed
Board Package	Arduino Mbed OS Opta Boards core
License	PLC runtime activation (included with hardware)
Network	Ethernet or Wi-Fi configuration as needed

Conclusion

The Arduino Opta represents a significant step in making industrial automation more accessible. By combining the familiar Arduino ecosystem with IEC 61131-3 standard PLC programming, it bridges two worlds that have traditionally remained separate.

For small to medium automation projects, building automation, IoT-enabled control systems, and situations where cloud connectivity matters, the Opta offers genuine value. Its open ecosystem, reasonable pricing, and dual programming capability make it particularly attractive for engineers comfortable with both traditional PLC and embedded development approaches.

The platform continues evolving with expansion modules, OPC UA support, and regular firmware updates. While it may not replace heavy-duty industrial PLCs in critical manufacturing applications, the Arduino Opta carves out a meaningful position for accessible, connected, and flexible automation solutions.