Arduino Opta Lite vs RS485 vs WiFi: Which Opta PLC Should You Choose?

The Arduino Opta Lite, Opta RS485 and Opta WiFi are much more alike than their names suggest.

All three share the same core PLC platform:

The differences are almost entirely about communications:

That makes choosing between them much easier than comparing three completely different PLCs.

Quick Comparison

Feature	Opta Lite	Opta RS485	Opta WiFi
SKU	AFX00003	AFX00001	AFX00002
STM32H747 dual-core MCU	Yes	Yes	Yes
8 digital / analogue inputs	Yes	Yes	Yes
4 relay outputs	Yes	Yes	Yes
10/100 Ethernet	Yes	Yes	Yes
USB-C	Yes	Yes	Yes
RS-485	No	Half-duplex	Half-duplex
Modbus RTU	Not through native RS-485	Yes	Yes
Wi-Fi	No	No	2.4 GHz 802.11 b/g/n
Bluetooth LE	No	No	Yes
Modbus TCP	Yes	Yes	Yes
Secure element	Yes	Yes	Yes
Expansion modules	Yes	Yes	Yes
Arduino PLC IDE	Yes	Yes	Yes

All Three Use the Same STM32H747

Every Opta variant uses:

with:

So buying the more expensive communications variant does not give you a faster PLC CPU.

All three have the same class of processing capability for:

• machine sequencing;
• logic control;
• Ethernet communication;
• data logging;
• predictive-maintenance algorithms;
• dual-core applications;
• Arduino and IEC 61131-3 programming.

The Core I/O Is Identical

All three variants provide:

The inputs can be used as:

and the four relay outputs are rated up to 10 A under the appropriate load conditions.

Opta Lite Does Not Mean Reduced I/O

The word:

only refers to the connectivity set.

Opta Lite still has:

• the same processor;
• the same eight inputs;
• the same four relays;
• the same Ethernet port;
• the same USB-C interface;
• the same expansion connector;
• the same secure element;
• the same PLC programming capability.

Ethernet Is Standard on Every Opta

All three models include:

with an onboard RJ45 connector.

This means even the cheapest Lite model can support:

• Modbus TCP;
• HTTP;
• MQTT;
• Arduino Cloud over wired Ethernet;
• local dashboards;
• TCP/IP industrial communication.

Why Ethernet Makes Opta Lite More Capable Than It Looks

If your control cabinet already has wired Ethernet, Opta Lite can handle a large percentage of connected PLC applications without either RS-485 or Wi-Fi.

Examples include:

• Modbus TCP energy meters;
• Ethernet HMIs;
• SCADA connections;
• MQTT gateways;
• cloud-connected equipment;
• LAN-based remote monitoring.

Opta RS485 Adds One Important Industrial Interface

The RS485 model adds:

through:

terminals.

This enables direct connection to:

• Modbus RTU devices;
• variable-frequency drives;
• energy meters;
• industrial sensors;
• remote I/O modules;
• serial gateways.

RS-485 Is the Main Reason to Step Up from Lite

If your machine contains even one important:

device, the RS485 variant avoids the need for an external USB/serial or Ethernet/RS-485 gateway.

Opta RS485 Has No Wi-Fi

This is worth making explicit.

Opta RS485 gives you:

but not:

It is intended for fully wired automation systems.

Opta WiFi Includes Everything in the RS485 Model

Opta WiFi includes:

so you do not sacrifice the industrial serial interface to gain wireless networking.

Wi-Fi Specification

The WiFi model supports:

through the onboard wireless subsystem.

It is not a dual-band Wi-Fi 5 or Wi-Fi 6 platform.

Bluetooth Low Energy

Opta WiFi also includes:

which can be useful for:

• local commissioning;
• wireless sensors;
• short-range configuration;
• mobile interaction;
• BLE peripherals.

Wi-Fi Is Useful When Ethernet Is Impractical

Opta WiFi makes sense when:

• there is no Ethernet drop at the machine;
• the machine moves or is difficult to cable;
• temporary installations need connectivity;
• cloud access is needed without changing the LAN infrastructure;
• BLE devices need to be integrated locally.

Wired Ethernet Is Still Preferable in Many PLC Installations

Even if you buy Opta WiFi, industrial control traffic often still belongs on Ethernet where practical because wired networking normally provides:

• predictable connectivity;
• less RF interference;
• simpler troubleshooting;
• easier segmentation;
• more stable latency.

Wi-Fi is then available for:

• maintenance;
• secondary telemetry;
• cloud connectivity;
• commissioning;
• temporary access.

All Three Support Modbus TCP

Because Ethernet is standard on the entire Opta range, all three can participate in:

networks.

This means Opta Lite can still be an industrial Modbus controller even without RS-485.

Only RS485 and WiFi Support Native Modbus RTU Wiring

Modbus RTU normally runs over RS-485.

Therefore:

No Onboard RS-485 Termination

On both RS-485-capable variants, Arduino specifies there is no onboard termination resistor:

If the Opta is installed at the end of the bus, add an appropriate external termination resistor according to the network design.

Do Not Choose WiFi Just Because You Want Arduino Cloud

Arduino Cloud can also be reached through:

which exists on every Opta.

So:

If Ethernet is already available, Lite or RS485 may be completely sufficient.

Security Is the Same Across the Family

All Opta variants include the:

secure element.

This provides hardware support for:

• protected key storage;
• device identity;
• certificates;
• secure provisioning;
• cloud authentication;
• secure boot workflows.

The WiFi version is therefore not the only secure model.

All Three Have the Same Relay Outputs

The four normally-open relays are identical across Lite, RS485 and WiFi.

The published maximum is:

under the appropriate load and voltage conditions.

The relay section does not improve when moving to a higher Opta variant.

All Three Use the Same 12-24 V Supply

The Opta family operates from:

making all three equally suitable for:

• 12 V panels;
• 24 V industrial cabinets;
• building automation;
• machine control.

All Three Have the Same DIN-Rail Form Factor

Mechanically, choosing RS-485 or Wi-Fi does not require a different enclosure strategy.

All three are designed around the same compact DIN-rail PLC format.

All Three Support Expansion Modules

The proprietary side connector is present across the range.

Arduino documents support for up to:

depending on the module mix and system configuration.

Available expansions include digital and analogue modules.

Expansion Is Independent of Connectivity Variant

You do not need Opta WiFi to use expansion modules.

A Lite installation can still grow into a large I/O system with:

• additional digital inputs;
• relay outputs;
• solid-state outputs;
• analogue inputs;
• analogue outputs.

All Three Support Arduino IDE

Every model can run conventional Arduino C/C++ applications using the standard Arduino environment.

This is useful when the application is better described as embedded firmware than as PLC logic.

All Three Support Arduino PLC IDE

All three models also support IEC 61131-3-style programming through Arduino PLC IDE.

Current supported languages include:

• Ladder Diagram;
• Structured Text;
• Function Block Diagram;
• Sequential Function Chart;
• Instruction List in the Arduino PLC environment.

Performance Is Identical

There is no reason to choose Opta WiFi because you expect more:

• CPU speed;
• RAM;
• relay capacity;
• analogue resolution;
• PLC execution performance.

The main processor and control I/O platform are shared.

Opta Lite: Best Fit

Choose Lite when the project needs:

but does not need:

Typical applications include:

• Ethernet-connected building automation;
• local pump control;
• lighting control;
• LAN-connected machinery;
• Modbus TCP installations.

Opta RS485: Best Fit

Choose RS485 when the project adds:

but the installation remains fully wired.

This is often the most logical industrial variant because RS-485 remains extremely common in control cabinets.

Opta WiFi: Best Fit

Choose WiFi when you need everything in the RS485 model plus:

Typical examples include:

• retrofit installations;
• remote machines without Ethernet cabling;
• mobile or temporary equipment;
• BLE sensor gateways;
• wireless cloud-connected control panels.

Which Model for Modbus TCP?

Any Opta.

All three have Ethernet.

Which Model for Modbus RTU?

Opta RS485 or Opta WiFi.

Both provide native half-duplex RS-485.

Which Model for Arduino Cloud?

Any Opta can reach network services over Ethernet.

Opta WiFi additionally allows Cloud access over wireless networking.

Which Model for a VFD?

If the drive uses:

choose RS485 or WiFi.

If the drive uses:

any model can work.

Which Model for an Energy Meter?

It depends on the meter interface:

Which Model for a Remote Installation?

If wired Ethernet is unavailable, Opta WiFi is the only member of the family with integrated wireless networking.

Which Model for a Secure Wired Cabinet?

Lite or RS485 may actually be preferable when:

• wireless radios are prohibited;
• cybersecurity policy requires wired-only networking;
• the control network is physically isolated;
• RF communication is undesirable.

Do Not Automatically Buy the Most Expensive Model

Because the control hardware is shared, buying WiFi provides no benefit if you will:

In that case Opta Lite performs the same PLC logic through Ethernet.

But Avoid External Adapters When the Feature Is Predictable

The opposite mistake is buying Lite when the design is likely to need RS-485 later.

An external:

adapter adds:

• another device;
• more wiring;
• another power supply path;
• more commissioning;
• another failure point.

If Modbus RTU is likely, the native RS485 version is normally the cleaner architecture.

Decision Table

Requirement	Recommended variant
Basic PLC with Ethernet	Opta Lite
Modbus TCP only	Opta Lite
RS-485 / Modbus RTU	Opta RS485 or WiFi
VFD over RS-485	Opta RS485 or WiFi
Wireless LAN	Opta WiFi
BLE sensors	Opta WiFi
Cloud via Ethernet	Any Opta
Wired-only industrial cabinet	Lite or RS485
Maximum connectivity flexibility	Opta WiFi
Lowest unnecessary hardware	Choose only the interfaces actually required

Quick Reference

Final Thoughts

The Opta range is deliberately simple:

All three have the same processor, the same eight inputs, the same four relays, the same security hardware and the same expansion capability.

So the correct model depends almost entirely on how the PLC must communicate with the rest of the system.

For a wired Ethernet-only installation, Opta Lite is already a complete PLC.

For conventional industrial devices such as VFDs, meters and Modbus RTU sensors, Opta RS485 is the natural step up.

For installations that also need wireless LAN, BLE sensors or easier cloud connectivity without Ethernet cabling, Opta WiFi adds those features without giving up RS-485.

For the terminal-level details shared by all three models, see our Arduino Opta pinout and I/O guide.