Arduino Opta PLC: First Thoughts
April 19, 2024
Blog
The Arduino Opta was announced in late 2022 as Arduino’s first foray into the world of programmable logic controllers (PLCs) which are commonly used in industrial automation. As someone who spent a considerable amount of time in that world, now deals with Arduino and Arduino-adjacent devices, I was excited to try this out as a part of my Developing With Arduino online training series. I’ll do a live demo of the device in the upcoming class 5, and in this article I’ll outline my initial thoughts on this little PLC.
Form Factor: Very Nice
Based on its size and design, it’s hard not to like this little guy. It fits comfortably in your hand, and its dark case gives off the vibe of something that would fit nicely in a control cabinet for a small machine. It has DIN rail mounting hardware and screw terminals as you’d expect, and its ethernet and USB-C connections are a welcome sight compared to proprietary connectors found elsewhere in the industrial world.
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Image Credit: Jeremy Cook
IO: Limited But Powerful
As a small PLC its IO capabilities are limited. The inputs comprise of 8 analog/digital pins (0-10V analog, 0-24V digital), a user button, and programmable LEDs. Outputs consist of four 10A, 250V relays. The relay capabilities are especially impressive, and having analog functionality built-in is a nice bonus, though some might prefer current measurement here.
User LEDs: Atypical PLC Operation
Working with traditional PLCs, each input and output will typically have its own LED that goes on with the signal. As far as I know, there is (typically) no way to disable or change this operation short of hardware surgery.
The Opta has four status LEDs that would seem to correspond to each output, but are actually programmable, and could be set to do anything that you would like. On the one hand, this opens up a lot of possibilities for the programmer, but if a third-shift technician used to traditional PLC operation is looking at this and finds that lights don’t come on as expected… expect a bit more downtime.
Programming:
I’ll cover this a bit more in my upcoming class, but the short story is that programming is pretty straightforward with the Arduino IDE. However, using the Arduino PLC IDE–which enables ladder logic and other IEC 61131-3 programming standards–was not a great experience. Unlike the standard Arduino IDE, it’s only available on Windows, and even after installing it on the appropriate system there were a number of hoops to jump through.
Unlike the vast array of info on many other Arduino products, there’s relatively little information available on using the Arduino PLC IDE.
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Image Credit: Jeremy Cook
The (Preliminary) Verdict:
If you like programming using the Arduino IDE, but want to use it for industrial control of very simple machinery, then this PLC presents a good option. Its powerful relay setup is likely its best feature, which makes sense considering it is a collaboration with relay and other electrical components manufacturer finder (which calls the Opta a smart relay). Its form factor is also quite nice, as well its USB-C and Ethernet interfaces.
One might say that it makes sense as the first PLC product from Arduino. At the same time, a list price of $146.40 for the Lite model, and more for the RS485 and WiFi versions, other small PLCs are also worth consideration. AutomationDirect’s Click lineup, for instance, starts at $92, though that price goes up with different options. The C0-00DR-D relay version of that PCB handles less current than the Opta. Being able to switch four 10A/250V lines internally is a huge selling point for the Opta PLC series.
