Today I have on my workbench an interesting PLC, awaiting review: the Industrial Shields ARDBOX PLC 20 I/Os, produced by Boot&Work Corp (Barcelona, Spain). With 10 inputs (5-12-24Vdc, plus 0-10V analog) and 10 outputs (two 0-10V analog outputs, 8 relays), digital outputs, SPI and I2C interfaces, plus RS232 and RS-485, this is one of the smallest PLCs in the Industrial Shields product range.
At a first glance, it offers more options than the Controllino Mini. Plus, it’s highly configurable: one can use the two switch banks to configure the communication interfaces. It’s also much bigger than the Controllino. But why?
Let’s take a look inside this thing…
Opening the case is quite tricky. There are four plastic tabs holding the two halves of the case together, one tab being located just under the red plastic tab used to hold the ARDBOX on the DIN rail. There’s also a spring under that red plastic thing, easy to loose if you are not careful when disassembling the ARDBOX.
The plastic tabs are quite small and easy to break. I’ve managed to break one (see the red circle in the picture below), even if I was very careful and I had good tools to open the case. To me that’s an acceptable loss, this particular ARDBOX is for my own use and testing.
Inside there’s a nice surprise: there’s an actual original Arduino Leonardo driving this thing. In a way, this device is nothing else but an Arduino Shield.
On the top side we have the power supply, then the Arduino Leonardo I’ve mentioned before, then the “shield” where all the fun happens. All the boards are held together using plastic raisers, which proved to be quite difficult to remove. I’d say this device will definitively work fine no matter the environment – vibrations and such. The only thing I would complain is that the capacitors on the power supply can touch the bottom of the Arduino Leonardo board. I don’t know if that would be a problem if the ARDBOX is subjected to a lot of vibration – only time will tell.
Note that some relays are connected to PWM-capable pins of the Arduino Leonardo. Extra care should be taken in software when working with those relays.
There’s a switching mode power supply implemented with two P3596 IC’s from Unisonic Technologies, delivering a current of up to 3A. The user manual specifies an input voltage of 12 or 24V, with a current of 700mA. For a 12V supply, with all relays ON, I’ve measured a current of 495mA. The current was below 200mA for a 24V power supply.
The “shield” board is where all the fun happens. I won’t go into a reverse engineering of this thing. I will only mention here the relays are from OMRON, model G5NB-1A-E, with a current rating of 5A @ 220VAC and 3A @ 30VDC. I’ve also identified some F207 optocouplers from Fairchild and a bunch of ST2902 low-power quad operational amplifiers. There are some chips where the marking was not clear, I suppose those are the RS-232 and the RS-484 tranceivers.
In terms of hardware, everything is high-quality, and this PLC goes right on the first position in my list of Arduino-compatible PLCs.
The user manual of ARDBOX PLC 20I/Os can be downloaded from the Industrial Shields website. We find there technical specifications, a connection guide, a well-explained section dedicated to setting the switches. We also find some waveforms for the analog section. Details for installation on DIN rail are also provided.
A separate pdf file provides pin layout and correspondence with pin numbers in Arduino IDE.
Finally, we find a CE Statement of Conformity. A rare thing. I haven’t seen such a document provided with other Arduino-based PLCs.
Besides the documentation, a code example in Arduino IDE is also provided – a good way to make the first steps and learn how to use the ARDBOX PLC.