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Geting started with PLCs

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I'm planning to get a PLC to learn the basics of PLCs and ladder logic. I don't have a specific project that needs a PLC right now, but I would like to learn enough to know when a PLC is the right choise and to hit the ground running if I need one for a simple project.

There are some low cost PLCs on AliExpress, but if they specify what software is required, it's Mitsubishi or Siemens software which appares to be very expensive.

Are there any brands of PLCs that have free software for programming and simulation?

Any suggestions for brands to use or avoid?

If you buy one (or a few) of those FX1N or FX2N PLC boards from Ali for around EUR20 to EUR30, then you'll probably find they're compatible with the software from one of those manufacturers you mentioned.

I bought one of these just out of curiousity, even though I abhor ladder diagrams and have no interest in PLC software myself.
I bought it because:

* Curiousity.
* STM32F103 CPU.
* Hardened I/O.
* Solid power supply section (Common mode filtering, SMPS, big Elco's)

You can choose between lots of versions Points to watch out for are:
* Number of I/O.
* Relay or Transistor outputs.
* PCB or DIN rail mountable.
* Connector quality. I prefer the green detachable connectors.

My version even got the STM32 programming pins broken out on some solder pads.
The only real disadvantage I've discovered on my PCB is that the RS485 driver is an SN75176 with no external extra protection. This is a very old and not very robust RS485 driver chip. But if needed, a SOIC-8 is not that hard to replace either.


--- Quote from: Doctorandus_P on September 29, 2020, 04:31:06 pm ---If you buy one (or a few) of those FX1N or FX2N PLC boards from Ali for around EUR20 to EUR30, then you'll probably find they're compatible with the software from one of those manufacturers you mentioned.

--- End quote ---

I'm trying to avoid the software from those manufacturers since I heard that the prices are in the four digit range. But I'v not actually been able to find a price on their websites so that may be incorrect/outdated.

Several years ago I bought one of those FX1N/2N something PLC "clones" from AliExpress. It came with a CD containing the official Mitsubishi software, I think it was IEC developer but I'm not sure (they've had a few development tools over the years). Most likely NOT legit but that's what happened in my case.

I was surprised to find that the "clone" had sinking output and sourcing inputs which is not quite what we're used to here in Europe but it's apparently more of the norm in places like Japan. The orignial FX1N/2N that I've used have had sourcing outputs and sinking inputs but it's quite possible the original exists in both configurations.

Anyway, I ordered it mostly out of curiosity, played around with for a bit and it seemed to work just fine - apart from the "inverted" I/O.

You could take a look at one of the smaller units like Schneider Zelio, Siemens Logo, Crouzet Millenium etc.

EDIT: Or you could look at Codesys. Get some EtherCAT or MODBUS I/O modules and run it on a RaspberryPi. Not something I'm personally experienced with but I've meaning to try it - one day.

I would suggest to try Unitronics. They have great PLCs for small and mid projects. The software is completely FREE, downloadable from their site.
I would suggest an all in one PLC+HMI, something like Samba series, or Vision.

If you want to learn, stay away from LOGO, Zelio logic, etc. They are not PLCs, but smart relays. Ladder is awful there...

In Europe i think that Siemens PLCs are still the most common, especially on bigger automation systems and process systems. In US, of course the Allen Bradly.
For a self learning beginner i would recomend to stay away from Siemens Simatic due to its complexity and price. I am familliar with TIA portal quite well, was even programming some years ago
Now i use it mostly for maintenance purposes and maybe sometimes for some simple changes. For everything else i leave it to a programmer who do this every day and know exactly what he is doing...


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