I’ve been thinking about Programmable Logic Controllers (PLC) again recently, not least because I am preparing a conference talk about them. While putting together the presentation I thought to myself “Why not make a list of PLC products out there, I wonder how many there are‽”
Turns out, there are quite a few! After three evenings of research I had a spreadsheet of 144 product lines. That number shouldn’t be a surprise given that this is a 50-year-old technology that is ubiquitous in factories, infrastructure, and machinery.
Of course, I’m barely more than an interested bystander to this industry, so I decided to ask real automation engineering practicioners about what I had missed in my review. No better way to get harsh feedback on your work than to put it on Reddit!
It’s three weeks later now and the trickle of comments has dried up, but I am still working on including all of the suggestions in the spreadsheet, which is currently 225 lines long. You can take a look and add your own comments here: Link to the Google Sheet
In the meantime, I also discovered Wikipedia’s List of PLC Manufacturers. Quite a few of the brands listed there are also still missing from my spreadsheet.
One day I might aggregate and summarize the information into a more digestable format. For now, I have collected a limited number of columns of metadata and started classifying the entries by a few interesting criteria relevant to me, such as whether they are modular systems. I decided to be strict about only calling things a “PLC” that support at least one IEC-61131-3 language, and labeled other entries “RIO” (Remote Input/Output) or “Smart Relay”. Some Reddit commentors called me out for not including many Safety PLCs, a subject I need to do some reading to do on before I can claim any level of understanding.
And there were, of course, complaints about not including DCS, HMI, SCADA, and other related product types. I don’t have the time to create those spreadsheets, but someone else should!