I recently came across an AVR (Arduino) based PLC controller kit here: https://www.universal-solder.ca/...
Price $39 Canadian 18 i/o's split between 0-10v digital/analog inputs and outputs.
I would not call this a beginners kit, due to the simple assembly instructions of "install all of the parts" so one needs to be able to identify the parts, the pcb is densely packed. I did identify one error in the design, the AREF pin on the Arduino module is tied to the VCC rail on the PCB, so the AVR can be damaged by a selection of internal BG reference as noted in my review of the product.
I'm looking forward to finding a cool project for this low cost kit.