I was given an opportunity to try out a Velocio PLC:
http://velocio.net/This PLC sits somewhere between an Arduino and a Micro PLC such as a Click or AB MicroLogix. It offers options of programming in ladder or flow chart. It was quite easy to get up and running. I made a video showing the programming software and using the Modbus mapping in order to create an AdvancedHMI application to communicate with it:
https://www.youtube.com/watch?v=RqwJq3Xtf6U
