Hi,
I am a teacher Technical IT at the Hogeschool Rotterdam.
For my students I’ve made an PLC simulator written in Python that generates C code for the Arduino.
So you first can simulate your control and controlled system before starting to assemble the hardware.
You can real time show and alter all variables, draw visualisations and time charts.
https://pypi.python.org/pypi/SimPyLC
Kind regards
Jacques de Hooge
Netherlands