This time my team were tasked with programming a Siemens S7-300 series PLC in ladder logic (only) to solve a ‘puzzle’ from an unknown arrangement and starting position. This ‘puzzle’ was to find and sort two stacks of discs according to the height of each disc in to their prescribed positions. A number of dormant, start-up, recover and e-stop sequences were also prescribed.
Within a PLC course, as an introduction, I was required to develop an application for the “Moeller EasySoft PLC”, a rudimentary PLC when compared to current industrial standards. During code development, PLC programming techniques and standards had not been taught beyond the mechanics of ladder logic processing, latching and memory use.
This application was widely recognised as the best in the class and the only project to fail-safe on controller power loss, attempt to recover from an error and to have verbose error diagnostics.