for the students struggling with their projects, as well as any other "newbies" that are stuck and need a "hand-up"; take a few sheets of paper, (recycled will do), and a pencil. and list what you want your project to do, in as much detail as you can, and in your preferred sequence of operation. make a list of all components and devices involved in the system, such as limit switches, "ice cube" relays, timers, motors, contactors, etc. after making your lists, sketch out a "home-grown" schematic of your project, in the sequence of operation you want, utilizing your listed components. if you spend some time and thought doing these things with pencil and paper, programming your PLC is much easier, because "what" you want to do and, "how" you want to do it, is already laid out for you. and, later on down the line, when your debugging or troubleshooting a problem that has arisen in your project, those rough notes you made will prove to be invaluable!
take it for what it's worth, from an "old ****",
danatech