There's a limit to what you can learn on your own.
Going to school and getting a degree is certainly an option. And book learning, either in school or with some "Advance PLC Stuff" book will only get you so far.
There are all sorts of things that you learn about when you have a real PLC program operating real machinery. Things that look good in on paper or on the screen, often don't work in reality for reasons that are sometimes quite subtle. Most of the time, it's a matter of "in the real world, things don't happen instantly". Sometimes thisgs that are supposed to happen, never do.
It's not THAT difficult to write a PLC program that causes things to happen in a certain order when everything goes RIGHT. The bulk of my job is planning what to do when things go WRONG.
- What should happen if THIS occurs?
- What should happen if THAT occurs?
- What should happen if both THIS and THAT occur?
Unfortunatly, the only way to know what can go wrong is to be there when things go wrong. Each time something doesn't work the way you expect, you learn a little something about
Things to Avoid. Sometimes, the lesson can be misleading ("I learned from trying to troubleshoot this: Never use Latch/Unlatch") But unfortunatly, no amount of schooling is going to teach you this stuff. You've got to be there, at the plant floor, writing code and making things happen and making, finding, and fixing mistakes.
So, then, how do you get on the plant floor? There are lots of different ways (see
THIS LINK for some of the paths taken). A degree WILL
help open doors. Buying a small, inexpensive PLC (new: <$300; E-Bay: ~$200) and then trying to make something, anything (an automatic pet food dispenser, for example) out of Radio shack and other parts is another. It may not go on the resume, but if you can talk a good game (because you know what you're talking about), you might be able to convince someone to take a chance on you.
But I don't know of any "Advanced PLC Stuff" books or courses. The really advanced stuff, as Ron said, isn't in using the individual instruction, but in combining them to solve problems. The ability to properly define a problem, and the creativity to come up with a solution is something that simply can't be taught, or at least can't be taught simply.