The Basics
Hi there Getbuggs,
I remember when you first got to the forum and were asking about how to learn to understand circuits properly, one of the commenters gave the good advice that Ohm's Law and Kirchoff's Law(s) would be a good start. Unfortunately you hadn't been very clear about
what things you already understood...
But these sorts of questions here do suggest that either you didn't already know these laws or you don't understand them quite well enough yet. If you study them well, so they're not just words on a page, you will probably find that understanding things like the current limiting etc in this project, make a lot more sense. In fact, there are probably not so many circuits that you will understand
at all if you don't properly understand Kirchoff's Laws, because they apply basically everywhere. Ohm's Law doesn't quite apply to everything but you still absolutely need to understand it well too.
There's "Kirchoff's Current Law" and "Kirchoff's Voltage Law", which are different but quite similar to each other. Like Ohm's Law, there are somewhat more consequences to these laws than just the
obvious meaning, and so it's a good idea to learn as much as you can about how they apply. There should be lots of stuff about them (and many other electronic theories) on the internet- try Google and Wikipedia, and also the "Electronic Theory" part of this site!!
But also remember the warning:
any idiot can make a webpage! (I should know, having done so
)- I've seen a few inaccurate claims on website tutorials, and so it's probably a good idea to use several different sources and see where they seem to agree and disagree. If you also have a book to work from, this will probably help even more. If you still have uncertainties, there should at least be fewer of them to ask about, and you'd be better able to understand answers to questions too!
If you manage to learn these laws well, you can then use them to learn (or better understand) concepts such as the rules for resistances in series and parallel, "potential dividers", "input and output impedance", "thevenin's theorem", transistors, and probably also "current sources" etc. These will in turn, let you understand even more complicated circuits. Experimenting with such things using breadboard and a multimeter is also helpful. But start with learning those fundamental things first!
After that, other things start making a lot more sense...