So I've been thinking about how to wire up my limit/home switches. I'm using these:

1PXS Inductive Proximity Switch 5mm Detection NPN | eBay

...and to avoid noise issues I'm hoping to run them off a 24v power supply that I'll commandeer from an old external HD or some such. Obviously, I'm unable to go straight into my BOB with 24v and I understand that somehow I need to have the 24v side of the limit circuit activate my auxiliary 5v circuit (via an optocoupler or a relay) which signals the BOB.

Well, that's one way - being an electronics buffoon, that might not make any sense to you guys who know what you're talking about - the closest description I can find of what it is I want to achieve is the following (quoted from the CNC Cookbook pages)

Sometimes you can use a Zener diode to run a higher voltage and convert it back to 5V for your breakout board. Run a 24V circuit and have the switch ground that. Then use a resistor in series something like 1K to the digital input, with a 5V1 zenner diode across the input and ground. (Bar of diode to input). The Zener diode will clamp the digital voltage at 5volts.

There are also opto-isolators that allow differential voltages so you could have +5V to your breakout (actually may as well go to the parallel if you are using an opto-isolator--don't need 2 of them!) and 24V to your switch circuits.
But (rather embarrassingly) even that makes little sense to me...

I've spoken to a few folks about how best to do this and I'm led to believe that it's relatively straightforward, the trouble is I can't find any resources out there that give clear instructions - heh, even the 4/5 people that I've asked about this seem to approach it in slightly different ways and probably need a bit more info off me to give me better answers.

So, any instructions (theoretical or detailed) / diagrams / parts lists that anyone can point me towards?

Thanks for your help!

Wal.