So there are lots of options out there but I was wondering if anyone had any actual experience so...

[G+_Jason Perry]

So there are lots of options out there but I was wondering if anyone had any actual experience so I am not buying blindly.

 

I am looking for a DC-DC step down converter to go from 24V to 2.5V to 12V. Any input, or is it just a matter of just buy the cheapest that will do the job?

[G+_James Hughes]

A buck converter with good reviews on Amazon should do the job.

[G+_Eddie Foy]

Need clean power?  Efficiency?  Size? Cost?

And what are the current requirements?

And from 24V to 2.5V back up to 12V?

[G+_Jason Perry]

Eddie Foy?, my goal is to use it in a diy home automation setup. My current thought is to get a punch down block, use cat 3 or 5, run power over 2 pairs, and TX Rx over another. For the most part it will be an arduino on the other end but in some cases there will be a need for 12V or 24V on the other end as well. I don't see myself needing to go down to 2.5V but I don't want to limit myself.

[G+_Eddie Foy]

What  com protocol you going to use over the CAT?

RS-232 has a limit of 25 feet, and probably less on CAT cable.

With RS-485/422, you might run into impedance issues. (yes I know you've seen plenty of stuff on the net using CAT for 485, but its not the right cable)

If its a DIY, make sure you have decent error corrections at each end.  Synchronous might help.

 

As for the PS at the ends, I've used the little adjustable  cheapos with good success.  Popped a couple.  Mind the current draw on the CAT cable, and overall system.

[G+_610GARAGE]

A linear regulator may be better for that application. There a lot cheaper, and at low current, and mild voltage drop, there more efficient.

[G+_Chris W]

It's not a small voltage drop.. 24v to 5 or 3.3 for an Arduino. A decent switching regulator is not that much more expensive - granted, a few dollars does seem expensive compared to a dollar or less, but you aren't saving much for one or two parts. Add in less external parts and longer life...

The switching noise though - running power over the same cable as data for any real distance, you'll want some extra caps filtering the power, especially with a cheaper switcher. So there went the less parts benefit. I know I'm a bit biased, but I still like a good buck switcher over a linear for small projects like this.

[G+_Eddie Foy]

If regulation isn't much an issue and small current just a couple diodes can't drop the voltage into spec.

 

A properly rated zener too.