[geeks] Recommendations for DC-DC power supplies

[James Fogg]

> An ebay search for instance yielded the following replacement ATX
> supply that accepts 12V DC( 9V ~ 18V) in:
> http://tinyurl.com/2zobqq
>
> Of course, I've never heard of this brand before (Jasuny), and I doubt
> it'll be a simple matter to replace the PSUs in some of my sun
> machines (u60/u2).
>
> Yes, I could buy a sufficiently expensive sine-wave inverter and keep
> my existing power supplies, but DC-DC seems to be more efficient and
> simple, unless there is something I am missing...


12V DC has always been attractive to me.

1) There's a huge supply of free 12V DC belt-driven generating equipment
from the automotive world.

2) Automotive generators (alternators, actually) can be driven by a
single cylinder "lawn mower" engine without fussing with shaft speed
regulation that is so critical to AC generators (where shaft speed =
line frequency).

3) Endless supplies of cheap 12V DC storage batteries from the
automotive and golf-cart worlds. Batteries make nice voltage regulators
and provide a window of time in which to fire up generator(s).

4) If you need more than one generator to match loads, you can tie
multiple home built DC generator sets together without fussing with
synchronizing the outputs (try doing this with an AC generator, it's not
simple).

5) 12V DC makes a nice basis for alternative energy (wind, solar, oddly
fueled generators, etc.), and allows for easy integration of multiple
sources.

6) You can easily add a street power to 12V DC source to your mix to run
from street power when you feel like it. This makes an attractive
solution for mixed source alternative power with immediate and automatic
failover to street power in a simple design (no line frequency
synchronization needed).

As for your computer power supplies, I've often taken the internals from
a new power supply and inserted them by whatever means required into
non-standard power supply chassis to fix broken supplies in equipment
that used non-standard power supply cases and/or output cabling.

The drawbacks are high DC current (depending on how many computers you
are powering) and the care and feeding of storage batteries (hydrogen
outgassing, acids, acid vapors, temp control and more).

It's a very attractive geek project. I didn't know 12V DC input supplies
were available.