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Re: DC power supply

Chuck Gadd comments:
> That's going to be one heck of a fan to need 4 amps!
>  He doesn't need the hood to fly, just wants a little cooling airflow.  :-)

Well, I really didn't think he wanted to fly the hood.  What you do not 
understand is that once you start to build a power supply, there is no 
particular savings to build one rated at less than 3 or 4 amps.  If the fan 
required 1 amp, you could build a 1 amp power supply, but you'll search far 
and wide to find a decent commercial one.  Cost of building a 1 amp supply 
would run around $25-$35.  Cost of building a 3 amp supply would run around 
$25-$35.  Cost of building a 5 amp supply would run around $25-$35.  
Commercial power supplies BEGIN at ratings of around 3 or 4 amps because 
there's no particular savings in building a smaller one.  Another factor to 
consider is that maybe he might end up wanting to run 2 fans, or 3.   
Ultimately, you have to take what's commercially available, or get out your 
soldering iron and start wiring.  A commercial 3 or 4 amp supply of any 
quality is about as small as they come if you buy your power supplies at the 
store.  Incidentally, why not just buy a 115 VAC muffin fan?  That doesn't 
require any power supply at all, and moves more air to boot.