[mythtv-users] NAS power supply

John Drescher drescherjm at gmail.com
Sun Oct 5 15:03:56 UTC 2008

On Sun, Oct 5, 2008 at 10:54 AM, John Drescher <drescherjm at gmail.com> wrote:
> On Sun, Oct 5, 2008 at 10:25 AM, Yan Seiner <yan at seiner.com> wrote:
>> I'm going to have to build an external HD enclosure.  What do people do
>> for power supplies?  Power itself shouldn't be a problem; assuming a
>> drive consumes 20W on spinup and 10W running then even 20 drives can be
>> handled by a (relatively) modest 450 W PS.  No mobo in the enclosure, so
>> no power for that.
>> I've heard about people using resistors on a normal PS when it's used
>> without a mobo.  I can only assume that the PS requires a load of some
>> sort on the mobo connector to operate properly, but I'm not about to go
>> slapping random resistors on the connector... :-)
> I did this 4 years ago on a server that is still in operation to add
> dual power supplies to accommodate 20 250GB WD SATA 1 drives to a
> system. The problem was that the antec 450W power supply required a
> 0.5A load on the 3.3V rail.
> So I put 2 10 ohm 10W wirewound resistors in parallel (and attached
> them to a metal part of the case with hs compound) to achive this:
> http://www.radioshack.com/search/index.jsp?kwCatId=&kw=10%20ohm&origkw=10%20ohm&sr=1
> Note that 2 parallel 10 ohm resistors = 5 ohms
> and by ohms law
> I = V / R
> so that for this circuit
> I = 0.66A
> which satisfied the 0.5A requirement.
> With all of that said I am sure today  you can find power supplies
> without a load requirement on the 3.3V rail so you will probably be
> fine.

Here is the guide I used when I did that:



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