[sdiy] Power-One HAA15-0.8-A Power Supply Questions

[Scott Stites]

For some reason, my email server flared up or something, I never saw my original
post go through, and I was surprised to see this response this morning.

On Tue, 22 Apr 2003 23:20:13 -0500, "J. Larry Hendry" wrote:

> I will offer an opinion on fuse protection that may be considered very
> conservative by some.  

When the subject is possibly frying myself or the house, I can take as much
conservative wisdom as possible!

> But, it comes from my background working in high 
> voltage daily.  I think the fuse is always the first order of business when
> the AC enters the cabinet.  I always put my fuse ahead of the switch in the
> hot line.  Yes, if you have 2 supplies on one switch and fuse, your fuse is
> effectively twice the size it needs to be.  With a fast blowing fuse in the
> 1-2 amp range, does that make a difference?  Maybe.  If it bothers you, use
> 3 fuses instead of 2.  But, the fuse ahead of the power switch is the most
> important in my opinion.  If I were allowed only one fuse, that is where I
> would put it.  A fuse a little large in front of the switch might make not
> be perfect protection for the supply.  But, if the switch fails without a
> fuse because the "perfect" fuse is in on the load side of the switch in the
> line to the power supply, you are now either relying on the house breaker,
> or starting some kind of fire (neither of which I recommend).

I hadn't taken switch failure into account!  I'll go with a 2 Amp fuse before the
switch, and fuse each power supply after the switch.  What is common wisdom for
selecting a fuse value - does one select a fuse as close as possible to the rated
maximum current of the power supply, or would a 1 Amp fuse for a 0.8 amp power
supply be reasonable?

> I never switch neutrals.  I don't see any reason to have both conductors in
> the same switch housing.  And, certainly I would never do that unless the
> hot leg is fused ahead of the switch.

I'll switch the hot side only.  Thank you, Larry.  This is very sound and
appreciated advice indeed.

Take care (I sure will!),
Scott


> ----- Original Message -----
> From: Scott Stites <scottnoanh at peoplepc.com>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Wednesday, April 23, 2003 12:25 AM
> Subject: [sdiy] Power-One HAA15-0.8-A Power Supply Questions
> 
> 
> Hi All,
> 
> I received a couple of the Power One HAA15-0.8-A power supplies from MPJA
> today.  Before I proceed, I want to double check for safety's sake -
> hopefully someone here can help.
> 
> The input and output are pretty straightforward.  Having 120 VAC AC mains, I
> know to jumper terminals 1&3 together, jumper terminals 2&4 together, and
> hook the AC up to terminals 1&4.  There's a note on the power supply VW1 and
> VW2 need to be cut for +/-15V operation (which I plan to use), and they are
> already cut, so I'm assuming it was configured for +/-15V in its previous
> life.
> 
> I plan to use a three prong plug AC cord and and connect earth to the
> chassis of the power supply with a lug.  I plan to eventually use both
> supplies.  So, it is my intent to have one power cord going into the
> cabinet, then run split hot to both supplies within the cabinet, split
> neutral to both supplies, and from the same point, split ground to both
> supplies.  Each hot line will have a fuse in it.  Should I place the power
> switch in the hot line, or should it be DPDT for hot and neutral?   Are
> there any safety flaws in the plans I've described here?
> 
> Any advice is appreciated.
> 
> Thanks,
> Scott

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