Mark, thanks for your tip - I'll try that out. I assume that either black
lead would do, but I'll use the one nearest the yellow.

Re using switches to power-down hard drives, I only ever do it when the
sytem is full off, because that's how my Trios drive selector works also.

And I've been using the switches solely on the yellow lead for about a year
now without ill effects - must be lucky I guess - it didn't occur to me that
there might be more than one wire involved in powering a HDD.

The whole idea was to reduce the electrical load and heat when the drives
weren't required, as the system is pretty well maxed out with all the stuff
I have running.

Ian Porter
Computer Guys Inc.
Arrowtown
New Zealand
[log in to unmask]

----- Original Message -----
From: "Mark Rode" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, March 04, 2003 8:27 AM
Subject: Re: [PCBUILD] Question about a power switch


> Well, first let me say that I would check with an EE before I would put a
> switch on the hot leg of a hard drive, as you write that you have done. I
> am not so sure that a hard drive ONLY uses the yellow 12 volt leg. It
might
> also be using the red 5 volt.  If you kill the 12 volt side the drive
> wouldn't work, but that doesn't mean the drive is fully powered off. You
> would have to look a hard drive schematic. And if I were to put a switch
on
> a hard drive, I would kill all four wires going into the drive, not just
> the hot. At least then you know that it would be a complete disconnect.
And
> I would never use the switch unless I was fully powered down.
>
> I would also want to be sure that inadvertently powering off like this,
> when the system is hot, could in no way damage the drive. Certainly, if
you
> power down when the computer is booted, then you risk making your PC
> unstable, and or losing data.
>
> The answer to your switch question is that you would hook the Supply up to
> the PS side of the 12 volt yellow wire. The load would be the hard drive
> side of the switch, and the Ground, which is the return for the lamp,
would
> be the black wire, or you could use the case, but I wouldn't.
>
> Note: I would test the lamp without the hard drive connected to the
> Load,  just to make sure the switch works correctly.
>
> There are better ways to do this. Removable hard drive Racks for example,
>
>
http://cyberguys.com/cgi-bin/sgin0101.exe?UID=2003030310552238&GEN6=00&GEN9=
5CG01&FNM=00&T1=168+0537&UREQA=1&UREQB=2&UREQC=3&UREQD=4
>
> I always install one of something like this on my computers, so that I can
> image another hard drive or move data around when a system is down. Prices
> for these can range anywhere for 12 U.S dollars up to 100. If your
> controller supports it, they even come hot swap able.
>
> Of course, I would never do this with a drive where performance was a
concern.
>
> Rode

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