combining 2 power supplies

Hi,

Over the years, I've kept a few ATX power supply from old computers. Now, I'm thinking about upgrading my computer and add more hard disks. The problem is the current power supply might not be able to support so many hard disks running at the same time. Instead of buying a new, more powerful power supply, I am planning to use one old piece (350w) to serve the motherboard, CD, and 3 hard disks, then another power supply (350w too) to serve 3 to 4 more hard disks. All components are connected to the same motherboard. I need to know how I could turn on both power supply with a single press of the power button on the case.

In other words, only one power supply can plug to the motherboard, how can I jam the wires together so that the second power supply receive the power-on signal when I press the button? I was thinking about the Power-On (Green), Power-Good (Gray) and 5 VSB (Purple) wires. the second power supply would only support the hard disks and nothing else, but I need them to be powered up at the same time other hardware are up (and down when it's shut down).

Thanks.

Reply to
lee
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green wire to black ground starts them up, but put a load on them first like youre drives. only the motherboard needs power good. if running with no load, use a 5watt 100ohm resistor accross the 5v+ to black ground for a dummy load.

powerful

I

power-on

(Green),

powered

Reply to
crazy frog

100 ohms may be too high. 5 ohms probably better. But an automotive taillight (incandescent) or dead harddrive also should work.

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Reply to
Sam Goldwasser

Do the numbers. Only 8 should not be a problem, if it's a real 350W.

15W * 8 = only 120W. Add another 100W for the motherboard, and you're pretty much fine.

Also. You'll want to do the numbers on life cycle cost. Yes, you may have 3 80G drives spare, that you can stick into a system. If you're going to be leaving them on (which increases drive life), then in some places, you'll pay for a new 240G drive in a couple of years.

Reply to
Ian Stirling

Thanks and I did my numbers:

I'm thinking a P4 9xx CPU and it draws around 100w alone, new display cards (ATI x series) also draws a lot of power. More than 1 web site said hard disks draws 25w so I use that in my calculation to be on the safe side. Plus RAM, DVD-RW, fans, and USB devices that might connect to the machine every now and then. Each of those costs little but they add up. 350w might not be sufficient all the time. In addition, I don't trust the PSU will produce 350w as claimed by the manufacturer.

In the meanwhile, thank you for everyone's help in this.

Best regards.

Reply to
lee

There's a lot of wattage inflation these days, following the stereo equipment makers in the 80s. The fact of the matter is that if you have a *quality* 300 or 350W power supply, it should run just about anything you can fit in the computer. I've measured a number of computers with a power analyzer and I have yet to see one which draws more than 250W from the wall under full load, most typical single CPU computers are down around 160-180W even with multiple hard drives.

Reply to
James Sweet

Don't fight it. People think that adding power supplies multiples the speed of the PC by the number of power supplies added. No way to talk them out of it. :)

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Reply to
Sam Goldwasser

is

in the

Reply to
crazy frog

got the info from silicon chip.

above

Reply to
crazy frog

And so you think this applies equally well to ALL power supplies? :)

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Reply to
Sam Goldwasser

is

in the

Reply to
crazy frog

how do you think my power supply is working.

above

automotive

Reply to
crazy frog

Perhaps a link?

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Reply to
Sam Goldwasser

is

in the

automotive

Reply to
crazy frog

cant fined the old article on pc power supplies. thay hav a new one on useing them as a 13v high power unit without a pc connected.

above

Reply to
crazy frog

you can use a 10ohm 10watt for heavy load. a 100ohm 5watt is ok for lite dummy load, connect whatever you want, a 10ohm will get hot and you hav to cool it with something.

included

FAQs.

:)

Reply to
crazy frog

What article?

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Reply to
Sam Goldwasser

Lets do a bit of maths.

5 V across 100 Ohms is 5^2 / 100 = 25 / 100 = 0.25 W. So you would only need 1/4 W restor, not a 5 W one.

However, like someone else, i think that would be totally inadequate as a minimum load.

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Reply to
Dave (from the UK)

True.

But I don't belive that 250 W drawn from the mains is a likely maximum now.

I was doing some calculuations the other day based on a pair of Opterons. According to AMD, they are about 100 W each. A very mediocre graphics card is probably 30 W. Disks take more when they spin up.

350 W is probably adequate for most things I would agree. My main PC (I don't use PCs much) has a 235 W power supply in it, but a pair of 450 MHz Pentiums and a 10,000 rpm SCSI disk. That seems to be OK

A more elegant solution if there are multiple disks might be to build a timer that delays the starts on them, as the power when running is probalby only half that when starting.

Personally, I think I'd just rather buy a bigger psu - they are not that expensive now.

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Reply to
Dave (from the UK)

On Sun, 26 Mar 2006 19:48:42 GMT, James Sweet put finger to keyboard and composed:

I've measured ~175W for my single HDD, Athlon XP 2500+ system.

These are my idling and standby power consumption data:

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Reply to
Franc Zabkar

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