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Old 18th April 2006, 09:18 PM   #1
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Default 2 PSUs or DIY?

Any probs using different PSUs in a computer?

I'll explain more.
For my next computer, I plan using an ATX PSU for the motherboard, while the HDDs, optical drives and fans would run off a linear PSU. (With the same ground...)
Will it cause any problems? Current flowback?

I'm not sure that's what I'll be doing exactly tho.

OR

Instead of using an ATX PSU, are there not-too-noisy options that are still power-efficient?

I never worked with SMPSes, so I'll ask dumb questions.

What about a big toroid with switching regulators, and big capacitors to clean the noise? Would it still be efficient?
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Old 19th April 2006, 12:49 AM   #2
lndm is offline lndm  Australia
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Considering you will need to deliver 100's of watts? It may take up case real estate. This is interesting but I still think the computer will produce its own noise (is this what you're thinking?).

You would need to consult the ATX specification for this.
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Old 19th April 2006, 12:59 AM   #3
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I already looked at the specs, but they don't talk about using different transformers.

Anyways... I think I'll just get a good PSU...
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Old 19th April 2006, 01:11 AM   #4
lndm is offline lndm  Australia
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The specs won't talk about toroids. The specs would be happy if you used a mouse on a treadmill, as long as it gives the required output


Anyway, good luck.
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Old 19th April 2006, 01:20 AM   #5
Variac is online now Variac  United States
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Is there any problem with using two ATX supplies to do this?
I have been considering the same , but both would be ATX supplies that I have. Use the secoond one to power the HDs, the burner and DVD drives, fans, etc. Obviously there might be space issues...
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Old 19th April 2006, 01:28 AM   #6
lndm is offline lndm  Australia
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The ATX supply is designed for software turn on. Also on the bench, they sometimes wont turn on unless they detect a load on the 5V rails. Why not use an AT supply (with a real switch) for the drives.
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Old 19th April 2006, 01:40 AM   #7
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In fact, I first thought of making 1 big PSU for all the system, but, after I read the specs, I found it isn't as simple as green wire grounded = turn the thing on...

(There are things like overvoltage, overload, overheat protection, a very short delay before power on which isn't nice if you use a big toroid)

To power a 2nd ATX from the 1st ATX, all you need is a relay powered from the first to short green wire to ground.

Quote:
The specs won't talk about toroids. The specs would be happy if you used a mouse on a treadmill, as long as it gives the required output
I meant multiple, not different. Doh!

Quote:
Why not use an AT supply (with a real switch) for the drives.
Maybe...

What I'm really looking for it to eliminate as much noise as possible, since my computer and sound system are right next to each other, and as I'm planning to DIY a case for my next PC, I told myself, why not DIY a PSU also.

I thought about a complete linear PSU, but linear regulators aren't really efficient... (And would make a 300W heater)

But, what's noisy in SMPSes, the 400Hz transformer, the switching regulator or all these answers? If I take a toroid and switching regulator, I probably put less junk on the power line, but what about RFI / noise / interference? Is the regulator making some itself or can just putting big caps on the power line fix things?
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Old 19th April 2006, 01:59 AM   #8
lndm is offline lndm  Australia
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Umm... multiple mice on separate treadmills? I feel sure they would be fine as long as you could coordinate turn on.

Noise from the power supply is only one source from a computer. It does not necessarily upset the operation of the computer. Even so, adding your own chokes and caps at the outputs is one way to achieve clean rails.

I guess you could also mount your computer far from anything critical, and consider power conditioning (even perhaps to stop noise getting back into the power mains?)
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Old 19th April 2006, 02:14 AM   #9
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I guess you could also mount your computer far from anything critical, and consider power conditioning (even perhaps to stop noise getting back into the power mains?)
Not in an already filled up 10'x10' room...

I'm starting to think about getting a Fortron PSU with (passive) PFC ... Supposed to put less junk on the mains. There's also Active PFC, but on twice-the-price PSUs.
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Old 19th April 2006, 02:31 AM   #10
lndm is offline lndm  Australia
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It seems someone finally woke up to this with PFC. Maybe it was the power suppliers, or maybe it's just hard to live in this world if you are an appliance that is susceptible to the noise, and your neighbours are noisy.

Just a thought, would anyone consider running the ground connection (that the computer's case is connected to), outside to a dedicated ground stake?
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