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Re: [OT] ATX-PSU and amperage on connectors...

Hello Douglas,

Am 2008-02-27 20:52:19, schrieb Douglas A. Tutty:
> Here are the wire sizes according to my copy of the 2002 Canadian
> Electrical cord (still in force), table 12 "Allowable Ampacity of
> Flexible Cord and Equipment Wire (Based on Ambient Temperature of 30C"
> Note that cables of 4 or more wires (e.g. if you shrink-wrap 4 drive
> wires together) would be 80%.
> AWG	Amp
> ===========
> 26	1
> 24	2
> 22	3
> 20	4
> 18	6
> 16	8
> 14	17

This AWG thing is nice, since I don not know I in Europe...
I am counting in mm²

> Elecrically, these would be fine with 26 or 24 AWG without overheating
> the insulation.  However, you don't provide inrush current requirements

Since I do not know them, I know only, what is written on the Drives.

> of the device.  Too much resistance in the wire could end up
> undervoltaging the drive motors.  

I know.

> Put the two most power-hungry devices on the same power cable: Teac-CDR
> and the AsusTek DVD for a total of 3.3A each of 5v and 12v, and you
> would need 20 AWG wire.  However, as I said in a previous entry, for
> moveable wire, the minimum (unless you went with some high-tech
> mechanically supported wire) would be 18 AWG (which is what my PSU's
> happen to use).

It seems, that the 3 cables (3 HDD connector on each cable)
on my 600W PSU has cables of 0.5mm²

> > one of my problems is, that most DC-DC-Step-Down-regulators do not
> > support High-Voltage entry and most are limited to 14-16 Vin.
> > 
> > This mean, I need some High-Power (>=25A) DC-DC Step-Down regulators to
> > get 12Vout from 18-30Vin and then I can build the +5V and +3.3V from it.
> And there will go your efficiency.  You could probably get 70-80% with
> one DC-DC converter but if you do two in a row, there's two places for
> waste.  If you have to go that route, its probably no more waste to use
> a true-sine-wave inverter to turn your 24VDC to 110VAC and then use a
> normal AC PSU.

Not realy right, since according to ATX12V the AC PSU should have an
efficiency of at least 66%.  Most standard AC PSUs have around 80%

So if my 24/12V DC Step-Down-Regulator make arround 90% and the 3.3/5V
DC Step-Down-Regulators arround the same, I have effectiv 81%...

If I use a DC/AC sin-wave converter, it will have not more then 80%
which result in a effectiv efficiency between 53% to 64%.

Realy bad...

HOWEVER, I have the need to be OVER 80%...

> > For what is the 8pin power connector?  --  I have never seen it
> Don't know.  Don't want to open my box while I writing email to look.
> What does the ATX speck on Wikipedia say?

This connector is not mentionedin ATX12V since it is currently NO

> IIRC, there's a single-chip solution for the -5 and -12V that comes in a
> TO-220 package (looks like a normal 1A regulator), one pin regulated +5
> (or +12V) in, centre pin common (connected to heat-sink), third pin is
> -5V (or -12V) output.  I know its linear but it doesn't really matter
> for 0.3A and 0.8A.  IIRC, they were made by TI.  

Dallas does the same thing but smaller...  cost arround 0.80US$/chip

> I needed these when I designed and built my own computer back in 1986.
> It had 8 Zilog Z-80 8MHz CPUs with an 8-phase clock running at 64 MHz.

8Mhz?  the standard version was only 2 and 4 MHz and the INCOMPATIBLE
C-MOS version 4 and 6 MHz.

How do you have gotten running this pig with 8 MHz?

Note:  I have bought the Sinclai ZX-81 in 1983 and in 1984 I have bought
       my first "real" CPU building my own computer...  Before I have
       used only 8038/39/49 (Single-Chip-Computers with many I/O and

> Everything was TTL including the static RAM (64K for each processor).  I
> started on it after reading two books for the first time: 2001 A Space
> Odessy, and Mitchner's Space.  Got me (a math flunky) into learning
> about calculating Hohmann transfer orbits (of all things) and I needed a
> 128-bit calculator...  Output was in hex, input was in hex.  Programming
> was in Z-80 machine code.  No secondary storage (who could afford
> that?).  PSU was a 30# (that I rewound) transformer putting out 50A
> rectified 8VDC then running to linear regulators.  PSU weighed about
> 50#, connected with 4AWG welding cables to the computer.  Bascially, the
> PSU was a welding unit by the time I had it made.  Don't ask me the
> efficiency.  It sure made a nice BBVVVWWWOOOMMMMMMMMM when I turned it
> on.  Just incase the electrolytic caps blew (each about the size of a
> 500 Ml Mason Jar), I built the cases out of the external cladding of a
> hot-water-tank: 14 gauge steel. :)


> Its amazing what ones parents let one build in the basement when they
> don't know what one can find in an old TV...

...  You are like me!   Oh, in 2 Month I am 40y.

> At what voltage?  At 3V that's 30A.  My MB doesn't have any 10AWG wire
> going to it, but then again, this may be why there's extra power plugs
> that go to the MB,  24-pin then the 4-pin.  Each wire on the 4-pin is
> good for 8A.

Hmmm, my 600W (redunant) PSU has 38A on 3.3V and 44A on 5V, 
25A on 12V¹ and 20A on 12V²

> Well, considering that Soekris boards run with CF cards off of a single
> 5W wall-cube...

:-)  ...but the CPUs are a little bit smaller.
They are only ARM7 and I use a VIA C5/1000MHz

> > One thing I do not know is, can the "normal" 80 GByte SATA TravelStar be
> > used 24/7 if there is only the OS on it and more or less NO access?
> Why not?  What's special about the TravelStar if its a SATA disk?  Are
> you spinning the drive up and down?

They are ALL SATA drives since today I would not more buy a PATA

The Hitachi E5K and E7K series are for Blade Servers and 24/7 use
while "normal" Hitachi K5K or K7K are only for 7/5 use...

So it can be, IF I have only the OS on it, they can run 24/7 since
I do not shutdown the drives before the die...

> You may give up some efficiency though; it may be more efficient to turn
> the 24VDC once into 24VHF and run that through the torid to the
> different power taps for your different voltages, then rectify those to
> the individual DC outputs.  Its been years since I looked at designing
> switching power supplies since they're basically off-the-shelf items
> now.  Since those days, I became a Stationary Power Engineer, then a
> degree nurse, then a CCU nurse, then left OS/2 for Debian, then a nurse
> prof, then a disabled nurse....


> > Last thursday I was in a Electronic-Shop in Offenburg/Germany and have
> > bought AMP-Connectors but unfortunatly I have gotten only the 20pin from
> > the mainboard...  Now I am looking for the 2pin, 4pin, 6pin, 8pin and
> > 24pin connectors to put on the modular boards.
> > 
> I think they are standard Molux (spelling? but its a brand name

You mean "Molex" but they are only the HDD and Floppy connectors.
I have seen only the cable plugs from the manufacturer AMP but not
the counterpart for the PCB.  However, I have ask the Electronic-
Shop to ask there Distributor, whether I can order it.

> origionally).  I think they were invented for the Apollo program.  Can
> you get them off a junk-yard computer?  They shouldn't wear out.  Do you

Unfortunatly not...

> have a pin-tool for placing and removing the pins from the housing?

Yes, I have all Tools to work with it...  (Expensive stuff :-/ )

> The other thing to keep in mind (but I don't know how to address it) is
> power-factor.  Since these aren't all resistance loads, you can't equate
> VA with Watts.  With the inductance loads of the drive motors, your
> current will be higher than the Watts/Volts would suggest.  This will
> also induce noise.  You'll need to have a power-factor corections
> circuit.

I know, curently I am learning about...

National Semiconductors have very good stuff apout it.  They have High
Efficiency Step-Down regulators (I was looking for one with 24Vin and
12Vout with 30A) which can have over 90% and there I have found a bunch
of Application Notes and other VERY useful documents of suff I have
never learned @university over 10 years back.

Thanks, Greetings and nice Day
    Michelle Konzack
    Tamay Dogan Network
    Debian GNU/Linux Consultant

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