Re: [OT] ATX-PSU and amperage on connectors...
On Sat, Feb 23, 2008 at 02:07:28PM +0100, Michelle Konzack wrote:
> Am 2008-02-22 11:51:59, schrieb Douglas A. Tutty:
> > Hi Michelle
> >
> > First, you do know that one can purcase DC ATX PSUs?
>
> Yes but with an efficienci horible... 40-70% only...
>
> I am working with chips from Dallas, Maxim, NXP and LM and get over 85%.
> And of cources, if you need a Vin of 24V (18-32V) you are lost.
>
> > Second, the individual drives don't take much power so I think the wire
> > size is for mechanical support, I wouldn't go with less than 18 AWG.
>
> I am not realy sure about this since I have for example:
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
>
> +5 V +12 V
> CD-Rom noname 0.35A 1.7 A
> CD-Rom Teac CD-512E 1.5 A 1.3 A
> CD-Rom Teac CDR-55S 1.8 A 1.8 A
>
> DVD-Rom AsusTek E616A 1.5 A 1.5 A
>
> HDD IDE IBM DHEA-38451 0.32A 0.26A
> HDD SCSI IBM DDRS-39130 0.55A 0.65A
> HDD SCSI IBM DDRS-34560 0.55A 0.65A
> HDD SATA2 Hitachi HDT725032VLA360 0.73A 0.64A
>
> Iomega ZIP 100 0.8 A
>
Elecrically, these would be fine with 26 or 24 AWG without overheating
the insulation. However, you don't provide inrush current requirements
of the device. Too much resistance in the wire could end up
undervoltaging the drive motors.
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).
>
> So if I take only the AsusTek DVD and the SATA2 disk which are two of
> the latest models, then the 4pin HDD connector need already
>
> 12V 2.22A = 26.64 Watt
> 5V 2.14A = 10.70 Watt
> -----------
> 37.14 Watt
>
> And if I see my "Enhance Electronics Co. Ltd" 300Watt PSU which has
>
> 20pin ATX connector
> 6pin ePCI connector
> 4pin P4 connector
> 2 cables with three HDD connectors
> 1 cable with two HDD and one Floppy connector
>
> + 3.3V 28 A \ 180 Watt \
> + 5 V 30 A / | 279 Watt
> +12 V 15 A /
>
> + 5 Vsb 2 A
> -12 V 0.8A
> - 5 V 0.3A
>
> 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.
> 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?
>
> > One PCIe 6 pin connector is on bus 1, the other PCIe 6 pin connector is
> > on bus 3 (these are for one or two video cards that need the extra
> > power)
>
> OK
>
> > SATA conectors are on 12V bus 1
> >
> > PATA drive connectors are also on 12V bus 1
> >
> > All of these connectors use 18 AWG wire.
> >
> > Floppy connector 12V is also on bus 1 but uses 22 AWG wire.
>
> Hmmm, for example, can this work:
>
> ATX-Connector +12 V 3.3A = RECOM RP40-2412SE
> + 5 V 8 A = RECOM RP40-2405SE
> + 3.3V 12 A = RECOM RP40-2403SE
> + 5 Vsb 2 A = RECOM PP10-2405SEW
> - 5 V 0.3A = RECOM ???
> -12 V 0.8A = RECOM ???
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.
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.
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...
>
> Which mean, on each of +12V, +5V +3.3V I have a maximum of 40Watt
> independant which will definitivly work for a 32-Bit Socket A CPU
> from Duron over Sempron to Athlon up to 2000 MHz
>
> My Workstation is a Sempron 2200+ (1500Mhz) with 1 GByte of memory
> and is working fine with it, but switching to an Athlon 3000+ kill
> the PSU (no, not the 3.3V but the 5V).
>
> > Given the design of this PSU, I can't say how much amperage goes, e.g.
> > only to the MB or for each drive. However, look at it this way.
>
> This what I am looking for.
>
> Maybe I will make a 24pin-ATX-Adaper in which I put ANALOG Ampermeters.
>
> The problem is, taht some CPU's are sucking realy 90 Watt alone...
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.
> On my Workstation I am testing a IDE/CF-Adapter with a 4 GByte SanDisk
> UltraII but I think I will switch to a cheaper 2 GByte one since I have
> no KDE/GNOME On-Board. /tmp and /var is in a ramdisk where the later
> one is saved and restored from an init script at boot and shutdown
> to/from a second CF-Card of 512 MByte as TAR-Archive which works perfectly.
Well, considering that Soekris boards run with CF cards off of a single
5W wall-cube...
> On my Test-Server I have curently the 3W8500S-8LP with three normal SATA
> Hitachi TravelStar 80 GByte (smaler where not availlable) in a Raid-1 plus
> Hotfix and each drive has ONLY 5V/1.3A.
Running current, not start-up requirements.
> Now I like to install four Hitachi TravelStar from the E5K or E7K series
> which allow 24/7 use on load... it seems, the consuming 5V/1.4A.
>
> 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?
> As I have writen, I like to make a 24V-DC-PSU modular, so one modul for
> the ATX-Connector, one for the ePCI, one for the P4, one for the HDD's.
>
> Which mean, I can addapt the PSU to my needs...
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
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
have a pin-tool for placing and removing the pins from the housing?
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.
Good luck,
Doug.
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