Re: [OT] ATX-PSU and amperage on connectors...
On Thu, Feb 21, 2008 at 07:31:45PM +0100, Michelle Konzack wrote:
> I am designing (with the help of Dallas/Maxim, NXP and LM) new DC-ATX-
> PSU's (with 24V DC entry to use it in Photopholtaik-Systems) and was
> searching for the amperage of the connectors of an ATX-PSU.
>
> Does anyone know, where I can get the specifications for it?
>
> E.g. the 24-pin ATX-Connector (24 pins) where we have
>
> or bl bk gn bk bk bk wt rd rd rd bl
> +---+
> +--------------------+---+-------------+------+
> |O O O O O O O O O O | O O|
> |O O O O O O O O O O | O O|
> +--------------------------------------+------+
> or or bk rd bk rd bk gr pu ye ye or
>
> +12 V ye yellow => ???
> + 5 V rd red => ???
> + 3.3V or orange => ???
> + 5 Vsb pu purple => 2 A
> - 5 V wt white => 1 A
> -12 V bl blue => 0,8A
> bk black => GND
>
> same for the P4 connector (4 pins)
> +12 V ye yellow => ???
>
> the 6 pin ??? conector
>
> bk bk bk or or rd
> +---+
> +--------+---+--------+
> |O O O O O O|
> +---------------------+
>
> + 5 V rd red => ???
> + 3.3V or orange => ???
>
> and what about the SATA and old HDD connectors?
> How many ampers must a cable support?
>
> If you want to ask why I need more or less exact values I respond:
>
> I have the need for 38 DC-PSU's for my own for a solar powered Project
> and since my money is very limited, I want to avoid to buy electronics
> I do not need...
>
> Also I like to make the DC-PSU modulable, which mean, a standard layout
> for the ATX-Connector and then modules which can be added if needed for
> P4 conector, 6-Pin-XXX conector or the HDD connectors. Also I want to
> use ISO or AMP connectors insteed of making fixed cables on the DC-PSU
> which bother me (personaly) if not needed.
>
> For example, I was planing to use DC-DC-Converters from RECOM which have
> a very high efficiency (>=88%) but are non realisable since a 40 Watt
> model cost arround 72 Euros which mean for the ATX connector:
>
> +12 V => 3,3A 40W 70 Euro
> + 5 V => 8 A 40W 70 Euro
> + 3.3V => 12 A 40W 70 Euro
> + 5 Vsb => 2 A 10W 25 Euro
> - 5 V => 1 A 5W 15 Euro
> -12 V => 0.8A 10W 25 Euro
> -------------------
> 145W 275 Euro
>
> and a HDD-Cable for three/four devices could be something like
>
> +12 V => 3,3A 40W 70 Euro
> + 5 V => 3 A 15W 30 Euro
> -------------------
> 55W 100 Euro
>
> So I can forget this nice DC-DC converters which simplyfiy design by
> factor 20 but of the costs...
>
> Even if I buy produce 1000 PSU's the price would be over 300 Euro
> complete per unit. (The "PicoPSU", a PSU on a ATX connector, support
> only 12Vin but provides 120 Watt and costs arround 100 Euro)
>
> Dallas, Maxim, NXP and LM offer step-Down regulators in 4x4mm to 6x6mm
> cases with 3.3V, 5V, 12V plus negativ voltages up to 60 Ampere for
> 0.68 US$ to 3.27 US$
>
> And yes, I have already tonns of free samples laying around in my
> appartement... (nice to solder TQFN packages... :-)
>
Hi Michelle
First, you do know that one can purcase DC ATX PSUs?
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'll give you the informaition from my ATX PSU's manual:
Cooler Master iGreen Power 600W User Manual.
Double Forward Switching Circuit for 85% efficiency
Compliant with Intel Standard ATX 12V V 2.2.
Compliant with SSI standard EPS 12V v 2.91
Output specs:
DC output Peak Continuity Max Power
=================================================
+3.3 V 25A 20A }
} 166 W
+ 5 V 25A 20A }
-------------------------------------------------
+12V (bus 1) 19.5A 16A }
+12V (bus 2) 19.5A 14A } 465 W
+12V (bus 3) 19 A 8A }
-------------------------------------------------
-12V 0.8A 0.5A 6W
-------------------------------------------------
5Vsb 3.5A 3.0A 15W
=================================================
So the only trick for your design is what plugs from the PSU are on
which 12V bus. Here's the breakdown:
Motherboard connector, 12V is from bus 1.
4-pin 12V power connector is on bus 2
8 pin 12V power connector: pins 1 & 2 are from bus 1, pins 3 & 4 from
bus 2.
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)
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.
---
Analysis:
Bus 1: 16A continuous, 19.5 A peak, is used for the MB connector, half
of the 8-pin connector, one PCIe video connector, and all the drives.
Bus 2: 14A continuous, 19.5 A peak, is used for half of the 8-pin
connector and the 4-pin connector
Bus 3: 8A continuous, 19A peak, is used for one PCI-e connector.
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.
Bus 3 is 8A is only goes to one PCI-e.
Bus 1 is 16 a and does most things including a PCI-e so if you figure
that a PCI-e is 8A that leaves 8A for the MB and half the 8-pin
connector, and all the drives.
I suppose the question is how much of a computer do you intend to power
on solar power? Do you need a video card that requires a PCI-e? How
many drives do you want to be powering? I don't want to open up my box
to read the rating on my Seagate Barracuda 80 GB SATA drive while I'm
trying to write email, but if this info would be helpful, send me an
email and I will (I can easily tolerate a powerdown, its no trouble at
all).
Let me know if I can help in any way.
Doug.
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