350w PSU cant power 8 hard drives...what gives?

[MrDudeMan]

i made a storage computer, and i got a 350w PSU to power it. it has a celeron 600, 1 IDE controller card, a pci video card, and 8 hard drives. it will not power all of it...

the motherboard/cpu combo cant be using more than 100w, so ill give it that to start. the hard drives use 11 watts each, so thats 188. the video card probably uses 40...im not sure, but id say its a decent guess. the controller card cant be using much, so that puts us at less than 250w.

is 350w an inflated value? i can use 2 PSUs if i need to, but id rather not.

edit: i took out the PCI video card and connected the monitor to the onboard video.


edit2: figured it out...check back in a week or so for pics of this thing. it will be cool...i promise!

 

[WobbleWobble]

What brand/model PSU?

 

[MrControversial]

How many amps does each hard drive draw?

 

[stevty2889]

It's probably got a weak 12v rail, and all the hard drive motors use 12v...

 

[MrControversial]

Edited my post to ask you further questions. Is the power of the hard drives correct? What's the specs of your HDD?

 

[MrDudeMan]

the hard drives are all the same. they are drawing .35A @ 12v and .8A and 5v

that should be a total of 2.8A @ 12v and 6.4A @ 5v

 

[jackschmittusa]

hds draw significantly more at startup that in normal operation. Additionally, a cheap psu may not perform as advertised in normal conditions, and if it is an old one, it may have deteriorated to a even lower output (all psus dereriorate over time, some a lot more than others).

 

[MrDudeMan]

hmm i could design some logic to make half of the hard drives startup 1 second after the other 4 kick in.

 

[Zepper]

Yes, SCSI host adapters have stagger start built in just to resolve that type of problem. A one or two step delay would help a lot. Probably trying to draw over 10A on startup with all pulling at once.

.bh.

 

[Coquito]

It isn't always sustained power. That would be my guess. That 350 might be 220 sustained.

 

[MrDudeMan]

Originally posted by: Coquito
It isn't always sustained power. That would be my guess. That 350 might be 220 sustained.

how do you verify what the sustained power is?



Zepper, thanks...im going to go design a circuit for that.

 

[Budman]

Originally posted by: WobbleWobble
What brand/model PSU?

????

 

[VirtualLarry]

Originally posted by: Bigsm00th
Zepper, thanks...im going to go design a circuit for that.

Wow, props for the hardcore-hacker approach. Most of us would just drop another $50 on a PSU with a more powerful +12V rail and some more molexes. A TTGI/SF with 8-10 molexes comes to mind here.

 

[Googer]

Originally posted by: MrControversial
How many amps does each hard drive draw?

Hard drives typicly draw 12-15 watts. Although a select few (notebook) draw less power that that (5-13). So assume that your drives USE 15 watts each and figure it from there.
15 Watts
x8 Drives
120 Watts

That leaves little room to power your mother boad, CPU, NIC, Sound Card, Fans, USB, ETC. Most PSU's cannot provide all of their rated power continuosly except PC POWER AND COOLING guarantees that you will be able to run 510 watts worh of stuff on a 510 watt PSU on a continous basis. PC Power is also the only company recomended by nVIDIA for Sli setups. http://www.nzone.com/object/nzone_sli_powersupplies.html

http://www.pcpowercooling.com/products/power_supplies/highperformance/index.htm

 

[MrDudeMan]

ok, i got it working guys. i got a 400w PSU and cut the molexs off of another PSU to make a combined total of 10 for the 400w. i made a circuit that turns on 3 hard drives with the motherboard, turns on 3 more after 1.25 seconds, and the last 2 .75 seconds after that. i made sure to have the drives that are connected to the motherboard turn on first, and the drives connected to the controller card turn on last. it is all working great now.

VirtualLarry, thanks I like to do stuff the hard way usually.

Googer, thx for the info.


ill post pics of the case and drives when im finished. everyone check back in a week or so! i promise it will be worth your time

 

[Sqube]

All I wanted to know was what kind of PSU you were using... why didn't you answer that question?

 

[Googer]

Originally posted by: Sqube
All I wanted to know was what kind of PSU you were using... why didn't you answer that question?

Umm, He is using an insufficiant one.

 

[Googer]

the controller card cant be using much, so that puts us at less than 250w.

The controller card uses about 10-35 watts depending on the type, Amount of memory (if any), and If it has an onboard processor.
http://www.lsilogic.com/products/megaraid/megaraid_320_2e.html

 

[MrDudeMan]

Originally posted by: Googer

Originally posted by: Sqube
All I wanted to know was what kind of PSU you were using... why didn't you answer that question?

Umm, He is using an insufficiant one.

no, it was fine, just wasnt strong enough. its a sparkle if you must know.

 

[Sqube]

Originally posted by: Bigsm00th

Originally posted by: Googer

Originally posted by: Sqube
All I wanted to know was what kind of PSU you were using... why didn't you answer that question?

Umm, He is using an insufficiant one.

no, it was fine, just wasnt strong enough. its a sparkle if you must know.

You know what they say about curiosity... thanks for the answer (as agonizingly delayed as it might have been... )

 

[MrDudeMan]

Originally posted by: Sqube

Originally posted by: Bigsm00th

Originally posted by: Googer

Originally posted by: Sqube
All I wanted to know was what kind of PSU you were using... why didn't you answer that question?

Umm, He is using an insufficiant one.

no, it was fine, just wasnt strong enough. its a sparkle if you must know.

You know what they say about curiosity... thanks for the answer (as agonizingly delayed as it might have been... )

i honestly didnt see your question until your last post.