How can I power 13 External Hard Drives (requiring 12V, 3A each) using 1 or 2 Power Supply Units?

Thread Starter

DayCaesar

Joined Feb 20, 2018
10
Hello

This is my first post.

As I'm dyslexic, its easier to ask my question via this video.

I don't have a background in electrical engineering, so if I've missed out any crucial information, please let me know.

Grateful for any advice / solutions :)

PS In the time it took for this video to upload, I found some useful posts on this forum.

So basically I have 13 devices:

1) 10 devices x 12V 3A = 360W
2) 3 devices x 12V 2A = 72W

So total power needed is 432W.

That's as far as I've got......
 

Thread Starter

DayCaesar

Joined Feb 20, 2018
10
Thanks for all the replies and advice.

I've decided on getting an 750W ATX as suggested by Dodgy Dave, and I've watched several youtube vidoes on converting, so I think I'll manage this up to a point, however, I'm not sure on 2 points:

1) Once I've gathered all the yellow 12V wires, how do I make this into a supply which splits 13 ways each with a
Power Supply Barrel specs of: Outside 5.5mm Inside 2.5mm (Positive Center)? Is there a tidy way anyone can advise me on?

2) Could you advise on putting a resistor on the 3.3v and/or 5v rails as Ian Field suggested above? Do I need to a resister on both rails? Can the resistor be 10 ohms in both cases? How do I actually do this...?

Again, any advice gratefully received :)
 

Dodgydave

Joined Jun 22, 2012
8,473
A 10 ohms 5W resistor only on the 5V rail will be enough to keep the psu on it will draw 0.5Amp, you need to join the Green wire to any Black to power up the atx,

You can join your barrel connectors to any yellow and black, or join all the Yellows together and join all the Blacks together and put them into a 30A strip connector then wire all your barrel connections to that.

download.jpeg
 

ian field

Joined Oct 27, 2012
6,539
Just stick a 10 ohms resistor on the 5V rail...
That's only 1/2A from an output that could be rated somewhere in the general direction of 100A.

The mark space ratio is determined by the sampled rails - the 12V rail usually isn't one of them.

One PITA customer was in the habit of checking ATX PSUs by sticking a hard drive on them - most hard drives draw high current at 12V and low current on5V. Most of the PSUs ended up in my goods in and I had to play hunt the faulty item.
 

crutschow

Joined Mar 14, 2008
23,531

Dodgydave

Joined Jun 22, 2012
8,473
The TS reqires 36A total so that could be a little marginal.
Likely more reliable to use two supplies and split the load between them.

Since that is stated to have a single 12V rail internally, perhaps it does not require a load on the 5V output to properly regulate.
YES it would be easier to use two 450W atx psus.
 

Thread Starter

DayCaesar

Joined Feb 20, 2018
10
Thanks again for all the replies :)

OK so it looks like I'm looking for either a single PSU or two PSU which give me at least 45A.

If I found a single unit which was rated at 45A or above, this seems to be the easiest (and most cost effective) solution.

If such a PSU had just a single 12V rail, would that also let me of the hook with having to add a resistor?

Lastly, thanks for the suggestion about using a strip connector Dodgydave. I saw this one, which is rated at 60A, which I'm guessing will suffice (assuming I find a suitable single PSU), and as it only has 12 connectors, and I need 13, I could just buy 2, and cut to size couldn't I?
 

Thread Starter

DayCaesar

Joined Feb 20, 2018
10
The TS reqires 36A total so that could be a little marginal.
Likely more reliable to use two supplies and split the load between them.

Since that is stated to have a single 12V rail internally, perhaps it does not require a load on the 5V output to properly regulate.
What does TS stand for here (excuse the rookie question!)
 

Reloadron

Joined Jan 15, 2015
4,591
Your numbers are a little high not that it really matters much. Here is an example of 15 Enterprise type drives starting so the start current is plainly visible. I have several drives laying around here and some include current on the labels. Some old non efficient Western Digital Raptors (10K RPM Drives) 5.0 VDC @ 0.70A and 12 VDC @ 0.75A. I also have a WEstern Digital External HDD which uses a 5.5mm Size K DC Power Plug, Powered by a 12 VDC 1,500 mA (1.5 Amp) external supply. All here nor there.

As to the connectors? I recently bought this 10 Pack from Amazon. The package includes one each male and female mating connectors. They are also AWG 18 wire which is nice. A Google of "terminal barrier strips" should get you dozens of hits, as to how to join things together.

Ron
 

MisterBill2

Joined Jan 23, 2018
4,055
Thanks for all the replies and advice.

I've decided on getting an 750W ATX as suggested by Dodgy Dave, and I've watched several youtube vidoes on converting, so I think I'll manage this up to a point, however, I'm not sure on 2 points:

1) Once I've gathered all the yellow 12V wires, how do I make this into a supply which splits 13 ways each with a
Power Supply Barrel specs of: Outside 5.5mm Inside 2.5mm (Positive Center)? Is there a tidy way anyone can advise me on?

2) Could you advise on putting a resistor on the 3.3v and/or 5v rails as Ian Field suggested above? Do I need to a resister on both rails? Can the resistor be 10 ohms in both cases? How do I actually do this...?

Again, any advice gratefully received :)
It is also easy to purchase a non-computer power supply that will deliver the 12 volts, well regulated, without any hokey load resistors on the other voltages, thus no excess heat and no wasted power. AND the power supply will be simpler to mount as well.
 
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