0

I'm building a mining rig and is planning on using a ESP120 HP 3kW 52V power supply. I've seen someone get it down to 48V with this mod, but I wonder some one got it down to 12V? Or is it not possible?

JYelton
  • 32,302
  • 33
  • 134
  • 249
Murillio4
  • 103
  • 2
  • Do you need all 3kW? – Ignacio Vazquez-Abrams Mar 20 '14 at 00:52
  • yes, or i need at least 2900w. I'm going to use two of these connected together in parallel to power 18 R9 280x + motherboards. – Murillio4 Mar 20 '14 at 01:07
  • Keep in mind that even if this is possible, quartering the voltage will quadruple the current. You're going to need some hefty conductors to carry that much. – Ignacio Vazquez-Abrams Mar 20 '14 at 01:10
  • i'm planning on using [this](http://www.ebay.com/itm/RED-BLACK-TRACER-30M-ROLL-BATTERY-CABLE-TRADE-3MM-AUTO-ELECTRICAL-WIRE-DC-12V-/281264890579?pt=AU_Car_Parts_Accessories&hash=item417cb1a2d3&vxp=mtr) cable. is it enough? And will the high current burn out my gpu's? – Murillio4 Mar 20 '14 at 01:22
  • @Murillio4; That cable can handle 20A. Your power supply can supply 57A, and that's before quadrupling the current as Ignacio says. This is dangerous territory. Also see: http://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings in regards to your second question (tl;dr No, the GPUs will only pull as much current as they need). – Chris Laplante Mar 20 '14 at 01:38
  • Normally power supplies will not function properly if connected in parallel. Is there reason to believe these would? – gwideman Mar 20 '14 at 08:08

1 Answers1

2

You would be better off to distribute the 48V-52V to the motherboards individually (about 3A per wire), and use a point-of-load DC-DC converter (there are many available commercially, and they aren't all that expensive) on each one to produce the 12V @ @13A that the motherboard needs.

This not only reduces the wiring losses, it also makes it easier to work on one motherboard at a time without shutting down the entire farm.

Dave Tweed
  • 168,369
  • 17
  • 228
  • 393
  • ah, super! could you send me a link on one you recommend? can i also wire them to the gpu's? so there will be 6 gpu's and one motherboard on one point-of-load DC-DC converter? – Murillio4 Mar 20 '14 at 01:57
  • i'm plannin on using [this](http://www.ebay.com/itm/dc-12v-120W-car-power-20pin-mini-ITX-DC-ATX-power-supply-PICO-BOX-Pico-PSU-f-pc-/111241652420?pt=PCA_UPS&hash=item19e684e8c4) to power my 24 pin, and 2*12v +/- to power the 4 pin. – Murillio4 Mar 20 '14 at 02:04
  • Well, I found [this one](http://www.digikey.com/product-detail/en/E48SP12020NRFA/941-1053-ND/2501325) in a quick search on Digi-Key; it can supply up to 20A per system. $50 each in qty. 10 isn't a lot compared to what you're already spending on the motherboards and GPUs. There might be cheaper suppliers on Ebay. – Dave Tweed Mar 20 '14 at 02:12
  • Thankyou! but how many of these do i need for 30 gpu's and 5 motherboards? ech gpu pulls 230w +/- on full throttle – Murillio4 Mar 20 '14 at 02:21
  • Ah, sorry, I misunderstood how your system is going to be configured. Didn't you originally say 18 GPUs? I thought your *total* power requirement was going to be 2900W -- with 30 GPUs, it's actually more like 7500W. You'll need one per GPU, plus one for each pair of motherboards, for a total of 33. You're also going to need *three* of the big power supplies. Connect 11 of the DC-DC converters to each of the big power supplies. The DC-DC converters are about 95% efficient, so you'll actually be drawing about 2700W from each of the big supplies. – Dave Tweed Mar 20 '14 at 04:03
  • Just out of curiosity... why is it thought beneficial to have one PSU convert to some high DC voltage, and then convert this again with DC-to-DC convertors local to the GPUs? Why not just use economical "AC-to-12V-DC convertors", also known as normal off-the-shelf PC power supplies? Not saying you're all wrong, just curious! – gwideman Mar 20 '14 at 08:07
  • Actually, your setup is borderline, and direct conversion to 12V might be appropriate for you. But in general, point-of-load regulation is used to avoid having large high-current power distribution networks, and it usually provides better regulation of the load voltage. Pretty much every motherboard made today uses POL regulators to provide the core voltage(s) to the CPU, chipset and memory. Also, doing two conversion stages allows you to perform the line isolation just once in the first stage, and then use simpler non-isolated POL converters (although the one I suggested is isolated anyway). – Dave Tweed Mar 20 '14 at 12:02
  • I'm going to go for the HP DL580G5 800/1200W AC Power Supply, since it's 12v. It's about 100A, so i need a good cable! But i need molex connectors, and they have a +5v 32A pin. Any DC-DC converters you could recomend for this? But i don't need a DC-DC converter for every molex plug, do i? – Murillio4 Mar 20 '14 at 12:21
  • is it harmful for the gpu or motherboard if the pci-e rizers are powered by different psu's? – Murillio4 Mar 20 '14 at 13:00
  • No, as long as the PSUs don't mind having their grounds tied together. – Dave Tweed Mar 20 '14 at 13:08
  • Then I'll try! but any solution on my previous question? :) (btw. sry for being a noob, haha) – Murillio4 Mar 20 '14 at 18:33
  • This is starting to turn into a shopping/system configuration question. I wonder if you would get better answers on [Superuser](http://superuser.com/) -- although I see you [tried there already](http://superuser.com/q/730374/187534) and the question got closed. – Dave Tweed Mar 20 '14 at 19:31
  • I've figured everything out :) thanks for all help!! – Murillio4 Mar 21 '14 at 13:02