working out Power supply size

enfield_freddy

in the process of building a new "mini" computer , motherboard is a asrock z97m-itx/ac see http://www.asrock.com/mb/Intel/Z97M-ITXac/ this is a fully functioning board , just add CPU and memory , I was going to use a i3 ****T series CPU rated at the lower 35w , as opposed to the non "t" models being 54w.


PSU 12v "brick" running thru a "pico" setup .


I scored a pico from ebay for £12.99 instead of the usual £45


as per http://www.ebay.co.uk/itm/201090012185?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT


now this is one of there better ones , rated at 160w , with a 24 pin plug plus the 4 pin plug .


so the question is the "brick" , what size , ie: ampage?


yup I know most are from china , and they lie like hell , CPC farnell is just up the road , and although dearer , have a good return system


how much extra wattage do I need to account for the m/board , there is no external vid card , so the CPU wattage on the i3(s) must inc the vid, small wireless card and 1 x 8g memory + 1 x ssd , that's all

enfield_freddy

ok , found this http://powersupplycalculator.net/ any comments?

Fightsback

160w is more than adequate, a 35w rated CPU lappy with a discrete card usually comes with a 90w-120w PSU.

Strider590

Well your power supply board is capable of output 160W, the ad states max output @ 12v is 3A, so your input needs AT LEAST 5A @ 12V. I would argue that in truth it needs more to account for the other rails, but it's pointless because good luck finding a decent quality and cheap 12V PSU that can deliver 5A nevermind even more.

Lets also not forget that it has to deliver that power without the voltage dropping off.
Take for example a 12V / 1A supply I have sat next to me, at 800mA the supply voltage drops to 10.5V, in a setup where voltages are critical, this sort of drop is unacceptable.

Laptop power supplies are probably your best bet, but are typically 18V. So unless that board can handle 18V (it doesn't say), you'd need to regulate that down.

Moneymaker

Strider590 wrote: »

Take for example a 12V / 1A supply I have sat next to me, at 800mA the supply voltage drops to 10.5V, in a setup where voltages are critical, this sort of drop is unacceptable.

A regulated PSU will provide the rated current at the rated voltage. Yours clearly isn't regulated OR you've been sold a pup.

Here's one: http://www.powerstream.com/ac-1250.htm

Strider590

Moneymaker wrote: »

A regulated PSU will provide the rated current at the rated voltage. Yours clearly isn't regulated OR you've been sold a pup.

Here's one: http://www.powerstream.com/ac-1250.htm

Your talking cheap Chinese made stuff, there's no way on this earth I would trust something like that.

The power supply i'm talking about is a good quality regulated SMPSU, but near it's limit any PSU will start to drop out.

Fightsback

Strider590 wrote: »

Well your power supply board is capable of output 160W, the ad states max output @ 12v is 3A, so your input needs AT LEAST 5A @ 12V. I would argue that in truth it needs more to account for the other rails, but it's pointless because good luck finding a decent quality and cheap 12V PSU that can deliver 5A nevermind even more.
.

Eh ? for 160w pico board you need at least 12v 180w ( to account for losses - note the 92% efficiency of the pico board) regulated psu to guarantee the pico board supply at 160w which is at least 15A not 5A. However that system will draw nowhere near that, 120w is probably more than enough.

Freddy look here to give you an idea of real world total system loads:

http://hexus.net/tech/reviews/cpu/56853-intel-core-i5-4670k-22nm-haswell/?page=9

enfield_freddy

ok chaps , thanks for all the comments


fightsback , thanks for the laptop comments (90-120w)


strider590 , the unit I have bought is only rated at 12v , as you can see its a Chinese "knock off" of the genuine Pico units ,


pico do make units that that will operate at 19v , however they are only 20 pin , and there are comments on HTPC sites , saying people have had to cannibalize old PSUs to add another 4 pin connector .


looking around ebay and amazon , this PSU seems the best buy http://www.amazon.co.uk/gp/product/B002SRJ9OG?colid=8YI9PK2OIAHZ&coliid=I3U9S1HEZJMIP8&ref_=wl_it_dp_o_pC_nS_ttl