Building fanless, but don't understand PSU issues.

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Burning Blue
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Joined: Tue Jun 19, 2018 6:14 am

Building fanless, but don't understand PSU issues.

Post by Burning Blue » Tue Jun 19, 2018 6:41 am

Hi, I'm about to build into a small form factor Streacom FC8 case. The system will include an Intel i3 8100 (Coffee Lake) and Gigabyte H370N Wifi (mini-ITX). SSD 250 GB, exact model undecided, and a Bluray or DVD burner, slot-loading type. No graphics card, and audio/video files will be mainly used via a powered external HDD connected by USB 3.

This is primarily an HTPC, running as a "Hackintosh". I don't have any real demands of it other than as a video player (local files and streaming) hooked up over HDMI to an AV amp and from there to a projector. I'll do a bit of DVD and CD ripping, or Bluray ripping if I can add a BR drive. It's not my main Mac OS system.

What I didn't quite realize before I went down this road, having built a few tower PCs and Hackintoshes before, was the power supply issues. I don't quite understand how much power I'm going to need to run this system: I've been looking at the Mini Box pico PSU-160-XT

Can I go lower than 160W, which is sort of my preference if it can be done, or is even 160 too low?

And in particular what I haven't understood well, after reading a few people's discussions back and forth, is how many amps are needed for the 12V AC-DC adapter - the power brick. Some seem to say don't go over 8A, others that you need more. I think I will be limited to the barrel plug connector, based on the back of this case.

Any advice on how to choose? Basically it boils down to 2 questions: how many watts for the DC-DC section, and how many amps for the AC-DC section?

Sorry if this has been dealt with before, but it's my first move away from large all-in-one ATX fan-cooled supplies, and it turned out to be harder than I thought.

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Re: Building fanless, but don't understand PSU issues.

Post by Vicotnik » Wed Jun 20, 2018 1:27 am

Hello and welcome to SPCR. :)

The picoPSU is not a full PSU in itself really. The brick (ac/dc-adapter) together with the picoPSU is what replaces the "normal" ATX PSU in a computer. That and the connection between the brick and the picoPSU.

The brick is the main part, it needs to be powerful enough to power the system. Who says not to go over 8A? :) The brick needs to be powerful enough to power the system. They cannot be too powerful if you ask me. A powerful brick will be large though, and maybe less efficient at very low loads. And expensive. So picking the right brick is important. You want a high quality brick that is powerful enough to power the system.

The way the picoPSU is priced I'd go with the picoPSU-160-XT for anything other than a very low power system, if I were to buy the picoPSU separately.

The barrel connector has caused me problems in the past, building relatively powerful picoPSU systems. I think it's rated for just 5A. Your system will not draw as much as 160W, maybe 100W when pushed, I dunno. I use barrel connectors for both my picoPSU powered systems, but if I intended to use either my main system or my htpc for any heavy work I would be more comfortable with something like this


The type of connector used in the higher end kits they offer -
Main: ASRock B85M-ITX | i3-4330 | 16GB DDR3 | Intel 730 240GB | HDPLEX H1-S | picoPSU | No moving parts | Idle 13.9W
HTPC: ASRock J4105-ITX | 4GB DDR4 | Intel 535 120GB | picoPSU | No moving parts
Gaming: Intel DH77EB | i5-3570K | GTX 1060 6GB | 16GB DDR3 | TJ08-E | RM750X
Server: ASRock N3150-ITX | ~30TB | G-360 | Idle ~25W

Burning Blue
Posts: 2
Joined: Tue Jun 19, 2018 6:14 am

Re: Building fanless, but don't understand PSU issues.

Post by Burning Blue » Wed Jun 20, 2018 5:13 am

Thanks for that reply - very helpful.

The 8A limitation was something I read about MiniBox's own recommendations, but if I recall the discussion correctly, it was later superseded. I can't remember how long ago that discussion was going on, or which website I found it on.

By the sound of it, I can go ahead with a Mini-Box 160W pico PSU and feed it with something like a 12V, 10-amp AC-DC adapter. The only models I can easily find are Chinese makes, the connector on that particular one is a barrel connector. I can also get lower amp models, 10A is the highest available from that maker (costing around $30). Any thoughts? I'm mainly going to play video files, and occasionally play discs from the optical drive, a bit of internet usage (such as Youtube and Netflix) and no gaming. I might be doing some conversion of video files - creating MKVs from ripped Bluray or something, but nothing I would consider heavy use or power hungry.

I'm going to give that a try, and if there are problems, I'll adjust the build at the power supply end, or reuse the board and CPU in another system and put something lower power into the HTPC.

Thanks for your help.

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