Log [12V] LiGHTPC ...a 5L gaming HTPC...

BaK

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May 17, 2016
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Hi guys,
This build is my first try with 12V and discrete GPU.
The K39 case housing the hardware is going to sit next to the TV set, not far from the couch.
I'm indeed in need of an HTPC, so why not make one with which I can play games?
But with such a small case and the ITX size GPU restriction, this is going to be a Light Gaming HTPC only. :)

The star of the show is of course the M2426 PDCB from @Thehack , which is going to deal with the 'always On' problem.
Indeed, when attached directly to a 12V PSU, a GPU is constantly fed with 12V even when the system is powered down.
But thanks to the M2426 and its 5Vsb and PS_ON wires acting as an On/Off remote, the MeanWell PSU stops providing 12V when the motherboard is shut down.

Here come the actual parts (*second hand), subject to be improved in the future:
- K39 black case (196*117*218mm 5L)
- MeanWell RPC-500-12-C 500W 12v AC-DC PSU (130*86*42mm)
- M2426 200W 12V PDCB
* Asus Z97I-Plus
* Intel i5 5765C CPU
- ID_Cooling IS-60 EVO (92mm bottom fan only)
* 2x 8GB DDR3
- 1TB SSD
* GTX 1660Ti

Electrically speaking, this is the plan:


The K39 case is designed for a Flex ATX PSU, thus the corresponding aperture at its back:


And that's what I am going to put in instead:

A C14 inlet, along with a fuse and a switch.
As there was some place left, I have also added a reset switch with an HDD LED.
The frame is made out of a 1mm aluminium plate that was lying around. It is a bit thin but works fine if you insert the power cable gently.
To prevent touching some live wires at its back, I've also made a little cover out of a plastic box and black tape for good measure.

[to be continued...]
 

jakejm79

Average Stuffer
Mar 22, 2021
60
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What's the issue with leaving the PCIe power plug powered all the time.

I've built multiple systems with either the EPS or GPU connected to a constant 12V source and no issues. If the system isn't actively on neither the CPU or GPU will actually pull any power even if there is 12V present on the connectors.

Also correct me if I am wrong, but wont killing power from the Meanwell PSU, mean that there is no longer power to both the GPU and M2426, thus killing the 5VSB signal meaning there is no way to remotely power the Meanwell PSU back on.

Isn't the M2426 meant to be used with ATX/SFX PSUs and not 12V only PSUs, the difference being how they are remotely powered on and off. ATX PSUs output 5VSB and then the power on signal wire is pulled to ground. The Meanwell PSU requires the Power On wire to be pulled high (2-5V), problem is once you kill the output from Meanwell PSU there is no power at the motherboard to pull the remote turn on wire high.

Also the wiring the way you have it wont power off the Meanwell PSU, since it will remain on when the PS_On signal is at 5V and 5VSB from the motherboard provides 5V in standby mode.

What you need is a way to pull the PS_On signal to 5V when pressing the power button and dropping it under 0.5V when shutting it down. This can be achieved by connecting one of the 5V wires from the motherboard for powering off, but unless you have an outside source for 5V triggered with the power button, there is no way to power it back on.

You seem to have things very backwards.

Your best bet, is to just do away with the M2426, use a standard inexpensive PicoPSU. Power the GPU and EPS direct from the Meanwell PSU, power the PICO psu also from the Meanwell PSU and then well you shut things down, just use the switch on the C14 socket to kill AC power to the Meanwell PSU thus killing power to the GPU and EPS in an off state, you will just have to switch the C14 switch back to on before powering the system back on. Or you could just not overthink the whole thing and leave the GPU and EPS powered at all times, it wont cause any issues.
 
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BaK

King of Cable Management
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May 17, 2016
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What's the issue with leaving the PCIe power plug powered all the time.
Even if the GPU doesn't actually turn on, there could be fans running at 100% or LED staying on with some GPUs.

Isn't the M2426 meant to be used with ATX/SFX PSUs and not 12V only PSUs, the difference being how they are remotely powered on and off. ATX PSUs output 5VSB and then the power on signal wire is pulled to ground. The Meanwell PSU requires the Power On wire to be pulled high (2-5V), problem is once you kill the output from Meanwell PSU there is no power at the motherboard to pull the remote turn on wire high.
The M2426 is indeed made for ATX PSU, but can also be wired to some compatible PSUs which have 5Vsb and remote On/Off, like the MeanWell RPS-400 and RPS-500.
There are two PS_ON connectors on the M2426, one for ATX PSUs and one for compatible 12V PSUs.
But let me quote @Thehack:
This is specific to MW RPS-400 12v but may applicable to other units.
RPS-400 has a standby function and 5vsb. The M2426 supports this standby function, so that you can hook up pcie power directly from the meanwell RPS-400 without having that "always on" problem.
If a 12V acdc has 5vsb/12vsb and Ps_on/remote on, then this unit will allow you to take advantage of turning that 12V unit on/off.

Your best bet, is to just do away with the M2426, use a standard inexpensive PicoPSU. Power the GPU and EPS direct from the Meanwell PSU, power the PICO psu also from the Meanwell PSU and then well you shut things down, just use the switch on the C14 socket to kill AC power to the Meanwell PSU thus killing power to the GPU and EPS in an off state, you will just have to switch the C14 switch back to on before powering the system back on. Or you could just not overthink the whole thing and leave the GPU and EPS powered at all times, it wont cause any issues.
That's up to you if you feel confident with such options.
While running a RGEEK PDCB on a low power APU build without problem, I will not advise cheap PDCBs for obvious reasons on more hungry hardware.
As well as powering the EPS from the PSU directly, going through the PDCB is the most reliable way of ensuring everything works properly on any motherboards.
I could have used the C14 power switch to power everything down, I'am actually doing that with a wall switch on my B01T3's build where the MW PSU doesn't have a standby function. Not having to do that here is a nice plus!
 
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jakejm79

Average Stuffer
Mar 22, 2021
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As stated. The M2426 supports both Hi and Lo PS_on signal.

It was made by an enthusiast ;).
Can you please indicate where that information is available on the website for the M2426, it doesn't seem to be documented anywhere, just that it comes with 2 connectors that support PS_On and 5VSB, it doesn't specify if there is any difference between them or if one is merely a duplicate of the other.

Maybe you might want to think about updating the website to provide a little more information?

May I suggest editing the pinout diagram to say PS_On (Hi) and PS_On (Lo) so people are actually aware they are different and which one is which.
 
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Thehack

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Mar 6, 2016
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Can you please indicate where that information is available on the website for the M2426, it doesn't seem to be documented anywhere, just that it comes with 2 connectors that support PS_On and 5VSB, it doesn't specify if there is any difference between them or if one is merely a duplicate of the other.

Maybe you might want to think about updating the website to provide a little more information?

May I suggest editing the pinout diagram to say PS_On (Hi) and PS_On (Lo) so people are actually aware they are different and which one is which.
(Mostly) No one uses it anyways and I’m a lazy/busy bum. One day it’ll be properly documented.
 
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Valantar

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Jan 20, 2018
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Subbed! Looks like a great build, looking forward to seeing it come together. Any particular reason you went massive overkill on the PSU? I know only the 400 and 500 have the PS_On header, but I would think the 400 would be the natural choice? Or are you just future proofing for some potential insanity with an RTX 3090 in there or something? :p

Also, really cool to see a build using desktop Broadwell. Those CPUs were really interesting.
 
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BaK

King of Cable Management
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May 17, 2016
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Subbed! Looks like a great build, looking forward to seeing it come together.
Good to have you onboard!
Hopefully not to save me again, but I'm pretty confident this time!

Any particular reason you went massive overkill on the PSU? I know only the 400 and 500 have the PS_On header, but I would think the 400 would be the natural choice? Or are you just future proofing for some potential insanity with an RTX 3090 in there or something?
Mainly not knowing if I would have room for a PSU fan, and the RPS-400-12-c being limited to 250W on convection, made me opt for the 500W (310W without fan).
Especially as you say, in case I find beefier components for an upgrade.
And I think the price difference is around 10$...

Also, really cool to see a build using desktop Broadwell. Those CPUs were really interesting.
I'm actually typing this on my MiniCube build, also powered by the same mobo/CPU!
Well you'll see however that the CPU is a special one...
 

BaK

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If that can help anyone wanting to dive into the 12V builds, here is exactly how I'm attaching everything together.
As well as the part list with buying links.


1)
Housing: JST VHR-3N
https://www.digikey.ch/product-detail/fr/jst-sales-america-inc/VHR-3N/455-1184-ND/608625
Terminal: JST SVH-21T-P1.1
https://www.digikey.ch/product-detail/fr/SVH-21T-P1.1/455-1133-1-ND/527367/?itemSeq=342751195

2)
Terminal: M3.5 Ring connector
https://www.digikey.ch/product-detail/en/te-connectivity-amp-connectors/2178506-3/A119654-ND/4898442
(works but not ideal, needs to put lots of force on the crimper)

3)
Housing: DF11-4DS-2C
https://www.digikey.ch/product-detail/fr/DF11-4DS-2C/H2019-ND/141249/?itemSeq=342866555
Terminal: DF11-22SC
https://www.digikey.ch/product-detail/fr/SVH-21T-P1.1/455-1133-1-ND/527367/?itemSeq=342751195

4) + 5)
Housing + Terminal kit: JST XH 2.54 3pin/4pin
https://www.aliexpress.com/item/32959016223.html

6)
Housing: 5557 4.2mmn pitch 4pin
https://www.aliexpress.com/item/32813227738.html
Terminal: Mini Fit Jr female
https://www.aliexpress.com/item/32795222262.html

7)
Housing: Mini-Fit 4pin
https://www.digikey.ch/product-detail/fr/1727081004/900-1727081004-ND/11565235/?itemSeq=342761558
Terminal: Mini Fit Jr female
https://www.aliexpress.com/item/32795222262.html

8)
Housing: Mini-Fit 8pin (6+2)
https://www.aliexpress.com/item/32860219124.html
Terminal: Mini Fit Jr female
https://www.aliexpress.com/item/32795222262.html

9)
Wire block connector: Wago 221 5x
Amazon product
 
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SFFMunkee

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Jul 7, 2021
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Definitely not an expert so just my opinion here, but I'd consider adding a secondary ground connection directly to the chassis. (In case the PSU chassis mounting doesn't provide solid connection back to earth, e.g. loose wiring / painted chassis / etc) - if the PSU is screwed through the chassis then it's unlikely a problem anyway (same as any ATX PSU/chassis).

Also it's worth noting that the RPS-500-C only needs a 25CFM, to get the rated output (25.8A/309W up to 41.6A/500W continuous) - will your design have any other fans that might provide some airflow over the PSU? Even a small amount could provide comfort it's staying within spec. :)

Nice find on the Intel Core 5675C too! They're rare as hens teeth but great little performers, especially given they were released ~6 years ago!
I remember being desperate for a low power i5 5xxx back in the day!
 
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BaK

King of Cable Management
Original poster
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May 17, 2016
703
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Definitely not an expert so just my opinion here, but I'd consider adding a secondary ground connection directly to the chassis. (In case the PSU chassis mounting doesn't provide solid connection back to earth, e.g. loose wiring / painted chassis / etc) - if the PSU is screwed through the chassis then it's unlikely a problem anyway (same as any ATX PSU/chassis).
Good catch! Schematic is updated.

I've got the PSU screwed at the bottom

That was close but the PSU fixing holes are matching the case openings, the screws making a good contact that way. I scratched some paint under the washers for good measure also.

Also it's worth noting that the RPS-500-C only needs a 25CFM, to get the rated output (25.8A/309W up to 41.6A/500W continuous) - will your design have any other fans that might provide some airflow over the PSU? Even a small amount could provide comfort it's staying within spec.
There is some room left for a fan under the GPU, will show you that soon.

Nice find on the Intel Core 5675C too! They're rare as hens teeth but great little performers, especially given they were released ~6 years ago!
I remember being desperate for a low power i5 5xxx back in the day!
As there are Broadwell fans around here, have a look at this one ;)
 

SFFMunkee

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Jul 7, 2021
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Good catch! Schematic is updated.

I've got the PSU screwed at the bottom

That was close but the PSU fixing holes are matching the case openings, the screws making a good contact that way. I scratched some paint under the washers for good measure also.


There is some room left for a fan under the GPU, will show you that soon.


As there are Broadwell fans around here, have a look at this one ;)
As I said, not an expert but it can't hurt

Ooooh - engineering sample i5-5675C! (All Broadwells had the 128MB eDRAM and Iris Pro 6200, right? That's the good stuff for mini PCs ;) )

I enjoyed the AnandTech article revisiting from last year: Broadwell with eDRAM: Still Has Gaming Legs
Intel’s eDRAM enabled Broadwell processors accelerated a significant number of memory bandwidth and memory latency workloads, in particular gaming. What eDRAM has enabled in our testing, even if we bypass the now antiquated CPU performance, is surprisingly good gaming performance.
As we move into more a chiplet enabled environment, some of those chiplets could be an extra cache layer. However, to put some of this into perspective.
  • Intel's Broadwell's 128 MiB of eDRAM was built (is still built) on Intel's 22nm IO process and used 77 mm2 of die area.
  • AMD's new RX 6000 GPUs use '128 MiB' of 7nm Infinity Cache SRAM. At an estimated 6.4 billion transistors, or 24% of the 26.8 billion transistors and ~510-530mm2 die, this cache requires a substantial amount of die area, even on 7nm.
 
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BaK

King of Cable Management
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I enjoyed the AnandTech article revisiting from last year: Broadwell with eDRAM: Still Has Gaming Legs
Thanks for the link!

They say:
i5-5675C *
* Sometimes listed as Core i7-5675C as some ES had an incorrect CPUID string


Which is what my i5 is displaying ;)


My reaction when I first saw that in the system properties of Windows was: 'Cool I've bought a wrong labeled i7 at the price of an i5!'.
But then CPUZ displayed only 4 threads...
 
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BaK

King of Cable Management
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Powering components ready to go inside the case!

Nothing fancy such as sleeved cables for this build, simple black 'ribbon' wires will do!
That's also for simplicity that I've decided to use the Wago connectors instead of soldering wires together. And after all I find them cleaner that multiple Y wires with heatshrinks, I will see if I do something for their orange part later ;)

 

Valantar

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Jan 20, 2018
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Powering components ready to go inside the case!

Nothing fancy such as sleeved cables for this build, simple black 'ribbon' wires will do!
That's also for simplicity that I've decided to use the Wago connectors instead of soldering wires together. And after all I find them cleaner that multiple Y wires with heatshrinks, I will see if I do something for their orange part later ;)

Looks good! Sleeved cables are silly for SFF anyway, far too thick. I'm a bit impressed that you've got the room for the Wago terminals, as even the slim type can get bulky. Are you using them to split a single fat gauge wire into lots of thinner ones for the connectors?
 

BaK

King of Cable Management
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May 17, 2016
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Looks good! Sleeved cables are silly for SFF anyway, far too thick. I'm a bit impressed that you've got the room for the Wago terminals, as even the slim type can get bulky. Are you using them to split a single fat gauge wire into lots of thinner ones for the connectors?
There is even spare space available at the bottom of the case with all the Wago in place, well... less than 10mm. Will post more pics later today.
I am indeed splitting a 16AWG wire on each Wago into several 18AWG wires. I could have achieved this with smaller 3x Wago connectors instead of 5x to provide 12V to the M2426 (see schematic above), but with 5x I have the option to attach a >75W CPU to the MW PSU directly if needed later.