Power Supply A Guide to 12V PSU

Shizzel

Case Bender
New User
Feb 23, 2020
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@smitty2k1 The HDD backplane uses a single Molex connector. You can use a SATA->Molex solid adapter to solve this issue and power the whole drive cage.

I would caution @Shizzel on using the 2.5" drives over 3.5" drives. Most of the power board-style adapters have a lot of 12V but not much 5V. 3.5" HDDs need both voltages to power on, but the majority of power draw comes from 12V, because 12V drives the motor. In a 2.5" drive, all the power is 5V and sometimes the 5V rail on these PSUs isn't so hot. Just make sure you check the spec sheets of your drives and the PSU. Your Meanwell only outputs 12V so you must rely on the stepdown of the ATX Power Board to give you 5V (unless you have a motherboard that does this as well).

Unless you're getting 2.5" SSDs in which case power becomes a non issue, for the most part. Your big issue there is that the backplane is only SATA2 speed (3Gbps) so you're really gimping your throughput.

Thank you for your reply. I understand what your saying about the 2.5 drive issue. I might go with 2 2.5" en 2 3.5" of the same size. Then I have "some" extra security in case of a drive failure because of the use of different types of drives (and voltage supply).
 

xredlinexx1

Average Stuffer
Mar 18, 2019
86
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Hi guys, I'm pondering using a Meanwell rps-500-12 as an external power supply. I'm thinking it would be cool to use an aviation connector from the Meanwell to the pc case, and from there to a One2 distro 400. I'm struggling to find any connector that is rated for a high current of around 40 amps (that's what rps-500-12 lists as the max output current). Most are 5 amps and some up to 15 amp. Am i misunderstanding something or is the amperage too high for these connectors?
 

Thehack

Spatial Philosopher
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Mar 6, 2016
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Hi guys, I'm pondering using a Meanwell rps-500-12 as an external power supply. I'm thinking it would be cool to use an aviation connector from the Meanwell to the pc case, and from there to a One2 distro 400. I'm struggling to find any connector that is rated for a high current of around 40 amps (that's what rps-500-12 lists as the max output current). Most are 5 amps and some up to 15 amp. Am i misunderstanding something or is the amperage too high for these connectors?

Yes.

Generally too high for most pinned, especially for something that is "off the shelf" as the aviators cables. They were designed to be tough and not necessarily high current carrying.

You should just use one with more pins. So an 8-12 pins depending on the rating should support it.

That or use specialized but expensive high current connectors.
 

xredlinexx1

Average Stuffer
Mar 18, 2019
86
23
Yes.

Generally too high for most pinned, especially for something that is "off the shelf" as the aviators cables. They were designed to be tough and not necessarily high current carrying.

You should just use one with more pins. So an 8-12 pins depending on the rating should support it.

That or use specialized but expensive high current connectors.
Thanks! When an aviation connector has an amp rating listed, do you know if that's total or per pin? Per pin would line up with what you are saying i think.
 

xredlinexx1

Average Stuffer
Mar 18, 2019
86
23
It's per pin. You a negative and positive pair. So an 8A per pin, 4 pin connector supports total 16A.
Thanks. So will using the 500w Meanwell require monster size wire on the dc output? Looks like around 8awg wire will be needed to handle the 500w, 12v, 40 amp output? There are only two terminals on the output... V+ and V-, so it's not even distributed at all.
 

Thehack

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Thanks. So will using the 500w Meanwell require monster size wire on the dc output? Looks like around 8awg wire will be needed to handle the 500w, 12v, 40 amp output? There are only two terminals on the output... V+ and V-, so it's not even distributed at all.

No. You don't need 8AWG, not sure if there are misconceptions out there with using the right gauge--8awg is huge. You're likely not using 500W continuous, I can't imagine most builds requiring that much. If you are then you need 500/12 = 42A. A 12 AWG pair can handle it (https://www.powerstream.com/Wire_Size.htm). You can also use 2x 14 AWG.

If you want to keep it simple, use high quality bullet connectors, instead of something fancy like aviation connectors.

Aviation connectors means you'll have to figure out a reliable way of splitting 1-2 wires to 6 wires. So either a PCB, some very clean soldering, or distribution block.
 
Last edited:

aquelito

King of Cable Management
Piccolo PC
Feb 16, 2016
952
1,122
Thanks. So will using the 500w Meanwell require monster size wire on the dc output? Looks like around 8awg wire will be needed to handle the 500w, 12v, 40 amp output? There are only two terminals on the output... V+ and V-, so it's not even distributed at all.

From Meanwell EPP-400-12 manual :




However, ripple is a bit too high on this unit and I am not sure the One2 board can handle a 500W load ?

Aviation connectors means you'll have to figure out a reliable way of splitting 1-2 wires to 6 wires. So either a PCB, some very clean soldering, or distribution block.

Butt connectors ?
 

Valantar

Shrink Ray Wielder
Jan 20, 2018
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From Meanwell EPP-400-12 manual :

Isn't that a bit odd, having a blanket wire gauge recommendation that doesn't take wire length into account? I guess it's rare using a unit like this very far from the power sink though, at least for the most common use cases, but it still sounds odd to me. And if 6mm2/8AWG is recommended for 40A, won't 6 1mm2/16AWG wires do the same job? Or four 1.5mm2/16AWG? Guess it could be tricky connecting them all, but it might be easier to get a hold of and work with.
 

Thehack

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Seems that meanwell recommendation is extremely conservative. It is two sizes over what is recommended.

If you compare the cross section, yeah you can spec your wires using multiple ones.

You just need to make sure your screw terminals are stacked and spaced properly with solid contacts between them.
 
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SpaceTofu

Caliper Novice
Jun 18, 2019
21
11
I hope someone here can guide me.
I have a low power ITX system powered by a picoPSU-150-XT.
My system really uses 80W maximum at full load, but I like knowing that the motherboard is supplied by the extra 4 pins of the EATX connector.

I was looking at getting a Meanwell as a AC/DC as right now I have a cheap one.
Can anyone help me discern between all of the different product ranges out there?

PFC, UHP, U-bracket, HEP, it is all quite confusing and an information overload for your average user. I only know to look that the AC/DC should have PFC, what else should guide my choice?
I am looking intothe 100/120W bracket.
Thanks
 

smitty2k1

King of Cable Management
Dec 3, 2016
967
492
I hope someone here can guide me.
I have a low power ITX system powered by a picoPSU-150-XT.
My system really uses 80W maximum at full load, but I like knowing that the motherboard is supplied by the extra 4 pins of the EATX connector.

I was looking at getting a Meanwell as a AC/DC as right now I have a cheap one.
Can anyone help me discern between all of the different product ranges out there?

PFC, UHP, U-bracket, HEP, it is all quite confusing and an information overload for your average user. I only know to look that the AC/DC should have PFC, what else should guide my choice?
I am looking intothe 100/120W bracket.
Thanks
You want something from the EPP or RPS range if you're doing an internal AC/DC. Make sure it is a 12v model if you're combining with the PicoPSU, as the run on 12v (unlike HDPlex which uses 19v). Meanwell recently released this tiny one: https://www.meanwell.com/newsInfo.aspx?c=1&i=726.
Otherwise the EPP-100-12 should be easy to source: https://www.meanwell-web.com/en-gb/ac-dc-single-output-open-frame-power-supply-output-epp--100--12
 

Valantar

Shrink Ray Wielder
Jan 20, 2018
2,201
2,225
I hope someone here can guide me.
I have a low power ITX system powered by a picoPSU-150-XT.
My system really uses 80W maximum at full load, but I like knowing that the motherboard is supplied by the extra 4 pins of the EATX connector.

I was looking at getting a Meanwell as a AC/DC as right now I have a cheap one.
Can anyone help me discern between all of the different product ranges out there?

PFC, UHP, U-bracket, HEP, it is all quite confusing and an information overload for your average user. I only know to look that the AC/DC should have PFC, what else should guide my choice?
I am looking intothe 100/120W bracket.
Thanks
What are you looking for in terms of form factor? Internal? External? If internal, are you comfortable with open-frame (with its inherent risk of shorts and electrocution if one isn't careful), or do you want something enclosed?

The EPP-120S-12 mentioned by @smitty2k1 above looks to be the best low-wattage AC-DC unit MW makes (tiny, high efficiency (>88% even at 12W!), excellent specs otherwise) but it only exists in an open-frame version.

If you want something more closed off the RPS-200-12-C is relatively widely used, though it is larger than the 120S above.
 
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SpaceTofu

Caliper Novice
Jun 18, 2019
21
11
Thamks @smitty2k1 and @Valantar

Indeed to clarify.
I need the DC side of it to be 12V
I am looking for internal, as small as it can be but it is not an utmost requirement.
I would prefer something enclosed for safety, but then I wouldn't mind building my own enclosure in aluminium.

The EPP-120S-12 seems to then be a good option, >88% at 12W is very appreciated (my system is in idle most of the time and the load @ idle is 20/30W)
I think I stumbled in the EPP-120S-12 in some other posts in this thread, I literally couldn't believe it was so small and I parked away the information under the brain category of "too good to be true, probably not suitable" ?
 

Valantar

Shrink Ray Wielder
Jan 20, 2018
2,201
2,225
Thamks @smitty2k1 and @Valantar

Indeed to clarify.
I need the DC side of it to be 12V
I am looking for internal, as small as it can be but it is not an utmost requirement.
I would prefer something enclosed for safety, but then I wouldn't mind building my own enclosure in aluminium.

The EPP-120S-12 seems to then be a good option, >88% at 12W is very appreciated (my system is in idle most of the time and the load @ idle is 20/30W)
I think I stumbled in the EPP-120S-12 in some other posts in this thread, I literally couldn't believe it was so small and I parked away the information under the brain category of "too good to be true, probably not suitable" ?
I believe @Thehack brought it up a few pages back. I looked over the specs when I came across their posts, and it looks like a fantastic little unit. Great ripple/noise (MW's test report says something like 35mVp-p IIRC, which is very good), good hold-up time, good rise time, great efficiency, and lots of protections.
 
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SpaceTofu

Caliper Novice
Jun 18, 2019
21
11
Fantastic! Thank you @Valantar , will read into it a bit more, but I think my made is made up.
Out of curiosity, where do you source from the info that the efficiency is >88% even at 20W?
In the tech sheet released by Meanwell I just find typical efficiency.

I see it also has an over-temperature protection which is great, since my system is almost fanless!
 

Valantar

Shrink Ray Wielder
Jan 20, 2018
2,201
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Fantastic! Thank you @Valantar , will read into it a bit more, but I think my made is made up.
Out of curiosity, where do you source from the info that the efficiency is >88% even at 20W?
In the tech sheet released by Meanwell I just find typical efficiency.

I see it also has an over-temperature protection which is great, since my system is almost fanless!
It's from the test report that MW publishes for each of their products, which covers testing of every single spec of the unit, including function tests for the various protections etc. Efficiency testing is point 7 on page 4, you can see they start testing at 10% load where it is somewhat above 88%, hitting 92% at 30% load and staying at 93% for anything above that.
 

SpaceTofu

Caliper Novice
Jun 18, 2019
21
11
Hi,

I received today the MeanWell EPP-120S-12 and all the components. All nice and well, besides that I ordered 16AWG wires instead of 18AWG.


So I temporarily hooked everything up - as it is a temporary assembly I didn't really heatshrink much and didn't prepare the earth cable. I didn't achieve the best crimpings but haven't done it in decades and also the thicker wires didn't help. I should receive the thinner ones tomorrow and I hope the crimps will look much smarter.


All decent enough and well, however..

...if I stand close enough to the MeanWell, it emits an intermittent high frequency noise / whirring.
Has anyone had that with this or other MW units?

I would like to mention a big thanks to @Thehack for writing the guide and @toddwas for the lovely diagram.
And still thanks to @Valantar and @smitty2k1 for the recommendation of this little unit, I am really loving it! (that is, besides this faint noise ? )
 

smitty2k1

King of Cable Management
Dec 3, 2016
967
492
Hi,

I received today the MeanWell EPP-120S-12 and all the components. All nice and well, besides that I ordered 16AWG wires instead of 18AWG.


So I temporarily hooked everything up - as it is a temporary assembly I didn't really heatshrink much and didn't prepare the earth cable. I didn't achieve the best crimpings but haven't done it in decades and also the thicker wires didn't help. I should receive the thinner ones tomorrow and I hope the crimps will look much smarter.


All decent enough and well, however..

...if I stand close enough to the MeanWell, it emits an intermittent high frequency noise / whirring.
Has anyone had that with this or other MW units?

I would like to mention a big thanks to @Thehack for writing the guide and @toddwas for the lovely diagram.
And still thanks to @Valantar and @smitty2k1 for the recommendation of this little unit, I am really loving it! (that is, besides this faint noise ? )

Nice! It's so tiny!

I've never put my ear next to my Meanwell 200w. I certainly never hear it in normal use (inside a case, a few feet away)