Power Supply A Guide to 12V PSU

[Supercluster]

The problem when wired in series is not the connection itself but further downregulation of voltage requiring more space, weight, cables... If the PSU-s logic does not freak out it works as advertised- two x PSU = 2 x voltage. Same when you put two batteries in a flashlight.

 

[Choidebu]

Yeah I'm just really wondering the electrical aspect of it - mind you my knowledge of ac dc converters is limited to old school transformers and bridge rectifiers.. say, things would go awry if, for example, internally the design is first to step down mains ac to less than 24VAC? Hoah I don't know.....

 

[Thehack]

Yeah I'm just really wondering the electrical aspect of it - mind you my knowledge of ac dc converters is limited to old school transformers and bridge rectifiers.. say, things would go awry if, for example, internally the design is first to step down mains ac to less than 24VAC? Hoah I don't know.....

There are a couple ways to do AC-DC. You don't necessarily have to step down the incoming voltage if you're using a power switching circuit.

120VAC> rectified and filter > power switched > isolation transformer (or step down) > rectification > filter

Think of power switching as like PWM, where the output is an average.

 

[Thehack]

The problem when wired in series is not the connection itself but further downregulation of voltage requiring more space, weight, cables... If the PSU-s logic does not freak out it works as advertised- two x PSU = 2 x voltage. Same when you put two batteries in a flashlight.

Correct. Most industrial psu we use work fine in series, but as always consult the manual.

 

[Choidebu]

Yeah makes sense... as long as it gets to dc as soon as it can then I suppose having another psu's output as your ground ref won't be catastrophic...

But still you'd isolate the second one's case right? It might be grounded..

 

[Thehack]

Yeah makes sense... as long as it gets to dc as soon as it can then I suppose having another psu's output as your ground ref won't be catastrophic...

But still you'd isolate the second one's case right? It might be grounded..

Most AC-DC don't have the DC side grounded. It is isolated from the AC side.

You'd never isolate an internal AC-DC power supply. External maybe, but most external above 120W are grounded.

 

[Choidebu]

Thanks @Thehack , I learned something new today!

 

[smitty2k1]

Most AC-DC don't have the DC side grounded. It is isolated from the AC side.

You'd never isolate an internal AC-DC power supply. External maybe, but most external above 120W are grounded.

So on a scale of 1-10 how bad is it that I used a 2 terminal plug (C8p) with no ground for my MeanWell 200w?

 

[Thehack]

So on a scale of 1-10 how bad is it that I used a 2 terminal plug (C8p) with no ground for my MeanWell 200w?

Depends on what the case is. For example the PS4 doesn't have a ground, but the case is made of plastic and is isolated from the power supply. The air vents are positioned in a way that makes it difficult to access the inside.

If it is a bare metal chassis:1
If it is an anodized/powder coat but well ventilated case:4
If it is an industrial passive case:8 (not bad at all)
If it is completely non conductive, isolated chassis, double isolated power supply: 10 just dandy

 

[smitty2k1]

Depends on what the case is. For example the PS4 doesn't have a ground, but the case is made of plastic and is isolated from the power supply. The air vents are positioned in a way that makes it difficult to access the inside.

If it is a bare metal chassis:1
If it is an anodized/powder coat but well ventilated case:4
If it is an industrial passive case:8 (not bad at all)
If it is completely non conductive, isolated chassis, double isolated power supply: 10 just dandy

Interesting, yup it's just slapped on my anodized computer case. I looked at my PS3 and that's why I went with the C8 connector. Guess I'll be buying a C5 and re-wiring this weekend!

 

[Chia]

Does any one know which chip is suitable for making a load switch with a 4-500W 12V power supply?
or maybe a car relay will be fine?

 

[DwarfLord]

Hello @Thehack,

a small question to the master of meanwell and 12v, if I may ^^

It's concerning the connection between a meanwell 200w and a picopsu-160-xt.
From the pico, on the molex connector, I have 2 awg16 (+ 2 awg22 shorting the 2 remaining contacts).
Would it be better to :
- do the same thing on the other side of the molex (but with awg18+awg22), and so only use two contacts on the jst connector on the other side of the cable connecting on the meanwell (which has a plug with 6 contacts)
- or connect 4 awg18 cables on the other side of the molex and thus also use 4 contacts on the meanwell side ?

If the second solution is better, is it not dangerous for the small awg22 cables on the molex (pico side) ?

Edit with picture :

 

[Thehack]

Hello @Thehack,

a small question to the master of meanwell and 12v, if I may ^^

It's concerning the connection between a meanwell 200w and a picopsu-160-xt.
From the pico, on the molex connector, I have 2 awg16 (+ 2 awg22 shorting the 2 remaining contacts).
Would it be better to :
- do the same thing on the other side of the molex (but with awg18+awg22), and so only use two contacts on the jst connector on the other side of the cable connecting on the meanwell (which has a plug with 6 contacts)
- or connect 4 awg18 cables on the other side of the molex and thus also use 4 contacts on the meanwell side ?

If the second solution is better, is it not dangerous for the small awg22 cables on the molex (pico side) ?

Edit with picture :

Your picture can't be viewed, but I would connect 4 pins on the JST to 4 pin Mini Fit Jr to connect to the 160XT. I would not call them "molex" because molex is the name of the company that designed them. "Molex" is used colloquially for this particularly type of connectors:

The 4 pin you're talking about is called Mini Fit Jr:

What you need, instead of 4pin Mini Din to Mini Fit JR adapter above, you need the 6pin JST to 4 pin Mini Fit. 4 wire should be connected. I recommend you use 18AWG for the 4 wires.

 

[DwarfLord]

Your picture can't be viewed

Oh ? Strange, I used imgbb as stated in a post I found here https://smallformfactor.net/forum/threads/free-online-image-storing-site.7461/
Edit : Is it ok now ?


Nonetheless, you understood my question perfectly, so that's good ^^ (and you're correct about my abuse of the molex term, bad habits I suppose, ahah)
So no danger at all for the small awg22 cable ? On your picture, the "shorting" seems to be done with an awg18 cable too, but it's not the case on my 160-xt (nor on my 120-WI-25V). Sorry for all those questions, but I would'nt want to overload the awg22 cable :/

 

[Thehack]

Oh ? Strange, I used imgbb as stated in a post I found here https://smallformfactor.net/forum/threads/free-online-image-storing-site.7461/
How did you insert yours ? They seem to be hosted directly on the forum server ?

Nonetheless, you understood my question perfectly, so that's good ^^ (and you're correct about my abuse of the molex term, bad habits I suppose, ahah)
So no danger at all for the small awg22 cable ? On your picture, the "shorting" seems to be done an awg18 cable too, but it's not the case on my 160-xt (nor on my 120-WI-25V). Sorry for all those questions, but I would'nt want to overload the awg22 cable :/

I recommend uploading to imgur.com as a host instead, if you have access to it.

1. Leave the connector as stock. Don't worry about it.

2. For the new connector you are making, 6pin JST to 4 pin mini fit Jr use 4 individual wires, use 4 pins for both sides. No "shorting." use the second diagram for making your connector.

I would also avoid the term shorting as it implies an unintended circuit. I do understand what you mean.

Most people indicate that as 2+2 or a jumped wiring.

I wouldn't worry about unless your build pulls over 150W.

 

[DwarfLord]

I recommend uploading to imgur.com as a host instead, if you have access to it.

1. Leave the connector as stock. Don't worry about it.

2. For the new connector you are making, 6pin JST to 4 pin mini fit Jr use 4 individual wires.

I've changed the link to the picture. I'll will change it to imgur if it's still not working correctly.

1. ok, perfect

2. I already have all the necessary parts (even the engineer tool ^^), so I'm good to go !

Jumped wiring, duly noted !

It's for a 2400G at stock clock, so it will never go that high.

Anyway, thanks a lot !

 

[toddwas]

I'm doing a build with the 'MeanWell EPP-200-12' + 'PicoPSU 160XT' using this thread's guide and Thehack mentioned I should post the visual diagarams I hacked together to help others with the cables. I'm an electrical n00b so it might help others in my position.

Here it is: https://******/f6LKJZ [v0.5 - 250kb PDF]

Thanks heaps to 'NateDawg72' and 'theHack' for feedback in private.

 

[smitty2k1]

I'm doing a build with the 'MeanWell EPP-200-12' + 'PicoPSU 160XT' using this thread's guide and Thehack mentioned I should post the visual diagarams I hacked together to help others with the cables. I'm an electrical n00b so it might help others in my position.

Here it is: https://******/f6LKJZ [v0.5 - 250kb PDF]

Thanks heaps to 'NateDawg72' and 'theHack' for feedback in private.

That looks great, thanks for sharing

 

[DwarfLord]

I'm doing a build with the 'MeanWell EPP-200-12' + 'PicoPSU 160XT' using this thread's guide and Thehack mentioned I should post the visual diagarams I hacked together to help others with the cables. I'm an electrical n00b so it might help others in my position.

Here it is: https://******/f6LKJZ [v0.5 - 250kb PDF]

Thanks heaps to 'NateDawg72' and 'theHack' for feedback in private.

I'm doing exactly the same combo ! Great guide

 

[teisysadmin]

Hey guys, I'm working on a little PCB to make 12V builds a little easier / intuitive. The intent is that you'll be able to solder an XT90 connector onto the board to bring power in, solder on a 4pin mini fit junior to power up a pico psu, a 4 pin cpu jack you'll plug the Pico's cpu connector to in order to switch a MOSFET on, and space for two 8 pin PCIe power jacks, and one 4/8 pin cpu power connector.

https://www.mouser.com/ProductDetai...hyDBzk1/Wi/D7Em5shE8qLkc5hPl0smFrCq3qpcjopQ==
This mosfet can do up to 69A with power dissipation of 347W, would I be correct in assuming that I should divide 347 by 12 to find the maximum amperage this can handle with 12V? How much wattage could I viably push through this thing without a heatsink? And considering 8 awg only does 50A, how can the tiny little leads on this package possibly hold up to such high amperage?

I'd like to use an XT90 connector. It's pretty big and bulky, but it can handle a ton of amperage for high powered builds. Do you think using an XT90 would make a board like this less helpful for the general community, or would most 12V builders be willing to throw XT90 connectors on their power brick of choice if it means they can use a little distribution board to minimize loose components / awkward connections?

Finally, how much temperature rise should I allow on the board? The more temperature rise I allow, the smaller I can potentially make the board.