leandroid
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Joined: Wed Sep 19, 2018 6:34 pm

Guide on powering Raspberry Pi 3 B+ with ATX PSU?

Wed Sep 19, 2018 6:46 pm

Hello everyone,

I'm planning to use a Raspberry Pi 3 model B+ with the OctoPi OS to handle my 3d printer jobs.
Since the printer has a heated bed, it is already being fed using a 500W ATX PSU. Thought I might as well use it to supply the power to the Raspberry Pi 3 B+ (that has been bought and is underway).
Problem is that I have NO knowledge whatsoever of electronics so I dont even know where to start?

I've read a few forum posts, and the idea seems possible, but I haven't found any guide that can tell me what to do considering I'm a newb.

Does anyone know of any resources that could show me how exactly to do that? Or where I can learn how to figure out how, so that I can maybe do a beginner-friendly guide in return (to give back to the community)?

Thanks in advance!

pcmanbob
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Location: Mansfield UK

Re: Guide on powering Raspberry Pi 3 B+ with ATX PSU?

Thu Sep 20, 2018 3:26 pm

Hi.

First off it would depend on how stable the 5v supply is on your ATX psu and then else is using it , as if you are driving motors from it you could find its subject to sudden voltage dips which your pi wont like.

Second how you actually connect this to the pi will depend on how the ATX psu has been modified to work with the 3d printer, as we don't know this we can say how you would make the connection.

Unless you can provide a lot more detail on what cables or output options are available on the ATX psu its going to be impossible for anyone to give you precise instructions on how to do this.

The basic idea is to take a 5V and ground cable from your ATX psu from some thing like a Molex 4 pin power supply connector and wire them to a micro usb plug so that you can connect it to your pi.
Red being 5v.
Black being ground.

You need to understand how your ATX psu is connected and being used by your 3d printer before attempting to connect the pi to it or you risk damaging your pi, you also need to do your own testing to prove the 5v output from the ATX psu is suitable.
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seanspotatobusiness
Posts: 151
Joined: Tue May 22, 2012 11:19 pm

Re: Guide on powering Raspberry Pi 3 B+ with ATX PSU?

Thu Sep 20, 2018 4:57 pm

pcmanbob wrote:
Thu Sep 20, 2018 3:26 pm
The basic idea is to take a 5V and ground cable from your ATX psu from some thing like a Molex 4 pin power supply connector and wire them to a micro usb plug so that you can connect it to your pi.
Red being 5v.
Black being ground.
This is exactly how I power my Raspberry Pis. I bought the microUSB plugs on AliExpress and after soldering, added a little hot glue before closing the plug casing to relieve strain on the solder joints. They might also have been crimped with pliers; I can't remember.
Raspberry Pi 3 B and B+
PRETTY_NAME="Raspbian GNU/Linux 9 (stretch)"
NAME="Raspbian GNU/Linux"
VERSION_ID="9"
VERSION="9 (stretch)"

leandroid
Posts: 2
Joined: Wed Sep 19, 2018 6:34 pm

Re: Guide on powering Raspberry Pi 3 B+ with ATX PSU?

Thu Sep 20, 2018 5:54 pm

pcmanbob wrote:
Thu Sep 20, 2018 3:26 pm
Hi.

First off it would depend on how stable the 5v supply is on your ATX psu and then else is using it , as if you are driving motors from it you could find its subject to sudden voltage dips which your pi wont like.

Second how you actually connect this to the pi will depend on how the ATX psu has been modified to work with the 3d printer, as we don't know this we can say how you would make the connection.

Unless you can provide a lot more detail on what cables or output options are available on the ATX psu its going to be impossible for anyone to give you precise instructions on how to do this.

The basic idea is to take a 5V and ground cable from your ATX psu from some thing like a Molex 4 pin power supply connector and wire them to a micro usb plug so that you can connect it to your pi.
Red being 5v.
Black being ground.

You need to understand how your ATX psu is connected and being used by your 3d printer before attempting to connect the pi to it or you risk damaging your pi, you also need to do your own testing to prove the 5v output from the ATX psu is suitable.
Thanks for the answer, pcmanbob!

My PSU is a Corsair CX500, feeding the 3d printer heated bed via the PCI-E power connector. No modifications whatsoever were needed to supply the printer via the PSU, I only connected the cable and it works.

I've read a few times also about the 5VSB line from a 20-24 pin motherboard connector? Also that there is a way to shortcut some wires so that the PSU is always able to deliver the 5V from this line and not only when it's on standby?

The PSU has the following DC output cables:

- 1 motherboard 20+4 pin
- 1 CPU 4 x 4 pin
- 2 PCI-E 6+2 pin
- 4 peripheral (molex) 4 pin
- 5 Sata 5 pin connector
- 1 floppy power

pcmanbob
Posts: 4364
Joined: Fri May 31, 2013 9:28 pm
Location: Mansfield UK

Re: Guide on powering Raspberry Pi 3 B+ with ATX PSU?

Thu Sep 20, 2018 6:09 pm

I don't believe you are only using the pci-e connector because you would also need to used 2 connections on the 24 pin motherboard connected to switch the ATX PSU on.

If you not using the 5v output of the ATX PSU then it may be very unstable as the voltage regulation requires some load before it can work reliably.

As I said you need to do your own tested to decide if you ATX PSU is stable enough to power your pi.
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Imperf3kt
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Location: Australia

Re: Guide on powering Raspberry Pi 3 B+ with ATX PSU?

Thu Sep 20, 2018 10:58 pm

Personally, I'd use one of the +12v lines (should be a yellow wire) and ground to power a suitable UBEC or other step down switch mode regulator.

You'll need to short two of the wires on the 20*2 connector so the PSU turns on, but I can't remember off the top of my head which ones.
User experiencing technical difficulties.


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davidcoton
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Location: Cambridge, UK

Re: Guide on powering Raspberry Pi 3 B+ with ATX PSU?

Fri Sep 21, 2018 3:44 pm

Or have a look at this (Disclaimer: not tested by me.)
"Thanks for saving my life." See https://www.raspberrypi.org/forums/viewtopic.php?p=1327656#p1327656
“Raspberry Pi is a trademark of the Raspberry Pi Foundation”

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