ItBeGary
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Custom Power for multiple PI's

Tue Oct 23, 2012 11:39 pm

We're looking at setting up a stack of PI's (when the backorder is finally filled). We are looking to run somewhere around 30 of them for a project (plus another 10 with external drives for storage). We're assuming that these will not be overclocked and each one will be running at 100% for 50% of the day.

I understand that it's ideal to run [email protected] regulated. Browsing the forums and other sites that talk about running multiple PI's seem to run each one on a seperate AC/DC power adapter.

My first throughts are that this is probably the most inefficient way to run several of them as there is some power loss on each of the adapters.

I was thinking of having an engineering friend whip up a simple regulated 200-400w PS, which should be overkill for a stack of 30. The other 10, with USB drives (SSD's) will have thier owe power, but it would be nice to wrap these into a consolidated power supply as well.

Before I do all of this and possibly reinvent the wheel, has anyone approached this problem and do they have a solution?

Is there any other recommendation on how we should approach this?

And yes, I'm aware that my Sun X4150 out powers this entire stack. This is what the user has asked and paid for ;)

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Lob0426
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Re: Custom Power for multiple PI's

Wed Oct 24, 2012 12:09 am

If you are running the Raspii without any USB devices then they run just fine on as little as 500ma PSU. My server runs with a 500ma PSU.

For the 10 with SSD's you should be able to run them directly from the RasPii if you either jumper the 750ma polyfuses or replace the polyfuses with a 1A or 1.1A piece(size 1812). I reccomend replacing the fuses. You may get lucky and they will run directly from the Raspii without any modification at all. It depends on what adapter you use to go from USB to SATA. Some of the adapters are power hungry, and how long their cable is. When looking for a USB to SATA adapter for the RasPi, shorter is better.

If you build a unified power system, rather than using 30 seperate wall plugs, it will be more efficient. again keep cable lengths as short as you can.

I am using a USB to SATA adapter on 2 of my RasPii. They run at about 4 watts but need about 5watts to spin up. The SSD's do not have a spin up.

SSD's with adapters probably will equal about 3 watts (600ma) apiece
Raspi's equal about 3 watts (600ma) under load.

10 SSD's = about 30 watts but go 50 watts to be safe.
30 RasPi's = 90 watts but go for about 120 watts to be safe.

So you need about 170 watts at 5V to power it all with some safety margin.
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elatllat
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Re: Custom Power for multiple PI's

Wed Oct 24, 2012 12:37 am

you could use a psu from a normal x86
SBC with 32GB RAM: https://hardkernel.com

FAQ : https://raspberrypi.stackexchange.com

Unanswered: https://www.raspberrypi.org/forums/search.php?search_id=unanswered

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Lob0426
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Re: Custom Power for multiple PI's

Wed Oct 24, 2012 2:34 am

elatllat wrote:you could use a psu from a normal x86
You would have to use a way over powered PSU to get enough output on the 5V rail. A 5V bench supply would be a better option. You are talking about a steady draw of at least 120 watts. 5V x 1A = 5watts, thats 24A draw!.
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ItBeGary
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Re: Custom Power for multiple PI's

Wed Oct 24, 2012 3:17 pm

That was my thought as well. I did think breifly about using a ATX PSU but then I validated the specs and found the 5v amp limitation.

I didn't even think about looking into bench power supplies. I know there's a couple sites that have them.


ItBeGary
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Re: Custom Power for multiple PI's

Wed Oct 24, 2012 4:29 pm

That would work. I'm figuring overkill so I can do the USB drives as well, so the 200W version (still under $50USD) seems to be a good option. Looks like I'll have to make some custom power cables though, but this should do it.

http://www.jameco.com/webapp/wcs/stores ... _202042_-1

Thanks eveyone for assistance. Sometimes you're too focused on the problem and don't realize the solution is already out there (and that you already know about it).

Levaillant
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Location: France, Paris

Re: Custom Power for multiple PI's

Wed Oct 24, 2012 6:57 pm

Why don't you use the GPIO for feeding all your RaspBerryPi's?
It's a simple way to do it with just a ribbon cable...

Just for my curiosity, what are you trying to do... a cluster?
Cheers

ItBeGary
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Re: Custom Power for multiple PI's

Wed Oct 24, 2012 7:30 pm

Levaillant wrote:Why don't you use the GPIO for feeding all your RaspBerryPi's?
It's a simple way to do it with just a ribbon cable...

Just for my curiosity, what are you trying to do... a cluster?
Cheers
TBH, I'm not sure what the final purpose of these will be, but some clustering will progably be going on. They have been purchased, I've been asked to install them. In the end, I could have just spun up 32 instances on my Sun X4250, but I think this is about component level usability testing, and communication.

As for using a ribbon for the headers, wouldn't this be more of a wiring nightmare than having some custom length micro usb cables and a consolidated power supply?

Levaillant
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Re: Custom Power for multiple PI's

Thu Oct 25, 2012 4:43 am

http://www.southampton.ac.uk/~sjc/raspb ... ampton.htm
See at it the end of this page the photo of the wiring with ...

With one ribbon cable, you should be able to feed more than just one RPi...
My english is poor, so i'm not able to explain myself better sorry...

ItBeGary
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Re: Custom Power for multiple PI's

Thu Oct 25, 2012 5:34 pm

Levaillant wrote:http://www.southampton.ac.uk/~sjc/raspb ... ampton.htm
See at it the end of this page the photo of the wiring with ...

With one ribbon cable, you should be able to feed more than just one RPi...
My english is poor, so i'm not able to explain myself better sorry...
I think I understand what you are saying. When I think of "ribbon" cable, I thinking of the old parallel style header cables. So yes, I can make a set of continuous cables that branch of each other having few leads, which might make sense from a cable management perspective. I'm not sure what the final design will be though.

I emailed the guy that created that cluster and got some information from him regarding his power requirements (and the logic for using single connectors).

Anyway, thanks for all of the feedback. I'm going to hopefully order the 5V power supply this week and get it wired so when the PI's come in I'll be ready to go. The cable(s) should only take a day to make, once I get those parts in.

s1ck
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Joined: Mon Jul 28, 2014 4:15 pm

Re: Custom Power for multiple PI's

Mon Jul 28, 2014 4:21 pm

Hi,
I'm also interested in building a cluster of raspberry / banana pi nodes and I am currently thinking about the power supply. Could you maybe write a bit about your experiences with the stated power supply and what extra work (the adapter cables) you had to to. Would be very interested in that! Thanks.

ertresvag
Posts: 39
Joined: Sun Oct 27, 2013 1:04 pm

Re: Custom Power for multiple PI's

Tue Aug 05, 2014 2:04 am

I found a 300W 5V powersupply on Ebay, Yes, that's 60A. That is more than I need for my little cluster which has only 10 RPi.
So try Ebay and see what you can find,

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AndrewS
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Re: Custom Power for multiple PI's

Tue Aug 05, 2014 2:10 am

Obviously sucking 60Amp through cables that are too thin could make things start to get a bit 'warm' ;)

spoonsphere
Posts: 4
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Re: Custom Power for multiple PI's

Fri Aug 08, 2014 1:34 pm

Hello!

I'm curious what you did for wiring multiple Pi's from that power supply.

Thanks so much!

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