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Author Topic: Alternative power supplies  (Read 27952 times)
westyd1982
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« Reply #15 on: September 02, 2009, 10:00:05 PM »

I'm very curious about what 5V regulator you're using that can handle the current draw of the Sheeva and the USB dongles you've got on it.

I've been running a Linksys NSLU2 as a small web and weather server 24/7 from a solar-charged 12v battery system, and plan to replace it with my new Sheeva Plug (The plug looks like it draws more power that the slug, but I haven't tested it yet).  I tried a number of power supply options for the NSLU2 (see http://www.nslu2-linux.org/wiki/HowTo/MakeABatteryPoweredSlug and scroll down to Powering a NSLU2 from a 12 Volt Battery).

I ended up using a very small, high-efficiency Murata Power Solutions 78SR 2 Amp Series that I bought from mouser.com.  I added part of a small circuit board, an electrolytic capacitor, and some terminal blocks.  The cost of the parts was less than $20 US.  I just need to build a cable to go from my power supply to my Sheeva Plug board, then I will run some tests and post the results.

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westyd1982
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« Reply #16 on: September 03, 2009, 10:26:49 PM »

I built a cable to go from my SheevaPlug (v1.3) to my solar powered 5v power supply.  I ran a few test with my multimeter measuring the current.  When the plug is on with nothing connected and at the marvell prompt, it draws 0.61A (3.05 Watts).  With the mini-USB, ethernet, and an SD card it draws 0.7A (3.5 Watts) at the marvell prompt.  When the system is booted up into Debian on the SD card, mini-USB connected, and ethernet connected and idling, it draws 0.41A (2.05 Watts).  When actively doing something, it draws a maximum of around 0.77A (3.85 Watts).  I am using the following kernel that was updated on Debian: Linux sheevaplug 2.6.30-1-kirkwood.  This is a lot less power than I guessed it would draw. 


* plugtestingmarvellprompt.JPG (266.01 KB, 1024x909 - viewed 1600 times.)

* plugtestingdebianidle.JPG (280.18 KB, 1024x930 - viewed 1610 times.)
« Last Edit: September 05, 2009, 08:40:45 PM by westyd1982 » Logged

DamonHD
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« Reply #17 on: September 04, 2009, 09:07:41 AM »

Hi,

I've just bought one of these:

http://www.maplin.co.uk/module.aspx?moduleno=115314

(A79GW, 3A 1.5V -- 12V DC-DC converter from 12V or 24V in.)

to run my new plug from my little 120Wp (12V nominal) off-grid solar, presumably at the 5V setting.

Haven't got any further than setting up converter yet, and I suspect its own draw maybe higher than I want given that for example I can't turn off the backlight, but never mind for now...

FWIW, I'll be writing up here:

http://www.earth.org.uk/note-on-SheevaPlug-setup.html

but it's going to take me several weeks to have enough time together to get to a working state!

Still, I may be able to shave another 0.5kWh/day off my mains-electricity consumption if I get it right.

Rgds

Damon
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diarmuidw
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« Reply #18 on: September 05, 2009, 08:04:46 AM »

westyd1982,

Those are nice numbers and go to show how much power (and heat) is created by the internal transformer.

Are these numbers pure 5 volt consumption or do they include some sort of voltage conversion.

3 to 4 watts is doable form a lithium polymer battery

Cheers

Diarmuid
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westyd1982
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« Reply #19 on: September 05, 2009, 09:43:41 AM »

westyd1982,

Those are nice numbers and go to show how much power (and heat) is created by the internal transformer.

Are these numbers pure 5 volt consumption or do they include some sort of voltage conversion.

3 to 4 watts is doable form a lithium polymer battery

Cheers

Diarmuid

Diarmuid -

These numbers are all at 5 volts, so amps*5 volts=watts.  I've been running my plug off my battery bank for a day or so and it is just slightly warm.  I also have half the case off right now.  I do think the internal AC power supply does create a fair amount of heat.  I plan on drilling a hole in the side of the power supply-side of the case and installing a dc power jack.  Then I can put the case back together.  I will then have a choice of switching between AC or DC power by only having to open the case and switch which plug goes into the board (although since it works well, I will probably only run it from the DC supply).

- Tom
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westyd1982
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« Reply #20 on: September 05, 2009, 08:38:00 PM »

Attached are a few photos of adding an external DC jack and cable to power my plug.


* plugbuildingpowercable.jpg (275.43 KB, 1024x685 - viewed 1648 times.)

* plugwithhole.JPG (174.59 KB, 1024x942 - viewed 1734 times.)

* pluginstallingdccable.JPG (337.59 KB, 1024x1087 - viewed 1654 times.)

* plugwithdcjack.JPG (172.06 KB, 1024x845 - viewed 1664 times.)
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westyd1982
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« Reply #21 on: September 05, 2009, 08:39:42 PM »

Attached is the assembled plug.


* plugassembledwithdcjack.JPG (154.54 KB, 1024x885 - viewed 1610 times.)
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CqCn
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« Reply #22 on: September 07, 2009, 01:42:17 PM »

I must have missed it.  What is the voltage you are supplying to this dc socket for powering the plug?
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Cordially, CqCn

westyd1982
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« Reply #23 on: September 07, 2009, 03:40:47 PM »

I must have missed it.  What is the voltage you are supplying to this dc socket for powering the plug?

5 volts
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DamonHD
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« Reply #24 on: September 14, 2009, 07:03:35 AM »

OK, got my stuff running off solar, and hope to keep it that way from now on!

(I'll have to put it back on mains when using the serial console from my also-solar-powered Linux laptop/server to avoid some unpleasant earth loops the way I have things set up now.)

Consumption is ~2.6W minimum up to ~4.1W when all the stuff is plugged in that I need for an idle machine!  Fab considering that I haven't been able to get the laptop/server down below about 4x that when idle!

Rgds

Damon

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DamonHD
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« Reply #25 on: September 15, 2009, 11:26:28 AM »

Well, today has been gloomier than the average for mid-December as measured by the energy collected by my grid-tie PV, and although I've been using the Plug fairly heavily (consumption up to ~5W building and running my Java app) the battery level is OK.  So I think I should be OK even mid-winter if I'm careful.

Rgds

Damon
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mojoRisin
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« Reply #26 on: September 30, 2009, 10:02:20 AM »

Hi,

Can someone provide a part number / manufacturer for the AC to DC supply used in the Sheevaplug? I checked the reference design, schematics and BOM but did not see the power supply module part number listed. I'm trying to figure out how much power is consumed by the module itself, its efficiency, cost, etc.

Thanks!
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DamonHD
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« Reply #27 on: November 26, 2009, 12:49:34 PM »

After a run of really crappy days I had to put the plug back on mains but I gave my batteries a break for a few days and got them fully charged and (so far as I know) happy, and put the SheevaPlug back on off-grid solar.

Today I also put in a little DPPT toggle switch in the power lines so that if the batteries run low I (or someone else with instruction) can flip to the original switch-mode mains supply and have the SheevaPlug run from that (albeit in minimal power ~4W mode).  The mains adaptor is plugged in ready but switched off to save its 'vampire' 0.8W unloaded draw.

(I've split the plug into the computing bit which can take its 5V from either my 12V to 5V converter or the now-physically-separate Sheeva power supply.)

I may be going to help with some wind farm prospectors for a few days shortly so I can flip it over to mains before I go and not worry about running out of solar juice again while I'm away.

Or I can let it ride and have my other half flip things over if the batteries fade.

Decisions decisions...  Should I tempt Murphy?

Rgds

Damon
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evoke
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« Reply #28 on: February 25, 2010, 01:52:01 PM »

Hey guys,
              I think this the best project and i can not believe the guys that designed it did not think of it.

How is the sheeva plug now after being off the mains. Did it last long.

I have a 6W solar panel with a 7Ah battery.  I have not got a 12V to 5V regulator which i will have to look up.


Has anyone got a similar project like this?
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