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Author Topic: How to power SheevaPlug with AA batteries?  (Read 4387 times)
kveroneau
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« on: September 24, 2010, 08:16:11 PM »

I have read on multiple forum posts that it is possible to power the board with AA/AAA batteries.  Since my plug's power supply has died, popped capacitor unfortunately.  I opened up the casing and noticed how simple the power connector is, and how common it is.  I live in North America, and we have a store here called "The Source", which sells battery enclosures for AA/AAA for electronic projects.  I do not know much about electronics and am not sure which casing to purchase and for how many batteries it should occupy.

Are there any special considerations for connecting the cable to the J3 input?  Which terminals from the batteries should connect to which pins/colors on the J3 input?  I would rather not blow the board from connecting the batteries in the wrong way.

Also, how would one build a USB power supply for the SheevaPlug board?  I would love to use the board much like how the Beagle is used, which is powered by USB power.  I know it cannot be powered from the JTAG microUSB port, but information on how to splice a USB cable and adapt it to the SheevaBoard's J3 input socket would be great.

Thanks.
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dattaway
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« Reply #1 on: September 24, 2010, 11:36:05 PM »

Some things to consider: 1) AA batteries have poor energy capacity.  If they held 1000mAhr, your Sheeva would last one hour.  2) AA batteries are unregulated.  Four AA's will give 6 volts.  Sheeva's likes 5 volts.  Will it boot?  Will it survive?  Will things attatched to the Sheeva's USB bus burst in flames?  3) USB power supplies average about 500mA.  The Sheeva really wants 4-5 times much that current on tap.  Too little current will trip the reset line and reboot.  4) Use the old power suppy connector as your guide.  Red positve, black negative.

But if you are going through all that trouble, I would just replace the toasted capacitor.  Mine tried to explode and got fat, so it was easy to see without testing.
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kveroneau
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« Reply #2 on: September 24, 2010, 11:54:43 PM »

Thank you for your reply.  I guess the Beagle Board uses different components to make it run from a PCs USB host, hmmm.  I was looking into the AA/AAA idea as I have an Open Source Game console, the GP2X, which runs on AA batteries and lasts about 3 hrs or so. Never actually took the time to count how long it lasted.  The GP2X also runs a ARM processor and Linux, but it is clocked much lower(I set it to 200Mhz for most apps) which would explain more battery drain from the Sheeva's ARM processor.

I'll look into either a separate DC adapter or see if a local electronics parts store is able to replace the capacitor or build me a new PSU.  However, I would love it to run from some sort of battery power.  I could change it from a Plug to a handheld Linux system with the proper parts.  USB touchscreen mainly. Cheesy
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Dammuozz
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« Reply #3 on: October 05, 2010, 01:25:00 AM »

if you need to run it on battery you can use a battery pack like rechargeable one...Ni-Mh or Li-Ion or Li-Po...

then put a voltage regulator on it! something like an L200 with one or two hi-power transistor like 2n3055...

I made a power supply from myself with a transformer,  a diode bridge rectifier, two 2n3055 with heatsinks and with two 10w 1ohm resistors, an L200 and some other resistor connected to the L200 to set the voltage reference...and

if you connect a battery you can skip the transformer and the rectifier and that's it!!



dammuozz
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scologic
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« Reply #4 on: October 11, 2010, 03:05:29 PM »

We've got the solution on paper to use a 7.2v 26000 lithium ion cell (off the shelf product) with charger that will run a unit for around 12 - 15 hours.

We've also developed a 10 inch touchscreen version of the plug(tethered currently) which is available to order and can have either a guru standard or a sheeva inside. It's not a light weight tablet tho... more a rugged slab - hence the products name 'the slab'.


sco logic
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bdewacht
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« Reply #5 on: October 14, 2010, 06:18:16 AM »

Quote
I live in North America, and we have a store here called "The Source", which sells battery enclosures for AA/AAA for electronic projects.  I do not know much about electronics and am not sure which casing to purchase and for how many batteries it should occupy.

I had the same problem (living in Canada) I went to KGE and bought a power supply for laptop 5V / 3A (about $15, DLINK I think), highly regulated. Opened up the case of the sheeva, removed the whole power supply, cut the red and black wire and connected to the new power supply (I also bought a female kinch-like plug ($5) so I can easily disconnect it from the laptop power supply).

It has been up and running for three months now, and I am very confident that the new power supply is going to last much longer.
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naugtur
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« Reply #6 on: October 15, 2010, 01:20:54 AM »

Let me point it back to the topic for a moment Wink

I would like to make SheevaPlug work on batteries, but not on daily basis (which has no sense - see post #2) but as a kind of UPS.

Plug would work with normal power support and if unplugged - stay up for 10 minutes on a battery pack. I could use small batteries as the capacity is not an issue.
It would save plug from accidental power outages and moving between sockets reboot.

All is needed is:
 1. a set of small batteries (AAA would fit in the empty spaces in SheevaPlug I guess, but they can hang out Wink )
 2. a tiny piece of electronics to kick in the battery source when the power is out and to keep the parameters good for the plug. (voltage can be reduced AFAIK)
 3. a connector so that when PSU is plugged via the electronics (2) you can plug batteries whenever you want

That's the idea and I'm not an electreonics guy, so good luck. And if I make my friend solder it up for me I'll let you all know Smiley
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Treacewek
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« Reply #7 on: October 18, 2010, 10:42:23 PM »

I dont believe you can the fan would have to support PWM and I have never checked how to measure a fan I usually just find the chassis details online which give you the information.
PS, I'm a happy user of
http://www.ps2netdrivers.net/manual/nec.dterm.ip.8d/
:->
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tubmanaxton
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« Reply #8 on: October 20, 2010, 11:30:10 PM »

If you remove the four plastic "feet" and remove the corresponding screws, the plug splits into two halves, one of which contains the main power supply and the other the main circuit boards. It's just a simple 5V supply with a 4-pin connector, the two red leads being 5V (actually 5.25V measured) and the two black leads being ground.
The power loss depends on the type of 12 to 5 volt regulator / converter used. The 78SR series switching devices have high efficiency. Small DC-DC converters are typically quite efficient too. Ordinary 7805 style devices use an internal series pass transistor, with excess energy being dissipated as heat.
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