Re: [Gumstix-users] 9V Battery Supply for Overo Air//Summit Troubles

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Hi again!

I don't really understand the talk about the TPS65950.
The TPS65950 is the overo internal powermanagment unit, that shouldn't 
borther you in any way (so forget about the 4.xx V to 6V).

The normal Wall-Mount adapter input of the sumit daughterboard connects 
to the TPS62111, with an input voltage range of up to 17V.
That TPS62111 now creates the voltage for the Overo - the needed 3.7V - 
and always 3.7V.
As long as you just add your batteries to the wall-mount input you are 
on the safe side.

There is one problem, that is noticed in the schematics of the summit 
board, that although the TPS62111 allows up to 17V
the capacitor C43 doesn't (most likely due to cost reduction), so you 
will damage only that capacitor if you apply voltages
higher than 5.5V. The trick is, just to remove it. It is good to 
stablize the input voltage, a battery voltage doesn't really need to be 
stablized.

I tried to hook up a single LiPo cell to my chestnut to, but voltage 
broke down to fast an i only got a few minutes (one completed boot) until
my battery was depleted under a treshold where i wasn't able to get 
linux booting any more.

If you don't want to build any special hardware yourself i'd recommend 
you a LiPo Pack with two cells in series (7.4V) - go to ebay and search 
for LiPo 2S
or go to the next store that sells RC controlled hellicopters or such 
things and by a battery charger and a battery. Remove C43 and somehow 
wire the LIPO cell
to the wall-mount input (or solder it to the back of the connector) and 
it will work =) without causing any damage to anything =)
The disadvantage of that solution is, that you need unplug the LiPo Pack 
for recharging.

Regards
Bernhard

Am 27.04.2010 15:42, schrieb Kimberly Turley:
> I appreciate the warnings - luckily I had only had time for about a 
> 30sec test to see if it booted at all.  I would like to fix this, but 
> I am having some trouble understanding:
> 1. What the defining voltage limiter on the board is - is it the DC-DC 
> converter?
> 2. What protections are already in place - C43 seems to play a role, 
> but it is unclear to me exactly what role it plays.
>
> McMurphy - On closer inspection of the summit board schematic 
> http://pubs.gumstix.com/boards/SUMMIT/PCB30001-R2563/PCB30001.pdf, I 
> see that it is supposed to use a TPS61202, which is rated to only 5.5V 
> http://focus.ti.com/docs/prod/folders/print/tps61202.html.  However, 
> when I examined my own board, the only TPSXXXXX I could find was a 
> TPS62111, which is rated to 17V 
> http://focus.ti.com/docs/prod/folders/print/tps62111.html.  Any idea 
> what's going on here, and what the real voltage limit is?
>
> Victhor - Did you add any protections to your circuit, or just hook 
> the 3.7V battery up directly?
>
> Alex - Are those components you can easily get, or are they very 
> specialized and need to be ordered?  And if you are describing a 
> circuit an undergrad engineering student might be able to build out of 
> spare parts//stuff picked up at Radioshack or Digikey, would you be 
> willing to share a circuit diagram of what you've done?
>
> I really appreciate all the help, and any additional advice you all 
> can provide - thank you so much!
> -Kim
>
> On Tue, Apr 27, 2010 at 5:30 AM, R. P. McMurphy <log...@gm... 
> <mailto:log...@gm...>> wrote:
>
>     Oh, sorry for the misinformation.
>
>     In the TPS65950 manual section 3.1 "Absolute Maximum Ratings" It
>     states 4.5V as the peak, not 4.6V. Either way the 6V is way too high
>     to be good for long term reliability.
>
>     On 4/27/10, R. P. McMurphy <log...@gm...
>     <mailto:log...@gm...>> wrote:
>     > I think that 6V for the Overo will already too much. The
>     TPS65950 chip
>     > is only rated to 4.6V max.
>     >
>     > Perhaps the 6V figure is for the older Verdex boards with the linear
>     > regulators?
>     >
>     > Certainly the Overo boards can easily run with 3.3V direct. And with
>     > one of the Gumstix made expansion boards, with the DC-DC regulators,
>     > they can also run down to 3.3V.
>     >
>     > I would suggest that you don't keep the input at such a high voltage
>     > of 6V. Damage may come quite quickly.
>     >
>     > On 4/27/10, Victhor <vic...@gm...
>     <mailto:vic...@gm...>> wrote:
>     >> I also recently tried a 3.7V Nokia phone battery that worked even
>     >> better(as the backlight was turned on). It discharged the
>     battery after
>     >> some time, though(indicated by the inability to start, once the
>     battery
>     >> is charged the reboot loops disappear).
>     >>> Can't thank you all enough for the responses.  I was afraid to
>     try 4
>     >>> NiMH batteries in series because of all the 6V warnings, but
>     it worked
>     >>> like a charm.  Also thanks to Bernhard for the more creative
>     solution
>     >>> - at some point when I have my project turned in, I'm going to try
>     >>> going through the schematic and see if I can figure out why
>     that would
>     >>> work and not destroy the board.
>     >>>
>     >>>
>     >>> Thanks everyone!
>     >>> -Kim
>     >>>
>     >>> On Sun, Apr 25, 2010 at 8:01 AM, Victhor
>     <vic...@gm... <mailto:vic...@gm...>>
>     >>> wrote:
>     >>>         I managed to boot my Overo Fire/Palo43/4.3" LCD with 4
>     NiMH
>     >>>         batteries in
>     >>>         series. While it would end up in a boot loop, I managed to
>     >>>         boot it by
>     >>>         grouding PWM10(which is connected to the backlight),
>     reducing
>     >>>         the
>     >>>         backlight intensity to a minimum. As long as the
>     backlight was
>     >>>         weak, I
>     >>>         was able to use WiFi and browse the web with it :)
>     >>>
>     >>> > Hey Kim!
>     >>> >
>     >>> > The problem problem of your setup will probably be that the
>     >>>         9V-block
>     >>> > isn't able to source that much energy,
>     >>> > and the fact that your are using a linear regulator (that
>     >>>         will radiate
>     >>> > half of the energy as heat) doesn't help that fact.
>     >>> >
>     >>> > There is a solution although, that might work:
>     >>> > Locate the capacitor labeled "C43" - should be near the
>     >>>         power plug and
>     >>> > remove it
>     >>> > (you might add another 10u capacitor with a rating of 10V or
>     >>>         higher).
>     >>> > Now you can remove the 7805 and just boot up your board
>     >>>         directly from
>     >>> > the 9V battery.
>     >>> > With an energy efficency about 40% higher the with the
>     >>>         previous setup
>     >>> > =)
>     >>> >
>     >>> > If that doesn't do the job, you can try (just for testing
>     >>>         purposes)
>     >>> > use two 9V cells in parallel
>     >>> > (but make sure you use two full or equally discharged cells,
>     >>>         so they
>     >>> > don't interfere each other)
>     >>> >
>     >>> > I use the Overo Fire with a dual LiPo cells, but with a
>     >>>         custom
>     >>> > powermanagment,
>     >>> > and it works just fine.
>     >>> >
>     >>> > Regards
>     >>> >
>     >>> > Bernhard Wörndl-Aichriedler
>     >>> >
>     >>> >
>     >>> >
>     >>> > Am 25.04.2010 08:18, schrieb Kimberly Turley:
>     >>> > > Help!
>     >>> > >
>     >>> > >
>     >>> > > I'm trying to power an Overo Air//Summit Expansion board
>     >>>         from a
>     >>> > > battery source for an embedded application.  I have an
>     >>>         ad-hoc wifi
>     >>> > > network that is able to auto-connect upon boot when I use
>     >>>         a
>     >>> > > wall-supply to power the board.
>     >>> > >
>     >>> > >
>     >>> > > I am using a 9V battery with an LM7805C voltage regulator
>     >>>         (.33uF cap
>     >>> > > at input, .1uF cap at output), and have attached all
>     >>>         sensors
>     >>> > > previously attached to the 1.8V and 3.3V outputs of the
>     >>>         expansion
>     >>> > > board to a separate battery supply.
>     >>> > >
>     >>> > >
>     >>> > > Unfortunately even with nothing but the processor itself
>     >>>         connected
>     >>> > > to the power supply, the board loops the initial boot
>     >>>         sequence
>     >>> > > continuously, and is never able to get past unpacking the
>     >>>         kernel.  I
>     >>> > > have tried booting both with the serial cable attached,
>     >>>         and without,
>     >>> > > waiting for the wi-fi to connect instead as a sign of
>     >>>         successful
>     >>> > > booting.
>     >>> > >
>     >>> > >
>     >>> > > I have observed the input voltage to be between 4.2 - 4.9V
>     >>>         at all
>     >>> > > times, and my understanding was that as long as the
>     >>>         voltage didn't
>     >>> > > drop below 3.3V it would still be able to boot
>     >>> > >
>     >>>
>     >>> (http://old.nabble.com/Summit-power-comsumption-td27766025.html).
>     >>> > >  The LM7805 regulator with a 9V input should be able to
>     >>>         supply up to
>     >>> > > 2A of current, which I can't imagine would be less than
>     >>>         the
>     >>> > > requirements of the Overo board, but I can't seem to find
>     >>>         a spec to
>     >>> > > confirm this.
>     >>> > >
>     >>> > >
>     >>> > > Has anyone had success booting from alkaline batteries?  I
>     >>>         have
>     >>> > > about a week to get a demo working, so I'm willing to
>     >>>         order lithium
>     >>> > > batteries overnight if necessary, if anyone can suggested
>     >>>         a tested
>     >>> > > power supply design that might solve my problem, but I'm
>     >>>         really at a
>     >>> > > loss for why this design isn't working.
>     >>> > >
>     >>> > >
>     >>> > > Any insights would be greatly appreciated!
>     >>> > >
>     >>> > >
>     >>> > > Thank you so much!
>     >>> > > -Kim
>     >>> > >
>     >>> > >
>     >>> > >
>     >>> > >
>     >>> > >
>     >>> > > --
>     >>> > > Kim Turley
>     >>> > > kim...@gm... <mailto:kim...@gm...>
>     >>> > >
>     >>> > >
>     >>> > >
>     >>>
>     >>>
>     ------------------------------------------------------------------------------
>     >>> > >
>     >>> > >
>     >>> > > _______________________________________________
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>     >>> > > gum...@li...
>     <mailto:gum...@li...>
>     >>> > > https://lists.sourceforge.net/lists/listinfo/gumstix-users
>     >>> > >
>     >>> >
>     >>>
>     >>>
>     ------------------------------------------------------------------------------
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>     >>>
>     >>>
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>     >>>
>     >>>
>     >>> --
>     >>> Kim Turley
>     >>> kim...@gm... <mailto:kim...@gm...>
>     >>>
>     >>>
>     ------------------------------------------------------------------------------
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> -- 
> Kim Turley
> kim...@gm... <mailto:kim...@gm...>
>
>
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