[Gta04-owner] [Community] OpenPhoenux Prototype of GTA04 based7 inch tablet

joakim at verona.se joakim at verona.se
Thu Nov 8 09:55:18 CET 2012

"Dr. H. Nikolaus Schaller" <hns at goldelico.com> writes:

> Am 07.11.2012 um 20:42 schrieb Flemming Richter Mikkelsen:
>> Since the display is so demanding, maybe a hardware display power
>> switch is in order?  That way one can boot without the display on.
> Or we could simply dim the backlight by software. But it does not solve
> the fundamental problem that the device will drain the battery even if
> connected to a power supply while being used.
> I think nobody would expect that it should be switched off/dimmed
> during charging and has limited operation time even if connected
> to the power supply. I.e. it does not work in picture frame mode...

This doesnt really solve the problem at hand, but its related.

I had a laptop that the screen back lighting broke down on. The laptop
was otherwise fully usable.

Instead of throwing away the laptop, I separated the backlighting from
the screen, and removed the cover. The screen then becomes transparent
enough so you can backlight it with ordinary sunlight outside.

It was quite usable, and was even superiour when working outside. Also
the power consumption was less since theres no back lighting at all.

You can do the same with an ordinary desktop screen, but the screen
controller board might get in the way.

Anyway, maybe this idea can spark some other more usable idea in the
current context.

>> The backlight may be controlled by PWM, but may still demand a lot of power...
>> I was thinking USB 3.0 could solve the power issue.  We got lots of
>> extra space...
>> Or maybe just a normal power connector would be better since chargers that talk
>> USB 3.0 is not easy to find. I know I would want to charge it at work,
>> at home and
>> from the car...
> I now understand why even small netbooks come with a 9V 2A supply.
>> I know some low power displayes, but they are either monochrome or
>> really slow (for ebooks) and with such a nice tablet it would be a
>> shame not to be able to watch videos.
> Exactly. I have studied the Pixel Qi 7 inch display but it has the same
> demand in full color mode. It appears to be a physical law that a
> sufficiently bright 7 inch display needs 1.5 Watt or more.
>> Maybe also a bigger or double battery pack would help a little.
> Not really. It is the balance between power supply and demand.
> Only the difference can be used to charge the battery - independently
> of its capacity.
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Joakim Verona

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