Current Drains By Speed And Device


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rv6502

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Aug 9, 2009
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can (did?) someone with an multimeter check the amperes for running some game at 600Mhz vs 900Mhz vs <600 vs idle (or almost idle == typing in open office), etc ?
I'm curious as to what proportion the cpu takes relative to the rest of the system.
maybe check the power drain at different gpu speeds and the different parts too.

did a quick search in the forum but could not find anything about that.

during "dvd" playback would be nice too (720x480p divx/mpeg4 AVI on SD, altho different SD = different current drain),

the trip from Montreal to Japan with stop over in Vancouver is about 8 hrs and then another 10 hours
(its a mental torture, with the dull onboard movies it could be considered a violation of human rights ;) )
and I doubt they'd let me ride with a spare battery (a long cylindrical-ish tube ? OMG!) <_<
 
If you have a search of MWeston's posts you should find what your looking for (probably many months ago). I dont remember the exact numbers but the cpu is a minor contributor to battery drain compared to the screen.

As far as I know there hasn't been thorough calculations of how each component effects drain. Id be curious to see the battery life with Full brightness, a fully utilized standard clock OMAP (the cortex, dsp and sgx), wireless on, bluetooth on, 2 SD slots, and using the audio amp. Also what the drain for just cortex and wireless on.

Also FYI, there has been talk of making a 5000 mah battery for the pandora (I'd assume it will cost at least $30).

Is there much amp draw with an unmounted SD card? How about an unmounted USB flash drive?
 
They said that the SD controller is almost nothing, it only uses power noticeably when you're actually accessing the cards.

However, USB devices have a high overhead since they're normally used on big laptops or desktops, and that just plugging in a normal USB device might cut the battery life to ~4 or 5 hours.
If you aren't using your flash drive, you should probably just unplug it. Why would you have an unmounted drive plugged in anyway? It'd be all sticking out...
 
Sorry to get OT: but deal extreme has very small microSDHC readers: http://www.dealextreme.com/details.dx/sku.25558
8GB microSDHC is only about $15 so its a cheap way to add a bit of extra storage.
 
I believe SD cards use almost nothing when not being accessed. I also believe USB devices are probably not so low power when not used because they usually have linear regulators to step down the 5V so the idle current will be higher but I would expect the NAND to go to sleep when not accessed just like in an SD card.

There are a billion tests I could do to monitor the current usage of everything. When you get your Pandora, you will be able to do it yourself as well. The battery fuel gauge will tell you the current being used at any time you want so you can plug something in and see how much it uses on your own. I find that rather fun to do because you can see just how bad USB based devices are for efficiency. They are designed for portability but not for portable power!

I did a couple of tests the other day to measure current in regards to overclocking and backlight control. The battery was low and it died shortly after this test so I would put the cell voltage somewhere around 3.6-3.7V. The backlight was on full for the PSX4all test and no SmartReflex power control is enabled for any tests. Audio was at mid volume for the first test.

Playing PSX4all at 500MHz: 599mA (peak value I saw) and at 800MHz: 692mA (peak value)

Here was an idling kernel with various backlight settings:
100% - 507mA
88% - 484mA
70% - 456mA
53% - 424mA
35% - 390mA
18% - 364mA
0% - 337mA

You can see that turning that backlight down when not needed can add a fair bit of battery life. You can also see that overclocking the ARM core does not have a significant impact on battery life (relatively speaking). It certainly will reduce battery life but 2x the clock does not mean 1/2 the battery life.
 
greendots said:
Sorry to get OT: but deal extreme has very small microSDHC readers: http://www.dealextreme.com/details.dx/sku.25558
8GB microSDHC is only about $15 so its a cheap way to add a bit of extra storage.
Click to expand...

If you want to add extra storage, try this: King Max 8GB Super Stick
It is about the size of a Trident bubble gum stick. I've purchased one of these to hook on to my key chain, very small and convienent.
 
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lulzfish said:
Why would you have an unmounted drive plugged in anyway? It'd be all sticking out...
Click to expand...

:lol:
cue the innuendoes
 
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MWeston said:
I also believe USB devices are probably not so low power when not used because they usually have linear regulators to step down the 5V so the idle current will be higher
Click to expand...

ouch!

I saw on hackaday.com a while ago some guy made a self-regulating minimal switching PSU with the device's own micro-controller.
using a spare ADC input and an output pin hooked on a transistor, an interrupt handler regulated in software the capacitor charge.

USB gizmo makers probably don't bother making something efficient when they can just use cheap linear regulator, there's probably some risk too (crash with the pin on charge for too long and burn the chip)

The battery fuel gauge will tell you the current being used at any time you want so you can plug something in and see how much it uses on your own.
Click to expand...

wow! that is a really nice and useful feature.
I can see myself spending an afternoon checking every USB devices and SD cards I have.
Pandora, the USB kill-a-(milli)watt :)

Code: 
0% - 337mA

speaking about that, the screen is not reflective so you can't see much with the backlight off ?

thanks for the numbers.
 
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MWeston said:
Playing PSX4all at 500MHz: 599mA (peak value I saw) and at 800MHz: 692mA (peak value)
Click to expand...

Wow, is that with increased voltage as well? Or is that stock voltage?
 
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The Pandora has a long flag battery that looks like a PCMCIA card so it's not a tube. Also for extreme battery backup I'd recommend a PowerTraveller Gorilla, looks like it'll last silly amounts of time.
 
Enverex said:
Also for extreme battery backup I'd recommend a PowerTraveller Gorilla, looks like it'll last silly amounts of time.
Click to expand...

its a nice device, cost (289$) almost as much in the US as a 2nd Pandora :p

OT:
Code: 
The power gorilla has also been on field tests out in Afghanistan.
Afghanistan is the new benchmark for devices.

so,
someone has to take their Pandora to Afghanistan,
clear the airport customs,
boot up their Pandora just outside the airport,
see if it works,
then board a plane back.

Afghanistan-tested. :rolleyes:
 
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