Power consumption: a590 measurements and waveforms. - page 3 - Hotwire! Hardware Mods, Accessories and Insights - CHDK Forum  

Power consumption: a590 measurements and waveforms.

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Offline fudgey

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Re: Power consumption: a590 measurements and waveforms.
« Reply #20 on: 09 / July / 2009, 14:40:07 »
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Other thing is I'm including mW because you do, but battery life is a tad more complex as batteries are rated in AH, not WH.  And AH depends on load (SLAs rated at their 20 hour rate, for example), temp and stuff. 
Power is handy in conversation rather than voltage+current (of which voltage is way too often forgotten, leaving measurements with a tolerance of tens of percents), mostly because it allows direct and accurate comparison between supply choices and camera models (CHDK supported cameras are being powered from 2 or 4 alkaline, NiMH or lithium AA cells, lithium packs and various external power supplies (for example I use a 12 V -> 3 V converter to run my camera from external power, meaning input current matters even when on external power)... all these have different voltage ranges.

It's true that most (but not all...) batteries are rated in Ah instead of Wh, but since efficiency vs. input voltage is known to be nearly independent of input voltage at least on dual AA cell cameras, a single input power figure for each operating mode pretty much suffices for use with any Ah rated battery configuration.

a) CHDK Batt mV displayed value seems to have a constant slope integrating filter the takes about 10 seconds to reach a step-changed battery value.  Dunno if that filter is in CHDK or the cam, but I noticed the camera operates on actual battery voltage for low-going event triggers (for example on the last picture of second measurement set when camera activated lens park and power down as soon as Batt V went below 2.0V ), not the displayed mV value.

From core/gui_batt.c get_batt_average() it would appear that it's CHDK's doing. You may want to modify that for your experiments (either define VOLTS_N smaller I suppose, or make it return direct battery voltage result or modify the gui function that calls it to use that get_stat_bat func instead). And now that you made me look (no, I didn't know it was CHDK doing this...) I think I'll be doing that for myself too...

Keep up the good work!  ;)

Re: Power consumption: a590 measurements and waveforms.
« Reply #21 on: 09 / July / 2009, 16:46:25 »
It's true that most (but not all...) batteries are rated in Ah instead of Wh, but since efficiency vs. input voltage is known to be nearly independent of input voltage at least on dual AA cell cameras, a single input power figure for each operating mode pretty much suffices for use with any Ah rated battery configuration.


Okay, that sounds like a good reason to keep mW :)  I may add percentage savings as that might be useful to people deciding on best power savings method -- lcd_backlight off is a little better than the easy AV matchstick option.  

But camera idle is best for long intervals between shots.  Trouble I do have with idle at the moment is for AF mode there seems no camera status value that tells if cam is asleep.  Can tell for MF mode requested idle as the cam wakes up in AF mode.  How tell for AF mode idle?

Quote
From core/gui_batt.c get_batt_average() it would appear that it's CHDK's doing. You may want to modify that for your experiments (either define VOLTS_N smaller I suppose, or make it return direct battery voltage result or modify the gui function that calls it to use that get_stat_bat func instead). And now that you made me look (no, I didn't know it was CHDK doing this...) I think I'll be doing that for myself too...


So I wasn't imagining that?  Good!  But every time I go look at the source I want to scream and fix the very creative white-space so it's easier for me to read.  My background is assembler (sorry, 8bit 6805, 8048, 8080, z80, not Arm) programming and thus I find free-form C very hard to read.

From: http://bugsplatter.id.au/chdk/a590-power-2.html
Here's the table again with percentage savings:

Camera mode, operation (a590 1.01b)           V      mA      mW    save%
------------------------------------------  ----    ----    ----   -----
Record active, MF mode                       2.5     584    1460     n/a
Record active, MF mode with AV lead in        "      530    1339     8.3
Record active, MF mode, backlight off         "      502    1255    14.0
Record active, AF mode                        "      504    1260     n/a
Record active, AF mode with AV lead in        "      448    1120    11.1
Record active, AF mode, backlight off         "      420    1050    16.7

Record idle, MF mode, camera idle [1,2]      2.5     148     371      76
Record idle, MF mode, script idle [2]         "       -       -        -
Record idle, AF mode, camera idle [1]         "      147     366      70
Record idle, AF mode, script idle [1]         "      138     345      73

Play mode, lens extended (AF or MF mode)     2.5     236     590
Play mode, lens retracted                     "      184     461

[1] Record Idle measurement is quite noisy and takes some time to
settle, I imagine this is due to thermal effects as the CCD is off
and camera innards are cooling down.
[2] Camera switches back to AF mode on idle.
« Last Edit: 09 / July / 2009, 17:26:00 by bugsplatter »

Re: Power consumption: a590 measurements and waveforms.
« Reply #22 on: 09 / July / 2009, 22:22:59 »
Interval-o-meter power requirements.

The test: daylapse script, 60s interval, Af refocus, AF lock focus and MF modes compared.  Cam set to display idle in 10s. Note that daylapse actually wakes up the cam for a preparation time before shoot, prepares then waits for shoot time, then shoot -- other interval scripts usually wakeup, prepare and shoot as soon as possible.  So these results may be considered a little high.

I think I've done the math right for energy cost in mWH per shot:
  
  cam_active_s * mean_active_mW / 3600 to get total shot_energy mWH, then subtract:
  cam_active_s * idle_mW / 3600 to get net shot_energy mWH
which could have been:
  cam_active_s * (mean_active_mW - idle_mW) / 3600
if I'd thought of that sooner :)

Results:
  AF mode refocus: 353mW plus 4.96mWH / shot
  AF lock focus: 358mW plus 3.88mWH / shot
  MF mode: 359mW plus 7.52mWH / shot

Also on bottom of http://bugsplatter.id.au/chdk/a590-power-2.html page if you want to see the pictures and check how the measurements were taken between the cursors.

Notes:
MF mode takes more energy because the cam needs time to restore MF mode after waking up, as well as the increased power while active.

AF refocus also takes extra time to refocus, test was done in a dim room, it's a cloudy day today.  Bright light focusing would be quicker.

Both AF refocus and MF modes turned on the AF assist LED.

The daylapse script uses 'shoot_half' to wake cam from idle, and is not yet fully optimised for lowest power consumption.  I'm happy to test other scripts if they're easy to use and work on a590-101b or a470-101b -- even a580-101b if you have a chdk port requires testing ;).


View from the cam.
« Last Edit: 10 / July / 2009, 03:38:27 by bugsplatter »

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Offline PEU

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Re: Power consumption: a590 measurements and waveforms.
« Reply #23 on: 05 / November / 2010, 12:51:58 »
Is there a way to disable the native battery sensor on the A590? Im running it out of an external power supply (self made provides 3.6v) and it always blinks in battery low mode while CHDK says battery is 100% full

It would be great to be able to disable this sensor via CHDK. Thanks!


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Offline fudgey

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Re: Power consumption: a590 measurements and waveforms.
« Reply #24 on: 05 / November / 2010, 13:15:09 »
Is there a way to disable the native battery sensor on the A590? Im running it out of an external power supply (self made provides 3.6v) and it always blinks in battery low mode while CHDK says battery is 100% full

It would be great to be able to disable this sensor via CHDK. Thanks!

The reason you get battery warning blink is most likely that either your power supply is too weak for the camera or you have too high cable and/or connector resistance (camera detects a severe voltage dip at its DC input when it works its lens motors and thinks that's due to a weak battery).

Once it has started to blink, it can probably be disabled using events, see http://chdk.setepontos.com/index.php?topic=4037.0

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Offline PEU

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Re: Power consumption: a590 measurements and waveforms.
« Reply #25 on: 05 / November / 2010, 13:39:35 »
you think that a bigger section cable should solve this? since the connector is not easy to find here I used one from a cellphone supply purchased on the street, the wire is really thin.

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Offline fudgey

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Re: Power consumption: a590 measurements and waveforms.
« Reply #26 on: 06 / November / 2010, 05:28:21 »
you think that a bigger section cable should solve this? since the connector is not easy to find here I used one from a cellphone supply purchased on the street, the wire is really thin.

If cable is the problem, then yes...1 ohm/m isn't unheard of and really is a lot at e.g. 3V 1A peaks. But if voltage dips at the PSU end of the cable as well, then no.

 

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