Power consumption: a590 measurements and waveforms.

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    Power consumption: a590 measurements and waveforms.
    « on: 05 / July / 2009, 11:13:18 »
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    Hi there,
    I've done a set of measurements with a590-101b.  This work confirms fudgey's observations and also provides screenshots of how various camera functions draw power.  http://bugsplatter.id.au/chdk/a590-power.html -- lots of pictures  8)

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    Offline reyalp

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    Re: Power consumption: a590 measurements and waveforms.
    « Reply #1 on: 05 / July / 2009, 18:09:39 »
    Excellent!

    Some things to try:
    AF lock vs manual focus mode
    LCD backlight on/off. (set_backlight in script)

    If you want to try some hacking, you can try monitoring the various clock speeds http://chdk.setepontos.com/index.php/topic,2139.msg20087.html#msg20087 or even forcing them to a specific value and watching the effect :)
    Don't forget what the H stands for.

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    Offline fudgey

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    Re: Power consumption: a590 measurements and waveforms.
    « Reply #2 on: 05 / July / 2009, 18:20:47 »
    Nice! Good of you to go through the trouble to make all them images... I've been meaning to do that for quite a while. :D

    I'm not sure how similar a590 is compared a570 in this respect, but did you try powering up to rec mode directly and see if the draw is any different from powering up to play and then switching to rec?

    I ask this because I've found that my camera just plain fails to start up (demands I change batteries) to rec mode using batteries whose resistance is too high (old or empty), but will always start to play mode and then it will often remain powered on when switched to rec from play mode...

    After it's finally running, I can take a 1-hour 1000 image timelapse with that fully charged pair of old NiMH cells! So either the camera draws more current when powering up to rec than it does switching from play to rec or the battery condition algorithm is more trigger happy during power-on than later when it has gathered a little bit more information on the current/voltage behavior of the cells.

    To be complete, I believe two things are missing from your measurements: effects of set_backlight and video plug. But that's not a big deal, they're just two numbers that don't need plots from a 'scope.

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    Offline fe50

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    Re: Power consumption: a590 measurements and waveforms.
    « Reply #3 on: 05 / July / 2009, 19:06:00 »
    Good stuff !

    What also would be interesting: the behaviour after using Canon's "Display off" feature (LCD off, registered to the print/share button) - since this normally cuts off the sensor (and also the AV-out electronics ?) the current should be the same as in record idle mode...


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    Re: Power consumption: a590 measurements and waveforms.
    « Reply #4 on: 05 / July / 2009, 19:13:08 »
    Some things to try:
    AF lock vs manual focus mode
    LCD backlight on/off. (set_backlight in script)
    That be different than pressing DISP button?  Yeah, I'll have a look.

    Quote
    If you want to try some hacking, you can try monitoring the various clock speeds http://chdk.setepontos.com/index.php/topic,2139.msg20087.html#msg20087 or even forcing them to a specific value and watching the effect :)
    Well, I might have seen that indirectly as the cam takes more power when set to 'auto' or 'heart' mode.  This is in a later group of shots I took in the early hours, not on the page yet.

    Edit: up now: http://bugsplatter.id.au/chdk/a590-power.html with some on page links near top.  Got AF lock vs MF mode for reyalp, yet to add other fudgey and fe50 suggestions.
    « Last Edit: 05 / July / 2009, 20:31:38 by bugsplatter »

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    Offline reyalp

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    Re: Power consumption: a590 measurements and waveforms.
    « Reply #5 on: 05 / July / 2009, 19:15:51 »
    That be different than pressing DISP button?  Yeah, I'll have a look.
    Yes, the display and sensor live view still run, so you can do MD etc.
    Don't forget what the H stands for.

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    Re: Power consumption: a590 measurements and waveforms.
    « Reply #6 on: 05 / July / 2009, 23:46:34 »
    I'm not sure how similar a590 is compared a570 in this respect, but did you try powering up to rec mode directly and see if the draw is any different from powering up to play and then switching to rec?

    Done that.

    Quote
    I ask this because I've found that my camera just plain fails to start up (demands I change batteries) to rec mode using batteries whose resistance is too high (old or empty), but will always start to play mode and then it will often remain powered on when switched to rec from play mode...

    Now this is where it gets interesting.  Last couple hours I been playing with the cam at low voltage, and it seems the cam will refuse to ''load firmware'' if the battery voltage is too low.  Makes sense when you think about it.  So when I get the cam operating and the lowest reliable voltage, starting up in play mode and loading firmware fails with a ''Change batteries'' message.

    As well, I'd made a longer cable for the linear regulator I'm using, and this, combined with the 0R1 current shunt proved an interesting combo -- like a battery with higher internal resistance.

    So I paralleled another 0R1 to make a 50-mOhm shunt and switch to a shorter 3V cable -- made a big difference to the measurements I was taking.  Having a break, I'll revisit later.

    But I can tell you that at 2.3V the cam draws ~600mA in active record mode, vs ~400mA at 3V.  The cam doesn't like loading CHDK at low battery voltage, probably a design feature to allow successful firmware flash? 

    More later.

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    Re: Power consumption: a590 measurements and waveforms.
    « Reply #7 on: 06 / July / 2009, 00:03:08 »
    Good stuff !

    What also would be interesting: the behaviour after using Canon's "Display off" feature (LCD off, registered to the print/share button) - since this normally cuts off the sensor (and also the AV-out electronics ?) the current should be the same as in record idle mode...

    I'll get there, quite an interesting exploration.  Helps me put off looking at the a580 port and/or fixing some of the missing bits for a590 -- such a lot to play with here ;)


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    Offline fudgey

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    Re: Power consumption: a590 measurements and waveforms.
    « Reply #8 on: 06 / July / 2009, 16:02:11 »
    I'm not sure how similar a590 is compared a570 in this respect, but did you try powering up to rec mode directly and see if the draw is any different from powering up to play and then switching to rec?
    Done that.

    Thanks. I guess that proves it's not drawing more current.

    Now this is where it gets interesting.  Last couple hours I been playing with the cam at low voltage, and it seems the cam will refuse to ''load firmware'' if the battery voltage is too low.  Makes sense when you think about it.  So when I get the cam operating and the lowest reliable voltage, starting up in play mode and loading firmware fails with a ''Change batteries'' message.

    Now that is interesting and does make total sense to require a fresher set of batteries for firmware upgrades than for normal everyday operation. I'll have to try experiment with starting the cam without CHDK using old batteries to verify your findings... would do it right now but the camera's out shooting a timelapse. If this is true, it could very well explain why more than a few people think CHDK makes their cameras consume more current (which, now that I've said it, is something you're welcome to prove wrong while you're at it...not that it hasn't been done a few times before :D). I can't think of much that could help, except starting via play mode to draw less current during startup.

    So I paralleled another 0R1 to make a 50-mOhm shunt and switch to a shorter 3V cable -- made a big difference to the measurements I was taking.  Having a break, I'll revisit later.

    Yea I once tried with a current sense resistor too large as well and got the cam to shut down each time it operated motors... didn't have time to tinker more that day.

    But I can tell you that at 2.3V the cam draws ~600mA in active record mode, vs ~400mA at 3V.

    My camera's is about 2% less efficient (power input wise) at 2.4 V than it is at 3.15 V. You seem to have a way bigger difference there (1.38 W vs. 1.2 W)... are you measuring the current you're supplying to the camera or the camera's input voltage (cable and current sense losses removed)?

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    Re: Power consumption: a590 measurements and waveforms.
    « Reply #9 on: 06 / July / 2009, 17:43:36 »
    My camera's is about 2% less efficient (power input wise) at 2.4 V than it is at 3.15 V. You seem to have a way bigger difference there (1.38 W vs. 1.2 W)... are you measuring the current you're supplying to the camera or the camera's input voltage (cable and current sense losses removed)?

    Measuring V and I at power supply regulator end of 25cm or 80cm cable to camera.


    That's why I'm taking a break, cam is running a timelapse script test for some hours yet.  Ended up with too many variables and my mental model needs some forgetting ;)  I've got the current sense in series with the cam 3V, so there's 50mV/A to account for there.  Now I have two cam 3V cables, one is 25cm, other is 80cm, so there's a V drop for that.  From memory about 1mV/cm at cam record active mode in chdk, assuming the cam Batt mV readout is accurate.

    I now have the DPO calculating output voltage - shunt loss (no differential input), but I need to take a cable resistance measurement as well, tell the cam to show Batt mV in play mode.

    While using the lower current shunt resistor and shorter cable stopped the cam shutting down when switching to record mode from play mode, it did not change the cam's refusal to ''load firmware'' at low voltage -- hence my conjecture on the firmware Batt mV safety factor.

    So I need to take more care in measurements -- that's why I like taking the screenshots, others can then spot an interpretation boo-boo as long as I accurately describe how the measurements were taken.


    Yesterday I also failed to create a bootable SD :(  I think cardtricks-144 is broken on Win7rc, as I had trouble getting a580 dump recently too.  But there seems more to making SD bootable than writing 'BOOTDISK' to 0x40 in MBR (from linux), as all I got was 'Card Locked!'  Maybe it has to be 'BOOTDISK',0x0?  Yet to try that.  So I was unable to check power up into CHDK mode.  But my recording of power up in play and load firmware showed no great increase in power consumption loading the CHDK and rebooting -- nowhere more than half record active mode power.

    And yes, there's no appreciable difference powering up in record mode or switching to record mode from play mode.

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    could very well explain why more than a few people think CHDK makes their cameras consume more current
    CHDK does not obviously draw more current, but there are things people could do to extend battery life.  Using the CHDK menu from play mode will consume about a third of the power compared to being in the menu from record mode.  It's not the LCD or backlight consuming the power, rather, it seems the cam's 'live view' accounts for two-thirds of the power in record mode (Edit: supported by temperature increase in CCD indicating power consumption).  Play mode power is not very different from record mode idle (within 25-30%).  This too is supported by the long play time battery life seen in the camera's specification.

    So yes, there will be a followup, maybe later today or tomorrow, I have the DPO on extended loan, lots of time to play 8)  
    « Last Edit: 06 / July / 2009, 18:25:26 by bugsplatter »

     

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