How much battery would you save if you could turn off the accelerometer?

Discussion in 'iPhone' started by TheSpaz, Mar 1, 2009.

  1. TheSpaz macrumors 604

    TheSpaz

    Joined:
    Jun 20, 2005
    #1
    Think about it... When you're browsing in Safari, the iPhone is constantly checking which orientation the screen is in right? I just wonder how they could offer a feature to turn the accelerometer off in Safari and iPod. It doesn't have to be global, they could add that option in the Safari and iPod prefs.

    As for landscape texting, maybe they could let us choose the format we prefer in Settings first and then when we open SMS, the screen could automatically flip for you (think about the way Maps forces you into landscape mode for streetview).

    What do you think of my ideas. Does the accelerometer use up a lot of battery? It's hard to say because we can't turn it off to test it.
     
  2. TheMBC macrumors 6502

    Joined:
    Jun 14, 2008
    #2
    I'm pretty sure the accelerometer "tells" the screen its been changed, the screen isn't searching constantly to see if the orientation has changed.
     
  3. Pixellated macrumors 65816

    Joined:
    Apr 1, 2008
    #3
    The accelerometer is a ball with some electrical contacts in it's housing. It uses a miniscule amount of electricity, and I believe that the energy gets recycled and runs through the accelerometer again. (or at least that is what my electronics teacher said)
     
  4. TheSpaz thread starter macrumors 604

    TheSpaz

    Joined:
    Jun 20, 2005
    #4
    What I meant was by having the accelerometer on, it would be in use in order to tell Safari which way the screen was rotated. Therefore, turning it off could save some battery power.

    That's interesting. How does energy get recycled though? I thought that was impossible. Anyways... that's good to hear.
     
  5. bytethese macrumors 68030

    bytethese

    Joined:
    Jun 20, 2007
    Location:
    Cranford, NJ
    #5
    But as he said, it's not on and only allows electricity to pass through when you move the device and the leads connect, thus signaling the device that the orientation has changed. :)
     
  6. kdarling macrumors demi-god

    kdarling

    Joined:
    Jun 9, 2007
    Location:
    Cabin by a lake
    #6
    An engineer replies...

    First, it doesn't use little balls. It uses micron-sized masses on springs that are measured via changing capacitance as they slide across sensors. (Vaguely like how the screen senses your finger moving across it.)

    Second, it has the ability to tell the main CPU when a preset threshold has been passed. This means the main CPU doesn't have to constantly poll it. When you make a major move, the chip will tell the main CPU. (Of course a program can constantly poll it if wished.)

    Third, it's probably always powered when the phone is on. It uses less than 1mW. Not much. In other words, if that that chip was the only thing running, the iPhone battery would go six months.
     
  7. Masquerade macrumors 6502a

    Masquerade

    Joined:
    May 16, 2007
    #7

    a ball and springs?? acording google and wiki, iphone uses MEMS small micro electro-mechanical systems. The chip is consisted of 4 cavities each one with a proof mass (maybe a gas) and one electrical beam that crosses it; when rotated, the mass centers of each cavity are moved and this difference value is achieved by the proof mass minus the reading of the beams.
     
  8. kdarling macrumors demi-god

    kdarling

    Joined:
    Jun 9, 2007
    Location:
    Cabin by a lake
    #8
    To be more detailed:

    The iPhone uses a ST Microelectronics LIS302DL three-axis accelerometer. According to their website:

    "The MEMS sensor of a linear accelerometer is based on a silicon, inter-digitated, comb-like structure composed of fixed and movable fingers. To sense the acceleration in different directions, these structures are packaged in orthogonal groups. The acceleration in each direction is sensed by measuring the displacements of the movable elements correlated to that axis. "

    Their picture of such a sensor (this one looks like a rotational version, because it's circular):

    [​IMG]
     
  9. Masquerade macrumors 6502a

    Masquerade

    Joined:
    May 16, 2007
    #9

    :) oops i had lost.. in the translation.. on on wikipedia.
    as kdarling is saying, springs. here's the original apple movie.
    http://www.youtube.com/watch?v=GxfL...layList&p=055A5D8D7B009506&playnext=1&index=5
     

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