What's the difference between accelerometer and gyroscope?

Discussion in '3DS - Console, Accessories and Hardware' started by Fel, Oct 24, 2010.

  1. Fel
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    Member Fel GBAtemp's Adventurer

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    What's the exact difference between an accelerometer a and gyroscope? I've looked on the wiki, but it seems very similar from the description. Does anyone know?
     
  2. nintendoom

    Member nintendoom Nintendoom

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    Accelerometer for proper acceleration
    gyroscope for maintaining orientation.
    ex. Wii nunchuk analog stick, open your nunchuk and you will see the gyroscope when you remove the analog
     
  3. Fel
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    Member Fel GBAtemp's Adventurer

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    What do you mean by proper acceleration? Can you elaborate a bit please?
     
  4. Cyan

    Global Moderator Cyan GBATemp's lurking knight

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    acceleration is for the moving speed from point A ========> point B
    moving your arm away from your chest for example.


    gyroscope if for rotation.
    It detects the Wiimote/3DS orientation

    for example : playing Monkey ball, you rotate/tilt the console.
    It doesn't involve the arm displacement from a point in space to another. only the orientation of the controller is read.
     
  5. Fel
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    Member Fel GBAtemp's Adventurer

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    Oh, so (to use an example) the Wii can detect your position in space because of something else and not accelerometer, right? So accelerometer only measures you speed and can be used for pedometers or the measurement how fast you swing something, right, While gyroscope tells you whether you have rotated or moved the object itself, but not where as in space, only whether the object has been tilted or turned. Right?

    So how do you make something register that eg. you're swinging your device like a sword in the exact same way as you did, do you only need accelerometer and gyroscope, or do you need some motion sensor as well, like in wii (since previously it did not have gyroscope)?
     
  6. Cyan

    Global Moderator Cyan GBATemp's lurking knight

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    The wii detects the position in space because of the sensor bar, and wiimote camera.

    The wiimote has 3 different detector :

    visual position : caméra+sensorbar
    accelerometer : displacement speed of the wiimote
    gyroscope : orientation, rotation, tilting (2 axis at a time, due to gravity, left/right, upward/backward, but cant detect your if your body is moving to the left or the right, it's the job of the visual position)


    the visual position also act as rotation verification for 2 axis :
    - on the axis from the TV and you, if you point to the TV, and tilt the wiimote from left to right without moving your arm away from your chest, the wii check if it's the same movement that the gyroscope detects (sometime, your hand cursor is upside down for a few second, because the sensor see the rotation but can't detect the side until to gyro tells it to the wii).
    - on the Z axis (moving your entire body to the left or right), the sensor "see" the wiimote moving from one point to another, until it's out of screen.


    The wiimote+ is another gyroscope/accelerometer, which detect the same thing as the one in the wiimote, but as they are 10cm apart from each other, their inclination and moving speed is different. Their differences give even more indications and adds a precision on what movement you are doing (even if the sensor can't see you).

    It then reproduce a sword movement correctly.
    But it needs a very good calibration of both detectors, that's why there's a calibration function in Wiimote+ games.





    For a little more specifications on the gyroscope and accelerometer :
    Actually the Accelerometer can do both jobs, but it's not always accurate.
    The accelerometer acts as a gravity detector to check which side the wiimote is facing.
    Moving the wiimote creates a force on the opposite direction.

    Moving =======>
     
  7. Fel
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    Member Fel GBAtemp's Adventurer

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    Thanks for the clarification! So that means the 3DS wouldn't be able to do the exactly same thing because it doesn't have the visual bar/sensors, right?
     
  8. Cyan

    Global Moderator Cyan GBATemp's lurking knight

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    There's only the Z(bottom to top) axis which the 3DS won't be able to detect. unless there's 2 accelerometers, one on each sides of the console.
    But, the 3DS still have a sensor : 2 camera on the front will (can) act the same as the wiimote sensor bar, analyzing the environments movement and create a Z axis based on it.


    There's already few games on DSi using this method.
    a Monkey ball clone, and a 3D depth emulator.
     
  9. Fel
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    Member Fel GBAtemp's Adventurer

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    Oh cool, thanks!! [​IMG]
     
  10. lostdwarf

    Member lostdwarf GBAtemp Maniac

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  11. Cyan

    Global Moderator Cyan GBATemp's lurking knight

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    if your comment was directed toward me, after reading your link, I'm pretty sure I gave the same global description.
    Except they are using "1" as reference for earth gravity instead of the 9.81, and that I said gyro instead of accelero in the bottom part. (I'll edit my post. edit: done)

    both can read the rotation, but they are both needed of course (or else, the wii can't make the difference between "up+left displacement" or a "rotate to right").

    my description intended to give a "quick" summary at how the movement was detected regarding the earth gravity, instead of 3 pages of mathematical explanations on which electrical values are given to the chipset.
     
  12. lostdwarf

    Member lostdwarf GBAtemp Maniac

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    not completely aimed at you, no, but accelerometers measure only linier movements, including tilt, not rotations.
    The wii remote ONLY HAS accelerometers.
    The nunchuk ONLY HAS accelerometers.
    The wii motion plus add on has the mems gyroscopes.

    Together they work really well. alone they are very limited, but as we have seen with wii and iphone's beginnings, accelerometers are enough for good fun.
    Gyro's added to the mix allow more precision and accuracy and can relay motions to appear onscreen happening 1:1 the same time as you moved.
     
  13. TerraPhantm

    Member TerraPhantm GBAtemp Regular

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    Accelerometers tell you how fast your speed is changing. With some relatively simple math, you can use this information to determine your position assuming: you know the starting position of the device, the starting velocity, and the orientation of the device never changes. It's safe to just set the starting orientation and velocity at 0 since you only need to deal with these in relative terms, but the inability to change orientation is definitely an issue. The gyroscopes allow the device to know it's 3-dimensional orientation, and now the orientation no longer needs to be held constant to determine position.
     
  14. dsfanatic5

    Member dsfanatic5 Team ICO Freak

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    Personally, I don't care how gyroscopically inclined my accelerometers are, just as long as I can "Snooze" my alarms. I remember a great game on the GBA called WarioWare: Twisted!, and damn what a great game it is (best played on GBA SP hardware). I'll throw the Wii's infrared tech under the bus, to promote this game, since its "Gyroscope" controls are amazing.

    Will the 3DS compete with a game 9 years old? We only hope so, since the tech provides the possibility, plus touch-screen, microphone, 3D, etc. WarioWare for the 3DS should be the most amazing game ever, since WarioWare: Smooth Moves is still the definitive party game for the Wii (in my opinion).

    Crap, you can rotate the 3DS using its camera, gyroscopes, accelerometers, just wait and see. Augmented reality, and Kid Icarus, 3D movies, why are people complaining? This will rock!!!!!!!1
     

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