# Tag Info

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It could be inherent to the sensor technology used. If they use spring-loaded mass for sensing, you might expect that the force vector is offset to a certain extent during lateral movement. If you assume, that total length of spring is limited, then it gets clipped on Z-axis to the remaining length allowed for movement. E.g. sum of forces E is constant 1 (...

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Each accelerometer (when stationary) gives you a 3 vector for the direction of gravity. Let's assume that both accelerometers are offset-free, and have the same gain on all three axes. If they are not that ideal, then it's fairly easy to obtain an offset and gain for each axis with a calibration step that involves rolling each to a large number of random ...

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You "removed gravity" from the Z axis by subtracting a constant. Obviously, this does not work if the Z axis no longer points "up". If the sensor cannot be maintained in a particular orientation with respect to the gravity vector, then there is no simple way to remove gravity. You'll have to do a full 6-dimensional motion solution (3 axis accelerometer, 3-...

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Inclinometer axes in general are sensitive to changes in angle when the axes are both perpendicular to the gravity vector (near zero.) As you rotate the axis from parallel to the earth's surface, the response from an axis is proportional to the sine of the angle. The difference between the sine of 0 degrees and 1 degree is .0175; between 89 degrees and 90 ...

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I rather doubt you can get 75%. But it doesn't matter. It's just a constant factor. Call this factor, $\eta$. There is $4.9\:\frac{\textrm{J}}{\textrm{kg}}$ available near the Earth's surface for the short drop distance of $\frac{1}{2}\:\textrm{m}$ that you are talking about. That's at 100% efficiency, of course. Your battery needs \\$10080\:\frac{\...

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This is essentially a physics question, but I'll humor you. The relevant capacity of the battery is its watt-hour capacity, not its milliamp-hour capacity. For a iPhone battery, this is roughly 10 Watt-hours. (You can get the exact Watt-hour capacity by multiplying the milliamp-hour capacity by the terminal voltage and dividing by 1000.) One Watt-hour is ...

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DC brush motors make electrical contact with the rotating armature with spring-loaded carbon brushes. The brush contact is a major source of friction. The armature bearings (at each end of the motor shell) also generate friction, but far less than brush friction. In the photo below, the red and blue brushes are pushed against the commutator: The armature ...

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