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Hey there!
at first, sorry for my english.
i'm getting started with hardware. a friend of mine is a proffessional steadycam operator (a cameraman with a device for balancing out the camera horizontally while running).
We want to make a spirit level. he's more the hardware guy and i'm more into coding, so i think we used an "ADXL sensor".
the libra itself isn't the problem, but the centrifugal force is.
if the device sits still, it works. you can tilt it and some LEDs light up. if you move it around perfectly horizontally (!) it goes like crazy*, because we can't distinguish between centrifugal force and angle.

* "like crazy" = if you move it to the left, the right LEDs lighten up and soon thereafter it's balanced again, and vice versa. it would be important to ignore the centrifugal force, so you could run and know that the camera is horizontal.

any ideas? how can we do this? what can we use?
i hope someone understands this smiley

regards,
orwell
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Switzerland
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I guess you need a so called "6D" or "6-axis" system where accelerometers are combined with gyros like the MPU-6050 (https://www.sparkfun.com/products/11028). This should give you enough information to calculate out the centrifugal forces.
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hey pylon, thanks for the reply.
hmmm... you mean, i can take this MPU-6050, get somehow the axis and subtract the acceleration? or would the "MotionFusion"-data be enough for doing the job?
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I don't know how the steadycam works but from what I imagine I guess that you probably have enought information with reading out the gyro sensor data. Gyros are used in DSLR cameras to optically reduce the shaking of the objective, your applications sounds very similar to me. With the gyros you get the rotational information, the accelerometers might help in damping the transitional movements (if that's desired).
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a small one looks like this:


problem being, the gyro sensors works through centrifugal force. it kicks in even when you just drag it. the application should be like:

green led: im high.
red leds (chorus): nothing to do here.
gyro: hey! somethings happening! whats with you, accelerometer?
accelerometer: nah, i just moved from A to B.
gyro: damn.
red leds (chorus): nothing to do here.
green led: im still high.

 smiley-razz
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A gyro detects changes in rotation. If gyros were ideal that would be all you'd need, but because they're not -- they slowly "drift" and report that they're rotating a small amount all the time -- you need also need an accelerometer to use as a zero point reference (because it knows where "down" is due to gravity).

To mesh the two readings together you need to research "Kalman filtering". You can find a number of references on this board as well as in quadcopter/UAV forums.
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yeah, sounds good. i will check that out. thanks! i will work on this...
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