Accelerometer(s), Camera, and Memory
OpenMoko at mauve.plus.com
Mon Jul 21 22:02:38 CEST 2008
Dee Ayy wrote:
> I just heard of OpenMoko and Neo FreeRunner today. Awesome!
> I noticed the Hardware Highlights lists "3axis Motion Sensors (2)" and
> would hope that the developers included 2 accelerometers for the
> purpose of sampling the rotation as well as translation. The
> "closedPhone" and "closedPod" only sample translation via their sole
> So my question is the same as Francesco Cat's. Where exactly are the
> accelerometers positioned on the device?
> Would someone please confirm why there are 2 accelerometers?
As far as I can tell, because someone decided it would be a good idea,
without doing the numbers.
From some basic numbers, you can do little with the fact that there are
The fundamental problem is that the accelerometer chips have a
resolution of some 16mg.
If the accels are 10cm apart - on the periphery of a circle 5cm in
diameter, then as accelleration is proportional to the speed squared
divided by radius.
0.016 = v^2/.05
.32 = v^2
v = .56m/s.
This is a rotational speed of .56m/s / circumference, or .56m/s / .3m =
And this is for one LSB, so it will be very noisy.
The accels can - if positioned appropriately - I don't know where they
are - pick up taps on the case, and their relative distance from each accel.
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