http://kamus-poweredblog.blogspot.com

This is the link to my Blog describing my accelerometer controlled light strips. Ideas or suggestions welcome!

It is pretty cool, but I think the accels will act differently in the air than they

do on the ground. Planes in the air, even when powered, are sort of in "free fall".

Not like being held in a constant gravity field on the earths surface.

Originally Posted by jglenn

It is pretty cool, but I think the accels will act differently in the air than they

do on the ground. Planes in the air, even when powered, are sort of in "free fall".

Not like being held in a constant gravity field on the earths surface.

Really?

Ever been on a commercial aircraft?
..a

Yes. The Airbus in the storm.

Not really, but did put an accel in the "tilt mode", so it was seeing earth, to create
a constant angle signal, used to stabilize pitch axis, on a hand toss glider.

It only gave a useful signal when close to level. Worthless. A plane is about like

a baseball you throw into the air. Ballistic flight. You really need an IMU.

Let me clarify the experiment. A PICAXE was used to drive the elevator servo from
the tilt accl sensor. On the ground, it worked perfectly. You could hold the plane and
tilt nose down, and the elevator would proportionally move up, to correct.

But in the air it worked entirely differently.

I also tried a GMR magnetic sensor to use the earth field. That worked well, but only
in one direction. Gave error going around the compass dial. Just some whacky experiments.

Funny. The level app in my iPhone works exactly as you'd expect while flying. I had great fun with that when I first got one a few years back..
..a

But that is when level? How about when doing loops and rolls?

The phone just has accels, no gyros?

I am no physics expert, have learned a little by reading about the people making IMUs,
the math is staggering. There does not seem to be any way to simplify it.

Sitting here watching a level app now as we follow the pattern and decend to land. When the 'plane banks, decelerates, whatever, the ball moves as expected..
..a

How steep can you bank? Your phone probably has an ARM cpu, and 3 axis accel, so
that is a lot of power.

But remember the trick of the stunt pilot, holding a glass of water, and doing a 360 deg
roll, the water stays in the cup. So that level sensor fails!

This isn't about aerobatics or coordinated turns.

You claimed accelerometers will not work in-flight as they are no longer subject to gravitational forces and are in constant free-fall. You are incorrect.
..a

I meant they did not work the way I expected in flight.

I was using "tilt mode", not the classic accel use, which is where you get an output
only when accel is changing.

It seems impossible to make a fully 3D level indicator with only accels, that's all.

The fact that IMU's use 3 accels and 3 gyros supports that.

Not sure why your phone level app works so well, there is probably an attitude of the
plane that will confuse it.