What I am wanting to do - prototyping at this stage - is get a 3 axis (or more?) accellerometer and have a 3 axis detector. On the "top" of the gymble thingy, there will be an arrow.
When working, if I tilt the unit, it will keep the "top" level.
If I roll it, it will keep the "top" level.
If I twist/yaw it, the arrow will keep pointing in the same direction.
This should be possible, but is how I explained it correct and are those devices the things I will need?
The other question if the motors. Stepper or Servo. :~
I have read the differnce, but for the sake of simplicity at this stage.....
If you're building a gimbal and just need to know the tilt of the .. whatever, then you're looking for an accelerometer. It will always tell you what direction is "down" (gravity) but will get confused for short periods of time if it's being shaken a lot.
A gyroscope tells you the rate of rotation of an object. If your object was spinning you could compensate for that spin, but lacking an external point of reference it would only take a few seconds for your object to have no idea what direction was "up" anymore. In that respect gyros are typically combined with accelerometers for a stable platform that are more immune to shaking.
A stepper is more precise than a servo (assuming you mean an RC servo) and is capable of continuous rotation but requires an external driver for the high amounts of current used to energize its coils. A servo typically only allows 180 degrees of rotation, is less expensive, and requires no external driver as it is self-contained in the servo.
One comment on that LIS302DL; that's an older technology accelerometer. It's not very accurate (8-bit resolution) and its 3V signaling requirements mean you'll need a "level converter" so an Arduino running at 5V will not blow it up when it's trying to talk to it.
Accelerometers measure accelerations. Gyros measure changes in orientation.
There’s a constant 1g acceleration for objects on the surface of the Earth so an accelerometer can usually tell you which way is ‘down’ - good for measuring the roll/pitch of a boat.
What an accelerometer can’t measure is rotations around the direction of acceleration. e.g. you can’t use it to measure changes in a boat’s heading (because ‘down’ doesn’t change when the boat turns left/right). For that you need a gyro.
When you rotate an object at a constant angular speed, which of the following has to be true:
1) there is force on the object (thus it can be sensed by an accelerometer);
2) there is no force on the object;
3) all of the above;
4) none of the above.
When you rotate an object at a constant angular speed, which of the following has to be true:
1) there is force on the object (thus it can be sensed by an accelerometer);
2) there is no force on the object;
3) all of the above;
4) none of the above.
dhenry:
1) there is force on the object (thus it can be sensed by an accelerometer);
If you're using an accelerometer to sense rotation, you're assuming:
1) The accelerometer is not at the center of axis of rotation.
2) The distance from the center of rotation to the accelerometer is known.
3) A second accelerometer is being used so tilt can be differentiated from spin.
4) All of the above.
But to answer your question, if an object is rotating at a constant angular velocity then there is no force being applied to it. Acceleration is a change in velocity.
dhenry:
Q1: You are going east at 1km/h, and then you go west at 1km/h. Is there a change in velocity?
Yes. The object has to stop to go in the opposite direction.
Dhenry, you are making yourself look worse and worse with every post you make. If you have any dignity left, before your next post, do some research on the subject.