I'm looking at building a tricopter, and I see that people use both a gyro and a few accelerometers. What's the difference between an accelerometer and a gyro? I've messed with the wiiChuck, which has an accelerometer in it, but never had the chance to play with a gyro, otherwise it might make more sense. Anyway, as always any info appreciated.
A accelerometer is used to detect magnitude and direction of an acceleration.
Gyro is to get an orientation.
However, acceleromter only work perfectly when the object is not moving or when it is not in free fall. If it does, acceleration will become 0.
If it is accelerating in a particular direction, that acceleration will simply be added to whatever acceleration is being provided by gravity.
Accelerometers are right in the long term but wrong (noisy) in the short term. Gyros are right in the short term but wrong (drifiting) in the long term. You need both--each to calibrate the other--to be right all the time.
http://diydrones.com/profiles/blog/show?id=705844%3ABlogPost%3A41145
An accelerometer measures rate of change of linear velocity , i.e. acceleration, hence the name.
A gyro measures angular velocity, i.e rotational speed, in radians (or degrees) per second.