Information on the Vex Joystick Accelerometer?

I am looking for some information regarding the Vex Joystick’s Accelerometers - I just found out now that they actually have one implemented and I am very eager to get working with it.

It says there are (2?) x-y accelerometers, how does this work?

EasyCv4


x_axis = GetJoystickAccelerometer( 1 , 1 ) ;
y_axis = GetJoystickAccelerometer( 1 , 2 ) ;

The Joystick Accelerometers are primarily used as “tilt” sensors,
measuring the gravity vector as acceleration.

There is a Youtube video showing a vex robotic arm following the tilt motion of a joystick, as an example application.

Actually, it’s a three axis accelerometer. However, we do not have access to the z-axis. only the x and y.
Here’s a video of it being used to mimic human arm movement (look around 1:00): http://www.youtube.com/watch?v=Y5tPkMS1_h8

And (possibly the one jgraber was referring to) one using it as a tilt sensor (look around 0:17): http://www.youtube.com/watch?v=HbxEerw6vk4

I don’t understand how they work though. They detect acceleration in a particular direction, so on which plan does the x/y detect the acceleration? I’m having a hard-time imagining an x/y accelerometer in 3D space.

Thanks :slight_smile:

One axis detects acceleration in the up/down axis. Another measures it in the left/right axis. The last one measures it in the front/back axis. If a joystick is held perfectly straight and still, only the z-axis will register any acceleration (of course, we don’t have access to that information, so it doesn’t affect us). If you have questions on how an accelerometer works, a google search will probably explain it much better detail than any single post on the forums.