Normal vector
Hi 
I have been trying to get a normal vector for the device without success. I tried rotating the up vector [0, 0, 1] by pitch around the x axis, then by the roll around the y axis, and finally by the yaw around the z axis. This appears to work (I'm streaming and displaying the data on a phone) except when rotating the device about its z-axis when the z-axis is perpendicular to gravity (https://mbientlab.com/tutorials/Orientation.html).
What's interesting is as I start to rotate the device in the previously specified orientation, the yaw changes. I would expect it not to change because when I rotate the device around the gravity axis when the device's z-axis is perpendicular to the gravity axis, the only value that changes is the yaw, so I would expect yaw not to change when the device is rotated about a perpendicular axis.
Thank you for taking the time to read my question.
Comments
Data and video?
Hi @Laura. After playing with the device a bit more, it seems that the issue is related to the device's magnetometer. It only returns changing values on the z-axis.
Video: https://www.dropbox.com/s/fo0za7v81f0hqor/IMG_1111.mp4?dl=0
Data: https://www.dropbox.com/s/sgt74qq358awydz/Metawear2_2020-02-24T12.23.03.904_D57E56C5D09D_Magnetometer.csv?dl=0
Is this a configuration issue or is this a problem with the device? I just received the devices last week, so they are brand new. Let me know if you need any more information.
Do you have an mmr+?
@Laura Yes
Please read the highlighted red text here: https://mbientlab.com/store/mmrp-metamotionrp/
@Laura Sure, but there's a difference between the data being affected vs. the data not changing at all though, right? The x-axis and y-axis values I collect do not change at all. That indicates a problem with the sensor to me.
Not necessarily. You would have to test this by removing the coin vibrator first.
You also haven't calibrated have you?
@Laura I did watch this video (https://www.youtube.com/watch?v=Bw0WuAyGsnY) and made the figure 8 motion and tilted the device at 45 degree angles but I don't have a windows computer so I wasn't able to download the software mentioned in the video. Even if I was able to download software, I'm not sure how I would connect it to the MMR. If I'm missing a step, please let me know.
The circuit board is hot glued onto the plastic and I don't see how I could remove it without damaging the board.
You can carefully try to remove the coin vibration motor from the board. Just be diligent and take your time.
https://mbientlab.com/tutorials/Calibration.html
Removing the motor fixed the magnetometer issues. Thanks Laura.
Yah... unfortunately magnets near magnetometers...never a good combo. We try our best to warn folks.