Useless magnetic sensors

After getting roll and pitch working through the Kalman filter, this week I wanted to move on to yaw. Too bad the magnetic sensors in the SparkFun IMU don’t actually work:

While I was recording those values the IMU rotated a full 360 degrees and was even turned upside down.  MagZ should have inverted when it turned upside down, at least.  I guess there is enough stuff going on inside the IMU that it mostly detects itself.

I tried using just the gyros to track yaw by dead reckoning, but they drift enough that the fish are turned 90 degrees after about ten seconds. I’ll have to wait to track yaw until I can get a magnetic compas that works or have vision-based tracking working well enough to use it to compensate for the drift.

~Joe


8 Responses to “Useless magnetic sensors”

  1. Ima_P replied on :

    Hello Joe!!!

    Actually I want to develop a 6dof IMU. I would like to buy the Sparkfun’s 6dof v4 IMU, because it is cheaper than the rest of commercial IMUs, but obviusly, without software…
    As I can see in your application pitch and row angles can be implemented efficiently, but yaw angle… is more difficult.

    Have you solved your problems with magnetometers’ measurements? I would like to share information with you.

  2. Ima_P replied on :

    Actually I want to develop a 6dof IMU. I would like to buy the Sparkfun’s 6dof v4 IMU, because it is cheaper than the rest of commercial IMUs, but obviusly, without software…
    As I can see in your application pitch and row angles can be implemented efficiently, but yaw angle… is more difficult.

    Have you solved your problems with magnetometers’ measurements? I would like to share information with you.

  3. Alen commented on :

    hey Joe, i jst recieved my imu, but im not finding a sofware to aquire data from from the imu ,can u help me telling me where u got the software from( my imu came without any software or Cd oor anything :S :( )

  4. Joe replied on :

    SparkFun doesn’t provide any software. There is this VB app that reads the data, but that’s about it: http://www.sparkfun.com/datasheets/Sensors/Mixer_V4.zip

    If you read the PDF on their website it will tell you the data format that this thing puts out. You have to tell the bluetooth dongle to connect to it, then tell it to start transmitting, then it will spam you with updates at whatever frequency you have set. It’s a big pain.

  5. Chris thought on :

    It’s a little bit off topic,
    but did you manage to translate the gyro data from the measurement values to degrees per second (or even to degrees / heading)?

  6. Joe replied on :

    I actually haven’t plugged in the SparkFun IMU since I realized the magnetic sensors were useless. Never got around to translating gyro data.

  7. Ersin commented on :

    Hi Joe,
    I have tried to acquire data from magnetic sensors on the Sparkfun 6DOF IMU v4 for a while. And i was thinking that sensors are useless as you’re thinking. But i realize that i was using set/reset function wrong. After I apply 1-2us set/reset pulse to the magnetic sensors , the output is getting meaningful.

  8. Guillaume replied on :

    Hi Joe!
    I bought a 6DOF v4 some time ago… and found an application for it provided I can use the magnetic sensors!…
    Did you finally manage to use it?
    Did you understand/try the comment from Ersin about the set/reset function? (I thought it was done automatically by the board)
    Any idea about a cheap alternative?

    Thank you for your tuto!

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