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Compass issues with AC 3.3

Posted by tom on January 10, 2016 at 8:26pm

Hi

I am using AC 3.2.` on pixhawk and it works good.

When I uploaded AC 3.3 I got compass issues, I was getting errors compass variance

Also when I tried to fly , I almost crashed it, my tarot got very unstable and banked to left and right

any thoughts about it?

regards

tom

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Replies

        • Dave Wood > Scott W January 17, 2016 at 5:38pm

          will try, but I am almost sure that the screws are the problem.

          before the mounting change, the offsets were around 50 - 100.

          I think that the steel screw could be your problem.

          At my frame, the next screw is around 5-10cm away.


          Maybe you can change the according screws to stainless steel v4a, brass, or aluminium ones.

          I have ordered the nylon screws and also v4a ones and will report back when I get them.

          I also use an external compass however, but I wanted to use the internal one for letting the EKF check plausibility.

          Did you check the AUAV at the bench?

          • Scott W > Dave Wood January 17, 2016 at 6:15pm

            I did have some issues w/ it on the bench, not mounted in a copter.  At the time, I was anxious to get it built, and didn't look in to it much.

            I just ordered some non ferrous screws, and will certainly try that! 

            • Scott W > Scott W January 31, 2016 at 9:47am

              I installed the screws, and the internal compass dropped from about 220 -50 -150 to about 150 -50 -150.  So, it did help. 

              Doing further investigation, I discovered it's not my internal compass that puts my heading about 45 degrees off.. It's my external csgshop GPS/Compass...  When I use it, everything calibrates fine, but it is pointing off 45 degrees clockwise.  (when copter is facing north, the mission planner display shows it pointing north east)

              I found this post about the same GPS, and the compass being connected incorrectly on this GPS, but I'm not sure I believe him... Else, I'd expect more complaints..
              https://groups.google.com/forum/#!topic/drones-discuss/a_OIlaa6Z1c

              Google Groups
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              • Dave Wood > Scott W February 1, 2016 at 9:33am

                Did you set up the right rotation for your external GPS/Compass in Mission Planner?

                I also installed nylon screws now and the offsets are still quite high..

                369 -154 238

                but a lot better than before

                • Scott W > Dave Wood February 2, 2016 at 4:22pm

                  No rotation seems to be correct.  All the others give me big problems. 
                  But, that is a confusing topic.  The magnetometer is upside down, on the bottom of the GPS PCB, but apparently "no rotation" is correct because the code expects the compass to be upside down.   It's definitely not rotated by 45 degrees.

                  I've got another flight controller and compass on the way for a different project.. I'll try to do some testing with this questionable compass while I've got it on the bench and everything is easy to access..

                  Worst part about this hobby is trying to figure out which components actually work properly, from the factory.

    • Vesselin Goranov > Dave Wood January 14, 2016 at 11:17pm

      The values depends of the metal around the controller and the Pixhawk hardware itself.

      I have several Pixhawk, and each is different. Best MAG data (offsets are about 10) gives a clone Pixhawk, unfortunately the baro diverge a lot....

      The original 3DR gives more offset (105 61 43), but the baro is very consistent.

      Always measure the controller outside the frame, on a wooden table (no metal around). Then compare with the frame offsets.

      A get BAD AHRS usually when the baro values floats. Normally, in quiet closed environment, the baro (ALT) should not float much (+- 20 cm)  The same clone mentioned above, floats about 5 meters after 8 minutes power on!

      3DR controller I measured floats no more 20-30 cm in 1 hour.

    • Derek > Dave Wood January 14, 2016 at 8:00pm

      Hi, I have 3 pixhawks and the internals on all of them have near those offsets. Not only that but if the calibration program is run successively, significantly different values are obtained. I also notice on dataflash logs the two mags when graphed diverge and converge. LSM303D strikes again (though it'd probably be fine if it were made external).

      Try disabling the internal and using only the external.

  • Ivan R January 12, 2016 at 7:27pm

    you need to post a log file for anyone to really be able to help

    • tom > Ivan R January 12, 2016 at 9:18pm

      I understand, however, it has nothing to do with my drone, the issue is with the firmware, after uploading 3.2.1, it works.   so for some reason 3.3 is causing issues.

      Thank you

      • Tony K > tom January 13, 2016 at 6:54am

        3.3 has worked flawlessly for alot of us.. what have YOU done to try and resolve this issue ? Did you take ANY steps at all ? Help yourself a little for others to help alot.  

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