Weirdest compass behavior today. Please help!

I went out flying a couple of hours ago and noticed some really weird stuff going on like where loiter would start out ok and then begin to swoop around bigger and bigger until I would have to take over in a panic and after looking at everything my compass direction is going about 90 degrees off in about 1 minute once I get in the air.  I can land and over about a 30 second period it creeps back to either the correct heading or slightly past the correct direction the other way.  This happened every time i lifted off ground.  Prior to today, this has never been a problem, and I flew it a few times just yesterday.

So thinking it could be a motor or ESC that just started going bad and sending out interference, I came home and swapped my whole electronics stack over from my home built B revision copy to a real 3DR C frame with it's own motors, ESCs, PDB, etc.  It's always done fine in its short life, it's almost brand new but has 5-10 flights on it.  So with my APM 2.5, uBlox, 3DR radio, and AR8000 stack on that frame, it does the same exact thing but the compass heading drifts around to the opposite side!  As soon as I land it slowly comes back around to the correct heading. 

So then I put the electronics back on my B frame and did a setup > reset and set everything back up from scratch.  Just took it out a few minutes ago and the same problem, compass drifted a good 90 degrees off to the right within a minute.  Landed it and it came right back to correct heading. 



This is an APM 2.5 with uBlox and 3DR radio, Spektrum DX8, AR8000, 3DR standard motors, 3DR ESCs.


Here are the logs from the last flight after I did the reset and set everything back up from scratch.  I kept it pointed out almost perpendicular to the back of my house the whole time in the air, kinda pointed directly at that road that T's off in front of my back door neighbors.  You can see when I land and disarm how the compass heading swings back around and actually overshoots the actual direction a little.





2013-02-15 15-52-33.tlog

2013-02-15 15-56 2.kmz

2013-02-15 15-56 2.log

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  • Guys i have an issue and ive had it for some time now, ive nearly lost my quad like 4 times over this issue. I could REALLY use some help.

    I am running the APM 2.5+, when in flight my controls change. Between pitch and roll the change half way through flight. The front of my quad will become the left and when i pitch forward, the quad will go right or visa versa.. This makes things EXTREMELY confusing. Then a power down and power up fixes things again for a while. I am sure this is compass related and i am unable to debug at the moment because i beleive there is a issue with the new 3DR Radios in the 433MHz range (interference from the usb power of something). I am not in simple mode and have "Use compass for yaw" (COMPASS_USE) enabled.

    Thanks for any help!

  • I went back out to the big field this morning and everything performed perfectly.  Compass direction was dead on, loiter was great, and I flew two different waypoint missions.  My auto-learned compass offsets have always been good and they remained unchanged from what I could tell during all this.  I noticed that today the satellite count was 10 to 12 and yesterday I think it was always 8 or 9, I'll go back and look at all the logs. 

    This is a long shot, but the asteroid that passed yesterday wasn't affecting anyone else's GPS signals was it? 

    Does the GPS signal affect the compass direction or is it 100% magnetometer derived? 

  • The power lines from battery or ESC could affect the compass if they are to close to APM.

    Try to keep fix your quad at the ground and just increase throttle (you would need to have the props in order to have high current/ampere in your motor and implicit in your power lines).

    In the same time look at the compass indication if it is moving. Should not move. If is moving, try to change the power line position vs. APM location. Hope this help

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