I am having huge problems with magnetic interference when I fly my quad. I had recalibrated the compass dozens of times, replaced the gps/compass, raised the gps as high as the wire will allow (10cm). I even moved the battery and power wires under the frame. But you can see in the logs where the magnetic field spikes which causes significant yaw drift and then soon violent toilet bowling.
System
DJI Flame Wheel 550
Pixhawk
External GPS on mast
Ardcopter V3.1.5 ( i even tried the latest beta release of 3.2)
8 45 blades
30C 2800 LiPos
You can see the toilet bowl effect and the magnetic field levels in the logs (attached). Please, any help would be appreciated
Replies
I believe I have found the problem. Poor wiring to the magnetometer. I replaced the wiring and now the interference is down to about 7% and I haven't seen TBE in 2 flights. Thanks for everyone's advice, it helped me take everything apart and figure this out.
Is it possible to check in the logs which magnetometer the pixhawk is using during the flight? I set it to use the external one but my understanding is that the pixhawk decides on its own which one to use.
compassmot doesn't work with pixhawk yet as far as I have learned. Yes, I actually attached the battery underneath the whole rig several times and tested with same result
Are you sure it doesn't work? I ran it just fine on my TBS Disco using a 3DR Pixhawk and GPS/Compass combo.
I read some posts from the developers saying that compassmot produced flawed readings with the pixhawk and was slated to be fixed in 3.2.
It might be worth trying some shielding to see how it works, I have had very good results with it. Best to use printing plate if you have access to it as it's very light, if not then copper clad circuit board. Get a piece a few cms bigger in diameter underneath the GPS unit. The 5.8ghz antenna is still way too close, best to orientate downwards to avoid interference (I know you have been disabling the tx). This fixed my gps issues, best of luck.
Thanks. It is setup as an X with the GPS and pixhawk pointing forward.
All the pixhawk setups I have seen online have the Pixhawk on the power distribution board and the battery on the top platform. Is that incorrect?
Have you done the compassmot test ?
Imo the battery might be too much close to the compass, try to put the battery under the frame,
The battery on top doesn´t cause this behavior. I am flying/flew several PX @ F450 (lately 3.2 rc5) this way w/o any TBE issues with an external MAG / 3DR V1.2/CSG NEO 8 . Even CompassMot isn´t really required, at least I didn´t even bother.
Just check that the internal MAG is not used, or use a sep. MAG BOB (e.g. cheap GY-281) just to verify that your MAG @ the V1.2 doesn´t cause this ..as well as bad SDA/SCL connections could cause trouble too.
Some examples of my working setups :
In the past I have made some measurements with a specific instrument to check if something could interfere with the mag and I have learn several things.
Batteries cables path is crucial, especially if you use more than a single battery as I do.
Non piezo buzzers interferes a lot and also iron bolts that might have become magnetic can play a role.
Most important aspect is the distance of mag from interferences, if I remember well interference decrease with the cube of distance.
Ted, I would suggest you to try to increase the distance of the mag from the frame.
Even 5 centimeters, 2 inches , will make a huge difference, the more the better and you should see a big improvement , if nothing changes, the problem is elsewhere .
How much efficient is your copter ?
I mean with how many grams / watts do you usually fly ?
If your copter need a lot of Amperes the magnetic interference will be higher.
The toilet bowling effect happens only when you are il Loiter mode , do you confirm ?
Make this test I used to do with 3.0.1 version: hover in Altitude Hold mode, with no wind and look at the heading of the copter.
If you'll see that the copter slowly start to rotate and finally , after 30 seconds and around 180 ° , become stable , then the problem is really of the magnetic interferences of the compass.
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