problems with cheap Chinese neo-6 ublox + compass v2.0

Hi all

       I have an apm2.5 with a cheap Chinese neo-6 ublox + compass V 2.0 board

and have been having problems in auto mode and circle.

 on investigation i found that the mission planer compass display was very non liner

compared to the actual heading  several re calibrations were tried some better some worse

on looking at the board i noticed that there is rechargeable battery underneath the magnetometer chip

so i unsoldered this battery, re calibrated  and all non linearity disappeared !! ( and low offsets)

placing the battery near the chip pulled the indication  way off

lesson learned (again)  Don't Bye Chinese Clones!!

 So if you are having strange bhaveyer in auto modes  and have this   v2.0 board

throw it away and get a real one

Tim Painter

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Hi, any compass should and will react to a magnetic field. And there is no way for a compass to distinguish the earth mag field from your DC current one.
So if the Chinese compass board uses the same IC as a 3DR one and if it doesnt have a mag field of its own (maybe the GPS sheetmetal got magnetic?) it will perform the same.
Regards, Søren

HI

   Yes i agree with your comments,

    Hi

My point is that the board is poorly designed with a magnetic battery( no current flowing   )

on the underside of the board overlapping the  mag chip.

why start out with a built in handicap like this ?.

 also current flowing  (therefor mag field)  presumably changes during  charging ?

Tim

Ah i missed the point that the battery was the onboard one and not the flight battery. If that it placed so near the chip that its charge current affects it, obviously its a poor design.
I guess some ppl still buy it becahse it's cheap. And if a more diligent Chinese developer designed a better board and tested it too, many would not buy it, it's Chinese but the other one is even cheaper :)
Actually I got many good things from China off ebay by not always taking the cheapest.
Regards, Søren

Hi

 Sorry I didn't make it clear that the battery i am taking about is  the gps backup battery which allows the saveing of  information in the ublox module, and is part of the gps board,

 Its odd that is made from magnetic materials?

 It affects the mag chip even when disconnected

 Tim

 Hi

    further  experiment revels  that calibration techniques  seem to alter calibration

( best seems to be level rotate about earth vertical axis,   nose up rotate   about earth vertical axis,nose left rotate  about earth vetical axis,nose right rotate  about earth vetical axis ,nose down rotate  about earth vertical axis, inverted rotate  about earth  vertical axis,)

Perhaps  some one  could clarify  the correct technique ?

I am going to relocate the battery to the opposite corner of the board where it seems to not interfere with the mag chip and gives  lowest offsets -80, 20, 25,.

I now get + - 2 degs accuracy which i think is pretty good

Tim

That is good enough for sure. Better than most compasses.

hi to all

I bought a not so cheap GPS + compass from witespyquad (http://witespyquad.gostorego.com/flight-controllers/ublox-6m-gps-w-...) and I get a horrible compass calibrations with apm 2.6. Values > 300. The Quad fly well but I dont not like so high values and mission planner is still waiting more data after >2000 points.

I just put a 3dr module and mission planner send me 80, 8, 40 after 500 points calibrations.

It is right that the huge battery is pasted under the compass. I put off the battery but values seem to stay aroud 300.

Any idea ?

Thank you !

Hi Max

        This looks like the same board as mine.

settings roll 0 orietation 0

       on mission planer look at the compass direction with and without the battery (just hold it in place by hand)

To see if makes any difference.

mine caused an error of 80 +. degs?

 Tim

If I understand well, there is no need to move the battery BUT we have to follow your rotate way ?

I get it ! Put off the GPS, put it on the back

https://www.dropbox.com/s/n69t48nlpkatoov/2014-08-14%2019.26.19.jpg

simple but I get offset of 50...

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