Compass mag_field hard interference: solved

I had really hard mag_field interferences compass in one of my custom copters (see Tridge analysis done in this other topic)

See the mag_field during a normal flight:3690923746?profile=original

The harness arrangement was done randomically inside the two main plates .In particular both red and black lines were independent (not good for mag_field!):


So, I decided to re-route the powerlines by substituting the old harness by independent highly twisted lines for each of the ESC´s starting from the battery. I´ve shortened also the battery cables to the maximum, and also twisted them a bit.

So the result is awesom: It complitely solved the problem (see second Image of a similar flight).


I hope this help others to solve in the root the eventual interference compass problems: lets "twist and shout"!

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  • Dying to see some photos! I have been having some issues regarding Random Yaw on my X8.  Would twisting wire always be a good practice in main wiring for future reference? I haven't really studied my logs yet, too busy reppairing and balancing props.  TIA :)

  • 100KM

    That's very nice Dani !   Unfortunately twisting powerlines would require a complete dismantling and rewiring of my copter, which I really don't see me doing.

    Surely we can't expect all users with yaw problems to rewire their copter ?  It worked fine before (2.0.49) so we should be able to get it working fine again.

  • Hi all,

    prior to using 2.5.3 I ha no problems with yaw.

    With 2.5.3 yaw would have a will of it's own, wandering about 25º to each side; I believe it must be some kind of process that now is more sensitive to mag interference,

    So I followed afernan's advice, high-twisted all power lines and moved the mag a bit further away.

    Tested it today, and yaw is back to rock solid.

    Thanks! great tip!

  • Extensive flight test results with new hardware setup

    The goal is try to get the best offsets for the better flight. Also to compare the three method we have:

    1. Using MP / hand rotation , motors off
    2. Using MP / TLOG offline calibration
    3. Compass_learn by Tridge

    Method 1):

    hand rotating (no motors) -43, 30, 25   repeteated again   -30,31,17

    Method 2):

    Using MP / TLOG offline calibration. I´ve got three long fly records (see attached TLOGs)





    2012-04-02 20-17-35

    -21 31 76

    -21 31 76

    -21 31 76

    2012-04-02 19-54-08

    -14 34 64

    -14 34 64

    -14 35 65

    2012-04-02 19-00-45

    -17 36 89

    -17 36 89

    -17 36 89

    2012-04-02 20-17-35


    2012-04-02 19-54-08


    2012-04-02 19-00-45


    Method 3):

    Compass Learn:

    Outdoor flight:

    After 2 min flight                   -2,40,-4

    After 5 min more                   -19,39,-14

    After 10 min more                 -18,52,-11

    After 15 min                           -16, 16, -95


    • Compass_learn gives very different values for "mz_off", but similar values for "mx_off" and "my_off".
    • Method 1 (hand rotating, no motors gives also similar values for mx, my but not for mz offsets.
    • So we can consider mx_off = 21 , my_off = 31 as good values since in all three methods are similar.
    • For mz_off I rely in second method, that is not so far than first method: let say mz_off = 65
    • A flight with this values confirms that they are good  (see TLOG graph 2012-04-02 20-17-35)

    Looking fordward your comments on this results to try to commint on one method for today until we get another.

  • Developer

    Nice one Angel!
    He was the one who flew avoid, but unfortunately it is inevitable ... "come on let's twist again"... :P

  • Very cool!  EMI issues are always a pain. Care to post a pictures with twisted pair harness?

  • Developer

    That's a great result Angel!

  • 100KM

    Great stuff afternan !

    Did it solve yaw problems you were having ? (if not, what symptoms did it solve ?)

    The thing that still bother me is this : with 2.046 till 2.0.55 I didn't have any yaw problems and my wiring was the same as it is now...  


    Power to my hexa motors is done in a starburst form *.  A central feedline from the battery is split into 6 branches heading into each arm

  • Developer

    Great write up! Thanks for sharing this information. I almost wonder if this should be a blog post so more people have eyes on it.... Its good information for everyone.

    Thanks again!

  • Clarification:

    What I want to say for "independent highly twisted lines" is the following:

    From the battery I´ve created four independent lines black-red (- & +) driven to each of the ESC´s. Each pair of +/-  cables are highly twisted in order to cancel its own magnetic field by its own. This is done for each of the four pairs of +/- cables .

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