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Magnetic interference P85D - Compass and DJI Drone

Discussion in 'Model S' started by AllDigital, Dec 24, 2015.

  1. AllDigital

    AllDigital Member

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    So, here is a new one for me. I've got a new DJI Phantom 3 drone. For the past 3-4 weeks it has been working well, but occasionally throwing compass errors on start-up. After a long drive today, I couldn't get the compass corrected at all to start up the drone (in the middle of a field). After some research online, I discovered that if the compass becomes exposed to a huge magnetic field it needs to be degaussed and the IMU and compass on the drone needs recalibrating. It took a LOT of degaussing to get it back to normal, but it got me thinking... what caused it?

    When I travel with the drone it is in a nylon case in my trunk, right above the rear coil on my P85D. Hmmm. That might be causing a magnetic field. So, I did a bunch of tests. Using a standard field compass in liquid, when I put it in the car in the back it pegs the needle to the floor (suspended in liquid) and the compass needle won't move -- with the car off. I have also found significant compass interference, just by putting it in the passenger seat, passenger floor (front coil?) and moderate amounts around the car. In a drive test, the rear compass test stays pegged while driving, turning, u-turning, etc. Not surprising, given what lies a foot away, but makes me realize that anything that is magnetic sensitive (e.g. a precision drone) might need to be shielded. I couldn't find a reliable place in the car (besides the drivers seat) without any compass interference.

    To test my theory, I took the degaussed drone five miles away in another car (one of those ICE cars) and no issue on start-up. Then I took it to the same field in the back of my Tesla and it needed compass calibration three times to get it started.

    I know there are other threads discussing EMF, but does anyone have a good solution to shield sensitive equipment in the back of a P85D? I can't be seen flying my drone and driving a gas vehicle.
     
  2. siucity

    siucity Button Pusher

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    I have a DJI Phantom 3 Pro, and I've traveled with it in a case (regular DJI case) in the frunk. Haven't had issues starting it up. Are you experiencing issues when it's stored in the frunk too?
     
  3. ecarfan

    ecarfan Well-Known Member

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    And you have a Dual Motor car. Interesting. Apparently the EMF is weaker due to the smaller, less powerful motor in front.
     
  4. mrElbe

    mrElbe Member

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    Airport security baggage Xray is also not kind to the drone compass calibration.
     
  5. MarkS22

    MarkS22 Member

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    Hmm. I've traveled quite a bit with an Inspire in the back of my P85D, both in the case and out and a couple times in the front seat. Never had any issues like this. Maybe the Inspire has better shielding? I do have an older Phantom that I could test.
     
  6. Denarius

    Denarius Active Member

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    I always keep my DJI Phantom 3 in the trunk of my P85D, I store it in a pelican hard case and have never had any compass issues. I only calibrate if I've driven > 20 miles from the spot I last used it.
     
  7. Tdriver

    Tdriver Member

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    I have a Phantom 3 and had it in the frunk for a 1000 mile trip. No issues in my 85D.
     
  8. EarlyAdopter

    EarlyAdopter Active Member

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    I've traveled a couple of times now with my DJI Phantom in the frunk of my dual-motor Model S, 300 mile round trips, with no compass errors.
     
  9. v8eater

    v8eater New Member

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    Make sure you register with the FAA before flying. :rolleyes:
     
  10. choatie88

    choatie88 Member

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    OT: Agreed the registration requirement is silly, but the problem of irresponsible drone owners interfering with aircraft is not.
     
  11. jeffro01

    jeffro01 Active Member

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    If people could just be responsible adults then drone registrations wouldn't be needed... Unfortunately it's only a matter of time before some idiot's drone gets sucked into a commercial airliner jet engine and then things will really get ugly from there...

    Jeff
     
  12. choatie88

    choatie88 Member

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    c.f. autopilot, etc etc
     
  13. pilotSteve

    pilotSteve Member

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    Not to go too far off topic (I have a DJI Phantom 3 so next time I take it traveling in my S85 I'll carry it in the trunk). HOWEVER I have serious concerns about the FAA's "registration" of drones. At the least its self-incrimination and quite possibly illegal anyhow. Consider reading The Problems with Mandatory Drone Registration - sUAS News.
     
  14. choatie88

    choatie88 Member

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    There are many problems with the FAA's drone registration program, but this is not one of them. Do you feel the same way about being forced to register your car and display a license plate?
     
  15. AllDigital

    AllDigital Member

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    Back on topic... I might have an overly sensitive DJI or something else might be going on, but the compass test I did in the car clearly indicates a significant magnetic field, even when off and parked. Enough to peg the compass flat. I'm sure the DJI sensor is more sensitive than an old liquid filled Boy Scout compass, so I would assume the DJI component compass is also "pegged" in place when I'm driving around. I'm going to experiment with a Mu Metal shield in the case to see if it helps.

    On the side topic of registration... I'm registered and I also think it is necessary. Interesting that it isn't drone registration it is pilot registration. The reg process doesn't even ask if you own a drone, the make or model. So, it is more analogous to a drivers license than a car registration, although you are supposed to put your reg id on all your drones. I didn't used to think it was necessary, but after flying the DJI for a while, it has become obvious that the tech has matured to a point where any 10 year old could fly a drone miles away and at thousands of feet high without any training. The price point will drop rapidly and millions could ship, creating real hazards and irresponsibility without some accountability. The next 3-5 years will be interesting as the FAA, cities and states struggle to find a balance. An HOA community near me just banned drones, which is funny, since they don't own or govern the skies above -- like banning airplanes above your property. A legal Wild West for a while.
     
  16. kennybobby

    kennybobby Member

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    Does it do this on the right side of the trunk toward the inverter, or on the left side toward the motor? Can you try the compass test underneath the car to pinpoint the source both when off and on--i would guess that it will be in the vicinity of the inverter.

    The large cables to the inverter make a dc current loop that creates a magnetic field, which it sounds like the North pole is pointing down.

    Any iron or magnetic steel sheet will work as a faraday cage to shield the magnetic field.
     
  17. MITE46

    MITE46 Member

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    I have the same issue with Phantom 3 pro in hard case...but I tested it with another identical setup, same exact model and case, and the 2nd one didn't have issues. This is right on top of the rear axle in the trunk.
     
  18. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    I carried a Phantom 2 in a hard case in the frunk of my P85+ for months, and now a phantom 3 is a soft case in the trunk of my P85D and have not had any issues with the compass.
     
  19. asudan

    asudan Member

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    Airplanes are designed to handle bird strikes from MUCH larger birds than these drones they are trying to register. This isn't the issue My DJI will not even fly near enough to an airport to be an issue and the smaller drones are really no issue.

    This is about control. It is about making a list, etc. Government oversight. It has nothing to do with drones being sucked into jet engines.
     
  20. jeffro01

    jeffro01 Active Member

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    You couldn't possibly be more wrong but don't let facts get in the way of your anti-government sentiment. Drones should be outright banned and they eventually will be if the current behavior issues some drone owners seem to already have. I know a fair share of pilots, some fly for well known commercial airlines and I can assure you they are extremely concerned about this scenario. The risk is even greater when talking about smaller aircraft like helicopters and such.

    The way this should work is you are not allowed to fly at all until you've proven you can responsibly operate your drone, much like a car or any other aircraft out there.

    Jeff
     

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