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Phantom drifting after wide and tall legs installed

Discussion in 'Phantom 1 Discussion' started by Wedeliver, Aug 18, 2014.

  1. Wedeliver

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    I am getting a bit more drift then normal after putting a set of those wide and tall legs. I tried to read everything about compass placement and what I read, most of it at another forum, was then it can go either lower or higher then original but what is important is that it faces the same way. With that it seemed to drift more so I angled the compass slightly in towards the center (as opposed to out away from the center) I didn't move it much but it seemed to help a bit. I have osd so I could see that under both situations I was getting about 9 sats. I would love to find an informative article that speaks to compass placement and what are the important things to do to properly move your compass if you change landing legs. thanks (elguano lol)
     
  2. Elwood58

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    Compass placement would have nothing to do with GPS reception. Did you force a compass calibration? If so, did the calibration complete successfully?
     
  3. Wedeliver

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    As always I got that "MC hot" message but I thought it worked ok. I will run the calibration procedure on the computer again and see if it helps any. I have looked everywhere for how to move a compass but not much info could I find. But I have read that it is ok to move it up or down but if you change the direction it faces that is what is important. I agree the compass placement will not do anything with gps reception, but the two do work together. I have been led to believe that the compass tells the quad a direction. Together with gps that is how the quad learns to say in one place. Without a compass you cannot fly in gps mode.
     
  4. RichW

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    I'm having the exact same issue and guessing that's its down to a slight rotation of the compass, no more than a degree or two. I'm still experimenting but recent bad weather in the UK has me grounded. I'd also love to see some informative info on this to know if my guess is right
     
  5. ElGuano

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    You're correct, they work hand in hand, and if your compass is off, you can get drift (forward, backwards, sideways, big circular swirls). Do you have an image of how your compass is currently mounted?

    It is a multi-axis compass so technically it shouldn't matter if the compass is slightly tilted as long as it faces forward; however it's another variable it would be good to eliminate if you are experiencing problems.

    I would stick a (nonmetal) rod or chopstick into one of the accessory grommet holes and firmly affix the compass to that, lined up to the ground and of course facing the exact same direction as stock. See if that eliminates the drift.

    Depending on your landing gear, it could also be the case that it is getting in your prop wash and affecting the behavior of the IMU. But I would test the compass first.
     
  6. Wedeliver

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    Thanks everyone, 'specially you elguano.. I will put a picture but in the meantime it is positioned the same way the stock compass was. Slightly lower on the leg, so a little further away from the gps unit, but it is facing exactly (to the eye) as the stock one. Now it is about 1.5" back from where the stock would be since the legs are wider. This is the gear I got.
    http://www.ebay.com/itm/like/281266956615?lpid=82

    I have gone into Naza software and re-calibrated and after the mc hot it did a complete calibration and I ended up with great numbers. I then went outside and after take off, having 10 sats, with sticks centered it was flying in a 15' diamater circle. When I would move forward after releasing the sticks it would continue forward for quite a way. So, it still is not working like it did before with the stock landing gear. I think I will take the leg that the compass was on and mount it so the compass is really close to where it was before. I will report on what happens. And I will take before and after pics.

    I have added iosd and fpv with a immrsion 600w tx and all that stuff, plus on this Phantom v1.2 I have a FC40 camera. so with this weight should I adjust any gains to compensate?

    On a slightly different subject, since the quad drifts so much I wanted to land rather then hand catch. As I got close to the ground the props would create lift and make it hard to land, but as my battery was going dead while I was doing this it landed itself very nicely. I hope I am explaining what happened, but I would love to land properly.
     
  7. OI Photography

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    Do you see the green blinking LED's confirming it's locked that many, or just the number in the top right of the iOSD? The flight behavior you describe sounds like it's in ATTI mode rather than GPS mode, which can happen for a number of reasons.
     
  8. Wedeliver

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    I have been experimenting with the compass and I have found that different compasses will give different calibration readings. One compass gave a mod of over 2000 and one of the axis was like 350, I put a different set of legs with a different compass and the readings go the other direction and the mod is like 1200. I calibrated the one over 2000 about 3 times and got it down to 1500 and the bird is flying ok. Now I need to put the wide and tall legs back on, to give more room for a 3 axle gimbal I am installing with a gopro. This is on a Phantom V1.1.1.

    I am expecting that after I do the swap of legs that when I go to fly I will not be steady in one spot but will be circling. Also when I let go of the direction stick the bird will keep flying for a little bit and not come to a halt like it should.

    I think a bunch of folks have put on the "wide and tall" legs that are sold on ebay. I was hoping someone might share how they got the compass to work properly.

    Thanks
     
  9. RichW

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    After having minor issues following fitting of taller wider legs I've now got my bird back to rock solid hover. When I originally fitted I was carful to place it on the vertical but was not 100% sure I'd managed to orientate it perfectly. A little experimentation by rotating it 1 or 2 degrees at a time and retesting now has it acting just as well as before I fitted the legs.

    Getting it pointing exactly right does seem quite critical.