GPS on posts

Discussion in 'Cinestar 8' started by Tyler Olson, Nov 13, 2013.

  1. Tyler Olson

    Tyler Olson Member

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    Does anyone put their GPS up on posts to get it up higher and away from the motor cables? I have heard that with a heavy load on the copter the GPS can start to act funny or unreliable. Wouldn't it help to get the boards away from the arm and up in the air 6-10cm?
     
  2. Chris Fox

    Chris Fox Active Member

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    G'Day Tyler,
    My GPS is sitting on three nylon 15mm standoff from the GPS mount. The navi board is happily sitting in the mix of that as well.
    Haven't had any issue with GPS performance and carrying the MōVI MR and D800.

    I have had some stability problems in manual flying at increased weights, but GPS has been good.

    Cheers
    Chris
     
  3. Dave King

    Dave King Well-Known Member

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    I have experimented with this idea by stacking nylon standoff's to raise the GPS and Navigation boards. I have not noticed any difference in performance with this mod.

    DSC_0010.jpg
     
  4. Steve Maller

    Steve Maller UAV Grief Counselor

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    That's interesting...I just got some 90° elbows to build a lift for the GPS stack from a couple of short CF tubes. I have a strong feeling that this will improve GPS performance. I intend to lift it just above the level of the battery tray with two 3-4" tubes. One rising vertically from its current location on Boom #1, and another angled backward to place the stack at the same location, just higher.

    I, too, believe that the toilet bowling and other anomalous behavior is being partially caused by the current draw caused by the GPS sticks, and it gets amplified when the copter is flopping about because of the increase in power. I've seen that if I level the copter a little the problem subsides. So I think that when the copter tips enough for one or more of the sats to end up "behind" the battery tray, the signal can be disturbed. Raising the GPS antenna high enough so this doesn't happen might fix this if I'm right.

    If not, I'm just out $50 for the joints, and I have a new carrying handle for my Cinestar. ;)
     
  5. Steve Maller

    Steve Maller UAV Grief Counselor

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    Dave, we were typing our posts at the same time. In your picture, I clearly see that the GPS antenna is still below the batteries. I'm quite curious about my mod I described above. I'm hoping to get that done this weekend. I'll let you know what I find.
     
  6. Dave King

    Dave King Well-Known Member

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    Hi Steve

    Yes its below the lipos but above all lipo wiring (including the wiring coming out of the lipo) which I think is the point of interference. I would try to raise it but my cables are maxed out. You would need to make up some custom cables to extend it higher.
    I also noticed that raising the boards made a significant difference in the center of gravity for the copter.

    Here in Pittsburgh essentially my flying time is over as average temps are in the 20's now and my one flight in the low 30's gave me 4 minutes flying time with the 7D. I"m now trying to finish my demo reel I have been working on all summer :) I can't wait to show you.
     
  7. Dave King

    Dave King Well-Known Member

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    One thing I didn't do after I made this mod was to recalibrate the compass which I think should be done.
     
  8. Steve Maller

    Steve Maller UAV Grief Counselor

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    Well, like I said, I will report back as to whether what I'm doing makes anything better. In PH, I often end up seeing this kind of thing. At this level of bank, it's easy to imagine that the batteries are blocking part of the GPS signal.

    [gloating comment about California weather deleted out of sudden rush of kindness] :)

    QuickTime Player-snap001.jpg
     
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  9. Tyler Olson

    Tyler Olson Member

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    Thanks for the thoughts guys. Let me know how it goes Steve. I'll do some tests here as well and let you know the results.
     
  10. Dave King

    Dave King Well-Known Member

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    Really? I never see that in PH!! It's amazing how much these copters perform differently with the same exact parts. Could that have something to do with the PID and the Gyro PID? The problem I experience is that sometimes my GPS just freaks out. One out of every 50 flights and it does it as soon as I engage PH. If I take it out of PH its fine and then reengaing PH it will be fine. I think that there is something going on with one of my boards but I"m just not sure.
     
  11. Dave King

    Dave King Well-Known Member

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    I guess it would depend how many GPS satallites are locked in at any one time.
     
  12. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    At that angle of bank I'd be more worried about Dave's placement of the batteries having an adverse effect on the copter's center of gravity! :)

    I do like your approach to the "boom in shot," thought Steve. If you can't fix it, feature it!
    (Hey did you see that MSFT's done away with stack ranking! 'bout time, no?)

    Andy.
     
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  13. Dave King

    Dave King Well-Known Member

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    Huh? What's wrong with my battery placement?

    DSC_1013.jpg
     
  14. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    The batteries are pretty high up, Dave and, at the angle of nick that was on Steve's copter (20 degrees?) the CoG of the battery pack would be moving out from the center of the battery plate and starting to make the copter pretty nose heavy. That was the concern.

    That said, I can now see that you've got a LiPo out on boom 6 that will offset that.
    Andy.
     
  15. Dave King

    Dave King Well-Known Member

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    Hi Andy

    I see. I use 60mm stand off's so I can have enough clearance between the fan and the upgraded ACC sensor. I think most are using the 55mm green ones?
     
  16. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Right -- I remember you installing that fan (and how effective it is).
    I would say, on balance, (pun intended) you should be OK as long as you don't fly like I do, and you're cautious when you fly like Steve does! :)

    Andy.
     
  17. Dave King

    Dave King Well-Known Member

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    Andy: One the subject of boom 1, do you often have to reshoot because boom 1 dips down in the picture as you are going forward with the copter? I was there was a heavy lift hex :(
     
  18. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I don't often have to reshoot -- most of the work I do is of outdoor landscapes and they don't tend to move around a lot ;) -- but I fly very slowly and gently so boom-in-shot is not usually a problem. For those follow-shots, I try and get up to speed some distance away so that I'm already doing 25 - 30 mph before the shot starts rather than accelerating in the middle of shot.

    Andy.
     

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