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GPS what's the hell is the point if it fails so miserably?

Discussion in 'Cinestar Misc' started by Justin Marx, Jul 14, 2014.

  1. Justin Marx

    Justin Marx Active Member

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    I had another recent almost catastrophic crash! was low to the ground getting ready for a shot with position hold and altitude hold on.. The copter decided to go at full speed in the opposite direction of where it was supposed to.. I did recover it and didn't crash, but it was a severe mishap that could have led to bad things happening with over $60k worth of gear. There was ZERO time to shut GPS off..

    All of you full manual flight people take it easy for a second.. I get the whole fly manual thing, but this was a gusty day the position hold was a huge help.. What's the point if you can't ever use it? I know how to fly manually but for some really precise shots in gusty conditions Position hold just seems smoother.

    Questions:

    1- when is it safe to use position hold? (Besides Venus aligning with Saturn, the sun setting, moon rising, low tide, with one foot in the air)
    2- does anyone else have these catastrophic failures with their MK System where the copter just takes off?
    3- is there any system that I can add to this that could give me some more safety features, redundancy, anything??
    4- is there a way to tell GPS to never throttle above a certain amount? Or never let the GPS sticks go to a certain number? Why should it ever be able to go full speed?
     
  2. Bart Cocchiola

    Bart Cocchiola New Member

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    was this a first flight of the day or the first flight at a new location that day?

    i've had weird MK behavior in GPS mode when I didn't let the GPS get enough satellites before flying and sometimes it takes longer than usual when at a new location.
     
  3. Justin Marx

    Justin Marx Active Member

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    Hi Bart,

    3rd flight exact same location doing exactly the same shot over and over. 8- satellites at the time of the issue
     
  4. Steve Maller

    Steve Maller UAV Grief Counselor

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    Justin,

    It sounds like you may have experienced some kind of transient interference or failure. Do you have a GPX file from that flight? I bet the answer to at least one of your questions is in there. Unfortunately, it may not solve your problems, though.

    The truth about the GPS system that MK uses is that it's a consumer-grade GPS, and there are no redundancy backups to it. In my experience with it, I've found that a careful survey of the flight zone and test flights can reduce the probability of problems. But until we have true redundancy, integration and intelligence, you will have to provide everything yourself.
     
  5. Justin Marx

    Justin Marx Active Member

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    Steve have you ever heard of any sort of system that uses something better then consumer?
    I hate to bring it up all the time, but my phantom NEVER has any issues and Ive flown over 500 flights with it.
    GPX File attached..
     

    Attached Files:

  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    What was the solar weather like at the time you flew? All it takes is a high energy burst of protons from the sun and GPS can suddenly go erratic. Check n3kl.org (http://n3kl.org/sun/noaa.html) -- the Estimated Kp Index (lower center) is a good measure. There is a solar weather forecast so you can anticipate when things are going to be bad (e.g. when Kp = 4 things can get unreliable, if Kp > 4, then I would not use GPS).

    Andy.
     
  7. Dave King

    Dave King Well-Known Member

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    Justin

    I feel your pain. Sometimes GPS can spaz out and you have to train yourself to turn it off if needed extremely quick. It's something you have to train yourself to do. You have to remember you are dealing with consumer grade GPS systems and for the most part they work extremely well but they were not designed for precision control and flying. There are some things that you can do to prevent GPS issues. There are practices that I mention below to help you. Since I have correctly wired and setup my new copters I have not had one problem with GPS being flaky.

    1. Don't use GPS where you have partial coverage like flying the GPS under trees or being surrounded by trees.
    2. Make sure you give the GPS enough time to develop a map after power up. I try to give it 3-4 minutes before I take off after power up.
    3. Make sure that you check off the features to prevent the copter from starting if you don't have a solid GPX fix.

    Now I will tell you one last thing which is extremely important. Make sure you wire your stuff the correct way. Lipo wires need to be either taped together or heat strinked together. Motor wires need to be "tightly" braided together or heat shrunk together. Any power wires need to be twisted together or heat shrinked together. Lastly the compass has to be higher than any power line including lipo batteries. If something is not right it can create intermittant magnetic fields that can mess with the compass and cause things like you mention.
     
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  8. Steve Maller

    Steve Maller UAV Grief Counselor

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    Thank you for clarifying that, Dave. I implied that was a possible cause in my note above, but did not completely explain why. During periods of very high current draw, you can see interference to your compass, and possibly even your GPS.
     
  9. Justin Marx

    Justin Marx Active Member

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    Great things to keep in mind.

    The copter is a RTF from quadrocopter, I would have assumed they thought of these things? The GPS/compass is about 3" from the Lipo and lower.
    I can't imagine they would send a copter out like that if it could make a difference? Even in the FREEFLY CINESTAR manual it has it in that location.

    At this point what your saying sounds like it makes so much sense though! My wires on all of my Lipos are twisted and zip tied (thanks to my friends Leo,and Jose!)

    So maybe I need some sort of bracket for the GPS/compass to bring it up higher ..

    Dave would you mind posting a picture or two of your copter? Thank you!!
     
  10. Dave King

    Dave King Well-Known Member

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    Here you go. These pictures are a little outdated. I have taped my lipo wires since these were taken.

    EXCOMPASS02.jpg

    EXCompass04.jpg
    EXCOMPASS03.jpg
     
  11. Justin Marx

    Justin Marx Active Member

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    Thanks formthe great pix.. Is the last one the compass?
     
  12. Dave King

    Dave King Well-Known Member

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    Yes. I have since use a double standoff mounting system so that it doesn't move.
     
  13. Jose Luis Ocejo

    Jose Luis Ocejo Active Member

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    Ok here is a question if the system on a flying copter that is flying with GPS ON looses power for a brief moment during flight due to lets say a connector not siting right or something else, would this brief power interruption essentially reset or reboot the navi and GPS boards in flight, rendering the copter to be in manual mode, and caching off gard an unexpected pilot? this may be a reason why some have experience lost of satellites in flight? and perhaps flyways

    today I was flying a small copter it has the yellow XT60 connectors very solid robust connectors, and on plugging the lipo connector I notice a intermittence connection I shake the well sited snug connector and clearly saw a break in the power
    most of this connectors EC5 EC3 XT60 and others are base on bullet design where the male part is divided in 4 or 2 to create a snug fit on to the female counterpart after inspecting the connector I realize that the male part on the copter was a little blackened and the spring characteristic was a little week also the female connector on the lipo was a little blackened too I guess from the small spark every time it gets connected so got to do maintenance more often to the connectors
     
  14. Steve Maller

    Steve Maller UAV Grief Counselor

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    If the entire copter loses power from the mains, even for just a second or two, I don't think it can recover. Remember, everything...the radio RX, the ESCs, the flight control board, nav board...all of it will turn off and try to reboot. And in the few seconds that takes to happen, the copter will probably be wrecked.

    Eventually we will all have truly redundant power systems that can survive that kind of thing. But for now, I guess the main battery connectors should be considered expendable.

    Apropos, I've thought about using a small battery to boot the copter (no spark if it's a 500 battery, I think), then putting one of the big LiPos on, then disconnecting the little battery and putting on the other battery. When I swap batteries nowadays, I do them one at a time so the copter never powers down. That way the caps stay charged and I don't get sparks (I think that's what causes it). The sparks make me nuts...
     

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