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GPS loss issues

Discussion in 'Cinestar Misc' started by Dave King, May 6, 2013.

  1. Dave King

    Dave King Well-Known Member

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    Over the past couple weeks I have been seeing GPS lost in flight. Is it common that you would lose GPS lock outdoors? I was filming test shots on 2 different golf courses and I had GPS lost on a couple occassions. Now Golf courses are out in the boonies but I also had GPS lost on 2 occassons as I was filming in Downtown pittsburgh where I was out in the open. All but one had GPS lost occurred after I took off (I have it set to not take off when I don't have GPS fix). The other time I had GPS lost was when I was in Downtown Pittsburgh near the river and it told me I had GPS loss when I was trying to take off. I also noticed that on my flight control board (my main one that fried) I had the lady with the voice tell me that I had GPS lost. They both have the same firmware. I thought that was odd. However my backup flight control board does not give me our favorite ladies voice when I lose GPS lock in flight. The main one did. Would the GPS board and shield be in complete control of the GPS signal? I would assume so?
     
  2. Steve Maller

    Steve Maller UAV Grief Counselor

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    Do you have a GPX file?
     
  3. Dave King

    Dave King Well-Known Member

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    Here's one from yesterday.
     

    Attached Files:

  4. Steve Maller

    Steve Maller UAV Grief Counselor

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    I see I2C error(s) in there, too. I'd take a close look at both your connections between the boards, as well as the routing of your battery and motor wires. I used to see that kind of error before I rotated my battery tray 90° and kept the LiPo wires far away from the Navi board and GPS receiver. But if you haven't seen this elsewhere, you could be having interference from nearby buildings or something. I've got very little experience flying in urban environments, but I know others have done it successfully.

    I also see a very high current draw on 2 of your motors (over 25 amps!). I'd be concerned about that.

    FYI I just uploaded a "healthy" GPX file that might be a good reference point. http://forum.freeflysystems.com/ind...-healthy-gpx-file-looks-like.1305/#post-17547
     
  5. Dave King

    Dave King Well-Known Member

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    Thanks Steve for looking at it. The I2C errors are always there, and they are the result from initial power up. They never go up during flight which according to MK is normal. I've had them from day one and even sent my PDB and FCB back to Quadrocopter and they were able to recreate the issues there. Some others on this board have the same issues and theres really no reason anyone can offer.

    All of my wiring of the batteries and lipo wires are good as they are directly in furthest back away from the navigation board. I twist all my lipo wires and heat shrink them so they can't seperately. The reason why you see high current draw is because I had to do some major correcting to land the CS8 when I lost GPS signal. I never have that type of current readings. I fly without PH as much as with it and normally the copter is smoot as butter in both modes. However when I saw the GPS loss probem the copter just went into spazmatic mode.

    I attached a GPX of a typical flight in this posts.

    I think there's just something screwy with either my GPS, or Navigation boards. I did have a crash in January where the copter came straight down because I cut the motors by accident on my very first flight!! It landed in snow and softened the impact but I kind of wonder about it now if there can be something intermittant. I am curious to get feedback from others that fly as to if they lose GPX fix often in flight????
     

    Attached Files:

  6. Steve Maller

    Steve Maller UAV Grief Counselor

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    The only time I've ever seen a GPS loss (or compass error) has been when I had my wiring less tidy than I do now.

    Nor have I ever seen a I2C error (except in a couple of cases where I had a super-rough landing...I believe you'd call that a crash). But the I2C errors were the result of the crash, not the other way around.
     
  7. Gary Haynes

    Gary Haynes Administrator
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    Replace the GPS and see if that solves the issue. If you were flying in the last three days the highest KP index was only a level 3, with most periods at 1. Also depending on when and where you were at the time it's possible that while you had a fix the quality level was low. It's easy to get 10 sats but if you look at a GPS elevation view chart you may learn that most of them were low to the horizon. S

    Looking at the file I suspect perhaps a loose GPS to Navi cable, faulty cable and after that a bad GPS, Navi or both. But since is is sporadic it will be hard to track down.

    Still puzzled over your I2C issues. Just don't see those in other peoples logs. Strange
     
  8. Dave King

    Dave King Well-Known Member

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    Apparently the I2C errors are normal upon startup as Quadrocopter was able to duplicate the errors on their bench with their own wiring. Holger verified this is common and has said as long as the errors do not go up in flight there's not a problem. I have never seen the I2C error count go up in flight or after initial startup.
     
  9. Dave King

    Dave King Well-Known Member

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    Thanks for looking Gary. I was thinking of taking that plan of attack. I definetely didn't have a loose nav cable as I hot glue everything really good but it could be in the wiring as well.

    I hear you about the IC2 errors, they come up on 2 different flight control boards so it's probably in the PDB. Adam @ Quadrocopter didn't think it was anything to concern about since the error counter never increases after initial power up. Did you ever lose GPS fix in flight?
     
  10. Gary Haynes

    Gary Haynes Administrator
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    Loss in flight, not that I know of. But I don't use it but occasionally. Could the hot glue have gotten into the contacts causing occasional circuit disruption?
     
  11. Dave King

    Dave King Well-Known Member

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    I just talked to Adam at Quadrocopter and he suggested that I move or disconnect the Xbee. Right now I have the Xbee on the hub at boom 1 and he say's that it operates on the same frequency so I need to move it for sure.
     
  12. Gary Haynes

    Gary Haynes Administrator
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    Never thought to ask where you had other bits and pieces located. Put the XBee back next to boom 5.
     
  13. Steve Maller

    Steve Maller UAV Grief Counselor

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    My Xbee is strapped inside the landing gear on boom 8 and it's always on, even though I rarely use it.

    BTW, I have my VTx fastened in a similar way to the rear landing gear. I only power up the VTx when I'm using the OSD (which is rarely). The Mondo Extreme sucks down a lot of power, and I share a 1200 mAh LiPo with the Radians (which are surprisingly thrifty about power).
     
  14. Shaun Stanton

    Shaun Stanton Active Member

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    I notice one thing is that several times you induce a very aggressive climb rate in excess 600Ft/Min inducing 25A on a single BL. Number 8 is adjacent to the compass and GPS, so it is possible that your motors started to induce an EM field over to your Nav stack. Even though you may have your wires braided that may not be enough to prevent fringe waves of the magnetic field over causing a disturbance. When current goes up the magnetic field perpendicular to the electron flow goes up. If there are small wires such as the ones connect the GPS to the Navi board those may be inducing an electric field if they are vibrating inside that magnetic field causing a disruption to the signal.

    If a wire moves inside an electric field it causes an induction current in that wire. Most of the time the induction is slight and negligible, but if conditions are right it could cause electrical spikes. This is prevalent to the days if you had a TV with Rabbit ears and you ran a vacuum cleaner and the TV's reception started to go out until it was turned off.
     
  15. Dave King

    Dave King Well-Known Member

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    Thanks Shaun. The reason for the aggressive climb rate was I was trying to avoid trees on the course because the CS8 went a bit loopy when it lost its fix.

    I have a new GPS board, Shield, Molex cable, and relocated the X bee to boom 5. Will do some testing this weekend.
     
  16. Shaun Stanton

    Shaun Stanton Active Member

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    If you can rule out environmentals than swapping out hardware is the best course of action. just to give you some insight, environments like trees and depending on where @Gary mentioned about the satellites in the horizon could cause interference. Thick foliage can attenuate radio signals as well depending on how high you are.
     
  17. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I can highly recommend avoiding trees. ;)

    Andy
     
  18. Dave King

    Dave King Well-Known Member

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    OK I put a new navigation board, GPS board, and GPS shield in. I'm seeing strong signals now as much as 11 channel 3D fix. I went back to the location in town where it wouldn't let me start the motors because it said GPS lost and I had 8-9 strong locked satellites. I think when my FCB blew up it took something in the navigaton/gps boards as well since they are directly connected.
     
  19. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    That sounds like a plausible hypothesis, Dave. The most important thing is that you got it working!
    Andy.
     
  20. Fredrik Hansson 2

    Fredrik Hansson 2 New Member

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    Happy to read this. I have had the excact same problem after a chrash. I have replaced it with new navi and GPS with no improvment or change in the result.
    From what i read here I guess a shield might help.

    Also get about 8-9 fixed sats it flies ok sometimes, manytimes it starts to turn (ride in an angle to the started flightpass) and sometimes it goes banans (turning back and forth to a point where it look like it will stall).

    Will move the GPS with shield from my CS 6 and test it, will get back with the result.

    I do not have a log but I will generate one if it fails again.
     

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