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Compass calibration how often?

Discussion in 'General Discussion' started by cosmonaut, Jun 15, 2014.

  1. cosmonaut

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    So I went to fly my FC40 at my Dads today and the first flight and battery the transmitter lost contact with the drone only 75ft or so away. I flew it still until the battery was exhausted. Second battery again I lost contact with the transmitter but I had a fly away and a crash landing but no damage. Third battery I chose to calibrate the compass. This time the drone flew fine and again with my last battery. I flew it maybe 200 ft away and all went well.
    The first two batteries were third party the last two stock. If that matters? My dad lives in a rural area on a hill top I can't imagine interferance would be an issue. But he lives ten miles from my last compass calibration. Is that far enough away to justify a calibration or could it have been another issue? One more thing both times I lost connection I got the flashing yellow lights. The first time it went into come home mode and returned and the second time was the fly away.
     
  2. BigTulsa

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    Considering I took mine out to a new place but it was only six or so miles from where I normally fly, this is my experience...

    Had a friend coming out to see the vehicle; he was interested as both he and I are licensed private pilots...well, not so much anymore as neither of us are current.

    Took it out above a large soccer complex (abandoned at the time) and flew it up to about 150ft. I'm in NAZA mode on the Vision so I decided to show him how RTH worked. It did, but as it got closer, it started acting a little weird, and I noticed the LEDs were alternating red/yellow/red/yellow. Flipped up on the S1 to GPS and nothing. It just hovered. So flipped back down to RTH, then selected ATTI and was able to get her back down to the ground. That 15 seconds of not knowing how the bird was coming back was scary.

    The whole time my friend is watching on the app on my Nexus 10. As soon as I land it, the thing starts screaming about compass calibration. So I calibrate, and it works just fine afterwards.

    So regardless of where I'm at now, I'm calibrating the compass. It's usually 45 seconds tops for me, and it's worth it to keep it from acting all goofy.
     
  3. Monte55

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    I live on three acres and have room to fly but I also have a park within 2 miles with a larger area free of trees etc. I always do the compass dance at a different area. Costs nothing and takes 30 seconds to do. I never have had an issue. I have the Phantom 1 ver 1.1.1 . Had it about a month and it's on 4.00. I have not upgraded it to 4.02. As long as it's doing what it's supposed to do, I see no reason. Things change in the environment that you may not be aware of so recalibration is a smart thing I think. Not sure if it's necessary but who cares. The only issue I have had is one day I was at the park and powered it up. Got the first set of many green flashes and then got distracted. Not sure if I got the second set of green flashes. Took off and it didn't hold position well so I brought it down and repowered it up again and paid attention. Flew well...no problems. To me, every flight is a test flight. I have a stopwatch on my tx. When I think my time is near to bring it in, I bring it down a bit and goose the throttle. If I get red flashes, it's time to come home.
     
  4. Miika

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    Its not advised to do the compass calibration as many times as possible. First of all, when doing the calibration on the field without a laptop, you cant see how well the calibration worked as you cant see the mod value. For Phantom to start giving compass related errors, the compass needs to be way way out. So recalibrating the compass might endup in a bad calibration you knowing nothing about it.

    Good mod value is around 1500
     
  5. Monte55

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    If its not advised, then post a link..and not by someone with no creditability, as to why it's a bad idea
     
  6. cosmonaut

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    So I learned something new I didn't know I needed to calibrate via laptop. I have replaced my motors to the T motors. I am not getting a second more flight time but am still with 8 inch props. It is however more repsonsive and maybe a little quitter. Stock batteries are only giving me five minutes. I have an alarm that goes off just a little ahead of the red light to insure I can get it down in time. The red light is blinking most often when it gets to the ground.
    I have upgraded firmware.
     
  7. Miika

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    Give me a link where its advised? DJI advises people to recalibrate the compass only when you have changed the geological location (a bigger change in location). If you get a good calibration, the only thing your doing by recalibrating the compass all the time is adding the chance of getting a bad one.
     
  8. Miika

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    You dont need a laptop, but after you have recalibrated your compass and want to be sure everything is ok... its wise to check the mod value of the compass in the assistant software. If I have a good calibration (mod value around 1500) I surely wont be recalibrating my Phantom all the time, as I cant see what it did to my mod value.

    Let's say you calibrate your compass in location A and fly with your Phantom. Check your mod value and its around 1500. Then you go to location B which is further away (not hundreds of miles away). You recalibrate the compass, but this time the mod value goes closer to 300 or above 2500. Even with bad mod values you get a succesful calibration, but your compass is giving mixed readings to the Naza.

    If you have good calibration, why would you want to recalibrate? The only thing your going to do with recalibration if its not needed is to add a chance of bad calibration.
     
  9. cosmonaut

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  10. EMCSQUAR

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    Cosmo - to answer a few of your questions:

    You should only need to calibrate your compass when you first get your Phantom and anytime you find it flying strangely - IE: toilet bowl hover, etc. I also make it a practice anytime I have mine open for anything to do an advanced IMU cal & compass cal. Doing compass cal when flying long distance from last flight is just precautionary and not mandatory.

    Re: your T motors and flight times - you might want to try lowering your pitch & roll gains by 10% and see if that gets you more flight time. Might also consider P2 props.
     
  11. TeamYankee

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    I fly in a few different areas with different geological features, grass playing field (park with trees), another park with open area field (used to have a railway through it) and an ex steel foundry area that is now a sports field area.

    I always calibrate the compass as I'm unsure what's under my feet... lots old iron under the ex steel foundry area even though there is no evidence on the surface. You never know...
     
  12. Miika

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    You should calibrate in a location where you know that there is no interference in the magnetic field. And for a double check see whats assistant software is saying about the compass mod value (should be around 1500).

    You shouldnt recalibrate if there's a metal structures around/below your quad... This will not make your compass work better in those surroundings, but instead will give you worse calibration. You should keep the calibration that you did when you knew theres no chance of intereference and fly with that. That way your Phantom has a good calibration and when your flying near to those bigger metal objects then it might have troubles with compass readings... But I surely wouldnt want to calibrate the compass when theres objects/structures/what ever causes of interference.

    In a nutshell: calibrating the compass when there are what ever reasons causing changes to the magnetic field wont make your compass to adapt to those surroundings.
     
  13. cosmonaut

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    Thanks I will do that.