Balancing Gimbal/Compass Calibration

Discussion in 'Camera Mount Misc' started by Andy Johnson-Laird, Sep 14, 2012.

  1. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,351
    Likes Received:
    1,160
    Just curious as to what other folks are doing regarding balancing the gimbal with different cameras -- assuming you find the balance point for the gimbal, how are you marking the setting for each camera with which you fly? For example, I use a CX760 and a 5DM3 and I have to reverse the orientation of the camera plate (obviously) tweak the fore/aft position of the camera, as well as some lateral adjustment on the forward transverse boom. I've used a silver pen to mark the lateral position on the forward transverse boom, but the ink wears off pretty quickly, so I was thinking of cutting some alignment jigs out of acrylic on a laser cutter. I've not found a good way of marking the fore/aft position of the camera on the mounting plate -- it seems generally quicker to pop the tilt servo belt off each time and re-balance it from scratch.

    The other related questions is: do you do the compass calibration with the camera mounted or not? The argument for doing it with the camera mounted is that the camera's going to influence the local magnetic field. The argument against it is that the weight of the camera (especially the 5DM3 + 24mm lens) makes the calibration twirling awkward and ugly.

    Thanks
    Andy.
     
  2. Josh Lambeth

    Josh Lambeth Well-Known Member

    Joined:
    Jun 29, 2012
    Messages:
    1,312
    Likes Received:
    213
    I personally don't use the compass at all on my copter so I just have it disabled... that solves my problem of calibrating it with the camera on.

    In the past though I would calibrate the system without the camera and never had an issue with it.

    Josh
     
  3. Bryan Harvey

    Bryan Harvey Member

    Joined:
    Nov 3, 2012
    Messages:
    227
    Likes Received:
    18
  4. SteveWilson

    SteveWilson Member

    Joined:
    Sep 29, 2012
    Messages:
    63
    Likes Received:
    4
    I'm a silver pen guy too, but a jig would sure be handy.

    I do my compass sans gimbal.
     
  5. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,351
    Likes Received:
    1,160
    @Tuber1der: No, I've not tried that. My "quick release" plate is the entire front transverse boom and the camera plate. You just loosen up the tiltbars (easy with an Hitachi electric screwdriver), and swap the whole thing over in less than a minute.

    @Steve: Hmmm. I suspect the gimbal plus camera would distort the magnetic field a bit -- just the magnets in the servos, plus the camera. But hey, if you find it works, I'll defer to reality over my hunches any day!

    Andy.
     
  6. Arthur Vieira

    Arthur Vieira Flight Squad

    Joined:
    Jun 29, 2012
    Messages:
    185
    Likes Received:
    24
    Andy,
    Silver pen guy here too, but I do balance the gimbal for the most used config only. I have a MKIII just like you with a 20mm lens, this is my default balance. I used to have a T3i that I used without any change on the gimbal and the only problem I had was that I had to trim laterally as the CS was a little unbalanced to on side. Of course the gimbal servos had to work harder.

    Compass. Always with the camera.
    You are going to get lots of different answers to this because this varies with the position on earth where the equipment is used. In North America the magnetic field is very strong, so the compass have a "clear" view of it. But here in Brazil we have one of the least strong fields on the planet so the smallest piece of metal makes a huge difference. I learned this from Holger (MK) :)
    This site have some interesting infos about this. http://magnetic-declination.com/
     
    Juan Pablo Pantoja likes this.
  7. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,351
    Likes Received:
    1,160
    And in the Pacific Northwest, the difference between True North and Magnetic North (the Variation) is around 16 degrees East -- doesn't help to have all that magma just below the mantle in the Cascade mountain range. So for us the magnetic field is "strong but wrong."

    I always compass calibrate with the camera on the gimbal -- but it's a bitch to do with a heavy camera -- best done with two people -- one hold boom #6, the other boom #3.

    Andy.
     
  8. Arthur Vieira

    Arthur Vieira Flight Squad

    Joined:
    Jun 29, 2012
    Messages:
    185
    Likes Received:
    24
    You guys think it's hard to calibrate the CS8 with a heavy camera???? Just imagine how they calibrated this! :D LOL!!!!
     
  9. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,351
    Likes Received:
    1,160
    Why do you think he's wearing a helmet? They had to rotate it in pitch and roll with the pilot attached. :)
    Bet you his gimbal was jittering too....

    Andy.
     
  10. Pablo

    Pablo New Member

    Joined:
    Oct 15, 2012
    Messages:
    15
    Likes Received:
    0


    Hi Andy, I wonder if at the time of calibration with the camera mounted on the 2 axis gimbal, the servos doesn´t forced when composing the axis in vertical position during the calibration?

    And what is the difference between calibrate with and without the camera
     
  11. Matt McCarthy

    Matt McCarthy Member

    Joined:
    Sep 21, 2012
    Messages:
    41
    Likes Received:
    4
    Hey Chaps, Feel a bit silly here to ask this but I have a question regarding compass calibration...

    I take it that your'e talking about the FC Compass calibration and nothing to do with the Radian (I,m still pretty fresh on the Radian),
    Assuming this then are you compass calibrating every time you change the Camera, it's position or the weight involved ?
    I,m on DJI WKM so once I set my compass calibration I don,t set it again unless I see something not looking right when in GPS lock.

    Should I compass calibrate every time I change location or area of flight, or camera being used (5d, Sony HDR PJ740VE, Canon 550D plus a Go Pro when I,m feeling silly) ?
    So far a few different locations and have perfect compass lock on my GPS.

    'if it,s not broken don't try to fix it' is in my head but i,m just wanting to know exactly what you are talking about with this compass calibration.

    Lastly I gather a few of you are MK users is it to do with that ?

    Thanks in advance

    Matt
     
  12. Gary Haynes

    Gary Haynes Administrator
    Staff Member

    Joined:
    Jul 6, 2012
    Messages:
    5,211
    Likes Received:
    460
    Matt most of us probably only do the compass calibration if we relocate to a spot more than 50 miles away east/west. Where I live 1 degree of longitude change is about 75 miles. Personal opinion is that the compass doesn't have that kind of resolution. Changing cameras etc should have no effect, unless, the new device is giving off its own electro-magnetic signal and then you should try to re-calibrate.

    There is a screen in the MX-20 for the MK stack that shows the difference between the compass expected vs. actual. It is on the Mk standard screen and if you press the set button for about a second you will see the bottom of the screen change to show MAG (like to see close to a 100% or higher) and the Mag Declin difference (I think it needs to be less than 10 in order to fly).
     
  13. Matt McCarthy

    Matt McCarthy Member

    Joined:
    Sep 21, 2012
    Messages:
    41
    Likes Received:
    4
    Awesome thanks Gary, thought maybe I,d missed something there but seems I didn't.
    Happy days
    Matt
     
  14. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,351
    Likes Received:
    1,160
    My personal preference is to calibrate the compass every day I fly even if it's at the same spot.
    Why? Well I reason that something may have changed on the Cinestar, wires in a different position, possibly a different camera, etc. and, as calibration doesn't take that long (although it's a bit awkward with a heavy camera and the props on -- much easier with an assistant), why not?

    The compass is used to help keep the Cinestar on course or at a steady heading in position hold -- it feeds into the Yaw control, so, as I say, my preference is to err on the side of caution.

    @Juan: Yes, the EDIT compass camera will create an effect on the magnetic field, but I do not know whether it would be enough to disturb the compass calibration. I need to do some experiments!

    Thanks
    Andy
     
  15. Matt McCarthy

    Matt McCarthy Member

    Joined:
    Sep 21, 2012
    Messages:
    41
    Likes Received:
    4
    Wow Andy you have a valid and cogent argument there and it terms of having the best system I'm not sure I could argue that ! Simply if you do it each time it,s going to be the freshest cleanest signal each time....mathematically ! I think I'll have to stand in the corner and revise my system for this ;) , great input as always !

    Matt
     
  16. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,351
    Likes Received:
    1,160
    Well, I'd always try and double check my Bohli compass every day I went flying in my sailplane -- it's an unusual compass that, you can roll left and right so that it's horizontal when you're cranking around in a thermal. In pinch you can use as an artificial horizon if you suddenly find yourself sucked up into the cumulus cloud you're working and haven't had time to spin up the gyros on the artificial horizon. It saved my rear-end a couple of times. But it also taught me that it was worth having an accurate compass. :)

    Andy.
     
  17. Nathan Reim

    Nathan Reim Member

    Joined:
    Oct 20, 2012
    Messages:
    112
    Likes Received:
    4
    I took some of that velcro strap stuff that you can cut to length and i attach it to the booms and then the gimbal so it locks it in place, then I calibrate, use them also when traveling so the gimbal isnt spinning around when you lift the copter
     

Share This Page