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Warning about Double Quadro2XL PDB

Discussion in 'Electronics' started by Ozkan Erden, May 18, 2014.

  1. Ozkan Erden

    Ozkan Erden Distributor

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    Hello everyone,

    With the release of BL Ctrl 3.0, MK came up with several ready to go boards, including Double Quadro2XL PDB for Octo copters.

    Basically, this is two Quadro PDB stacked over each other and soldered through several points. The connections between these two Quadro boards are, I2C lines (C and D), Buzzer (+) and battery lines (+ and -)

    The buzzer of the copter stopped working suddenly, and while checking the buzzer, I noticed that the connection of the buzzer from the first quad PDB to the second PDB was broken. That was the reason for buzzer wasn't working.

    When inspecting the board I noticed that, one of I2C lines (C) was also broken. It was just touching barely. If it would break up totaly in the air, the copter would collapse.

    So, the weakest point of the new Double Quadro 2XL PDBs are the connection points. The battery connections will never come loose, but, I2C lines are also lethal and they should be soldered to each other with another pair of wires for safety. The links for I2C lines between two boards are very fragile and weak.

    I was lucky to see it before it happened. Just double check yours and take precautions.
     
  2. Steve Maller

    Steve Maller UAV Grief Counselor

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    Thanks for the warning!
     
  3. Michael McVay

    Michael McVay Active Member

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    Nice catch on the I2C line...thanks for passing this along to us.
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Good catch, Ozkan.
    Have you also told Holger about this?

    Andy.
     
  5. Ozkan Erden

    Ozkan Erden Distributor

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    Hello Andy,

    Yes,I have sent them email also.
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hi Ozkan:
    Thanks -- please post Holger's response. As you say an I2C failure is a Really Bad Thing.

    Andy.
     
  7. Ozkan Erden

    Ozkan Erden Distributor

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    I will post some pics of the problem, and picture of a small fix to make the PDB much more reliable.
     
  8. Wilhelm

    Wilhelm New Member

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    Hmmm, the wires for the Buzzer and the I2C are 1mm². Also the Double Quadro is tested from MK.
    Such wires will normally not break without reasons. So as you wrote you did not get the Double Quadro with broken wires - right?
    How did you assemble the Board on your Copter? Did you use metal screws (which is not recommended) or plastic crews?
    Maybe on your copter you have strong torsion's during flight and this are the result of it? Is you copter a heavy copter?
    How did you transport the copter? Also if the copter is shaking / jumping in your car this can happen. I know this very well ;-)
     
  9. Dave King

    Dave King Well-Known Member

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    I emailed Holger about this thread and this is what he replied back to me.
    Hello David,
    yes, we saw that. We have no Idea what happened there.
    We were trying to break these contacts, but that needs extremly high force.

    The wire we are using is 1mm² and is protected by a plastic tube in the current designs.
    If the Board is mounted through the screw holes, the connection would be safe.

    The wire for the buzzer is weaker, but that is not a critical part.
    Anyway, we will change the wire to 2mm² in the current design. The hole is big enough.


    Regards,
    Holger
     
    Steve Maller likes this.
  10. MIke Magee

    MIke Magee Active Member

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    Really looking forward to these shots. Thanks.
     
  11. Ozkan Erden

    Ozkan Erden Distributor

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    Let me clarify some points:

    * The PDB is installed with plastic screws.
    * The wire is more likely "slipped out" the solder blob. The compression was holding them together.
    * The copter flew like 120 minutes max without any hard landing.

    Here is the picture of the problem:

    20140519_084907.jpg

    I soldered a small wire between each the lines:

    20140519_090343.jpg

    So they are more reliable right now.

    Another note:

    For safety reasons, I also always solder CD lines and +/- lines between PDB and Flight Controller in case molex connector come loose. I lost a copter in the past because the molex connector came loose.
     
  12. Dave King

    Dave King Well-Known Member

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    I can't get your first picture to load.
     
  13. Ozkan Erden

    Ozkan Erden Distributor

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    I'm uploading again:
    20140519_084907.jpg
     
  14. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    So this looks more like a manufacturing error, Ozkan -- "The wire is more likely "slipped out" the solder blob" suggests that someone made a classic "dry joint" where the wire has not properly fused with the solder.


    Andy.
     
  15. Gary Haynes

    Gary Haynes Administrator
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    Why wouldn't the wire go completely through both boards, similar to the way the old boards attached with the capacitors and C/D wires?
     
  16. Ozkan Erden

    Ozkan Erden Distributor

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    This one(OktoXL combi) is built as you described:

    https://www.mikrocontroller.com/ind...id=811&zenid=479ba4ff2d31cdab71f5b20af8387e5b

    But, OktoXL combi is rated for 120A, while Double QuadroXL is capable of total 240A. The ESCs are bigger, so it would be huge if it was designed as a ring. So they choose a stack system. Hercules III is also stacked over each other.

    Once I seperate the boards, I will see if it's a break or bad solder. But either, we need to take precaution to make it more reliable. I suggest everyone to do it. It is just 5 minutes process.
     
  17. Wilhelm

    Wilhelm New Member

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    Sorry, I don't know what you see, but this looks like a broken wire. Did you not see the cut right under the upper PCB?
    And Ozkan, you did not send a picture how you assemble it. So you are sure that this can not be a problem of your copter (strong torsion's during flight) ? Also you did not tell us how you transport the copter. Also if you think this can not be the problem, it can. ;)
     
  18. Ozkan Erden

    Ozkan Erden Distributor

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    On a Cinestar frame, I put the spacers (I use soft rubbers for vibration dampening), and than put some plastic screws for tightening. No way for over tightening since there are plastic standoffs between these two boards.

    The copter was transported several times by a car to a 5 minutes distance. So I don't think this is also related with transportation nor installation.

    I'm using MK electronics since 2009, I can't remember how many times a capacitor leg broke on the previous PDBs. (It's not more than 5 though:) ) We needed to check their health on regular basis. (Even though they were secured by hot silicone)

    On these new PDBs, I also think the integrity should be checked on regular basis. I accept my circumstance can be rare but, these small vibrations will eventually weaken those points on a long run. Most of us used old MK systems quite a long time so we know their drawbacks. These new boards are just out and we don't know what's going to happen in the long run. The fix is quite simple, it's better to take precaution before we wait to happen.
     
  19. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Wilhelm: I thought that was just shadow. If that's a broken wire, that, as you say, is a major problem.

    Andy.
     
  20. Bo Tornvig

    Bo Tornvig Member

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    Hi all,
    Has anyone tried to do this:
     

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