UGH! BL Limitation Error on new PDB, but nothing in LOG file! SOOOOOO Frustrated!

Discussion in 'Cinestar 8' started by Ben Freedman, Feb 18, 2013.

  1. Ben Freedman

    Ben Freedman Member

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    Hello all once again...

    Really, I'm a very happy person normally. You wouldn't know it from my posts here, however.

    So, today I did 3 flights without incident. On the last flight the MX20 registered a BL LIMITATION error...

    Now, I am flying with a very light NEX camera. Nothing heavy. Ambient temp of 50 degrees. Not hot.

    So, instead of finishing my job with my client, I pack it in and head back to view the log file. And what do I see? NOTHING! No errors recorded, and it appears that the BLs are NO WHERE NEAR their limits...

    Can anyone shed some light? GPX is attached.... :(

    Best,

    Ben
     

    Attached Files:

  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hmm. Check the summary of the GPX file using MK_GPXTOOL, Ben.
    The motor currents look a bit odd:

    Motor1: 4.5 6.3 9.6 A Temp: 19 57 73 °C
    Motor2: 1.3 2.3 3.2 A Temp: 16 50 59 °C
    Motor3: 1.6 2.6 3.9 A Temp: 14 50 60 °C
    Motor4: 3.8 6.6 9.1 A Temp: 13 58 70 °C
    Motor5: 4.5 6.2 9.1 A Temp: 18 54 65 °C
    Motor6: 1.3 2.8 4.2 A Temp: 21 58 75 °C
    Motor7: 0.8 6.0 7.6 A Temp: 27 62 78 °C
    Motor8: 0.8 5.0 7.6 A Temp: 23 52 66 °C
    Motors 1, 4 and 5 seem to be pulling a lot more current than they should compared to the other motors.
    When you landed the bird, did you happen to notice whether any of the BL-Ctrl's had red LEDS lit or flashing?
    It's hard to know quite what the problem was, but I'd start by checking the the each motor's prop blade tips line up with the neighboring motor tips just to eliminate motor alignment as an issue.
    Apart from that, the GPX file looks normal.....very odd as to why the MX20 would have announced a BL LIMITATION error. Makes me wonder about the telemetry it was getting.
    Andy.
     
  3. Ben Freedman

    Ben Freedman Member

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    I don't get it myself, unless there's something wrong with the motors. If it was a balance issue, you'd expect opposite motors to have opposite readings (ie. left motors running harder than right motors). If it were YAW, you'd expect the odd or even to be higher or lower. I don't see any correlation there...

    Also, the higher motors don't necessarily have higher temps.... and NONE of the motor's temps seem to be in the range to cause a BL limitation error...

    I'm thinking of sending ALL the motors back to QC for replacements, since some are making nasty crunchy noises too...

    <sigh!>

    At least it's flying... and so far, still no crashes! :)

    Best,

    Ben
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Before you send all the motors back, mark motors 1, 4, and 5 with their current boom numbers (using a silver pen, say), then move them to different booms and see if the higher current follows them to the different boom. If it does, then it's motors. If it doesn't, then it's likely to be something else....

    As you say, flying beats crashing any day.

    Andy.
     
  5. Gary Haynes

    Gary Haynes Administrator
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    Andy (the code talker) what triggers the BL limitation from the MK boards to the telemetry? I don't see this listed in the voice messages list from the other day. Ben was it voice or text on the screen? If it was text then there must be another list in the Graupner SD card for txt messages.
     
  6. Josh Lambeth

    Josh Lambeth Well-Known Member

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    Just an FYI, when i was flying before my upgrade I would get that error every so often on my TX but it would never log the error. I just kept flying... never had an issue unless it was on over-temp issue... I would always be watching that.

    Josh
     
  7. Howard Dapp

    Howard Dapp Active Member

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    How's the soldering for the ESC's power and motor wires?
     
  8. Ben Freedman

    Ben Freedman Member

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    It was a text message. The soldering is solid, as far as I can tell...

    B.
     
  9. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I was looking for that. There is a current limit (you can see what this is set to using MK Tool to get to the BL-Ctrl data display -- but the value is something like 45 Amps for a single BL-Ctrl.

    I've not found the specific temperature limitation -- I think that is set in MK Tool for the BL-Ctrls as well.

    I don't have the copter on my bench right now so I cannot bring up MK Tool to check.... but you can see it illustrated here:
    http://www.mikrokopter.de/ucwiki/en/BL-Ctrl_2.0 (scroll down a bit and you'll see a heading "Display of the measured values in MK Tool").

    Andy.
     
  10. Gary Haynes

    Gary Haynes Administrator
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    So that text message is apparently this one:

    24 "BL Limitation"

    • A BL-Controller is in limitation - either overtemperature or overcurrent
    So if the log is correct and we don't see either one of those in the log then the sensor or software might be the issue. Perhaps try re-installing the firmware. Or, and I've never seen nor heard of someone doing this, perhaps the firmware on one or more of the BL's somehow got corrupted?
     
  11. Josh Lambeth

    Josh Lambeth Well-Known Member

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    Im wondering if the BL is seeing some sort of really quick power spike that happens to fast for the log to pick it up? Could explain why the Tx sees the error but the log never does. I would get them at least once a day, sometimes more, but never once had a log file capture it.

    Josh
     
  12. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    It's certainly true that the sampling for the GPX file will miss any low frequency events. What I don't know is the sampling frequency for the MX-20 telemetry.

    That, of course, still leaves the question as to what on earth would cause those low frequency spikes?

    Before I upgraded to the HOTT v4, what I've seen (well, heard) in the past, is that right after takeover on a third or fourth flight, I'd hear the bong-bong-bong tone from the MX-20 -- as though there was a low voltage alarm, but not see any visual indications of a problem -- nothing in the GPX file, not flashing LEDs on the C8 booms, etc. Now I'm wondering whether there are similarly transient events that don't get logged.

    I'll email Holger and ask about this -- I'd be rather surprised if these kinds of errors were not "latched" so that, if they occur in between log file sampling, they would be recorded -- but that's what the evidence suggests.

    I'll let you know what I find out.
    Andy.
     
  13. Josh Lambeth

    Josh Lambeth Well-Known Member

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