Need Help For Crash Log File Analysis

Hi All,

My quadcopter suddenly fall down after 50 seconds.

Before the fall I flew 3 minutes successfully at Alt Hold mode.

After crash I measured battery and it showed 23.74V but at flight log CURRENT:Volt value is 21.71Volt at last log row. Before the flight battery module was calibrated.

Thanks for any help.

My Quad specs;

Arm length motor to motor : 80cm

AUW : 3.7kg

Battery: Tattu 16A 6S

Motors : T-Motor Mn4010 - 370KV

ESC: T-Motor S35A 600Hz with SimonK

Gps: 3DR ublox gps

Telemtry: 3DR 433Mhz

Fligth Controller: Pixhawk

Power Module: Dshot® APM 2.5.2 2.6 Current Sensor Power Module


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  • Your log ends midair.All signs points towards pixhawk being suddently shutdown, (brownout) the CURR.Vcc variation during flight is not *too much* or dangerous in any way, but it did vary between 5.099v and 5.175 flight, and 5.22 during flight.  , I think it's"interesting" that the last  CURR.Vcc record shows 50.90v (the lowest one, only recorded once before during the flight)

    While voltage above 4.2v will not brownout a Pixhawk,  , any temporary drop below 4.1 will cause reboot.  , but remember that power is logged at 1Hz, and that's a lot of time in the terms of electronics, so much else could have happened.

    Did you had power redundancy ? (did you power it using the DF13-6 power connector *and* had power applied to USB or Servo rail ? )   - and : were the extra power between 4.5 and 5.7v ?   - this is important - because 6v on servo rail would *not* be connected thru the power management chip if primary power failed.

    • 50.90v should, of couse , be "5.9v" :)

      • Thanks Andre,

        I am using standart 6-pos DF13 cable with Dshot® Power Module because it supports 6S battery.

        No power applied to USB or Servo rail. No extra power.

        Is it normal last logged 21.71 Volt battery voltage?

        Because I measured battery and it showed 23.74 Volt after crash.

        Best Regards.

        • Yes, your battery voltage is fine, it's normal to be lower under load, and even 21v/6cells=3.5vcellvoltage , no reason to crash, besides,even if the battery were depleted, you'd expect Pixhawk logging until impact.

          Wrote from my phone, if admins of this site don't fix the outdated google login, I'll be gone as my browsers cookies expire.
          • Hi,

            It could be voltage sag problem?

            Best Regards.
            • As an electronics engineer, I do not know that "voltage sag" is  - apparently some people invented that phrase without explaining which technical term it was supposed to represent :)

              If you think about a voltage drop due to high internal resistance of battery,  or wiring resistance - while under heavy load,  yes, voltage may drop under load, (your log did not have a aggressive climb in the moments before)  but before your main battery drops to way below 4.8v (which pixhawk needs)  it will not affect the flight controller.

              If you think voltage from your (only) 5v regulator dropped, below ~4.8,  yes, that's most likely scenario for a brownout and reboot, or just shutdown, the question is why it dropped, bad connection, was it too weak and a thermal protection kicked in etc..   

              • Thanks Again.

                I am learning a lot of things.

                Battery Fail Safe voltage was 22.4 Volt. Last seen voltage value is 21.x volt.

                Could It be activated?If It was actviated Could We see it at logs?

                It is seen a connection problem I think.

                Stupied me :)


                • Most likely a faulty connection, yes.

                  Failsafe was not trigged, but that would never give such result anyway.

                  For some reason your log does not contain FS_BATT_ENABLE or FS_BATT_VOLTAGE , so it's impossible to say.

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