Any help would be greatly appreciated. I'm just getting started with the Pixhawk on a XAircraft 650-X8 frame. With Cobra 2217 motors and Afro 20A ESCs using Genfan 11x4.7 props to lift a NEX-5 camera. I made several auto test flights with the equivalent weight of of the camera. Everything was fine. Made several auto test flights with the camera again worked fine (took off, flew to waypoints, landed). Then yesterday I had trouble arming it due to high HDOP but finally it went down enough to arm and hit the auto mode. It flew to the first waypoints properly but then it started rising in elevation (from 150ft which was planned to 200+). it then switch to stabilize mode by itself, Since I had the throttle position low it dropped like a rock (about 50 ft) then switched back to auto mode by itself and climbed back to 200+ ft. It did this twice the second time is when I saw it happen and I switched it to RTL and it came back and landed. Looking thru the logs I can see where it happened but can't determine why. This is a false assumption. ( I'm guessing since I didn't have the Kalman filter on it was getting a bad reading from the barometer.) Turns out it is VCC look at a lower reply. And that somehow triggered the flight mode switch. Today I turned on Kalman filtering and put it in Loiter mode for ~9 min. about all my 3S can handle. it Loitered properly. I then planned a mission to take 45 photos at 50 meters. It flew the mission fine with no problems. Could someone take a look at these logs and let me know what happened? The flight doesn't start until about 60% into the tlog.




2015-03-16 14-47-41.tlog


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  • MR60

    The isuue you had has nothing to do with Vcc, which by the way looks totally normal on your graphs (stays between the limits 4,6V to 5,6V).

    Your issue is like Tom said a PWM instability on your channel5. Check your radio and receiver.

    • Thanks for the help everyone. Newbee learning curve here. I'll give this a shot and report back.



      • 3702690490?profile=originalI reset my Tx to have a wider variation in the PWM scale between switch settings on the three way switch. I also set all of the intermediate modes to Auto so if there is variance it will stay in Auto which is what I think hotelzululima was telling me before he deleted his response. If you look at the screen shot I'm using "Flight Mode 1, Flight Mode 4, Flight Mode 6" as the three postions on the switch and everything else set to Auto. Before I had left these Flight Modes on the default Stabilize.  I think this fixed the issue.

        Thanks for everyone's help,


        • All 8 rc inputs show fluctuation when the mode changes.

          I'd say it was you're transmitter, receiver or the encoder that is the problem. When it switched to stabilise your throttle output went to maximum which put a huge strain on the battery as it pulled it down to 7volts which probably caused the vcc to drop down.

  • I have an Aurora too, check your PWM values that aren't near limits


  • Your problem is most likely with your RC RX or Tx. If you plot your RCIN for channel 5 (the channel that changes the Pixhawk's flight mode) you'll see that the PWM values seen by the Pixhawk changes. Thus the Pixhawk switched flight modes....because that's what it thought you were telling it to do. The signal it was seeing from your RC receiver was changing.

    I don't think the issue has anything to do with Vcc. When the Pixhawk switched to Stabilize your throttle stick must have been up a bit because it went to a high throttle level with a resultant high current. That probably caused the voltage to sag just a little bit.

    You didn't say what sort of RC Tx or Rx you are using, but I think that's your problem. It could just be something as simple as PWM drifting on channel 5, with the dividing line between Auto and Stabilize very close.

    • Thank's Tom. I'm using a Hitec Aurora 9 Tx and a Hitec Optima 9 Rx with the 3DR PPM encoder. So what I saw was the X-8 falling without power during the mode switch, then when it hit the stabilize mode (because of the throttle setting it climbed) causing the Vcc to drop. Then it switched back to auto mode. Is the Vcc supposed to bounce around this much on the Pixhawk vs. the straight line graphs I saw for the AMP 2.5? So if I make the dividing line higher between the flight modes should that prevent it from occurring?



      • Vcc will move around a bit and I'd say your's is OK. It looks within normal limits. Maybe tweak your transmitter's flight mode settings a bit, if possible, so you are more centered in the ranges, as Cala suggested below.

  • Admin


    An auto analysis of your 31.bin file revealed the following:
    Size (kb) 5359.5205078125
    No of lines 71376
    Duration 0:05:04
    Vehicletype ArduCopter
    Firmware Version V3.2.1
    Firmware Hash 36b405fb
    Hardware Type
    Free Mem 0
    Skipped Lines 0

    Test: Autotune = UNKNOWN - No ATUN log data
    Test: Balance/Twist = GOOD -
    Test: Brownout = GOOD -
    Test: Compass = FAIL - Large compass off params (X:218.00, Y:107.00, Z:89.00)
    Large compass offset in MAG data:
    X: 218.00
    mag_field interference within limits (14.72%)

    Test: Dupe Log Data = GOOD -
    Test: Empty = GOOD -
    Test: Event/Failsafe = FAIL - ERR found: FS_BATT
    Test: GPS = GOOD -
    Test: IMU Mismatch = GOOD - (Mismatch: 0.31, WARN: 0.75, FAIL: 1.50)
    Test: Parameters = GOOD -
    Test: PM = FAIL - 29 slow loop lines found, max 11.68% on line 1608
    Test: Pitch/Roll = GOOD -
    Test: Thrust = GOOD -
    Test: VCC = WARN - VCC min/max diff 0.308v, should be <0.3v

    As you can see you have a compass issue, a Battery Fail Safe event occurred, there was a PM failure, and your VCC appears to have varied more than 0.3vdc.



    • Yes I ran the auto analysis, but it doesn't tell me what caused the flight mode to switch from auto to stabilize, then back to auto, then back to stabilize, then back to auto by itself.



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