Arducopter: Motors turn on while disarmed!

I have suffered a little accident at home with my quad when motors suddenly turned on while it was disarmed! A very strange behaviour that I still don't understand even after review the  tlog and look for something like that in the diydrone forum. No failsafe message, not arming, not using my TX.

I was just configuring the APM with the quad on the table and I was handling the camera' shutter cable. Fortunately only a little cut in my hand and 3 propellers broken (I only could crash it down to the ground when it took off next to my head!). Until now I only have seen a drop in voltage just before motors started to turn on (battery fail safe?).  Some one have suffered a problem like this? Any information about this is welcome. I think that is a very important safety issue that I shouldn't to repeat.

I am using APM 2.6 with last arducopter firmware (3.1.2). Please, find here-attached my parameters and logs

Thanks in advance

2014-03-14 18-00-58_accident.tlog

2014-03-14 18-00-58_accident.rlog

2014-03-14 18-00-58_accident.param

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  • Developer

    I guess this is more of a MAVProxy question but in any case, you should just be able to type:

    ALT_HOLD (to get the vehicle into alt-hold mode)

    arm throttle

    rc 3 1500

    and it should take off!

  • Thanks to all for your comments!

    @Randy, my ESC are DJI 30A opto. In fact, I installed them because a lot of people trust on them. In my first setup I used blue F30A HK reflashed with SimonK but one of them got burned and also its motor (in the same way that already happened to Marco Robustini, if I am not wrong) so I decided to change all of them.

    I agree that is safest to manipulate the quad without battery. But I had the battery connected because I was configuring the 2 axis gimbal and the camera. By the way, I power gimbal' servos by a 5V Bec connected to the APM's RC output (although their Signal wires are connected to A10 and A11). And APM module is powered by a 3DR Power module, without jumper. I think that I was handling the relay wire connected to A9 when motors turned on. Could this setup cause this odd behaviour?

    I don't know if that is right but now I am thinking in changing this setup powering the servos directly from the BEC (i.e., not through APM's RC_output, keeping only signal wires on APM for control them).

    I am not an expert reviewing tlogs, but the only extrange thing that I see what I told you regarding voltage mesured by 3DR power module, that dropped down from about 15V to below 10V -more or less when the incident and the goes up again to 15V, and I don't know why that happened. Could that be related, as @Scott suggested? I can replicate that behaviour if I press the reset button.

    @Alexander, I am sorry but I don't know Mavproxy.

    Anyway, I will extreme cautions.

    • Developer

      I think you're right that handlign the A9 wire may have been the cause.  My guess is this caused a spike that somehow got through to the signal wires connected to the ESC.  It's a bad idea actually to be connecting and disconnecting things from the system while it's powered.  We've recently found that this is at least one of the causes of the 3.3V regulator burnouts that many have seen.

      • Thank you very much again, Randy. I will never do it again in that way.

        • hi eladio,

                for gimbal adjustment it may be safest to just remove the props , i know a drag but for a quad a small drag, think of the folks hacking on x8 or duodeca configs .. ouch..

          did not initially consider this failure mode but now that its happened to a few unfortunate fold i will be removing iris props for power on circuitry debug of the  minim osd cabling i have added.


          • I agree HZL, thanks. I learned the lesson and now I am more cautious with this kind of handlings

  • A safety issue:  We talk about "armed" and "disarmed" as though they were absolute terms. "Armed" in the context we are using it means the aircraft motors are capable of spooling up in response to a particular command, external or internal. "Disarmed" means the motors will not spool up in response to those particular commands. But neither term guarantees that a motor will or will not do what is expected, and that it is therefore safe. Compare it to a firearm. All our "disarm" has done is flip on a safety. There is still a live round in the chamber. Are you going to look down that barrel? Of course not. You will first empty the chamber, or in our case, disconnect the battery.  "Disarmed" does not mean "safe" - keep that in mind. 

    • Excellent analogy.

  • hi Eladio, do you know about mavproxy? currently im using it to control my quadcopter. But somehow, i can't override the channels using RC_OVERRIDE_CHANNEL command which is "rc all 1000". The quadcopter seems to have no response at all...... Any advice? Thanks

  • Developer

    I strongly suspect if the motors spun up that it was an ESC issue.  From looking at the tlogs the copter remained disarmed the entire time (as you've said) but also the output sent to the motors is always the minimum value.

    3701685193?profile=original3701685203?profile=originalThere are some badly behaved ESCs out there that will turn when they misinterpret a spike on the signal wire as a pwm message.  What kinds of ESCs are you using?

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