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How to create an _immediate_ kill switch on PX4/APM?

Posted by Paul Atkin on June 1, 2015 at 9:51am

Hi,

I tried to test some different modes and frankly nothing else comes to my mind anymore other than to put a heavy 40A relay to a main power line and attach a servo to it, so I could map it to one of taranis switches so in a case of malfunction or lost orientation I would be able to kill drone in the air or on the ground and stop props _immediately_.

Any other option I tried - a combination of 'land' mode with throttle cut off, an improved failsafe on remote switch off - none of that cuts power feed to props immediately, and quite often it leads to horrible results, like if in loiter mode drone suddenly gets to a GPS free zone or glitch, and starts something erratic, or flips over and tries to destroy everything around spinning props at full power ignoring remote commands to cut throttle input to zero.

I had only 3 incidents like that and I know now what it is, but it does not make my platform any safer.

What do you do for a physical kill switch? Do you have one built? If yes, how was it done?

Please respond.

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Replies

  • John Brownlow September 1, 2015 at 6:49pm

    I believe this would be a very useful thing to backport into 3.2.x for APM.

  • Rob_Lefebvre June 1, 2015 at 10:00am

    AC3.3 will have two Aux Switch functions which will do what you want.  Called Emergency Stop, and Motor Interlock, both can be used to immediately command the motors to full stop, no matter what mode it is in.

    • Paul Atkin > Rob_Lefebvre June 9, 2015 at 6:32am

      Rob,

      I installed current version of 3.3 on the AUAV board, I do not see those modes in the MP list.

      What are the codes for them?

      I also see CH7_opt - CH12_opt parameters - do all of them work or are they only reserved for future use?

      • Jimmy Oliver > Paul Atkin January 17, 2016 at 1:37pm

        I am wondering about this too.

        • Scott W > Jimmy Oliver January 17, 2016 at 1:52pm

          This is implemented in Arducopter, and will be in the px4 stack w/in days. 
          Be sure your copy of Mission Planner updated to the latest, and the options should be there.

          • Jimmy Oliver > Scott W January 17, 2016 at 1:56pm

            Sweet. So I should be able to see options with X8R via smart port? 

            • Scott W > Jimmy Oliver January 17, 2016 at 2:08pm

              Yes, depending on which channel you want to use... 
              I don't have my copter/mission planner here to look at, so this might not be exactly correct..

              In mission planner, go to the config/tuning tab, and then extended tuning, and you can set it to be on channel 6 or 7 via a simple drop down menu.. 
              If you want it on a higher channel, you go to the full parameters list, search for ch## (lets say channel 12, search for ch12_opt, and it will list the options.. I think it's 31, but check first.

              • Jimmy Oliver > Scott W January 17, 2016 at 2:21pm

                Ok. I have a kill switch project for the landing leg to land on moving vehicle in concert with IR Lock. 

    • Paul Atkin > Rob_Lefebvre June 1, 2015 at 10:42am

      Great news, I was not aware of that. I will build new Tarot 690 project on PX4 but current one - a quad - I want to keep on the APM that is running 3.2. version.

      As I understand 3.3 will not ever work on APM and will not have any (limited) port for APM, ever, is it correct?

      Would it be possible to retrofit this functionality into old 3.2 build to make it available for APM platform?

      • Rob_Lefebvre > Paul Atkin June 1, 2015 at 5:31pm

        That's correct, no 3.3 on APM.  I suppose one could hack the feature into 3.2, but it's a fairly pervasive change that would take a bit of work.

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