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Pixhawk and SBEC 5.6V output

Posted by Teoria on January 13, 2017 at 9:10pm

Hey guys,
I am powering my Pixhawk with the Power Module, but my plane uses a SBEC with 5.66V output for my 4 micro servos. I read that if I plug my SBEC to the servo rail in the pixhawk it acts a power backup, but I read that it mustn't be higher than 5.7V, because it can cause a Pixhawk reboot. So I'm very close to the limit. My question is: if my Pixhawk is using the Power Module, do I have to take care about my SBEC output voltage? If my Pixhawk is using the Power Module, could it be rebooted for a 5.7 SBEC voltage?
How can I do to avoid connecting my SBEC into the servo rail but not power the pixhawk?
Thanks in advance,
Marcus

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Replies

  • Teoria January 17, 2017 at 7:40pm

    https://pixhawk.org/modules/pixhawk

    "Servo rail input (4.8V to 5.4V) UP TO 10V FOR MANUAL OVERRIDE, BUT AUTOPILOT PART WILL BE UNPOWERED ABOVE 5.7V IF POWER MODULE INPUT IS NOT PRESENT"



    Hugues said:

    Teoria, if you go over 5.7V on the servo rail of Pixhawk, the latter will shutdown for protection, even if you use a power module. This is why as a precaution, you should connect in parallel a zener diode (5W recommended) with an avalanche trigger at 5.6V so as to trim any short voltage spikes above the limit.

    All is described in the wiki here : http://ardupilot.org/copter/docs/common-powering-the-pixhawk.html

    Good also to add a capacitor in parallel to the zener diode.

  • Teoria January 17, 2017 at 7:37pm

    I undestand that you shoud use a zener diodo ONLY if you use the Pixhawk servo rail as a redundant power source. As "Andre K" wrote, I think I can use up to +5.7V but not usable as a reduntant power supply for the Pixhawk.

    If I put a zener diode into the servo rail (and my intention is not to use the backup power supply), I will damage my SBEC.


    Hugues said:

    Teoria, if you go over 5.7V on the servo rail of Pixhawk, the latter will shutdown for protection, even if you use a power module. This is why as a precaution, you should connect in parallel a zener diode (5W recommended) with an avalanche trigger at 5.6V so as to trim any short voltage spikes above the limit.

    All is described in the wiki here : http://ardupilot.org/copter/docs/common-powering-the-pixhawk.html

    Good also to add a capacitor in parallel to the zener diode.

  • MR60
    Hugues January 17, 2017 at 6:06am

    Teoria, if you go over 5.7V on the servo rail of Pixhawk, the latter will shutdown for protection, even if you use a power module. This is why as a precaution, you should connect in parallel a zener diode (5W recommended) with an avalanche trigger at 5.6V so as to trim any short voltage spikes above the limit.

    All is described in the wiki here : http://ardupilot.org/copter/docs/common-powering-the-pixhawk.html

    Good also to add a capacitor in parallel to the zener diode.

    Powering the Pixhawk — Copter documentation
  • Andre K. January 16, 2017 at 8:53am

    It will not "cause" a reboot, but will not be used for redundancy. (which may cause reboot/shutdown if the powermodule is overloaded/fail)

    Pixhawk has triple power source, to keep redundant, you can feed it +5v from another source

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