APM2 Octo + UBEC: Power "In" from where?

Hi All,

Just got the APM2 and am beginning my Octocopter build.

I decided to separate the Rx/APM2 power feed from the ESC/Motor feed,

just to discover I might have a wiring issue. So here goes (see attached image, Yellow Squares):

1. To eliminate the power from the ESC on the PWM outputs of the APM2,

   I plan to cut BOTH the RED & BLACK wires, leaving only the WHITE Signal

   wires going respectively from outputs 1-8 to the ESCs.

2. Separately, the UBEC supplies 5V to the Rx/APM2 combo via the Power hooks

    on pin 1 of the PWM/Output rail.

Q1: Can I do this, or must I leave the BLACK wire connected?

Q2: If the BLACK ESC wires need to stay connected to the APM2, How can the UBEC connect?

Thanks -



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  • @ Andy: I couldn't find the reply by Ellison on the switch topic. Can you post URL here?

    @ Chris: Thanks! Now life is so much simpler :-)

                   I will update the diagram to reflect your input, to include more stuff as I go & as a reference for others.


  • 3D Robotics

    Nicely explained! The diagram helps a lot. There's no need to connect any additional black wires--as shown here you've got a common ground across the whole system. 

  • Developer

    The black wires do not need to connect from the ESC to the APM. 

    The ground is shared between the BEC and the ESC (via the battery), so the black from the BEC provides the same ground as the ESCs, if that makes sense. 

    I also have a BEC like you show and connected the APM1 with only signal from ESC:


    Oh and don't forget to make sure that SW2 is rated for the total amps of the motors at peak. Mine has to handle 68A which is A LOT and requires a specially selected switch (this was helpfully pointed out by Ellison on my post about wiring yesterday)

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