Double checking ESC to Pixhawk connection

Hiya

Getting towards end of my octo build and just want to double check Im doing the last bits right esp since involving power and Ive read it not hard to burnout if done wrong.

1) 6S Battery

Reading a few threads and wiki it looks like for my 6S battery some modification is needed. So Ive ordered the attoPilot 180A.

This will monitor my 6S whilst a smaller 3s battery powers the Pixhawk and accessories. I'll be modifying the 6pin cable to go to both as per wiki:

http://copter.ardupilot.com/wiki/common-using-a-current-sensor/

Sound ok?

2) 8x Esc to Pixhawk.  So the 8xEsc I am using has the standard 3 wire (red,white ,black) which would fit into the pixhawk outputs. But from what Ive read I should only connect the red cables to the signal row of the pixhawk outputs. If I allowed all 2 to connect could risk power issue on that rail?

Is that correct?

The only other plug on there is the RC

I have connected my Taranis from X8R sBus to pixhawk RC and that worked instantly, no configuring needed at all, just Radio Callibration and flight mode switches NICE!!

Cheers in advance for the peace of mind :)

-P

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  • Hi

    Digging up an old thread.

    I jsut read on a RC thread about pixhawk that the way I have followed here of just using the white signal lead from PX to ESC is not good and that I should have included the ground as well?

    Can some one please clarify this?  Sadly I jsut rewired everything last weekend and cut the black and red wires to get them away LOL

    Thanks!

    -P

  • Yaya success.

    We have spinning motors!!!

    Thanks

    -P

  • Hi

    So since then Ive done a trial run with the tethered octocopter. Seemed most things working , but did get intermittant power to the motors. I set min_thr to a few values but not always getting all motors engaging at once.

    I hear crackling sounds, but not sure if that just esc engaging/disengaging.

    Whatever it is, its meaning not all motors engaging correctly at same time.

    One thought Im having is maybe its due to the ground not being connected on the esc?

    I keep reading threads with Pros/Cons against connecting just signal or all 3, or signal ground (for backup power)

    Here is a diagram (see below) of my setup at moment. (Note attopilot 180A is coming..I havent installed yet, but IM not actually flying yet either , just ground testing)

    To do the Esc calibration do I need to have all 3 ESC pins connected to the pixhawk??? (as opposed to my single signal at moment)

    Lat thought..is it worth adding a BEC for backup 5v power from 6S to the pixhawk output pins. Ive heard that makes a nice backup it the 3S power cut out for some reason? (as opposed to using one or more of the actual esc grounds, as that may put more heat on them if power is needed)

    Thanks for your time

    -P

    3701696104?profile=original

    • MR60
      Hi Paul,
      If you are using two batteries, they must share the same ground. In your current scheme the ground of Pixhawk comes only from your 3S battery while your ESCs only have their ground from the 6S battery. So when your pixhawk outputs the ESCs signals it is relative to its ground which is a different ground than your ESC have.
      You just need to connect the 3S battery ground to the octo PDB ground.
      In that case it is ok to only use the signal wire to the ESCs because your ESCs and Pixhawk are then sharing the same ground reference.
      Ground Engineering Ltd Home Page
      Ground Engineering Ltd providing Land Surveying, Topographical Surveying services all over India.
      • Hi Hughes, thanks for reply!

        So its ok for the 3S ground to connect to the 6S ground on the Power board?  The different ratings not going to interfere? Im guessing not an issue since the positive connections never connect except via the 5v ESC signal cable?

        If I do ground the 3S to the power board closing the circuit, does that also mean the ESC will act as backup 5v power source to pixhawk along the servo output rail? Or would I still have to connect a ground from the ESCs for that.

        Once the attoPilot arrives Im using that to connect the 6S to the pixhawks power in just on the 3 cables that read the V,I,Gnd etc. Would that effectively ground the 2 together?

        That is what  I thought I read to do in, but looking again Im not so sure.

        http://copter.ardupilot.com/wiki/common-using-a-current-sensor/

        Pixhawk_Non3DRCurrentSensor2.jpg?width=400

        My goal is to monitor the 6S as that is the battery that will run out long before my 3S (which is just powering the pixhawk and some other electronics)

        Is it possible to still keep the 3S and 3dr power module connected to the pixhawk , and as per wiki divert the 3 other leads (black, yellow purple on wiki image) to the 6S for V,I ,Gnd ?

        Oh and finally........ once grounded correctly, just the singal signal is enough to run the calibration also?

        Cheers heaps,  Learning lots!

        -P

        • OK.

          More progress!! I had an idea, and just plugged PB  to the 3S battery power module for short calibration. Everything worked and the motors spun (slowly as on 3S) cleanly.

          Going back to 3S and 6S like above didnt work

          So like you said Hugues (oops sorry I misread as Hughes in previous post) its that ground connection.

          So Im thinking to adapt in a  cable from the 3dR power module XT60 out Gnd (Black) to one of my power board Gnd outputs. Should that be sufficient?
          Will this ground loop carry much  current? I presume I should use a reasonable size wire (same as the battery wires)

          Thanks again....... ALMOST THERE!

          -P

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