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I just want to use knob on the TX to move a servo connected to the pixhawk.

Posted by Mr Flying Pizza on November 17, 2015 at 6:15am

Spend an hour reading how to do it and i'm confused and intimidated.

I just want to tilt a FPV cam using a servo from a knob on the remote. That's all.

So far I learned I have to connect the signal servo wire to AUX1 on the pixhawk and preferably power it up from a BEC instead of the pxihawk. But that's it.

Should be simple right?

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Replies

  • Sandy Sound November 30, 2015 at 11:27pm
    Need more information. What "remote" do you have and what receiver?
  • Moderator
    Graham Dyer November 28, 2015 at 10:35pm

    There some info here: http://plane.ardupilot.com/wiki/common-servo/

    You can connect your servo directly to the Rx or have it controlled through the Pixhawk, either from mission planner or "pass thru" the Pixhawk.

    We have flaps controlled directly with a switch from the Tx and tilt, pan, zoom and lights controlled by Mission Planner. At one point we had auto flaps that could still be controlled manually by a switch on the Tx so it's possible to do nearly anything.

  • James masterman November 28, 2015 at 10:16pm
    Try this. Assign a channel to the knob on your Tx. Say it's channel 6 for this exercise.

    Connect your servo to the channel 6 output pins on the pixhawk.

    Go to mission planner, parameters screen. View all parameters and scroll down to RC6. Open that up and enter the value in RC_FUNCTION to do RcPassthru. I think that is number 3, but it will tell you in the description in mission planner. Check the RC6_MIN and RC6_MAX while you are there. They may be both the same which means you will get no movement. Set them to 1300 (min) and 1700(Max) to start with and see how the servo responds
  • Brian Kling November 26, 2015 at 6:13pm

    Is there a reason not to hook the servo directly to the receiver?

    • George Kelly > Brian Kling November 26, 2015 at 6:33pm

      I'm not a Pixhawk guy yet.

      But, Pixhawk takes a single ppm input - merging all channels from the receiver into one signal into the FC. Either your receiver is capable of outputting all channels as one PPM signal, or it isn't.

      I think it's all-or-none. Select PPM output from receiver, and you select all channels (no receiver channels available, then, independently to control anything directly from the receiver).

      I don't think you could send 'some' receiver channels to the FC as a single PPM signal, while leaving other receiver channels separate to control a servo directly from the receiver.

      Unless (maybe) your receiver outputted PWM to an intermediate PWM-PPM encoder device, then on to the Pixhawk as PPM. Maybe then you could limit the number of receiver channels sent to the Pixhawk and save some for independent use. I believe such encoders exist (even on the 3DR webstore).

      I guess servo control has to go through Pixhawk. But, as suggested, powering the servo through the FC is risky, so you want separate power to the servo, and signal-only from the Pixhawk.

      (?)

      George

      • Brian Kling > George Kelly November 28, 2015 at 8:29pm

        Ah, yes. That would be a reason.

        I may be wrong, but I thing that would depend on the type of receiver.

        • Sandy Sound > Brian Kling November 30, 2015 at 11:35pm
          With a Taranis and X8R you can have the first 8 channels output on the SBUS to communicate with Pixhawk plus channels 9-16 on the conventional channel outputs.
          And yes you need to power the servo seperately.
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