Redundant power supply

Hi all,

I’m running a Pixhawk with all the peripherals, P/M, telem, sonar, etc.
I have a backup power supply connected to the servo rail on the Pix.
On a FrSky X8R I’m sending the Pix channels 1-8 on the PPM bus, The RX is also powered by the PPM line.
Directly on the X8R I have channels 9-16 which will run a few servos and retracts.
My question is, can I connect an BEC directly to the servo rail on the X8R in lieu of making a semi complicated wire harness to power the servos and retracts and only receive the signal from the RX?
My concern is, that in this case the X8R would be powered from the PPM in line and its servo rail. Could this be a problem?
Also, if this would work, would it be a second back up power supply if the P/M and existing BEC both fail.


Should be fine. Just make sure there’s a zener diode in there some place across the ± rails. I have them at the Pixhawk, but in theory is should make any difference if it were at the RX rails.