Please be aware of the following:
Despite some information available on the Internet on how to power the pixhawk cube, supplying voltage to the servo rail DOES NOT offer redundancy.
Well, for me a mystery was solved. I couldn’t figure out why I crashed, thinking I had redundancy:
https://docs.px4.io/en/flight_controller/pixhawk-2.html#power-system-and-protection 3
It says:
"Voltage Ratings
Pixhawk can be triple-redundant on the power supply if three power sources are supplied. The three rails are: Power module input, servo rail input, USB input."
And this is about pixhawk 2. Including picture and specification.
Thanks to Andras Schaffer I got the correct information:
http://www.hex.aero/wp-content/uploads/2016/07/DRS_Pixhawk-2-17th-march-2016.pdf 3
" FMU and peripherals will NO LONGERaccept power from the servo connector"
As a conclusion, I would say there is conflicting information on the Internet that some people rely on (including me) that can lead to a crash.
Yes, I can see how someone reading the PX4/Dronecode docs, which I don’t bother with, could get caught by that. The following info posted there under Normal Operation Maximum Ratings (in Bold) is cryptic enough that if you don’t already know that the servo rail only powers I/O and not the FMU it could be misunderstood. The problem would seem to land on the PX4 documentation.