Specification on Servo Rail Voltage Range

I was trying to refresh my memory of the allowable voltages on the standard carrier board servo rail.

The closest I could find was this doc about the Mini Carrier board - which may have the same spec.

There’s old discussion in the ArduPilot wiki about powering the servo rail and using that as a source to power the flight controller - old pre-cube pixhawk docs. In my case, I merely wish to use the servo rail as a power distribution bus for accessories such as cameras and gimbals.

Is the voltage range listed on the Mini Carrier board valid for all carrier boards? In particular, the ADSB carrier board.


Yes exactly.


I tried powering the servo rail with the BEC of my F55A pro II 4 in 1 ESC, thus a 10V BEC. Although it seems to be working (powering the motors just fine through MAIN 1-4), I can’t get a power output from the other MAIN channels.I measured with my multimeter across the other MAIN channels (between + and -) and I get 0 Voltage.

I tried using a BEC +5V to power the servo rail and now I could measure a 5V difference accross the MAIN Channels just fine. It seems weird that when I use the 10V BEC I cannot measure a Voltage difference and thus not use the other channels on the servo rail to power up different things (like a rangefinder)

Interesting - thanks for this comment Christos -

I have the same ESC, but have not used the 10V BEC output on the ESC.

Silly perhaps to ask this - but have you checked that the ESC is actually outputting a voltage?

I think I remember threads indicating that the servo rail can actually support higher voltages - but I can’t remember the specific requirements or limitations.

On some Pixhawk docs, it says that if 5V are available on the servo rail, the flight controller will use that voltage as a backup should the main power source fail. So I can imagine that the voltage limitations on the servo rail tie in to this capability.

Hello Joseph,

yes I have confirmed that the BEC outputs 10V (checked that with the multimeter). I have also used the BEC to directly power my rangefinder (TeraRanger One v3.0 → needs 10V), but this poses the limitation that I can only power up one device.

I’m really confused with this problem. Maybe I’ve done something wrong with the wiring but I dont know.

Very odd.

The only other thing I can think of is that your Rangefinder draws more current than the servo rail can handle - but that doesn’t seem likely. I seem to remember each servo rail output is good for 1A.