Pixhawk servo rail powering needs to be clearer in the wiring quickstart

[hamishwillee]

The Pixhawk Wiring QuickStart explains where the control signals are connected for each platform but does not make it clear that the servo rail is not powered by default (this is covered in Powering the Pixhawk) so your servos would not run, and this might damage the Pixhawk.

On copter you don't have to to power the rail for the ESCs, but you do need to supply power to the rail for your receiver, so again not covering power is a mistake.

On plane usually battery connects to power module which then connects to an ESC (for throttle motor) which connects to plane's motor. The 3 pin cable on that ESC then connects to channel 3 on the Pixhawk (or wherever you are powering the servo rails).

These instructions may be relevant for Plane on this topic - from http://ardupilot.org/plane/docs/px4fmu-plus-px4io-wiring.html.

• Wire the PX4 boards servo out signals to your Servo / ESC control inputs.
• The ESCs BEC or a separate UBEC can supply servo power to the Servos via the PX4's Servo connector BUSS
• Run the 3 wire servo cables from the ESC (and its built in BEC) and Servos to the 3 x 9 Servo Connector on the PX4IO board.
• Or, clip the power lead on the ESC and run power and ground from a separate UBEC to the bottom pins of the Servo connector.
• The PX4IO board connector for Servo 1 is at the edge of the connector next to the Battery power in wires.
• Insert the Servo and Motor ESC signal wires arranged progressively from that edge, (1,2,3,4,etc).
• You can put the ESC / Servo Signal wires into a single inline connector with the correct number of pins for your Plane.
• The ESC / Servo Signal Wires / connector should be plugged into the top row (furthest from the board) of the PX4IO boards 3 x 9 Servo Connector.

[auturgy]

The RC-In is powered from the fc, not the servo rail, but this does need to be clearer. Perhaps just a note, stating that the servo rail is not powered, and linking to powering-your-pixhawk?

[Krishna-web-hub]

Hi @hamishwillee, @auturgy

I'm picking this up and will be working on the Pixhawk Servo Rail power documentation fix.

The plan is to add a clear .. warning:: block under the Connect Motors section of the Pixhawk Wiring Quick Start page to emphasize that the servo rail is not powered by default and requires an external BEC/UBEC. This addresses the core issue of potential damage and non-functional servos.