PX4 6C Sensor input

I’m interested in adding this capacitive sensor to a drone build utilizing a 6C controller. I’m working on integrating it to sense and interrupt an autonomous mission because of low fluid condition while spraying a fluid. Currently I have the issue that my FMU I/O channels don’t output 3.3vDC. Does anyone know why I’d be seeing 1.6vDC on the power pins and If that is indeed where I’d want to land a discrete input?

Sensor link:

The power pins of the ones switched on should be 5v. Which pins did you check?

Okay I’m using QGC as my ground station. I measured the (+) and (-) points on the FMU PWM out board. To switch those on in QGC, do I need to give the AUX # a function and arm the drone to see the 5vDC? I’ve never seen more than 1.6vDC armed or disarmed with a function specified from what I recall. In QGC I can’t pick a sensor as the function. They’re all output functions from what I can tell. I’ll provide a screenshot that shows the QGC display that I’m referring to. Thanks for your help!

These pins are not meant to provide power, otherwise you can have the case where a servo draws too much current and would make the Pixhawk shut off. Therefore, you need to bring your own power source to this rail. For instance you can use some sort of UBEC or BEC that comes with an ESC.

I appreciate the help. Okay I’ll source it power externally. I was concerned about damaging the input pin by providing a voltage higher than the 1.6vDC that is present on the power pins which I now now are not intended to provide power. If I power the capacitive sensor separately with 3.3vDC will it trigger that input to be high so I can call it in a code to pause a mission and display a message on the ground station software using MAVSDK?

You want to pause a mission? I would use MAVLink (or MAVSDK) and send the command to change the flight mode to loiter.

Yes that is correct. I’d like to pause the mission and loiter until the operator acknowledges this and returns the drone to the landing site so the mission can be resumed after a low fluid state is resolved. Does that seem doable in MAVSDK?

Yes, use mission->pause_mission which essentially switches to Hold/Loiter flight mode.