Y-Splitter Servo Cable on Pixhawk sending input to only one servo

Hello everyone,

I’ve posted this info across a large number of places with no response or feedback for troubleshooting, so I thought I’d post here. Any ideas would really be appreciated to diagnose this issue.

My plane is setup with two servos to control each aileron, designed to be hooked up to one servo output cable with a y-splitter servo cable. However, the control signal is only being sent to one servo, UNLESS I unplug that one servo - then it sends the control signal without issue to the other servo. Note, no matter what order I plug the Y-Splitter in, the Pixhawk only ever moves the SAME servo.

Listing out what I’ve done to test:

  1. Switching the cable connectors around
  2. Switching out different Y-Splitter cables (have tried three, same result each time)
  3. Splicing in a +5V from another servo output slot, to the one servo that will not run while both are connected
  4. Passing through servo control through an AUX servo channel (this partially works because the autopilot/stability operation of the Pixhawk does not get passed through, only the radio control)
  5. Connecting directly to the receiver instead of the Pixhawk to the Y-Splitter cable (this works!)

I guess the answer is really then something is up with how the Pixhawk is sending control input along the control wire. It is very strange to me that only one servo (and ALWAYS the same servo) would work in this scenario. If it is an issue with the control wire being split into two, then it seems to me that neither would work, or that the working one would be random each time I connected.

How are you powering the servos?
Since the Y cable delivers the same signal to both servers it must have something to do with the power supply.

I am powering it with a BEC attached to the servo rail. I am not noticing issues with powering servos - I can move all the servos at once without any issues there. However no other servos have split control wires in parallel (but I have tested on those actually with the same issue)

I guess one option would be somehow changing the pixhawk channel output so that another servo channel is left aileron, and another channel is right aileron. Is there a way to do this somewhat simply? I actually see that there is a fixed wing standard plane Airframe which has two aileron output channels setup. Does anyone know if I’ll suffer any consequences for using an airframe setup that does not match mine physically? E.g. will the accelerometer or autopilot behave differently or have different parameters I’ll need to adjust?

Sounds peculiar, to eliminate power problem, you may try to connect each servo red and black wires with different cables, connected to a spare servo out, and use Y-connector only on the data line.

Yes, I gave that a try without success.

To solve my issue, I ended up using a different standard plane airframe: the Bortamec… something. It has two channels for ailerons.

Interesting, never tried two servos on one channel on pixhowk… will try later, i have one free to check it out.

Checked Y-Connector on the pixhawk.
Found one of my cable with transversed wires… but with a good one , both servos worked on the same output.