Servo travel on startup (help!)

Archive
1

Hello,
I’m having a weird issue where on boot of the APM, one of my servos is pushed 100% in one direction. This only happens if the signal wire is plugged into the APM. The only way I can avoid this is to wait for the APM to fully boot by unplugging the signal cables from the APM.

Here’s a video: youtube.com/watch?v=JcvV9iAkSxc
When I power the APM the servo closest to you in the video is pushed all the way down, which is causing damage to my wing. When the APM fully boots it returns to it’s neutral position, and when I push my RC sticks to max, it never maxes out like it does on boot. How can I stop this all together?

Would appreciate any input. attached my params as well. I can get away with unplugging/replugging signal wires but this is not efficient.

flying wing (tbs caipirinha)
APM 2.6 + gps/external compass
3DR power module
Plane 2.78b

Best,
Raph

2

I have that too. I’ve always written it off as an annoying part of the initialization process of either the APM or the PPM decoder, but if there is a way to stop it from happening I’d love to know…

3

any devs can chime in? sorry to pester… there must be a way to change this behavior. thanks so much

Sent from my iPhone using Tapatalk

4

From my experience this behavior happens when the rx is outputting no pwm signal because it hasn’t established a connection with the tx yet when the system is first powered on. I think the APM interprets the inputs as 900ms which would drive the servo to the extremes. One test you can do is to power up the rx first before powering the apm.