APM2.5 3.1 servo twitch

I recently upgraded to 3.1 on a trex 600 running digital servos and I am getting a random twitch. I thought at first it was the ppm encoder so I re-flashed it like I have done before on other APM flight controllers. After doing so I didn't see any changes and it seemed to twitch just randomly like before. 

On another note I did see more twitching if I ran higher voltage to the servos. 

Of course I haven't flow it in this configuration.  

Has anyone seen this problem?

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  • I got some new twitching problem, very interesting one.

    Just upgraded from Turnigy 113MG to 306G, upgraded PX4 to 3.1.2 and started to set up. As soon as I long press the safe button, servos started to move like normal, but the aileron and pitch servos are twitching like crazy without stopping. these two servos jump up and down at the same time and they jump very fast.

    Having been looking for the cause for a while until I realized the twitching is synchronized with the interference noise coming out of my speakers. It's the telemetry. As long as my finger touches the antenna, the twitching is gone. If I disconnect the telemetry, twitching is gone as well.

    I can't explain why this happens, seems the 433Mhz wave may have generated some signal into PX4 but my finger sure won't block the wave totally. Maybe it's a grounding problem, I don't know. Besides, using the 113MG servo doesn't reveal this problem, I have rarely twitching with 113MG. Further more, I'm not sure how much it has to do with the wiring, my wiring is now very simple and direct. The servo doesn't twitch at all if I haven't release the safe mechanism of PX4, and the position of the telemetry doesn't change the twitching behavior.

    • Yeah, we used to have problems back in the day with Xbees telemetry modules causing a problem very similar to this.  In my case, it was more of a slower or smaller movement you could hardly notice, but same idea.  It seemed like some servos were more prone than others.  And there was some relationship to ground and power wiring of the servos.  But the telemetry was the root cause.  Something about the ground plane of the module.  Touching the antenna would stop it.

      3DR Radio modules completely cured it.  I haven't thought about it much after that.

    • I ran into this problem as well. What I found was my connection between the 900mhz link and the wires that plug into it were not very tight. I was able to fix this by crimping new ends on the wires. Now when I plug it in its got a nice tight fit. Those plugs can only be taken on and off so many times before they become loose. 

  • I'm also having this problem using ppm, but since I can't adjust the frame rate on an 8fg I'm going to switch back to a standard pwm rx setup.

  • Rob I think it’s OK, I got a bit twitchy about the collective jumping down and I checked it again.
    It’s the RC TX7 taking down the throttle on my 450 when switching the throttle hold switch, which also controls the CH8. I might have to change to another switch on the TX7 which lives the throttle alone when switching CH8.
    This domain may be for sale!
  • And if you in the air and by mistake switch the motor off (CH8 low) then you get full negative collective pitch, your heli is dead. To cut the motor for a fraction of a sec would not be a big problem, but to get full negative collective is.
  • And if you in the air and by mistake switch the motor off (CH8 low) then you get full negative collective pitch, your heli is dead. To cut the motor for a fraction of a sec would be a big problem, but to get full negative collective is.
  • Are you guys using APM?

    I still have an APM on my 450 with 3.1, runing HV servos on 2S direct, and I haven't had any twitching issue.  I have had a twitching problem with my PX4, that I have sort of solved...

  • Hi Sean,

    I have the same problem with  my TR 700 E DFC  High voltage servos. But did not have it in v 3.01 at all. The Heli was flying pretty well in 3.01 with most of your param. from July 2013 I believe.

    My 700 had the exact setup in 3.1 as Manfred D. did setup his TR 600. ESC got signal direct from RX not from APM. That setup has crashed Manfred's 600 in v3.1 at the first test flight, to a total write off. His TR 450 was fine in v 3.1 before!

    I have changed immediately  so APM Ch8 output to ESC. Everything is working but I do have the same twitching in the 3 servos but not at the yaw servo. It is in ARMED or DISARMED and when Motor is running or not. But when I change to ALT HOLD and LOITER it is totally gone. Armed or not Armed.  So this problem appears  in Stabilize and DRIFT only,

    Have not tried to fly with those strange appearances.

    I can not help you further because I am waiting for Manfred D. to get his opinion first. He has far more experience than me.


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