Discussions

Pixhawk causing motor sync issues.

Posted by xoltri on March 10, 2014 at 10:50pm

I believe I have a problem with my Pixhawk and was hoping for some help. Also posted this on rcgroups.

The issue is that when my speed controllers are hooked up to the Pixhawk they exhibit a bad sync issue. However when they are connected to my old APM (3.1) or just a receiver directly they do not exhibit these symptoms. This has resulted in 4 crashes now until I just tonight narrowed down the issue to the Pixhawk.

Can anyone advise what is going on? Here are the specs of my setup:

Afro 30A ESC's with SimonK firmware (have tried all versions, and made my own with various parameters)

Tiger MT2216-9 1100kv motors

4S 3700mah battery

https://www.youtube.com/watch?v=i7_gVoY8q8M

https://www.youtube.com/watch?v=VTK81IANyUE

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Replies

- Developer
  
  Lorenz Meier > Christian June 11, 2014 at 7:27am
  
  Pixhawk is *NOT* outputting 2.4V levels. You either have a faulty unit (please check with the manufacturer) or did get the grounding wrong - how did you ground your setup?
  
  These are the real voltage levels:
  
  http://pixhawk.org/users/actuators/pwm_escs_and_servos
  - Christian > Lorenz Meier June 11, 2014 at 10:21am
    
    Hi Lorenz,
    
    thx for your answer. GND is connected to Servo Rail.
    
    I've tested different input methods, 5V BEC, 5V USB and 5V of current sensor supply. Always same output voltage. As you mentioned on your site, 2,4V could be enough for my ESCs. One important fact is to set 400hz for pixhawk, isn't it? So users here should be informed as well. For luck I did it already.
    
    btw, users can check outputvoltage with multimeter by messuring between GND and Signal. To get a correct reading, u need 400hz-490hz and to multiply the voltage by 2.
    
    Bin übrigens aus GER. Schöne Grüße!
    
    Christian
    - Developer
      
      Craig Elder > Christian June 11, 2014 at 12:20pm
      
      Ardupilot automatically uses 400Hz not 490Hz when it runs on Pixhawk
      - Christian > Craig Elder June 11, 2014 at 12:34pm
        
        Thanks Craig!
    - Raph > Christian June 11, 2014 at 11:18am
      
      so you're saying all pixhawk users should set their timing to 400hz? can someone confirm this?
xoltri May 22, 2014 at 7:13am

Craig, the hardware I sent you was delivered May 10, have you had a chance to test it out and if so did you find anything?
- Developer
  
  Craig Elder > xoltri May 22, 2014 at 10:09am
  
  Yes. So far I have not been able to reproduce any problems
  - xoltri > Craig Elder May 26, 2014 at 7:51am
    
    Well, I wonder what you are doing differently than I was in my video. The problem was very reproducible.
    
    Anyway, I finally got my quad working well with the 3DR esc's and had a couple FPV flights. It feels very locked in now.
Moderator

John Church May 5, 2014 at 9:21pm

Regarding connecting ground, it might be a good idea to update the Pixhawk manual as well. The images in the "Connecting Outputs" section are a bit misleading.

http://3drobotics.com/wp-content/uploads/2014/03/pixhawk-manual-rev...
- Erich Greenebaum > John Church May 26, 2014 at 1:08pm
  
  On this note - I am sitting here trying to figure out if I may have a sync issue causing flips on my original 3DR Y6 with a swapped in Pixhawk. I connected everything according to the quick start guide for the pixhawk, which certainly shows only signal wires, not to mention that with the original power distribution setup of the Y6, I'm not clear how I go about connecting each ESC's ground...
  
  Am I missing something? Is this thread stating that 3DRs current documentation is explicitly incorrect? Does this mean I have to completely rewire my power distribution to have a properly grounded system? Or am I (hopefully) just confused about the context..?
  
  Some clarification on this would be greatly appreciated!
  
  Thanks