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

- - Emin Bu > Christian June 30, 2014 at 2:04pm
    
    +1
    
    but...
    
    "Buy other ESCs, perhaps they don't accept 3,3v or maybe 2,4v if you have clone Pixhawk"
    
    I don't understand that part..
    
    Also this might help someone to understand why Afro ESC is no go...I do not,can someone elaborate please..
    
    MOTOR_ADVANCE=15 for Afro_nfet, but is =18 on the standard tgy.asm that I've previously used to flash
    
    DEAD_LOW_NS = DEAD_HIGH_NS = 300, whereas the standard is 450 and 8000 respectively.
    
    O_POWER & O_GROUND at 180 and 33, but standard are 10 and 1.
    - Dan Houldsworth > Emin Bu July 1, 2014 at 12:49am
      
      I've done a bit more digging on the Afro / SimonK params:
      
      O_POWER & O_GROUND are ohms to power, ohms to ground. Which I believe is a voltage resister divider to get a reference voltage at the PWM sense pin. It's always used as a ratio so the absolute values are not important. The significance of it is this : changing the ratio will directly effect the logic threshold whereby it interprets the PWM as High or Low. I'll experiment....
      
      MOTOR_ADVANCE is used in conjunction with TIMING_OFFSET to adjust timing for different motors. Why this would be different across boards I don't know.
      
      DEAD_LOW/HIGH_NS. My layman's understanding fails at this point and have no understanding of these params.
    - Ritche M > Emin Bu June 30, 2014 at 5:57pm
      
      Hello... I previously used Afro 30A for my MultiStar 2216 800KV on PixHawk (quad setup) with no issues at all. Only the signal wires were connected on the 3 ESCs while the last one has the ground, positive, and the signal wire connected.
      
      My sync issues was with MultiStar 3508 640KV and MultiStar 30A Opto ESCs in PixHawk. I flashed the ESCs with SimonK and the sync issues are now gone. The ground and the signal wires are now connected to the FC.
      - Dan Houldsworth > Ritche M July 1, 2014 at 12:50am
        
        Hi Ritche - do you recall what props you were using on each set up?
        
        Also, which version of SimonK did you flash?
        
        Ritche M > Dan Houldsworth July 1, 2014 at 1:14am
        
        For the MultiStar 2216 800KV with Afro 30A, prop used was 11x45. No issues encountered.
        
        For the MultiStar 3508 640KV with MultiStar 30A Opto ESCs, prop was 12x38 and 11x45. Sync issues were encountered in the original ESC firmware. No sync issues after flashing SimonK with Jan 2014 version.
        
        No sync issues when doing ESC calibration with the orig FW of the MultiStar 30A Opto ESCs.
Ravi June 25, 2014 at 8:13am

hello fellow drone flyers, about 15 days back i had posted that there are issues with simonK firmware loaded afro 20A ESC and sunrise BLHeli loaded 20A ESC with pixhawk. I was wrong. There is no issues with these ESCs with Pixhawk loaded with AC3.2-rc2. The problem was with one of the motors. I am using Turnigy 2830-980KV 14 poles. out of the nine motors i bought one is glitching. I am not sure why but i have never seen a motor glitching. probably of magnetization. The AC3.2-rc2 is flying great. I have done RTL, auto, Loiter, Takeoff. all modes are working fine. The RTL accuracy is within 3m of takeoff point. i apologize for posting wrong information.
- Christian > Ravi June 26, 2014 at 1:32am
  
  Ravi,
  
  never mind, surely some written tips helped other people..
Steve Pharis June 13, 2014 at 7:28pm

Add me to the list of pixhawk users with sync issues even after following all the information I can find on the topic. Using signal ground, 400Hz, modifying min throttle, esc. 0 issues during calibration or on other flight controllers, but issues on the pixhawk. I can get sync problems immediately, or sometimes none for nearly a whole battery pack. On my hex it is always the same 2 motors. I have removed all connectors and swapped ESCs and motors. Using RCtimer SimonK flashed 30A.

Is it the end result that simonK can't be used? Seems like a red herring considering the number of FC out there with no issues on simonK.

I can't trust it enough to put a camera under it.
- Steve Pharis > Steve Pharis June 13, 2014 at 9:45pm
  
  So I think I've narrowed mine down to the throttle idle. If I allow the motors to idle, I lose sync. If I don't idle when armed and instead go to throttle low from off, I am not losing sync. I'll have to test more to confirm as I only ran 2 more batteries, but so far this seems to be the symptom.
  - Steve Pharis > Steve Pharis June 14, 2014 at 5:35pm
    
    So setting idle speed to around 150, and min throttle to 180 I'm not getting sync issues anymore. I'd like to know if anyone else can replicate this.