Pixhawk causing motor sync issues.

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



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        • Hi DG

          I did not buy any specific LAN cable, I just had some of it laying around and since every LAN extension cable has at-least 4 such twisted wire pairs which are enclosed inside the outer jacket you need a relatively short LAN cable for this...I have not used anything specific, it was just the usual lot you get at the computer hardware store 

  • My combination was  Pixhawk/Afro 30/Jdrones 5010-358/4cell/ 15x5.5,  and it wouldn't get off the ground at all, just tipping over, and making strange noises. Flashed with BlHeli, and tried all kinds of settings, but to no use.

    After consulting Jdrones, I purchased Hobbywing Xrotor 40A esc's. They are working perfectly right out of the box. Haven't changed a setting.


  • looks like a signal aliasing issue....when the PWM rate is 400 hz the sync problems show up but when the rate is reduced to 100 Hz these issues resolve themselves ....I think the low voltage levels coupled with higher refresh rates make the esc's vulnerable to signal distortion resulting from resistive and inductive effects in the esc signal wires...Lorenz's observations were right when he said that the ESC input signal processing in the afro esc's was a problem...but the low voltage levels are not helping this issue....one would not come across sync issues when tested with Rx's generating 3.3v PWM signals because these signals are limited to 50 hz refresh rate...any comments on this would be interesting


  • fyi, here is the well known noise when sync is lost. Motors RCTimer 5010, ESCs RCTimer SK-30 with SimonK

  • Ok motor heads, please watch the takeoff in this video and tell me if you think it is a sync issue, a motor issue, or no issue.

    The rest of the video is just testing PID settings in Loiter.

    Also, at high and full throttle, there is a "miss". It flew at 24 m/s, but to me it sounds like it isn't quite right. So basically, to my ears it occurs at low throttle and wide open throttle.


    I should add that doing all-at-once ESC calibration, the motors throttle up nice and sound good in that mode, but once re-arming, they don't sound good.
  • Did AT today, went well although not sure about the results yet.

    So later I decided to take her up later. Temperature outside was about 25 degF and I've heard it's good to acclimate the copter to ambient conditions so I let it sit for about 15 minutes. Then armed it....barometer glitch. Ok, shut down and restarted.....armed.....everything good until.....oh oh, sync problems are back, so I thought. Here's what it sounded like:


    I recalibrated the ESC's to no avail, then brought it inside for ~20 minutes. The motors were considerably more difficult to spin by hand. Over time they spun freely as normal, so I tried again:


    Conclusion: Cold temperatures affect my copter's performance until the motors warm up.

  • Final update from me on this situation. My HK blueseries escs are working well. I have put about an hour of flight on them now with no issues. No heat from the escs or heat from the motors. All seems good.  

    I did drop my Afro 30a's off with Craig from 3dr this past weekend. Hes going to see if he can get them to lose sync on the bench. I was too impatient to bring my malfunctioning copter down to san diego with the afros still mounted. Hopefully they can recreate the problem and get to the bottom of this. 


    I'm confident now to say the ZTW Spider 30A OPTO Small ESC's are performing well.  After 6 flights no hint of sync issues. 

    Now on to tuning and all that good stuff.

    Oh happy day.

    • That's what I told you, but they do seam to run hot, unless they are 2x max current, than they run moderately warm. BTW, are you using new slim spiders? 

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