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

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

   

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.

Lars

I just ordered the Rotorgeeks BLHeli 30Amp V2 ESC. They don't even have a signal ground.

Are these safe to use with the Pixhawk? Mostly everyone in this thread says you need to connect the signal ground. Why would the Rotorgeeks ESC not even have a signal ground!

This is what I ordered: http://rotorgeeks.com/index.php?route=product/product&product_i...

Bummer! What do I do?

Does that make these ESC's a complete No No? Just ordered 4. They come with BLHeli OneShot but have ONLY the signal wire. There is no Signal Ground!!!

Did I make a bad purchase?

http://rotorgeeks.com/index.php?route=product/product&product_i...

Its been a while since I posted on this blog ...but I wanted to share my experience using the afro30Amp esc's with the T-motor Mn3508-580 Kv motors with 13x55 CF props powered by a 4S lipo...initially I faced serious problems trying to get these ECS's to work with the Pixhawk...I had all of them flashed with BLheli and throttle rate at 255...PWM frequency at 16Khz motor timing with demag compensation enabled and Lightly damped mode selected....my Esc's are placed beneath the motors for cooling so the FC to ESC signal wires are very long at least 60 cms long....I had problems with the throttle getting stuck while testing for sync issues ...I have a video here which shows this https://www.youtube.com/watch?v=BfiL_wt22a0

I had a tough time figuring this out and every time I thought of this issue the most common doubt in my mind would be that the signal reaching the ESC's is getting distorted to such an extent that the pulses can no longer be measured by the Hardware interrupt pin on the Afro ESC's....this problem is compounded by having high signal wire resistances due to long FC to ESC distances...even if these resistances are minute using aluminum servo extension wires or other non copper based extensions can exacerbate this problem....I tried using various servo extension but failed ...the other day that I got a suggestion to use twisted wire pair LAN cable wires .. these wires being reasonably flexible-ish are low impedance copper cored and are specifically designed to carry digital signals for relatively long distances without required intermediate repeaters....I decided to give them a try and THEY WORK AWESOME!!!....RC_SPEED set at 490 and with all the above Blheli setting I went crazy with Rate PID's tied my Hex to the ground and just threw my Roll/Pitch/Yaw sticks around....no sync issues ....motors follow the sticks ....no stuttering...no cogging...I have my hex up and running without any issues...but haven't run auto-tune...I just tuned my copter manually coz' I like my copter to feel the way I want it to.....and Autotune gains have been known to be a bit on the higher side..but you can do it if you like

I would like others to try this out ...any feedback on this would be welcome         

 

its no but..ground must be somewhere near signal on ESC board, remove isolation and solder ground wire..that's easy....harder part will be to solder 3 tiny wires for programing ESC with BLHeli software in order to have newest version of it and to change parameters according to your needs...

The programming connector looks to have all three wires. Connect signal ground there to your controller?
Lars

I'd like to just confirm for anyone else who has these ESC's that I soldered on the GND wires and they work fine with the Pixhawk.

Of the 4 ESC's one of them has a BEC which I have left connected to act as a backup power supply for the PIXHAWK.

@Emin: harder part will be to solder 3 tiny wires for programing ESC with BLHeli software in order to have newest version of it and to change parameters according to your needs...

They actually come with the programming leads presoldered and exposed as a servo connector.

AKcopter,

  Do you have a link to the LAN cable wiring you used? I am having sync issues still after all this time and 3 different ESC's (not including the 3DR ones from my Y6B).

This is beyond frustrating. I calibrate the ESC's, everything seems ok then over time they de-sync again.

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 

I posted this elsewhere with no responses. I'm hoping someone in this thread can help me.

I too am using Afro 30A ESCs with my Pixhawk. I had a crash and I can't tell if it was a motor sync issue or not.

All was going well until I switched from loiter mode to stabilize mode. My throttle lever was a little low when I switched to stabilize mode, so the copter started descending.
I increased the throttle to compensate, but nothing happened. When it started falling faster, I went to full throttle. No response.


My Setup

  • Pixhawk running Arducopter 3.2.1
  • Afro 30Amp ESCs
  • 800KV TMotors
  • 12X3.8 props
  • 4500mAh 30C battery


I've attached the log file from the incident. Can someone with more experience have a look and see what could have caused it? I'm thinking it's the ESC's.

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