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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Just the BEC on the Afro ESC.

I assume that means the update frequency is a non-issue. Another item checked off.  Before trying out these ZTW Spiders, I'm taking notes.....lots of them.

An update to my story. I have received my usb flasher and flashed all my Afro 30a escs to the latest simonk firmware. This has reduced my problem but not cured it. So to recap. Initially I was using only a signal wire. Motors sounded like they were grinding at anything above idle and would miss at idle and click. I connected ground wires for all escs. Motors would idle ok but at higher throttles they would still grind and lose since. Now with updated firmware and grounds still connected I do not get the intense grinding sound. I get a high pitched whine and under quick accelerations get a bit of a grinding sync sound. I have no confidence to fly the quad. Below is a video from the latest test. I test all motors individually at 30% power, then again at 20% power then arm and do some throttle ramps. The sync issue is most noticeable towards the end of the video when I am giving quick jabs to 50/100% power from zero. Reminder none of these issues were present with I had the quad configured with APM.  I will be either taking a trip down to Craig at 3dr with this issue or at the least sending my escs in for them to test. 

https://www.youtube.com/watch?v=-f-PJLe7mYU&feature=youtu.be

Update: RTF Y6B running 3.2 vs 3.1.5 Pixhawk

3.2 motor6 always spins up but at some random point drops sync before regaining sync.  Frame drops left arm.  From Zero throttle 1st time is smooth.  Subsequent throttle ramps from zero all motors jump up to about 30% throttle, above 30% all good.

3.1.5 No sync issues.

Tried: Replaced ESC-6 No change

Replaced Motor-6 No Change

Reflashed Board No Change

Swapped ESC-6 and Motor-5 for ESC-6 motor-6 Not change Motor-6 still dropping sync.

Checked all connections, tried moving power/ground from 3DR power module to Motor-7 port, no change

Checked logs for power issues, no faults.

Reverted to 3.1.5, All good, no sync issues.  Motors spin up smoothly as expected every time.

I will try another 3DR Pixhawk board.

Any ideas?  I tried the support forum but go no response I also raised this issue way back on 3.2rc-2 but though it would be sorted with the release version or that I would have located the problem. It feels like an ESC/motor or wiring problem but I have replaced and swapped all of the possibly faulty components and the problem never moves and it always works fine with 3.1.5.

That's interesting because this new Y6 was started out of the gate with 3.2; never thought about reverting back to 3.1.5, may do that with these ZTW Spiders if I have the same problems as with the Maytechs.

Hi all. Has anyone tried to reduce the RCSPEED parameter in MP to 400Mhz or less? I had a few issues with escs some time ago and now I change that param on every fresh install. I don´t have enough knowledge to ilustrate why it could work but I guess it´s a simple test

A long time ago, it doesn't fix the problem.

I'm looking to put together a 680 hex, and I'd prefer to use a Pixhawk.  I've selected the SunnySky V4010 motors (KV375) and 6s batteries.  Each motor will draw less than 20A at peak.  With that low per motor current draw and a 6s system, my ESC options are somewhat limited (if I want to avoid using oversized ESCs).  I had originally thought of using Afro ESCs, but I'm glad I stumbled across this issue before ordering them.  Maybe re-flashing Afros will work, but I'm hoping to do better than "maybe".  I've clearly learned form this thread that the correct method is to attach both the signal and ground wires from the Pixhawk to the ESC.

I would just suck it up and order the ESCs from 3DR, but I only see one model of ESC listed, and it's only spec'ed for up to 4s systems.  Other than 3DR's ESCs, are there any options that can be used with 6s voltage and can be recommended with a fairly high confidence that there won't be sync issues when used with a Pixhawk FC?

Good news, I think, so far, so good.  I changed the Pixhawk for another one I had set aside for a fixed wing build (Both 3DR original units) and my Motor6 issue has gone away.  I am thinking it is a hardware issue with that particular board.

However, first time arming and spinning up all motors run properly. I have noticed two things, if I drop the throttle to zero and then spin the motors up they jump to about 30%,(Same on previous board) and separately to this if I ramp up to about 30% on the first spin up of the motors they will idle nicely for about 3 minutes and then speed up to about 40% percent.

At all times, when applying flight power (ie above 30%) all motors seem solid and running at the correct speed.

I have not noticed this on my test quad running Afro ESC's but only on the Y6B running 3DR ESC's.

I will keep bench testing until I am confident that the motors won't desync and see how it flys.  Changing the Pixhawk seems to have done the trick although I am still curious why 3.1.x does not produce the same fault on this board.  At least I seem to have identified my issue with my No 6 Motor losing sync by changing boards.

BTW, to get GPS to work I had to load the Beta version of 3.2 via Mission Planner.  The default 3.2 loaded OK but did not recognise the GPS.

If your motors draw 20A @6s and you want SK ESCs, go with at least double the amps. With simonk f/w 20A ESCs tend to run really hot even with max 17-18amp per motor current draw -tried 20a spiders, 20a multistars, Sunrise 20a all good ESCs which happily run on 4s setups. I think this is because sk firmware makes very fast and frequent throttle changes.  40-45 amps ESCs are just warm after the flight. Considering that difference is about 10g per ESC between 20A and 45A go for 45amp ESC. Very good SimonK ESCs I have found are ZTW Spiders. Hobby Wing xRotor40A are also  a good choice, not as responsive as SK but much faster than platinum pro and run just barely warm to touch . If you are into flashing your own f/w and price is not an issue I have found Turnigy Kforce 40A flashed with blheli as responsive as spiders, but they run at ambient temperature so for extra piece of mind and if the budget allows definitely go for them. spiders work with pixhawk and 22pole 380kv motors at 6s, but need airflow to remain warm, get somewhat hot in between the plates. Currently using HW xRotor 40A, those are solid, run barely warm even with 0 air flow, not as responsive as spiders, but I am using them on my AP rig and I like it being smooth anyways, autotune yields similar PIDs.

Artem - thanks very much for the suggestions.  From this thread, it sounds like the most likely to be problematic combination is Afro (SimonK-based) + Pixhawk.  The max. I can get eCalc to generate (with different prop options) is about 15A, so using 30A+ rated ESCs makes sense.  The ZTW Spider is currently looking like the best option.  It's widely available, not a lot of reports of problems (with Pixhawk or otherwise) and fairly light at 25g for the 30a model.  Having the option to re-flash to BLHeli in case of problems is also appealing.

I have 6 ZTW OPTO 30A Small Spiders ready to install, but also have a set of HW XRotors coming. 

I'm hoping to try out the Spiders this weekend and will post if there are issues. 

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