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[HELP] Death roll
#1
Hey everyone,

I experience some death roll or flip when going full pitch/roll.   

First my quad (edited):  
• frame: 210mm nox5  
• motor : r2205 emax red bottom 2300kv
• ESC ltb 20A  
• Battery Tattu 4s 75c 1300mah
• RX FrSky X8R and I use sbus. It is directly connected to the fc
• PDB Core 2.3
• ImmersionRC Raceband 200mw vtx
• Kingkong 5040 x 3 (and sometimes 5045 x 3)




I join some Black Box Files. I hope it helps. this is the first time I try to use BlackBox.
It seems that  a  motor go at 100% and stay there until the crash. Sometimes it's another motor.

EDIT: I also add a video from the dvr where you can see the problem.


I had some similar issues previously and it was the motor. 
I detected it by going from 0 to full power in the motor tabs on each motor.

This time it appears to be something else. 

Also, I know this quad is not tuned yet. Any help on that based on your read of the bb files would be very appreciated Smile

Thank you for taking the time to help me.

Cheers
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#2
Hi Tox!cFPV,

Can you give us some more details? For example, when does the unusual behavior begin, is it on liftoff, or after you're already in the air and start to apply inputs?

is it always the same roll or flip or is it some sort of combo of the two
carl.vegas
Current Quads: Operational: Diatone GT2 200 In need of repair: Bumble Bee, tehStein,  Slightly modified Vortex 250 
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#3
First thing to try is: increase min_throttle.

If in the logs a motor is commanded to 100%, this means the motor didn't produce enough thrust to begin with and the FC commands it higher and higher in order to make up for the lack of power delivered.
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#4
Since all the motors lock the signal at 25%, 25%, 25% and 100%, this has probably something to do with the FC. I have the same problem with my Xracer V3.1 with BF 3.1.7 and 8K looptime.
Another guy I know had the same problem and by lowering the looptime to 4K the problem went away.

What FC, firmware and looptime are you running? it looks like some FCs have this problem if the looptime is set too high in BetaFlight 3.1.7
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#5
I just realised you are running 8K gyro update and 2K PID loop. Try lowering the Gyro update to 4K
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#6
Thanks guys for your responses.

@Carl.Vegas : So the quad flight great. I can punch the throttle and do aggresive turns without any issues. It is when I attempt to do a simple roll or flip that the problem occur. I updated my first post with a video link.

@fftunes My min throttle was at 1020. This was the highest valid value of the four motor. I increased it to 1070 and it does not fix my problem.

@oyvinla: My FC is a demonrc Soul F4 (http://demonrc.eu/product/demon-soul-f4-...ontroller/)
The firmware is Betaflight 3.1.7. I will look into this
[-] The following 1 user Likes Tox!cFPV's post:
  • fftunes
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#7
I think Oyvinla is right. Lower your gyro update. I have had the same thing happen when I had mine at 8k.
Quads:  RealACC X6R ; RealACC X210 Pro, Omnifbus F3 FCs; RunCam Swift 2 & Swift 2 Rotor Riot, Emax OG Red Bottoms, Emax RS2205S 2300kv; Fatshark DOM V3 YouTube - Mr.E_fPv
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#8
Soul F4 will handle 8k/8k wth no issues.

What is your rx and what do you have on 5v rail, how is it filtered?

EDIT: i'd rather look for a brownout or interference issues
Find me on Youtube and Instagram. I currently fly: DRC Aura, NOX5R, Minimalist 112 and drive a scrap RC car
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#9
(07-Jul-2017, 04:59 AM)KonradS Wrote: EDIT: i'd rather look for a brownout or interference issues

I spotted this RX cap on BG supposed to help with brownouts? Don't see why any  other cap with the same rating (4700uf 10v) wouldn't do the job?

Please note these are suggestive questions not 'help!'  Wink
Windless fields and smokeless builds
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#10
(07-Jul-2017, 04:59 AM)KonradS Wrote: Soul F4 will handle 8k/8k wth no issues.

What is your rx and what do you have on 5v rail, how is it filtered?

EDIT: i'd rather look for a brownout or interference issues

Yes it should, but it could be brownout issues like you mentioned. I know at least my problem quad is noisier than my other builds as it is a 4in1 esc with a capacitor on the battery pads
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#11
(07-Jul-2017, 04:59 AM)KonradS Wrote: Soul F4 will handle 8k/8k wth no issues.

What is your rx and what do you have on 5v rail, how is it filtered?

EDIT: i'd rather look for a brownout or interference issues
Hey KonradS, 

Thank you for your response.


Here is the FC schema for reference 

My rx is a  FrSky X8R and I use sbus. It is directly connected to the fc from com3
I have nothing connected to com2  (so nothing on 5vout)

Also I use a PDB   from Demonrc: the  Core 2.3.
 I use to power on the FC 5v  and the VTX 12v (ImmersionRC Raceband )
 The camera is powered from the vtx.
I don't have anything else on the quad
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#12
(06-Jul-2017, 11:01 PM)oyvinla Wrote: I just realised you are running 8K gyro update and 2K PID loop. Try lowering the Gyro update to 4K

Can you point to me where I can find this information ? I am kind of newbie about it.

Also where can I configure the gyro and pid loop ? I never touched that.
Cheers
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#13
(07-Jul-2017, 09:46 AM)Tox!cFPV Wrote: Can you point to me where I can find this information ? I am kind of newbie about it.

Also where can I configure the gyro and pid loop ? I never touched that.
Cheers

It's set on the Configuration tab in the Betaflight configurator. Scroll down to "System Configuration" and you will see "Gyro Update Frequency" and "PID Loop Frequency".
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#14
(07-Jul-2017, 09:27 AM)Tox!cFPV Wrote: Hey KonradS, 

Thank you for your response.


Here is the FC schema for reference 

My rx is a  FrSky X8R and I use sbus. It is directly connected to the fc from com3
I have nothing connected to com2  (so nothing on 5vout)

Also I use a PDB   from Demonrc: the  Core 2.3.
 I use to power on the FC 5v  and the VTX 12v (ImmersionRC Raceband )
 The camera is powered from the vtx.
I don't have anything else on the quad

This is a good combo, brownouts are probably not the issue unless you try to pull too much amps from the pdb 5v, but this one is strong enough to power fc, rx, osd, few leds and probably more...
Find me on Youtube and Instagram. I currently fly: DRC Aura, NOX5R, Minimalist 112 and drive a scrap RC car
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#15
What motor protocol are you using?
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