zukenj

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Lost power mid air
« on: February 21, 2017, 12:12:02 am »
[Hello,

How can I find out what is the problem or what is cousin the issue of loosing power in mid air for 1 second, and can't recover.

Please see video:



Thanks
« Last Edit: February 21, 2017, 12:49:52 am by zukenj »
FS-TH9X RC
F450 Clone
Revolution FC
EMAX 2213 935 KV
HK 30A ESC UBEC running BLHeli 14.4
10x4.5 Propellers
DJI Naza clone Ublox M8N GPS

Re: Lost power mid air
« Reply #1 on: February 21, 2017, 04:44:04 am »
It looks like you have two problems:

Loose power for a second:
This is usually caused by RC signal loss which makes the FC go into failsafe.  (Some RC's have an Rx LED to show if it ever lost signal in that flight.)  The default for FC failsafe is to stop the motors.  Do you have your RC configured to stop sending servo signals (makes it go into FC failsafe, that is good, so it doesn't fly away) when it is out of range or to go to pre-set positions (must have it set for low throttle or it could fly away)?  If your quad has lots of carbon fiber or metal (these things block the signal) it is easier for this to happen.  Even a battery can block the signal.  RX antennas should be away from metal and carbon.  Another cause (that happened to me) is intermittent connection (bad connector) from RC receiver to FC.  The way to figure these out is to use OpLink telemetry to log your flights (GCS -> Tools -> StartLog), and when it happens you can look in the log to see if the FC went into failsafe, or whether the inputs from the Rx were ever disconnected.

Can't recover:
It looks like that quad is underpowered and once it starts falling, it can't recover quickly or maybe even at all.  A good rule of thumb is that it should have twice as much thrust as weight.  You can test this by taking it up high and slowing the motors way down for a second and see how long it takes to recover.  Maybe use a weight instead of your camera and gimbal.

zukenj

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Re: Lost power mid air
« Reply #2 on: February 21, 2017, 01:41:03 pm »
It looks like you have two problems:

Loose power for a second:
This is usually caused by RC signal loss which makes the FC go into failsafe.  (Some RC's have an Rx LED to show if it ever lost signal in that flight.)  The default for FC failsafe is to stop the motors.  Do you have your RC configured to stop sending servo signals (makes it go into FC failsafe, that is good, so it doesn't fly away) when it is out of range or to go to pre-set positions (must have it set for low throttle or it could fly away)?  If your quad has lots of carbon fiber or metal (these things block the signal) it is easier for this to happen.  Even a battery can block the signal.  RX antennas should be away from metal and carbon.  Another cause (that happened to me) is intermittent connection (bad connector) from RC receiver to FC.  The way to figure these out is to use OpLink telemetry to log your flights (GCS -> Tools -> StartLog), and when it happens you can look in the log to see if the FC went into failsafe, or whether the inputs from the Rx were ever disconnected.

Can't recover:
It looks like that quad is underpowered and once it starts falling, it can't recover quickly or maybe even at all.  A good rule of thumb is that it should have twice as much thrust as weight.  You can test this by taking it up high and slowing the motors way down for a second and see how long it takes to recover.  Maybe use a weight instead of your camera and gimbal.
Thanks TheOtherCliff.

The FC is set to failsafe return home, flight position 5 in my case, and I tested it by turning the TX off. The quad immediately gain altitude‚Äč and come back, then land perfectly.

I Will log the flight. I will try to give it a try today and post back results. 

Sent from my SM-N900P using Tapatalk

FS-TH9X RC
F450 Clone
Revolution FC
EMAX 2213 935 KV
HK 30A ESC UBEC running BLHeli 14.4
10x4.5 Propellers
DJI Naza clone Ublox M8N GPS

Re: Lost power mid air
« Reply #3 on: February 22, 2017, 07:06:19 am »
Do you have RTB programmed as an RC failsafe or an FC failsafe?
There are two failsafes, RC and FC.  (Props off) Unplug the Rx to FC data wire to see what it does for FC failsafe.

Re: Lost power mid air
« Reply #4 on: February 23, 2017, 08:56:35 am »
I had another thought...  If you are using stock, unflashed ESC's, the Low Voltage Cutoff must be disabled or set to Nicad.  That would cause it.  You have to use a lipo voltage alarm or time your flight, not use LVC.

(search ebay for 8s lipo alarm)
http://www.ebay.com/itm/1-8S-Lipo-Li-ion-Fe-Battery-Voltage-2IN1-Tester-Low-Voltage-Buzzer-Alarm-FE-/332115167362

zukenj

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Re: Lost power mid air
« Reply #5 on: February 23, 2017, 09:02:07 pm »
In GCS I have Failsafe to swith to channel 5 (Return to base). RC not set for failsave. RC: FlySky FS-TH9X.

I have HK 30A ESC Flased with Simonk. Do I need to configure any value?

Thanks
« Last Edit: February 23, 2017, 09:05:18 pm by zukenj »
FS-TH9X RC
F450 Clone
Revolution FC
EMAX 2213 935 KV
HK 30A ESC UBEC running BLHeli 14.4
10x4.5 Propellers
DJI Naza clone Ublox M8N GPS

Re: Lost power mid air
« Reply #6 on: February 24, 2017, 01:24:27 am »
SimonK does not have LVC.  Nor does BLHeli.  So you don't have to worry about that.  :)

Forgive me.  I'm still not sure whether you are using RC failsafe where the RC receiver tells the FC Flight Mode Switch to go to RTB when you switch the transmitter off,

or whether you have told the RC receiver to stop sending pulses when you switch the transmitter off, and you have told the FC that when there are no pulses from the receiver to go into RTB mode.

In the first case, a loose connection between the receiver and the FC will cause it to drop from the sky.

zukenj

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Re: Lost power mid air
« Reply #7 on: February 24, 2017, 05:25:38 am »
For what I know there is no fail save on the TH9x, but I may be wrong. The only thing I did was in GCS.

Raining the last 2 days, not been able to flight and log. Friday will be storms passing by... No flight again  :-\

Sorry if I am not clear. Let me know what I need to do to get you a clear answer.

I am the one interesting in fixing the issue, so anything I can do to get more clear information, I'll do.

Thanks
FS-TH9X RC
F450 Clone
Revolution FC
EMAX 2213 935 KV
HK 30A ESC UBEC running BLHeli 14.4
10x4.5 Propellers
DJI Naza clone Ublox M8N GPS

Re: Lost power mid air
« Reply #8 on: February 24, 2017, 07:53:51 am »
Oh!  Another thing.  If you have an I2C aux mag there is a very common problem such that some GPS/mag brands have weak I2C signals.  To get it to work correctly you may need to add a pair of say 2.7k (2k to 5k is all right) pull up resistors from 3.3v to the SDA and SCL lines and shorten your I2C cable as much as possible.  Adding pullups is probably best done inside the GPS/mag shell.  Most of the GPS/mag units I got for testing have this issue to some extent.  What happens is short "lock ups" when the I2C driver can't read the data.  Sometimes the FC even reboots.

You can test for reboots by connecting your quad to a 12vdc power supply that is powered by AC and let it run for a long time or over night.  Make a note of the time you powered it up.  When you look at it later with GCS, look at Firmware -> FlightTime.  It is the number of seconds since it was powered up.  If it was started up 8 hours and 10 minutes ago the FlightTime should say something close to 29400 ((8hours*60*60) + (10minutes*60)).

While you are at it, go into Scopes, enable Window->EditGadgetsMode and change one of the scopes (not the Uptimes scope because it gets reset to zero each time the FC reboots and that is good information to have, you may want to increase the DataSize for it as well, see below) to Alarms and disable every scope alarm except CPUOverload, Sensors, Mag, and I2C.  Then do Tools -> Options -> Scope -> Alarms and set DataSize to however long you expect to run the test (3600 seconds per hour :) ).  Press OK.  Now you have that available and running when you do the above test and it will show you if you had any lockups that were not reboots.

Be aware that INS13 (if you are using it, like for GPS flight) goes crazy (the EKF diverges) if it is left for a long time perfectly motionless.  Your attitude and PFD may be crazy when you come back.  That is normal.

Re: Lost power mid air
« Reply #9 on: February 24, 2017, 07:58:30 am »
If you didn't set up the transmitter failsafe to use the RTB switch position and you did set up failsafe in the FC, then it seems pretty certain that you are using FC failsafe.

If you are comfortable doing it, you could try hovering at 10 to 20cm high and switching off the transmitter.  I can imagine that first you get low throttle and then no pulses so it drops, then does FC failsafe (RTB).  A momentary signal loss would be a drop but no RTB.  If it drops then you have found the issue.

No, that may not be safe.  If it does drop and then try to do RTB it may flip or chase you.  Starting RTB from the ground is also dangerous because GPS drift can make it skid along the ground and it might flip over.  The safest way is to firmly tie it down with no or very little slack.  (I have done this by running screws through the landing gear feet into a large heavy piece of wood.)  Run the motors up to half power and switch the transmitter off with motors still at half power.  Either the motors will drop for a fraction of a second or they will not.  If they stop you have found the issue.

If you have a telemetry flight log you can replay it and look at some things like system health and System->DataObjects->ManualControlCommand->Throttle (and other things) to see if it was commanded to stop.

zukenj

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Re: Lost power mid air
« Reply #10 on: February 25, 2017, 04:52:34 pm »
TheOtherCliff,

I think I got really good data. Yesterday I flew yesterday. No GPS or AUX I2C, and it happened again.

I do have the log but. How do I read it. LOL.

Attached is the log. Please advice on how to open it and how to review it.

Appreciated.
FS-TH9X RC
F450 Clone
Revolution FC
EMAX 2213 935 KV
HK 30A ESC UBEC running BLHeli 14.4
10x4.5 Propellers
DJI Naza clone Ublox M8N GPS

f5soh

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    • LibrePilot
Re: Lost power mid air
« Reply #11 on: February 25, 2017, 08:01:48 pm »
Just before crash you got intermittent INPUT alarm.
This mean a rc link lost or bad wiring with only one PWM wire.



For Log replay, just look the dropdown menu close to the connect button (bottom - right), choose log and click connect

zukenj

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Re: Lost power mid air
« Reply #12 on: February 26, 2017, 06:17:56 pm »
f5soh,

Thanks I see the alarm.

https://www.youtube.com/watch?v=dpW1Vzf36Qs&feature=youtu.be

How can I trouble shut the faulty  :-[  Wire

Thanks
FS-TH9X RC
F450 Clone
Revolution FC
EMAX 2213 935 KV
HK 30A ESC UBEC running BLHeli 14.4
10x4.5 Propellers
DJI Naza clone Ublox M8N GPS

zukenj

  • ***
  • 202
Re: Lost power mid air
« Reply #13 on: February 26, 2017, 07:41:35 pm »
Here

FS-TH9X RC
F450 Clone
Revolution FC
EMAX 2213 935 KV
HK 30A ESC UBEC running BLHeli 14.4
10x4.5 Propellers
DJI Naza clone Ublox M8N GPS

f5soh

  • *****
  • 4572
    • LibrePilot
Re: Lost power mid air
« Reply #14 on: February 26, 2017, 07:50:02 pm »
Yes, the SystemHealth > Input uses the Alarm.Receiver trace displayed in the scope i posted.

Can be one input lost or all inputs lost due to a stopped signal / failsafe from receiver.
The faulty input or receiver with no signal cannot be detailed without firmware modifications.