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Unable to calibrate A2 S900 GPS
2877 6 2015-4-26
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tony_bish
lvl.1

United States
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I have a DJI S900 with A2 controller, IOSD MARK II, Lightbridge, and Zenmuse Z15-GH4 with a Futaba T14SG Transceiver. All controls seem to be calibrated correctly. Im able to control the gimbal, control the gears, and have video link. So everything, I believe, is connected correctly. Ive successfully done all the upgrades and calibrated everything EXCEPT the GPS. Right away it begins flashing Green and Yellow which means misconfiguration of GPS. I try to put it into calibrate mode by flipping the U switch 7-10 times from manual to ATTI GPS, but it never turns blue and does not enter calibration mode. This is the last calibration I need to perform before I fly. Why would this not work when everything else does?

Thank You
2015-4-26
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HMArnold.msn
lvl.4
United States
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I have a very similar system, except on an S1000+

My first thought would be that the GPS Attitude switch signal is not making the entire trip out of the Futaba, to the Lightbridge Ground unit, up to the Lightbridge Air unit, then to the A2.

On the A2 Assistant there is a screen that shows actual switch changes. When everything is turned on and you are plugged into the A2 with the A2 Assistant, does the GPS/Attitude switch show each of the 3 positions on the screen when you cycle through the switch on the Futaba?

If not, you need to track backwards down the path all the way back to the Futaba.

Same goes for the IOC and Failsafe switch changes
2015-4-26
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tony_bish
lvl.1

United States
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Hi Thank you for your response...I was able to get it calibrated after I changed some settings in my Futaba remote (End to 80 and Travel to 100) found on the following posting:

http://forum.dji.com/forum.php?m ... p;tid=9672#lastpost


I successfully calibrated the device twice...Then came the very short flight...

After calibration, I tested most of everything: Gimbal controls, Gear, ETC and the GPS/Attitude was cycling correctly.

The remote was on manual mode for takeoff and I started the props and began to throttle up...About 10 feet, the GPS light turned blue ( if anyone knows what caused this I do not know, first time with spreading wings equipment and A2) It quickly drifted right and flipped over hard, really hard (I still had the throttle on). The drone is...not in the greatest shape...but should be fine with some work

First, any suggestions why this could have happened? That was my first time operating that type of drone, so it may have been setup or operating error? However it seemed really out of whack, it completely lost control without me touching any controls (besides throttle up).


Also, any suggestions on warranty, repair, parts and accessories etc...

S900---5 of 6 Frames, motors, and wiring good. 6 broken propellers ( already have extras)
1 landing gear leg broken
Center Board, all good except one small chunk out of it, I can't see it effecting anything

A2, LightBridge, and IOSD appear fine

There are a few torn can cables and such.


Month old Zenmuse Z15-GH4 Gimbal---Servo 1 and 2 good...Servo 3 took a blow and does not rotate well...repair?

GH4 camera and lens----Good, things a tank


Spent lots of time preparing it, to bad it ended on its backside but it should be repairable

Any suggestions are appreciated!
2015-4-27
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project41
lvl.3

United Kingdom
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There are 3 things i would look at, firstly i would not fly or take off  in Manual mode, you are bypassing all the aids you have for flying, Most people (including me) set manual mode so that they can enter the compass calibration mode then find out what a beast it is in manual mode.
I am not saying it is not safe or flyable in this mode but it takes a hell of a lot more skill.
i would recommend setting your flight mode to ATT, GPS and Failsafe  and take off in ATT mode, also check failsafe works on the ground before take off and that you have your home point set, put the control switch into failsafe mode and see if the led flashes blue.
Second point
make sure that your gps antenna is in the right position and not vibrating, also make sure that the IMU is facing the right direction,  on the A2 IMU the cable comes out of the front of the unit so use this as your marker.
Third point
If you use the A2 assistant app i think you will find that you can enter compass calibration under the tools section, also check your gains settings, remember that the gains recommended by DJI are expecting you to have a payload of a Z15 and camera attached, if you don't  have a payload attached for testing or are using a lighter payload you will need to change the gains.

I hope this helps, we all know that feeling then your expensive drone crashes but you need to be methodical with your investigation, test everything individually first and take your time.

Finally remember that your drone can also be effected by outside sources, e.g. radio interference magnetic fields, power lines etc so don't rule them out but check out your build first and confirm all works as it should before you start looking in other areas.

2015-4-28
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tony_bish
lvl.1

United States
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project41@me.co Posted at 2015-4-28 16:18
There are 3 things i would look at, firstly i would not fly or take off  in Manual mode, you are byp ...

Thanks for the info, the one thing I did not consider was the gains. I have to believe now that, that was probably the cause of the flip, I used the default gains that DJI had listed and it probably wasn't considering a GH4 with gimbal. I used the Assistant app to calibrate the compass. The Compass and IMU was facing the correct direction, I didnt check vibrating but it did not appear so and it was screwed in well.
Its also good to know not to take off in manual mode.

What are the recommended gains for a s900 with gh4 ad gimball?

Thanks
2015-4-28
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HMArnold.msn
lvl.4
United States
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As for the blue flashing LED, I have an S1000+ system with dual Futaba 14SG transmitters hooked up with training cables into the Lightbridge.

Although I have never looked up the definition of the blue flash of death, I take it to mean "no control signal coming from the ground".

If I see it before I take off I check all the plug connections and make sure I remembered to turn on the Lightbridge ground unit.

If it happens in flight, since I always fly in GPS mode, the platform will hover while I desperately look for what has come unplugged.

My training cable wire harness has a "Y" splitter with the cable going into the back of the Futabas being only about a foot long, then what looks like a standard a stereo plug.

I pulled that connection free so many times I finally put tape around it to keep it together.

It's also very easy for the stereo male plug to work it's way out of the bottom of the Lightbrige enough to make the connection fail.

All these situations mean a blue flash from the A2
2015-4-29
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project41
lvl.3

United Kingdom
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The blue flashing LED on the A2 means that it is in failsafe mode (page 48 of the manual) its not explained very well.
easy way to check is to setup your failsafe positions on your radio, save them and then turn it off with the flight controller running, you should see the led flashing blue, the same as when you set failsafe on your flight mode channel.

Gains for the S900 fitted with the GH4 gimbal i would start with the recommended settings set out by DJI as you now have a payload, if you want to test without the camera weight the camera and lens and make up a dummy camera box out of cardboard and fill it with weight to the same as the camera, make sure it can not move around, use this as your test camera, this will give the correct weight for the gimbal and platform for testing.
another thing that i do on initial ground testing is to tether the platform to the ground with a 100ft length of para cord, at least this was you have a safe testing radius (make sure you are outside of it) make sure the line does not go tight as the flight controller will try to compensate for it.
We used this method when eliminating interference problems on a S900 setup, problem was caused by a combination of the video tx too close to the graupner rx and devices plugged into the wrong can bus port.
2015-4-29
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