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Stick calibration and loss of thrust
862 16 2017-1-25
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quality
lvl.2

United States
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Hi, I'll just start off by saying I'm brand new to the forum, so if I make any mistakes please let me know! I'm pretty much a noob with drones as well, and was kind of thrown into the deep end when my company was hired to do a shoot needing aerial photography. I Got my part 107 license, and we bought an RTF s900 Spreading Wings with an A2 IMU (I know not the best first drone. I don't need a lecture about this.)
I've managed to crash it once which broke an arm and leg mount, and I've tipped it over a couple times as well. After ordering new parts, I've got it all back together and successfully flown without issue a few times.


Today I wanted to learn a bit more about the Radio TX (we are using a futaba T14SG). I opened up the A2 configuration software, and after turning on my radio, was delighted to see that by moving the sticks I could see the corresponding values. Noticing that a few of the values didn't quite go all the way to their maximums I did a recalibration. I followed all the steps in this video:

calibrationGUI

calibrationGUI


After calibration, I went out to fly. Immediately after starting it up, I noticed my throttle stick didn't feel right. I was having to push it way too far to even get any thrust. I gave it a bit more juice to get liftoff but it tipped instead snapping two props. {:4_154:}

After bringing it back in and re-doing the calibration I was a bit hesitant to just go and fly again (couldn't anyway, till spare props come in). I took off all my props and did a motor test in the A2 software. One motor seemed to spin up a bit slower, but after repeatedly testing them they all seemed fine. I then did some tests with the throttle. Not even sure if this is a good idea. But I tested going through the full throttle range. Obviously I can't tell if it's getting enough thrust,  but one motor did give me the yellow LED when at full throttle. I powered down and then back up and repeated the test...but now only red and green LEDs on the arms like normal.

My question is how do I know that my throttle is properly calibrated? Do you spot any holes in what I'm doing? Also is there any software or way to test motor speeds?

Thanks for reading this novel and for any and all advice you may have.

2017-1-25
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DJI-Jamie
DJI team
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United States
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Could you happen to post a video of how it's behaving in the Assistant Software? Just to clarify, you only calibrated via the Assistant and did not change any settings on the Futaba itself, correct?
2017-1-27
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quality
lvl.2

United States
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DJI-Jamie Posted at 2017-1-27 08:15
Could you happen to post a video of how it's behaving in the Assistant Software? Just to clarify, you only calibrated via the Assistant and did not change any settings on the Futaba itself, correct?

I appreciate the response DJI-Jamie!

For clarification, yes, I only calibrated via the assistant software...no changes on the futaba. I'll take a video today of what it's looking like.

I went out yesterday with new props and attempted takeoff again, but got nervous when I wasn't lifting off near half throttle. The sticks just aren't as responsive as they were.

I contacted the company I bought it from about the issue, but so far they haven't been super helpful. They  say that its normal for the drone not to take off before 50% throttle...which leads me to believe they had changed something (throttle curve? ) before I got it. But seeing as I didn't touch the Futaba, I'd think that should be the same.

All I know is that it was much more sensitive before I did the stick calibration in the assistant software. I'll do more testing today and report back as well as get a video

Thanks for help. Sincerely appreciate it!
2017-1-27
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DJI-Jamie
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quality Posted at 2017-1-27 08:25
I appreciate the response DJI-Jamie!

For clarification, yes, I only calibrated via the assistant software...no changes on the futaba. I'll take a video today of what it's looking like.

Whenever you can would be great. Just to make sure I'm on the same page, you didn't change any other settings in the Assistant Software such as gains etc.? Did you update any firmware?
2017-1-27
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quality
lvl.2

United States
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I didn't mess with the gains or update any firmware. The only thing I did was set the top Control Mode Switch back to "Atti" I had it on Manual, but decided I'm not ready for that yet.

Here is a link to a video of my settings:
2017-1-27
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quality
lvl.2

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Well, I seem to have gotten it working. After calibrating again everything seems to be fine. Although it still feels like the sticks aren't quite as sensitive as they used to be (maybe its all in my head). I'm wondering if I didn't power cycle before. Just got in though from a successful flight.
2017-1-27
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ducpeter
First Officer
Flight distance : 62175 ft
Germany
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check your GPS mounting numbers Z = -200 it's wrong -> maybe -20
2017-1-27
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quality
lvl.2

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ducpeter Posted at 2017-1-27 11:41
check your GPS mounting numbers Z = -200 it's wrong -> maybe -20

Thanks for pointing that out ducpeter. I haven't touched that value since I got the drone, but if my understanding is right that number should be calculated from the center of gravity of the aircraft right? From my top plate the GPS unit sits about 17cm, but the CG would probably be more around where the battery is (I don't currently have a gimble on) If that is the case it is more like 30 cm from that point, which would come out to -30 in Z. Does that sound right to you? I'm still figuring this all out.

I'm assuming the vendor I bought it from was thinking I'd have a gimble and large camera on it which would lower the center of gravity (although negative 200 does sound like way too much). How does one go about finding the center of gravity accurately? Or do you just estimate?
Thanks for the help!
2017-1-27
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quality
lvl.2

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I should add that when I change the value to anything lower than -200 it turns red....not sure what that means, but red is usually bad. Any thoughts?
2017-1-27
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DJI-Jamie
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quality Posted at 2017-1-27 14:28
Thanks for pointing that out ducpeter. I haven't touched that value since I got the drone, but if my understanding is right that number should be calculated from the center of gravity of the aircraft right? From my top plate the GPS unit sits about 17cm, but the CG would probably be more around where the battery is (I don't currently have a gimble on) If that is the case it is more like 30 cm from that point, which would come out to -30 in Z. Does that sound right to you? I'm still figuring this all out.

I'm assuming the vendor I bought it from was thinking I'd have a gimble and large camera on it which would lower the center of gravity (although negative 200 does sound like way too much). How does one go about finding the center of gravity accurately? Or do you just estimate?

Are you getting a toilet bowl effect when you fly? If not, then you should be ok with the values you've got.
2017-1-27
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DJI-Jamie
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quality Posted at 2017-1-27 14:32
I should add that when I change the value to anything lower than -200 it turns red....not sure what that means, but red is usually bad. Any thoughts?

When you change a value, it turns red to let you know there's a change. Once you hit 'enter' it will go back to black.
2017-1-27
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quality
lvl.2

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DJI-Jamie Posted at 2017-1-27 16:42
Are you getting a toilet bowl effect when you fly? If not, then you should be ok with the values you've got.

I does have a little instability now that you mention it. I will adjust this value and do some tests.
2017-1-27
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ducpeter
First Officer
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Germany
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the value off the puck for me makes sense about -25 to -27cm
toilet bowl will be interesting when i know which GPS you have  from the A2 GPS Pro or GPS Pro plus
2017-1-28
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quality
lvl.2

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ducpeter Posted at 2017-1-28 08:01
the value off the puck for me makes sense about -25 to -27cm
toilet bowl will be interesting when i know which GPS you have  from the A2 GPS Pro or GPS Pro plus

I have the  pro plus GPS. I still need to play with those values...trying to get voltage telemetry onto my futaba right now...I'll get back to you on GPS position adjustment results.
2017-1-28
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DJI-Jamie
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quality Posted at 2017-1-28 15:35
I have the  pro plus GPS. I still need to play with those values...trying to get voltage telemetry onto my futaba right now...I'll get back to you on GPS position adjustment results.

Let us know how it turns out.
2017-1-29
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quality
lvl.2

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DJI-Jamie Posted at 2017-1-29 15:27
Let us know how it turns out.

Will do...I may have to wait a week till we get out of below freezing temps around here.
2017-1-30
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DJI-Jamie
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quality Posted at 2017-1-30 09:45
Will do...I may have to wait a week till we get out of below freezing temps around here.

Whenever you can would be great.
2017-1-30
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