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Posted by mandevil | Mar 11, 2018 @ 05:02 PM | 1,197 Views
Today I drained two batteries with my DJI F550 hexacopter to test new camera (Firefly 8S, more on that in further post). The flights went OK, but when I was watching the footage at home, I was very surprised that at one moment the hex totally flips over and immediately rights itself. It was a moment where my video downlink was poor so I didn't notice that and the craft was out of visual line-of-sight. There is nothing suspicious in the video, so I was at a loss as to what happened. The drone continued to fly fine and there was no damage, even upon close inspection. Eventually, I downloaded iOSD logs and studied them a bit. At the event time few things suddenly spike: acceleration, altitude drops a bit, main voltage has spike downwards to 14.5 V, which is completely fine on 4S battery. I found no errant user input (like accidentally triggering manual mode). My conclusion is that sudden force was exerted on the aircraft which immediately compensated and righted itself. Given that the craft was at sufficient height to avoid any collisions with trees and wires, there's only one thing left: bird attack.

DJI F550 unexplained mid-flight excursion (see description for update) (0 min 35 sec)

Posted by mandevil | Mar 07, 2018 @ 01:40 AM | 975 Views
My first attempts at correcting the Mavic Pro video:

Mavic Pro Color Correction Breakdown (2 min 17 sec)

Posted by mandevil | Feb 19, 2018 @ 03:17 AM | 1,559 Views
So after buying Mavic on Mondey I finally flew it on the week-end. I took six batteries worth of flight so here are my first impressions:

The good:
  • It flies, it's very docile, catching it by hand and starting from hand is pretty easy, the overall stability is pretty great; controller is decent, though I still find the smartphone part bit awkward, though I understand why DJI do it this way.
  • I use Android phone and I thought of dedicating my old HTC One M7 for this, but it sometimes experiences partial image blackouts and also feels little sluggish. My current HTC One A9 on the other hand seems to be completely OK, so I guess that's what I am going to use.
  • It's cold here and my fingers are freezing after few minutes so I haven't tried anything too wild, like flying into great height or distance, but at about 500 m the signal seems to be rock solid.
  • The setup is quick. I don't even have a good bag yet, but it still far cry from setting up my F550. I look forward to taking this on trips.

The bad
  • Remote controller battery drains fast. As if that wasn't enough, it also charges Android phones. What the hell, DJI! You could easily limit the provided current, but you don't care. I tried to few utilities on my (rooted) M7 to disable charging, but none worked. This sucks. I think the remote can last three batteries, but I am pretty sure there's no way it can make it through the fourth. This is stark contrast to my FrSky Taranis which I charge like... 5 times a year?
  • And now for
...Continue Reading
Posted by mandevil | Feb 15, 2018 @ 05:44 AM | 2,594 Views
I have had a DJI F550 hexacopter for about 3 years. I eventually it equipped it with everything needed for a good aerial photography "gunship". But this Monday, I eventually bought a Mavic Pro. Let me briefly rant why I have eventually given up on the F550.
  • The hexacopter itself -- the design is not ideal for aerial photography; the intended camera position in front places it right into the downwash of the front propellers. This could be (maybe) fixed by equipping some retractable tall landing gear, but that is going to add some weight and failure modes. Still, this is probably the lighter complaint.
  • The gimbal -- I have the Zhyiun Tech Z1 Tiny 2 gimbal. It appears to be pretty well made mechanically, but the support was never too great and soon the company dropped it altogether, so no more firmware updates. The gimbal has some minor horizon drift issues and also isn't stable enough for pro-grade footage. My assumption is that some vibrations come from the force of the prop downwash, which is not insignificant. Also when flying faster or in wind the gimbal had tendency to start vibrate wildly. It is possible that this could be fixed with some PID tuning, but I don't have the experience and even the calibration never worked for me in the first place, so I didn't even try.
  • The GoPro Camera -- Unfortunately, GoPro maybe the most pressing issue for me. Foremost, I hate the fisheye distortion, it is totally out of place for aerial shots and removing it in post
...Continue Reading
Posted by mandevil | Jan 22, 2018 @ 04:26 AM | 1,977 Views
Quick and short edit of my recent flight.

Nakléřov, a flight with DJI F550 (2 min 29 sec)

Posted by mandevil | Dec 30, 2017 @ 01:12 PM | 1,921 Views
Posted by mandevil | Dec 03, 2017 @ 01:49 PM | 2,318 Views
After one abortive attempt (motors rotating in the opposite directions because the translation of the DJI manual for F550 states wrong direction of rotation) I re-maidened my rebuilt F550 with the iOSD Mark II incorporated. This allowed me to rid of the extra battery that I used to power the VTX/FPV cam for some minor weight saving. Funny enough, the balance that this extra battery provided made the main battery to move forward to the limit. I also soldered XT90 connector for battery connection (my Gens Ace Tattu batteries have these) and the joint was fairly hard to solder for me, so I pray to patron saint of model aviation that the joints are good and won't come apart in mid-flight. Another mod was finishing the proper attachment of the Z1 Tiny gimbal using four M4 screws and proper attachment of the RunCam – these were held by duct tape before. I hoped to reduce the vibrations that creep into the GoPro image when it's windy or at high speeds. Doesn't seem to have helped, so I guess it wasn't fault of the attachment to begin with.

Following short video shows the iOSD in action. The flight was made in freezing temperatures and quite windy weather, so you can notice significant pitch/roll of the FPV cam picture compared to the GoPro image.

The iOSD works nicely, there was no issue connecting it. I decided not to use the video switching feature and use my SmartFPV switch instead, because the way video is switched with the iOSD is rather awkward. The navigational data show look pretty great, the "direction to home marker" seems to be spot on. What surprised me that the persistent "red blinking LED" problem I encounter very often is not loss of GPS lock, because I've got it with 10 satellites locked.

F550 with iOSD Mark II (2 min 41 sec)

Posted by mandevil | Nov 25, 2017 @ 01:34 PM | 2,189 Views
Three weeks ago I had an out-of-LoS landing with my DJI F550 hexacopter. I lost orientation in fog and GPS hold somehow wasn't holding location and wind blew me few hundred meters away. The craft landed softly, but after few seconds it flipped over for unknown reasons. My explanation is that loss of control signal triggered fail safe that tried to take off. Anyway, the copter survived mostly intact (or so it seems), but all props were ruined and they also sprayed soil all over.

I took the hexacopter apart to clean it and also started to think about improving it. To my surprise, DJI iOSD mkII price went drastically down -- to about third of what it used to cost when I last checked. So I ordered it and started to work on putting it all together. After lot of research I decided not to use the video switching feature to switch between FPV camera and GoPro and use my trusty SmartFPV video switch. I mix OSD only to FPV cam while leaving GoPro picture without OSD. After few days of work all is finished and ready for the re-maiden.
Posted by mandevil | Jul 01, 2017 @ 10:05 AM | 3,481 Views
I have bought my F550 hexacopter new batteries -- Gens Ace Tattu 4S 6750 mAh. The difference this makes! Now I seem to be easily reach 15 minutes in the air where before I did not dare to stay past 8 minutes (with aged Turnigy 4S 5000 mAh).
Posted by mandevil | Apr 16, 2017 @ 04:45 AM | 4,455 Views
Yesterday, when I was fixing gimbal mode selection not work (turned out to be a loose pin in the JR connector) I decided to investigate different gimbal version. So I loaded 1.11p version into it. Well, it seems to work, but now I cannot perform any more upgrades. When I try the gimbal apparently stops responding and goes completely slack. So it seems that I'm stuck with what I loaded in.

The new software is the 'p' version, which is the PWM input directly commands the position as opposed to the 's' software that commands speed and sense of change. There are some advantages to the position version -- you can adjust your transmitter so that the slider detent is neutral position and the maximum deflection is some other position like 90 degrees downwards for the pitch axis. The downsides are that you can't easily do the very slow movement. I have added a delay for the pitch axis and see how it works. Also, the movement is limited in this version, so the 90 degrees down is the limit and you can't pitch upwards as well.

Also, the Zhiyun Tech website no longer lists the gimbal, so it looks like they discontinued and no new version of the control SW are coming. Sigh.
Posted by mandevil | Apr 01, 2017 @ 02:34 PM | 4,695 Views
Today I have installed video switch from SmartFPV (this one), so that I can switch between RunCam and GoPro cams. This will allow me to use gimbal controls in flight. Everything worked pretty much out of the box. The last thing I need to do is to affix the gimbal to the aircraft frame properly -- the duct tape is a shame. New videos can be seen here.
Posted by mandevil | Feb 25, 2017 @ 03:07 AM | 5,232 Views
This is video from my vacation in November, but it is still my distance record.

FPV flight to 1.3 km (2 min 25 sec)

Posted by mandevil | Feb 18, 2017 @ 01:18 AM | 5,080 Views
Finally, I have replaced broken landing gear on my F550. I also soldered gimbal power supply to the main power bus, so now only the cam and the video transmitter are powered off a separate battery. Below is short video from the first session with the repaired hex:

Winter with DJI F550 (2 min 1 sec)

Posted by mandevil | Nov 04, 2016 @ 12:33 PM | 5,129 Views
Yesterday, I dodged not one, but two bullets while flying my F550 hexacopter.

The first close call happened as I was flying near Vimperk. I flew to about 100 m AGL to gain a view of the town. After short while filming I decided to return. And guess what, I couldn't find my starting place no matter what I tried. Video link got quite spotty and I thought I am above myself, but in fact I was behind some trees and not very close. I tried to recognize the terrain (meadows with groves) but I couldn't no matter how hard I tried. Eventually, I decided that it's better to land at unknown place than to fall while searching fruitlessly. Fortunately, the craft did not lose the control link (that would trigger RTH which I don't think would work as I suspect that GPS fix was lost). After about 15-30 minutes I found the copter intact in the middle of a meadow. Video from the camera eventually showed, that the landing was fairly smooth, if bit fast.

The second close call happened on different place, where I decided to finish off the same battery from the previous flight. It was showing 14.75 V (4S battery) or so, so I thought I can eke out a minute or two. Bad decision. After I reached my target some 300 m away I noticed that my main voltage is 9 V! Before I could do anything, the copter started to descend rapidly. Fortunately, I was just a few metres above the ground, but even then the impact was more violent then in my previous screw up. The landing gear legs snapped on one side, but apparently gimbal did not hit the ground. So it seems nothing but the landing gear broke. Of course, now I need to order new one, before I fly again.

Lessons learned:
  • on unfamiliar location don't just fly away, but look back and find some orientation landmarks that will help you find your way back
  • make sure you're receiving GPS coordinates in telemetry; make sure your transmitter is displaying all pertinent navigational data: AGL height, ground range, distance!
  • have alarm for low voltage that triggers at about 13 V

Edit: Video of the above is available.
Posted by mandevil | Oct 31, 2016 @ 04:21 PM | 5,065 Views
Third session with my DJI F550 hexacopter with new Zhiyun Tech Z1 Tiny 2 gimbal. Very roughly edited because I'm on vacation and don't have real editing software here.

Aerial from Šumava (quick edit) (5 min 39 sec)


The occasional vibrations occured again. They never happen when low, sometimes just turning into opposite direction will make the flight smooth again. I am more and more conviced it's the prop downwash impinging on the gimbal platform. I tried to move the gimbal back a bit, but no discernible improvement. But it definitely needs to be resolved, since it seems to be able to ruin otherwise good shot.
Posted by mandevil | Oct 28, 2016 @ 02:51 PM | 5,069 Views
So, as promised, today I took the Zhiyun Tech Z1 Tiny 2 brushless gimbal to flight. I compiled a video from today's footage (total of about 24 minutes cut down to some 6 minutes). I couldn't do much processing since I'm on vacation and my video editing workstation is not with me.

Overall, good impression -- it just works. Horizon is level, heading stays put, stabilization looks mostly pretty good. There were some periods where there were considerable vibrations visible. Not sure about that, but either there was some wind up there or something is not quite right with the copter.

I don't have video switching in the copter yet, so I couldn't try remote control of the gimbal.

Zhiyun Tech Z1 Tiny 2 gimbal maiden flight (7 min 0 sec)

Posted by mandevil | Oct 27, 2016 @ 01:07 PM | 4,768 Views
I completed equipping my F550 hexacopter with Zhiyun Tech Z1 Tiny 2 gimbal. Since I am on a vacation, it's not the final solution yet, but it should be airworthy enough for a few flights.
  • Had to extend gimbal control wires; spent entire evening making JR connectors agonizing without proper tools
  • The hang frame supplied with the gimbal does not fit my landing gear's rail I decided that I will just affix the gimbal's top plate to the rail platform but I don't have the screws/nuts for that; temporary solution: duct tape! Much professional, much strong, much wow!
  • Mode selection doesn't work on the completed rig. Not sure what went wrong, I checked both the cable and the mode setting before installing. I don't want to take everything apart again, so default mode will have to do.
  • Takeoff weight is 2 kg. DJI spec says it should fly.

See you tomorrow.
Posted by mandevil | Oct 26, 2016 @ 05:31 AM | 4,931 Views
I ordered Zhiyun Tech Z1 Tiny 2 gimbal after reading positive reviews and good experience with it. Also, Banggood had it in their European warehouse and for a good price (about 30 EUR lower than in their China warehouse!) It arrived in about 10 days -- just few days before my vacation.

So now I am in the process of adapting the F550 so that I can install the gimbal. I installed the "tall legs" landing gear that include a rail for installing the gimbal. Unfortunately, the rails spacing cannot be adjusted and of course, it doesn't match the Z1 Tiny's hang-mount frame. So I will just screw it in the gimbal mount plate supplied with the landing gear (being on vacation, I don't have the screws...). BTW, I don't feel too good about the landing gear as it seems that both plates extend will into the down-wash of four out of six props.