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My Tello VPS freaked out on today’s flight !

CamFlyer

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Today it was sunny and almost free of any wind. My plan was to fly at the supermarket that has some restoration work going on. I was curious to know if the crane is more than 30m tall. After start and reaching the 30m height limit it was obvious that the crane’s height is around 10 meters over my altitude limit. While getting closer to the crane some features on the ground seam to trick the VPS so I got about 5m higher than I was able to get to at my start position. Later in the flight the crane or the buildings around it tricked the VPS more and more till Tello rose to about 40m altitude! Also the drone dropped many meters while I pushed my stick downwards (I was thankful that it did not fly away) but the altitude measured by the VPS only dropped a fraction of the actual height I lost at this time. I decided to land the drone to re-calibrate the VPS. At the moment of touchdown the indicated altitude was 16.5 meters!

Lesson learned:
Large structures in the flight area that are visible for the VPS (I expect the bottom facing camera has at least a 60° FOV) indicate false ground levels to the VPS and so the height measurement get messed up. A barometric sensor would help. I once read that there is on in Tello, but this flight let me believe that there is no such device in Tello or the software does not take this data and uses it to “calibrate” the VPS.
I also experienced that moving things like the river let’s Tello think it’s drifting and compensates this. The strange thing was, that it was compensating in the opposite direction. I have a short recording of the incident since I very quickly get back over land to not lose the drone.

 
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Ansia

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You should fly at the shore. When the waves hit the sand, the Tello moves with the waves. It's fun to see it in the after video.
 
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Ansia

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I would like to view a video of that effect. Do you have one ?
I recorded one earlier today but I deleted it, because I was having frame skip issues. I should be going to the beach next weekend and try again. If I make it work, I'll post it in the forums.
 
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raulvolador

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@CamFlyer,

I'm afraid your video only shows an optical illusion due Tello's tilt and software stabilizated image.

It's well documented Tello measure it´s height using a barometric sensor. I can remember a funny video starring by Tello into a moving elevator.

VPS system using underneath camera is only for self positioning and stable hover.

Infrared sensors are short range only useful for soft takeoff and hand landing.

All together these sensors makes fliying Tello a wonderfull experience.

Raul.
 
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Guorium

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@CamFlyer,

I'm afraid your video only shows an optical illusion due Tello's tilt and software stabilizated image.

It's well documented Tello measure it´s height using a barometric sensor. I can remember a funny video starring by Tello into a moving elevator.

VPS system using underneath camera is only for self positioning and stable hover.

Infrared sensors are short range only useful for soft takeoff and hand landing.

All together these sensors makes fliying Tello a wonderfull experience.

Raul.
what is a soft takeoff?
 

CamFlyer

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@CamFlyer,

It's well documented Tello measure it´s height using a barometric sensor. I can remember a funny video starring by Tello into a moving elevator.

Raul.
Yes Raul, I did the elevator test too, and going down with the elevator, the drone "glued" itself to the ceiling. And going up it landed forcefully. Exactly as predicted if it uses the barometric sensor. Also on the vendor's website the barometric sensor is mentioned.
This is the video I found on YouTube:

But I did another test: My apartment is quite good sealed. If I turn on the kitchen ventilation on full speed a slight under-pressure builds up. Using a barometric altimeter on my smartphone I measure a 2-3 meter higher altitude ! If I let the Tello hover inside my apartment while turning on or off the ventilation it rest at exactly the same height. So I think the reason the Tello tries to stay at the same altitude in the elevator is because it uses the acceleration sensors in addition to the downward facing camera to hold the altitude.

According to or nearest official weather station the air pressure changed in the hour during my flight from 962.1 to 961.9 hPa.
I found this info about air pressure in the Phybox app: ( Sensor: Pressure )
As the pressure sensors in phones are designed to determine the user's vertical location within a building, they usually give surprisingly precise results. Most sensors can easily resolve a height difference of 1 meter, which is about 0.1 hPa = 0.1 mbar.
So this fallen air pressure would result in a indicated height increase of 2 meters and the drone would compensate that by flying 2 meters lower.

Here a test measurement:
Screenshot_20190218-011729_phyphox.jpg
I started with the phone in my hand. At around 30 seconds it was on the floor and at 40 seconds I held it as high as I can, about 2.3 meters. At 60 seconds I started the kitchen ventilation and stopped it 15 seconds later. So if the drone relies on the barometric sensor while flying indoors it should be react as clearly as in the elevator. But it stayed absolutely stable at the same height about 1.5 meters above the floor. I would like a confirmation for my observation if someone can replicate this test and measure the air pressure at the same time with a smartphone with a accurate barometric sensor.

Anyway, I think my problems on this flight where the result of a confused VPS with the street below and the buildings, containers and the crane all in the visibility of the sensor. It is impossible that on such a calm day the air pressure would fluctuate so much in under 5 minutes.
 

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Guorium

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Do you guys notice that this guy flies with a bt controller (I don't see a cable there) and he has zero frame skip? Video is mostly buttery smooth except fot the part he was behind the building and over close the the crane. The area is pretty urban so I bet wifi crowed too. I fly with my phone in flight mode without bt controllers in my bedroom (wifi crowded) and I get get 1 frame skip per rotation at a fixed angle. I wonder what is the deal here.

Also. VPS sensors include inthe IR sensor which detects close surface so tello can lift itself if it glides over some surface that is close, try putting your hand under it and tello goes up on its own (it is about 30cm is detection range), the camera locks the horizontal position of tello so it does not drift horizontally, the barometer holds its vertical postion. I guess tello has this smart feature built in where it adjusts height to compensate for air pressure change unless there is a command from you to change altitude. Sounds like exactly how altitude hold should work. It gets wind gusts up there sometimes...
 
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CamFlyer

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Do you guys notice that this guy flies with a bt controller (I don't see a cable there) and he has zero frame skip? Video is mostly buttery smooth except fot the part he was behind the building and over close the the crane. The area is pretty urban so I bet wifi crowed too. I fly with my phone in flight mode without bt controllers in my bedroom (wifi crowded) and I get get 1 frame skip per rotation at a fixed angle. I wonder what is the deal here.
.
I have bought a GameSir T1s Gamepad before I had the Tello. This Gamepad can be used via USB, a 2.4 GHz dongle (included) or with Bluetooth.
My test to use the controller via Bluetooth connected to my Galaxy S8 where a total disaster ! :mad::eek::ROFLMAO::(
I had glitches before takeoff where the distance was 2m. It got unusable at 10m distance. The only possible way to improve the connectivity was to separate the controller from the phone about 1 or 2 meters. But like that the setup is totally worthless.

I then tried to connect the controller to the phone with the included micro USB cable and the original Samsung OTG adapter. No interference anymore :cool:(y) and much easier to setup (no hassle with Bluetooth). But the setup wasn't very neat with the way too long cable. I then ordered 3 micro USB to USB-C OTG cables from Aliexpress. On should work for a Mavic controller, but did not work with my Gamepad. Also the second cable that arrived did nothing. The 3rd one did work, but I had to trim the a bit too big micro USB connector : DANSPEED 25cm OTG Cable Micro USB Male to Type C Male Cable Adapter Angle Cable Data Sync Charger

You can see the setup at the end of the video liked in the first post of this tread.
 

HoverHappy

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So are you saying that to connect the controller and phone I need a double male mini USB. My phone has a mini USB identical to the charger port on the controller. This site you sent me to has multiple cables can you show me a picture of the one you use sure would appreciate it!! Is it Plug and Play? The main reason I even wanted a controller was to use a set of goggles. Kind of glitchy but if the cables work better I could use the knowledge you have. Appreciate it
 

ZWActual

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So are you saying that to connect the controller and phone I need a double male mini USB. My phone has a mini USB identical to the charger port on the controller. This site you sent me to has multiple cables can you show me a picture of the one you use sure would appreciate it!! Is it Plug and Play? The main reason I even wanted a controller was to use a set of goggles. Kind of glitchy but if the cables work better I could use the knowledge you have. Appreciate it
What's the exact manufacturer/model of your phone?
 

ZWActual

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Please validate but:

The LG K20 has a micro-USB port:

If you're contemplating the Gamesir T1s controller, it is also has a micro-USB port:

You would need this OTG cable (or equivalent):

or just this:
 
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HoverHappy

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This looks like it'll work I'll give it a try. Is there any configuration I need to set up to make this work or is it just plug and play
 

ZWActual

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Running a similar setup but with a legacy Sony PS3 controller (via TelloFPV app). Should be plug and play as long as the LG K20 supports OTG functionality. Good luck. Keep us posted.
 

HoverHappy

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I live in a very small town in East Texas that might be awhile till I can go to a big town to retrieve a cable that will work properly I'll keep you guys posted and thanks for all your help really appreciate you
 

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