Just another day in paradise

I’m adding new topics for this blog. This is from last week paragliding. I’ve trimmed 1h flight to this 3 minute video. Flying next to gliders and paragliders. Good stuff.

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Trying openpilot quadcopter


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One of the propellers got unsqrewed and quad was grounded. Besides that, openpilot seems to be really impressive platform. I’m happy with their ground station firmware, cheap and well developed hardware. Thumbs up!

No time for FPV, but still in the sky

From time to time, I do get a chance to get out with paragliders. I’m still learning to get para-pro license. Flights are not very long, but quite fun. Hopefully it won’t be a step away from FPV, just a leap.  So I’ll share few photos of my flights. In some of these fields I’ve been reaching for 7km FPV distance. Time passes, toys changes, but the intentions stays the same.

Virgis21 from RCG is working on that machine down below.

One step over the clouds.

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DIY thermal camera

Few months ago I’ve got idea to make FLIR (thermal imaging) camera. Professional grade equipment is very expensive. I’ve found few ideas how you can do that. On of them is instead of using expensive infrared matrix, use single point thermal sensor, and put it on servo motors, to scan view in X and Y axis. So I’ve taken MLX90614 thermal sensor with 5 degree FOV, and STM32 dev board with color LCD. Frankly results are even better than I’ve expected.


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Synchro copters [beautilful]


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Somewhat different fpv

This season I’ve included paragliding to the hobby list. Seriously cool activity ;)


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Easy glider finally in the air

After long break, I’ve came back to RC. EZ glider has been lying unassembled for about half a year, and I’ve finally finished it. The test run wasn’t very smooth:

- I’ve threw glider without motor applied to see if it glides ok, it bumped nose to the ground. Nose heavy? I’ve measured COG 70mm from the leading edge, and it balanced perfect. On the second try I’ve switched on motor, and it went up real nice, but of course I had to compensate elevator trim.

- I haven’t mixed tail with ailerones, so it was kinda lazy on the turns. I still haven’t mastered coordinated turn, so I’ll fix it with the mix.

- I forgot to program the brake, so the folding propeller was not going to fold.

- Propeller adapter came off during the flight. It was fixed firmly before flight. Not sure what’s happened. My first folding propeller, maybe I’ve missed something.

Hopefully next time I’ll go with fpv gear and fixed plane.


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Finally received GOPRO2!

Finally came my GOPRO2 from USA. New and improved. Better resolution, handles dark better, more pro. Haven’t installed it on a plane yet, but took it on my ride to work. It was pitch black, so you can evaluate how it works at night. It’s not a night camera, but even at such conditions it’s sensitivity is reasonable. I promisse to make more videos during the daylight, once I see it.

Video taken 1080p at 30 fps.

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Dodging cliffs by PeeMax in Iceland

Simply great flying.

Flown with Dragon Link LRS
Plane: Bixler
2.4GHz 1000mw Tx (using 2.35)
Tx antenna:IBcrazy’s half wave dipole
Rx antenna: 11dbi Omni from hobbyking
Turnigy Basic FPV goggles
GoPro HD Hero2 recording 60fps at 720p


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Video on the internet: FPV adventures

Some video I’ve found on RCG. Nice scenary, music and action.


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Converted DOSD power supply to linear

My gps unit was unable to lock stable signal. I’ve found out that interference source was DOSD swithing power supply unit. I’ve removed it, and inserted linear 3.3V voltage regulator (LM1117-3.3). Works like a charm. Stable satellite lock near window where was no at all.

Adjusting video level on DOSD

While lines
I’ve recently purchased DOSD. The first I wanted to fix was these white lines on the screen. They appear if black borders are enabled in the settings and signal is fed through RF video link. When DOSD is directly connected to the goggles or the computer, this problem is not noticeable.

As I’ve noticed on youtube clips this problem is not rare one. Few of my friends has bought Dragon OSD and had the same problem.

The problem is in the black level in the composite video signal

As you may notice on the scope view, very short bursrs of signal means white letters being drawn on the screen with black border. The lower amplitude is, the darker the view is. But it should stay above reference black level, which goes right after the sync signal. Here we see, that it goes under. That probably confuses video TX or maybe RX AGC. You may hide this problem by loading video signal with parallel resistors on the composite cable, but this might degrade your contrast, colors or even a synchronization. THIS IS NOT A MAXIMUM VIDEO LEVEL PROBLEM!!!

When I’ve looked at the DOSD PCB I’ve found that two signals comes from microcontroller. One of them draws white pixels, another is for black ones. White pixels right now probably is not the part of the problem, so I’ll draw only the black color part . This scetch shows how the parts are connected (guess only, based on observation):

Accidentally I’ve damaged onboard transistor, and tried to replace it with pin-to-pin compatible BC847 (100MHz). This general purpose NPN transistor seems too slow for this task, the image was very shady. So I’ve searched and found very good and kinda cheap transistor: BRF93A. It is able to work up to 6GHz (!). It worked really nice. Not sure what was the original part number, but text in the picture now is crystal clear.

To limit voltage being shorted to ground by transistor, I’ve inserted 100 Ohm resistor on the emiter, and it solved a problem. You can see in the video how I’ve tried adjustable resistor to find optimal blackness level in the picture. There was no slot for the load resistor, so I had to lift transistor and solder 100 Ohm resistor nearby. Not very elegant, but .. it works.

As you may see, I have great picture in the screen. With solid black border and no white shading ;) .


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Hope this will help someone to improve the image!

_________________

Never tried, but maybe there is even easier way to solve this, by increasing marked resistor:

FPV range calculator including terrain topology

Ligowave has created very useful radio link calculator http://www.ligowave.com/linkcalc/, which evaluates terrain topology, Frenell zones, radio wave attenuation, rain and foliage. You need to point on the map where are you going to fly, enter your frequency, tx power in dBm (~27), receiver sensitivity (~ -95), antennas height and you get the results. There are two modes. One calculates if you are yousing directional antenna, you’ll get information about link margin. Another point to multimpoint (P2MP) mode calculator assumes you are using omni antenna in the ground station. Even program is designed for digital links, it’s quite good for analog FPV videos too. Free registration required to use this tool.

GoPro employed

Chasing Twinstar2 with Twinstar2. It was very windy, so planes were difficult to aim at. Next time will be better! Footage is 1080p, 127 degrees FOV.


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TS2 crashed because of empty battery. Headwind was quite strong.


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Trying to reach 7km with Twinstar2

This time I was not able to achieve roundtrip. Even the plane reached 7 km, the battery depleted on the way home. No damages this time.


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Twinstar2, 8×4 props, 100ish g motors.
2700 mAh 3S1P Zippy 25-30C battery
Sunsky 500mW vtx + inverted vee antenna
Lawmate vrx + 11 dBi biquad 1280 Mhz antenna
ChainLink @ low 200mW power mode.
Smalltim OSD, modified for CL LRS
Fatshark cam

Testing biquad antenna, perfect picture over 4 km

After 2km flight with omni antennas, I've decided to make biquad antenna described by IBCrazy. It impressed me how good this antenna is. I had no video reception problems what so ever for the whole 4km flight.

RSSI level shown by OSD is not calibrated, so it show no RC control, even I had a solid control and no failsafe's.


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Finally reached 2 km range

I’ve tested my new Lawmate 1.2 GHz video rx. It seems it’s quite good receiver. Sensitivity was slightly better than sunsky rx, but selectivity is much better. It was quite immune to nearby 433 MHz LRS, contrary to sunsky vrx. Due to omni antennas signal wasn’t very strong, but good enough to do the flight.

Twinstar2 3S 2600 mAh, 8×4 APC. Inverted Vee antenna for 400mW @1280MHz sunsky video tx, omni stock antenna on lawmate video rx. Archos AV500 DVR. ChainLink 433MHz LRS stock antenna 200mW mode. Fatshark camera. Also fatshark 2.4 GHz 100mW video tx on ground station, to retransmit signal to fatshark goggles.


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New ground station, new LRS

Finally I've purchased ChainLink LRS. It has switchable power between 0.1mW (range test, 0.2W and 0.5W). 12 Channel receiver. We've tested it in the city without ling of sight, signal faded in 2.4 km, which was very similar to popular DragonLink (DL). I've modified Smalltime OSD to show RSSI level. Problem was in SN777 camera which was very noisy. I've did modification to remove that noise (will be described later). I've did some changes to the ground station also. I've used photo camera tripod. That helped to reduce multipathing. I've attached 100mW 2.4 GHz fatshark transmitter near after 1.2 GHz receiver to retransmit the signal to the goggles. It gives more freedom around the GS. The main reason I've did this, to reduce CL influence to video receiver, because atleast 2 meters are recommended.
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Fatshark review

Recently I’ve bought FatShark 2010 Aviator edition video goggles. I’ve been using laptop as my primary navigation screen. I’ve started with EasyCap USB video adapter. It was very cheap (~7$), and very crappy product indeed. Then I’ve switched to Avermedia PCMCIA adapter. It was ok. The mayor problem is laptop screen itself. It’s very difficult to seen even there is moderate sun light outside. Even the laptop is in the dark car trunk, reflections are still very bad.

So I finnaly decided to get these goggles which I’ve heard so much about. Aviator edition is different from standart edition, because it has integrated 2.4Ghz or 5.8 GHz video receiver. Also it came with 100 mW transmitter. I didn’t tested it outside, but I don’t expect much from that power.

I had VR920 video goggles before, so I can compare them. First of all, the things I like:

+ Good field of view (FOV). It’s declared as 40ish degrees. It would be nice to have more, to get even more immersion, but it’s really enought to navigate and feel yourself in the plane. This is where it outperforms VR920.
+ Good contrast. My camera doesn’t produce good colors, so I can’t tell if there colors are good, but picture is quite good.
+ Really good sun shading. Foam around the eyes completely covers everything around, even with the bright sun outside, I’ve seen only screen. No silly caps or covers needed.

I know it’s not a big list, but it’s very important freatures in FPV goggles I think. Now what I didn’t like:
- The most important issue for me with this goggles is eyes fatigue even after very short usage. I must admit my eyes are quite bad, maybe there is something to do with it. But few people with good vision also confirmed this. I think there is something to do with focus distance and eye degree. The goggles are focused for 2 meters virtual distance. But eyes are looking straight forward, parallely into infinitive. Eyes quickly adapts to this and you can see fine in the goggles, but when you take it off, eyes needs to readjust and it feels sick for a few moments. Maybe this is something I need to get used to, but I didn’t like it at all!!!
- Lenses are very close to the eyes. Some people complained about it, personally I had no big problem with that. I guess it was needed to achieve such good FOV.
- Even you can change lenses distance to fit the distance between the eyes with two sliders in the front, it’s almost impossible to get clear picture in the whole screen. Sometimes left, sometimes right, or sometimes both sides are blurry. It’s not very big issue for me, because my osd shows main information near the center of the screen, but other people, could have some problems with osd like dragon OSD. They say that 2010 edition fixed this problem. I wonder how horrible it was before this edition?
- Battery charged came in US mains plug version. I need to buy aditional adapter to use it. I had to cut the cable, fir the T connector and use it with my primary battery charger.

Here are some pictures:

I like this label “inflatable shark not included”.

It’s not easy to take a picture of the view, because you need to be really close to the lens to see the whole picture.

This 100mW transmitter came with simple wire attached instead of antenna. I can live with that if it’s tuned to right frequency. I didn’t tested yet properly, but I’m sure inverted vee antenna will outperform this wire.

I hope this review will help you to decide if you want to purchase this unit. They are not great goggles. They are ok and do their job. Not sure if it’s possible to get anything better for such price though.

TwinStar first launches


Incorrecg CG and some other problems. Will be fixed soon


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Let’s see some twinstars


Right now I’m assembling my plane, so there is no much to show. Rather see some Twinstars made by others:


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Server upgrade

We’ve finished server upgrade. Now pages will work even faster.

Hexacopter in Cameroon

William Thielicke (Mr. Shrediquette) from Cameroon


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Calibrating OpenPilot quadrocopter


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Trying new DVR

Archos AV500 60GB


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