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TwinStar II with custom OSD & 23cm downlink

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Posted (edited) · Report post

A while ago I decided to build a TwinStar II for FPV use.

The plane is not ready to fly yet, but I hope to get it ready within a week. Actually the only thing missing is 30cm silicon wire for the left motor (I made 5 out of 6 cables, and went out of wire). The paintjob is done with black and silver acrylic spray paint.

It will be equipped with the following gear:

- AR7000 2.4GHz diversity R/C receiver

- 4 x Hitec HS-81

- 2 x Turnigy 2213 20-turn brushless motor

- 2 x TowerPro w25A ESC

- 3A UBEC

- 2 x Aluminium spinner

- 2 x 9x6 APC propeller

- 11.1V 4000mAh LiPo

And the following FPV-equipment:

- KX131 video camera

- 1.3GHz (23cm) 1W video transmitter with a four radial GP-antenna

- Totally custom OSD based on the BOB-4 video overlay board

- EM-411 SiRFStar III GPS

- TinyTrak 3

- 3A 5V switch mode regulator

As said, the OSD uses a BOB-4 module for video overlay. I originally controlled the BOB-4 with a PIC16F88, but the increasing amount of float variable calculations and other demanding operations forced me to upgrade to a PIC18F1320. More technical information about the OSD will come later.

It is now fully working (not as seen in picure 16 on the OSD-page below).

The TinyTrak 3 is used to transmit lat./lon. and altitude to the ground station to calculate azimuth and elevation angles for the receiver antenna. I will proceed the development of this system as soon as the basic FPV/OSD system runs satisfiable. The AX.25 decoding on the ground is done with a PIC16F88, and the trigonometrical calculations is done with a PIC18F1320.

The plane so far:

photo16.jpg

The FPV-stuff so far:

photo14.jpg

More pictures:

http://skagmo.com/projects/TSIIOSD

http://skagmo.com/projects/TSIIbuildingprogress

http://skagmo.com/projects/TSIIvideoTX/

Edited by jonpet55

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Posted · Report post

what osd /gps system is that?

switch mode regulator

As said, the OSD uses a BOB-4 module for video overlay. I originally controlled the BOB-4 with a PIC16F88, but the increasing amount of float variable calculations and other demanding operations forced me to upgrade to a PIC18F1320. More technical information about the OSD will come later.

It is now fully working (not as seen in picure 16 on the OSD-page below).

The TinyTrak 3 is used to transmit lat./lon. and altitude to the ground station to calculate azimuth and elevation angles for the receiver antenna. I will proceed the development of this system as soon as the basic FPV/OSD system runs satisfiable. The AX.25 decoding on the ground is done with a PIC16F88, and the trigonometrical calculations is done with a PIC18F1320.

The plane so far:

photo16.jpg

The FPV-stuff so far:

photo14.jpg

More pictures:

http://skagmo.com/projects/TSIIOSD

http://skagmo.com/projects/TSIIbuildingprogress

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Posted · Report post

Very interesting project! Be sure to test the AR7000 for issues from the 1W 23cm video Tx's harmonics. There has been some reported troubles with such things. For sure, keep the A/V Tx and the R/C Rx far apart.

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Thank you for the comments.

Rking: The OSD is made by me, so it is not a commercial solution.

Mr. RC-Cam: I have tested the 23cm TX with both the GPS and the AR7000. The TX is much more high quality than Lawnmate transmitters etc., so there is almost no harmonics. I was expecting the TX to block out the GPS though, but testing shows that the signal is just slightly reduced even when the transmitter is 2-3cm close. I guess I can thank the saw-filter on the GPS for that (EM-411 has a saw-filter right?). The AR7000 also performs very well close to the transmitter, but to be sure I bought a 36" extension cable for the remote receiver, so it is now located at the tail, while the 23cm TX antenna is on the nose. Almost 1m separation.

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I've added some pictures of the 23cm TX. Check the bottom of the first post.

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Posted · Report post

Sounds like you've covered the RFI issues. It is nice to hear that everything plays well together.

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Totally awesome setup! I really like the paint job on the Twinstar! Your OSD looks sweet. Some of the things you guys on this site build just blow me away. I really really want to learn how to build this kind of electronic equipment. I'm planning on taking classes this fall...

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Posted (edited) · Report post

I haven't visited the thread for a while, so sorry for my late reply.

Philtyy; Thank you for the kind words! :)

The software for the OSD and the other stuff is now more or less finished.

In the video below I use a cheap 2.4GHz transmitter - not the one in the picture.

Check out a video of the first OSD-test here.

A picture of the completed FPV stuff:

gearl.jpg

Edited by jonpet55

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Posted · Report post

Very nice work. Glad to see it's ready for flight.

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This stuff just boggles my mind to see it all working and in action. I'm still used to tubes, paper capacitors, and 5 pound transmitters...........

OH so much to learn and so little time..........sigh

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^_^

I tried to test the gear yesterday. I put it all in a Java 150 electric glider, but the thing dropped like a rock... ;) The motor was way too small anyway, so I've ordered a motor giving more than twice the thrust. Hopefully I will maiden the TSII very soon as well. Have to wait till I get some grass to land on (the snow has just melted away).

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Posted (edited) · Report post

WOW! I just flew the TS2 for the first time, and it was insane! :D

I'd never imagined it was so fast and responsive.

Lucky for me the kids in the area had just left, so I was alone when I started flying. I threw it into the air with full throttle, and wasn't prepared for the speed at all. I also had way too much response, but didn't dare to look down on the DX7 for the D/R-switches. I tried to think where the switches was located (just switched to the DX7, so I'm not used to the radio yet) and steer the plane at the same time. After a few seconds I remembered, and enabled D/R on ailerons and elevator, giving 50% travel. It got easier to control, but still not what I would call easy. After getting a little more confident with the plane I flew it over a larger area with more altitude. I also discovered that about 15-20% throttle is enough for level flight, so I was applying much more throttle than needed. I tried to fly the plane low with little throttle, and then with full throttle and elevator. It flew vertical at incredible speed, becoming a little dot on the sky after a few seconds. I landed it perfectly some minutes later, using flaperons. When I applied full flaperons it stopped like a car. It was incredible to watch. I had to apply lots of elevator up to keep it level though, so I'll try to add some elevator to the flaperon-mixing.

After landing I discovered 10-15 people were standing right behind me watching me flying, and I hadn't even noticed...

I think I've got to fly the plane a few more times before adding FPV-gear, because this wasn't at all what I expected... Very fun to fly though, and the plane is still in perfect condition!

Edited by jonpet55

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Posted · Report post

That was just cool to read. Congrats on not wreckin!

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Thanks headhunter23 :) I flew the plane today as well and it was easier this time, probably due to less wind, less nerves and a better pilot. The plane didn't fly as fast today. Just the right speed for me. Last time it was actually pretty windy (today it wasn't any wind at all), so thats the reason why I got the extra speed. I was pretty close on crashing today. The problem was that I flew the plane a little too long, and suddenly one of the ESC's cut off due to low battery voltage. I couldn't see that one of the propellers had stopped, so I didn't understand why the plane started to drift to one side. I gave full throttle to compensate for the lack of thrust, and came _very_ close to a tree. A moment later I realised what the problem was, cut of the throttle, throttled up again and landed. In other words still no damage... :)

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Alright Jonpet55!

now that you've mastered your new Twinstar's flying characteristics, I think it's time to start working on that antenna tracker you promised to your self (and us...) ;)

Dimitris

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Haha. You sure haven't forgotten that antenna tracker. But you are absolutely right, the tracker was actually the reason I started this project, so I should start on it pretty soon - just don't know when. ;) At least I need to fly the TSII in FPV and mount the gear in the plane, then I can start thinking about the ground station.

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Posted (edited) · Report post

Of course I didn't forget! :)

I just hope we have a tracker sometime before this flying season ends...

Do you guys have nice weather too, like it is here in Göteborg?

Dimitris

Edited by Dimitris76

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I'll try to make the tracker before the the season ends. BTW the weather is just perfect here. I haven't seen a cloud in about a week. Now it's 18°C in the sun (9°C in the shadow), and allmost no wind - perfect weather for flying! I've heard the rain is coming again tomorrow though.

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