Archive for June, 2009

White hawk down

Vieną vakarą nusprendžiau paskraidyti nepaisant stipraus vėjo. Sekės neblogai, bet darant mirties kilpa palei žemę, nepavyko išimti kampo (tikėtina, kad vėjo gūsis). Tai toli gražu ne pirmasis kritimas tiesiai nosimi žemyn šiuo lėktuvėliu, bet šį sykį buvo neapsiribota nosies sulamdymu. Kadangi buvau išpjovęs plyšį mobiliam telefonui, vieta ties sparnų laikikliais pasidarė žymiai silpnesnė. Neatlaike ir apsauginė izoliacija. To pasekoje sugadintas sparno laikiklis, suskilus šoninė sienelė. Panašu, kad remontui reikės ne tik iziliacijos, bet ir klijų ;)

Once I’ve decided to fly despite the heavy wind. Everything went ok, but doing a loop near the ground the altitude was too low (mayby a wind rush). It was not the first time the plane crashes, but this time it was damaged a little bit more. I’ve made a hole for a mobile phone, so wing support became much weaker. The result was cracked wing support and side wall.

Even so I have to admit that foam planes are difficult to kill, even after tens for crashes plane can fly without much repair.

Reikia pripažinti, kad putinukai sunkiai “užmušami”, tik po keliolikos kritimų, konstrukcijos pakeitimų lėktuvas nebegali skristi be remonto.

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Istorijos moralas – mažas aukšis, didelis vėjas, nemokša vairuotojas gali privesti prie “crash’o” :) .

Moral of the story – low altitude, wind and unskilled pilot can lead into crash.

Flight over Nemunas and Neris

We’ve tried to launch in junction of Nemunas and Neris in Kaunas. We didn’t flight fast, because there were many people around. First launch with cell phone integrated into the front of the plane. Have a good show.


YouTube Direkt

Mounting the cell phone:

Picture 001

Picture 009

The day when EasyStar was lost

Very educational story how you shouldn’t fly above clouds without the clue where you are. Story with happy end, and pilot has reclaimed the plane. Nice view, good soundrack. Have a good show.


YouTube Direkt

Risky flights

Interesting flight collection from internet. Quality is average, but content is perfect ;)


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Even bricks can fly

As Giedrius have said, with modern motors even bricks can fly.


YouTube Direkt

Mobile phone in the air

I’ve decided to make a flight in the evening. Plane was damaged a little bit with a mobile phone attached so aerodynamic was not great. Anyway, this one of our first video records so I’m posting a results.

I’m using Nokia E51. Even this phone doesn’t have a good camera, results are much better than Siemens CX75. Resolution is much bigger, much less squares, better colors etc.


YouTube Direkt

Autopilot

After some flights I’ve decided that it would be interesting to leave some functions for autopilot. For example keeping constant altitude, rotation angle, or safe return to the landing zone (after loosing the transmission). Commercial products are not interesting. They cost too much. The second reason is simple, I want to make something for myself :)

I’ve tried to evalute what type of components I will need:

- Main component is microcontroller working with some kind of firmware. For this purpose I’m planning to use Atmel AVR (atmega8 or similar) from 8 bit serries, or NXP LPC21xx ARM7 32bit microcontroller. I did some projects with these microcontrollers, so I’m familiar with them. Both of them has good core clock, enough PWM channels, so there are no reasons to decline any of them. If I will see that flight algorithm requires much of RAM, I’ll probably stay with LPC2131 mcu, which is also faster. The only isua is with it’s power supply, it requires 3.3V, while AVR is 5V, which would alow use it dirrectly from ESC.

- Very important component is GPS receiver. I have few candidates. One of them only 2 grams module, which is able to scan 32 GPS channels at the same time. I’ll write about it more when I’ll choose on of them. Expected price 30-60$ including shipping. 5 Hz versions are more expensive but in my opinion it will pay off.

- Electronic gyroscope. Mayby I’ll stay with 2 axis inclinometer or 3 axis accelerometer. Not sure right now.

- It would be good idea to put GSM module inside. There are very small modules int the marked under 30 $. It would be very useful after crash landing. If you’ve lost your plane, call to the plane’s SIM card could return you GPS coordinates in NMEA standart. Using googleearth or similart software you can spot your plane. This idea came when I’ve saw how often people loose their FPV models.

I’m planning FPV flight (hoppefully :) ), so required component is OSD ( on screen display). It overlays telemetric information on transmitter video signal. I’ve saw some projects based on software with Atmega microcontroller. Designing this system I’ll try to include this feature. There are commercial modules for 250$, it would be great if we could achieve something similar with lower price.

This sistem should be located between receiver and servo motors. Right now my plane gas 3 channels, so 4th is unused. This channel could be used to activate/deactivate the autopilot.

Radio equipment

For my first radio set I’ve chones 2.4 GHz Hobbyking 4 channels transmitter and 6 channels double receiver. It’s possible to find this set for 32$ + shipping. FPV flights require more advanced equipment, but it’s perfect to learn how to flight. First of all it doesn’t require much investements, and second 2.4 GHz radio is new technology, which slowly takes over old 35,75 mHz radio sets.

2.4 GHz 4 channel radio (29.99$ at Hobbyking)

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Receiver has diversity antenna. It should be mounted at some distance from main antenna. It should be a distance of  2.4 GHz wavelength (~12.5 cm). If one of the antennas is in the “dark spot”, where signal is very low, there is possiblity that another one still has a reception. Theroy tells, that such placement of the antennas increases receivers performance incase of multipath  transmission. I dodn’t tested how it works with single receiver. Both of them weight very little, so I’ve put them both in.

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Assembling the foam plane

This is my plane’s configuration:

- Upper wing foam plane

- 23 A, 3000 KV (rpm’s per volt) brushless motor

- GWS propeller. ~6 inch diamters, ~4″ angle.

- 30 A Supersimple speed regulator with 5V voltage regulator.

- 1550 mAh capacity RHINO LiPo battery, 2 cells, total 7.4V

- Hobbyking 2.4 GHz 4 channel transmitter and double 6 channel receiver

- 2x HXT900 9g servo motors. Cheap servos from China, but works perfect.

Contruction requires very few tools: knife, soldering set, placking tape, glue and similar things. I was recommended to get glue “Kleiberit” (~8$), so I’ve decided to get cheap glues (~3$). Which declared: not suitable for glueing foam. As soon as I’ve started using it, I’ve understood why they say that, so soon I’ve had to get epoxt adhesive EPO-2 for (4$). I’ll get back to that topic.

I’m posting a picture, how the plane looked like before the flights. We won’t see that shape anytime in the future :) . It’s been chaning a shape with every crash.

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To see the difference, this is how it looks after two weeks of training: READ MORE

Battery charger

Battery charger is important part of the system, so I’ll dedicate whole post for it. Battery price can be in rage from tens up to hundreds of dollars. It’s performance degrades when it’s used improperly.

LiPo (Lithium Polymer) batteries is charged slightly different from Pb, NiCd or NiMH. These batteries should be charged with constant current, while 4.2V cell voltage is reached. Then battery is charged 75% of it’s total capacity. Then it should be switched to constant voltage mode, until the current reach zero amps.

Cells are connected in series, so we see only sum of voltages on the connector, which does not reflect each cell voltage. The balancing connector is used to monitor voltage of every cell. Usually it’s smaller connector, because only small part of the current passes it. Charging all cells individually prolongs battery life and capacity. This is one of the reasons to choose good charger. When you pay more for the charger you will save that money not buying new batteries. Save you money and environment ;) .

Other useful function is battery discharge. It’s very useful for NiCd and NiMH batteries, because this type batteries suffer from memory effect (capacity degrade when partial discharge occures). Using LiPo you get information about your maximum capacity. It can be useful to evaluate flight time and estimate how much battery is weared down.

7A battery charger (59.99$)

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First flights

http://www.fpv.lt/fpv_media/fpv2

http://www.fpv.lt/fpv_media/fpv3

Foam plane construction took about 2 weeks. Job had to take 3-5 hours, but my plane had not eleron’s pullers, so they had to be manufactured.

First flight took about 5 seconds :) . I’ve gave a little too much throttle, plane went far up and then straigt down. So my first advice would be: don’t puch throttle too much, 50-60 % should be fine. If it will be not enought you will slowly land on the ground. Seconds flight was done when I’ve changed new propeller. Old one has splited into two pieces. I didn’t glued old one for two reasons: motor is quite expensive, human life also. Motor’s rotations is quite big so propeller fault can make much problems. Many forums tells same thing so I don’t have a reason to doubt it. Save somewhere else, not on the propeller.


YouTube Direkt

Second flight was much more successful. With some light crashes I’ve discharged my battery and plance was still in ok. I had to agree, simulators gives very valuable lessons. Last two weeks I’ve spend in Aeroflight simulator with different models. I’ve got some skills there. Don’t expect that your sense and reaction will be enought to fly plane for the forst time. When situation changes you need to act fast, and it won’t be possible without proper reflex. Like all begginers I’ve had hard time to master controlling plane when it flies toward me. Controlling directions inverts, so some problems occures. Learn, learn and once more learn (Lenin).

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Hello world!

I’ve become interested in RC planes. I’ve got some ideas and notes on this topic. Zebediejus pushed my toward creating this site. I’m also thankful for server machine. I’ll try to post some info about what did we encounter when we’ve started to fly RC plane. Mayby it will be interesting for someone, and I’ll have where to show photos and video.

I don’t suggest to use solutions which you will see on this site, they won’t be the best ones. The purpose of this page is not to be novice guide, but sort of “how it can be done” version. I’ll show you what equipment I do use, why I’ve chosen it and what’s wrong with it.

Why site name is FPV.lt ? FPV is an abbreviation from First Person View. It’s what the human would see being in operated object. That’s my purpose: to do such plane. There are plenty commercial producs, they are pretty much expensive and dull. I don’t want to invest much money in it, but also I don’t want to do everything from the scratch. Some say it’s impossible to do fast-cheap-good. It’s trye, we’ll to it cheap and good.

So much for a now. If you have any notes, commends about this page please use comments or just email me stgedas at gmail.com. We need feedback from you to become better.

Cheers