INAV Basics - Flight Control Boards

October 2017 - Betaflight is the most recent firmware for flight control boards (FCBs) and INAV is the GPS enabled
re-write of Betaflight which also caters for fixed wing models.

All the setup is done using the iNav Configurator. Works on PC and Mac as long as you can locate the correct drivers for the board you have. All the information on INAV is kept in the INAV Wiki on GitHub

I'm quite new to all this auto pilot stuff and there is a steep learning curve, so I thought I could pass on what I have learned so far.

So far I have experience with the Paris Sirius AIR3 F3 board with GPS from Multiwiicopter
Omnibus F4 V1 board
Matek F405 Wing
Matek F411 Wing
Ublox Neo M8N GPS module

The value of the AIR3 board is that it comes mounted in a gel damped housing with all the connectors and GPS sensor, and it's pre-loaded with the latest stable iNav firmware. Most of the tricky stuff is already done for you.

The AIR3 is an F3 board and doesn't have a built in OSD, but an addon OSD is available. The AIR3 OSD is configured using the MWOSD Chrome App, and partially by using your transmitter sticks.

If you're handy with a soldering iron and want to do it all yourself, you can follow Matt Ogbourne's video series on the Omnibus board setup. You will have to do all the soldering, firmware flashing and setup yourself. The Omnibus F4 does have a built-in OSD, which is configured in the iNav Configurator.



UPDATE 2018: The Matek F405 Wing and F411 Wing boards have changed the game. They are dedicated fixed wing boards with more servo outputs and a built in BEC specifically for servo power, as well as separate filtered BEC's for video, RC receiver and other gear.

Servos, Camera / VTx and receiver can be powered straight from the board.

A quick tip for soldering on the battery and ESC plugs. Silicon covered 16AWG is the best size wire, 18AWG is OK for low current light weight planes, but 14AWG is a bit too thick and difficult to solder onto the pads.

Power supply for non Matek Boards
The connections to FCBs are a little more tricky than normal ESC/receiver/servo connections because FCBs are more sensitive to incorrect or fluctuating voltage supply. With voltage spikes, FCBs can shut down, brown out or reboot causing total loss of control of the model.

It is highly recommended that the board and servos are powered by an accurate and stable 5.0V BEC like the AIR3 INAV BEC. You need to make up a power distribution cable so the BEC can plug into the board, and power the servos separately. As the 5.0V is being supplied to the FCB by the BEC you must disconnect the 5V line (red wire) from the ESC. Not a good idea to have two power sources for the FCB. Then all the signal wires from the servos and ESC connect to the board. The ground wires can either connect to the BEC or the board.

Another recommended precaution is to plug a voltage smoothing capacitor into your FCB, like this 3300uF 25V from MultiWiiCopter. The capacitor connects to any spare output pin-set across the power and ground pins, and absorbs any voltage fluctuations. Can also be plugged into receivers for added safety.

If you want to live dangerously you can just plug the servos and ESC straight into the board. like you would with a receiver, but you are only one voltage spike away from a crash.

The Boxler - Packing box plane

For years I have wanted to make a plane from an RC plane polystyrene packing box.

In the recent Hobby King sale I bought a Bix3, so here was my opportunity to give this project a go.

For speed and simplicity I decided to make a simple 3 channel motor glider with no ailerons. I covered the foam with packing tape and used fibre reinforced tape like spars on the wing and fuselage. I also decided to try a flat wing with no airfoil and dihedral tips.

This video shows the build from start to finish.

Here's the maiden flight which went better than expected.

I then made a hot-wire cut Clark Z airfoil wing to compare to the flat wing.

The airfoil wing had a much better glide slope and smoother flight performance.

Here are some mad wing tests using the flat and Clark Z wings.

Dimensions in cm

Specs

Wingspan1.3m

Length 100cm

Flying weight 590g

with 1300 3S Lipo

Motor 2822 1450kv

7" x 4" prop

What FPV cameras do I use?

I'm no FPV expert and actually prefer line of sight flying. However I do dabble with fixed wing FPV occasionally and really enjoy having the plane in the video view. This could be called Third Person View maybe. I have very little interest in FPV multirotors.
Here is a playlist of all my FPV reviews - Youtube link

FPV Cameras
There are so many options these days with Foxeer and Runcam competing almost weekly with new dedicated FPV cameras, and most action cams offering FPV or TV Out as well.

It's important to note that our analogue video transmitters only send standard definition video. The picture quality is not great compared to even the most basic Action cam recording. High definition digital video transmitters are now being released, but they are still bulky and expensive.

You can use dedicated FPV cameras or Action cams for FPV, but it's probably safer to use a dedicated FPV camera because Action cams can shut down or freeze with low battery or insufficient storage space. Dedicated FPV cameras tend to have much less delay or latency in the video feed than action cams as well, which is important for control at high speed. FPV cameras are usually 4:3 aspect ratio and Action cams are 16:9.

Dedicated FPV cameras
These are really just fancy security cameras, mostly with CCD sensors but a few with CMOS sensors. They usually have screw mounted lenses ranging through 2.8mm, 2.5mm and 2.1mm. I prefer the widest view of a 2.1mm lens and these can be purchased from places like Banggood for a few dollars.
Either the sensor or the lens will have an Infra Red filter fitted. In most cases the IR filter is on the sensor so you would buy a lens without the IR filter. Most are 4:3 aspect ratio and standard definition. 16:9 aspect ratio cameras are becoming available. If the option is available it is a good idea to turn on High Dynamic Range or DHDR in the camera setup to give the best video feed in difficult lighting conditions.

Surveilzone, Foxeer and Runcam HS1177
This is the first FPC cam I bought, mainly for it's small low drag casing. It turned out to be the most commonly used FPV camera in the RC community. It has a 4:3 600TVL CCD sensor which handles light and dark areas better than the cheap CMOS cameras.

Here is a review of the Runcam PZ0420M and Foxeer HS1177

Runcam OWL plus 4:3 - Gearbest link

In the above review I also look at the Runcam OWL plus with it's enhanced low light sensitivity.

This camera is a night flight specialist.

Runcam EAGLE 16:9 CMOS - Runcam link

The Eagle is the first of a new breed of FPV cam using a CMOS sensor with enhanced global high dynamic range. That means that the video image is processed to ensure there are no blown out skies or dark foreground. The effect is amazing and makes FPV flying a wonderful experience. With cheaper cameras on cloudy days it's almost impossible to fly because all you see in the goggles is black ground or white sky. The Eagle brings back all the detail and comes in a wide screen 16:9 aspect ratio version. Most other cameras are 4:3 aspect ratio. This is quite an expensive FPV camera at about A$80 and the default sharpening settings are too high, giving jaggy and shimmering edges, but after adjustment this is a superior FPV cam. This is my favourite FPV camera for old school cruising because it fills the screen of my 16:9 goggles with an unstretched image. However it doesn't have flight battery voltage OSD.

Foxeer MONSTER (Version 1) 16:9 - Tomtop link

This is a cheaper 16:9 aspect ratio camera with 1200TVL CMOS sensor and 2.8mm lens. It's a great camera in sunny conditions with that lovely screen filling 16:9 view.

There is a second version now available with on screen display and WDR added.

Foxeer New Arrow - Tomtop link

Foxeer Arrow 3 - Banggood link

Runcam Swift 2 - Runcam link

These are the latest high quality 4:3 aspect ratio FPV cameras and are currently the most commonly used in the RC community. They have evolved from the early HS1177 to offer excellent HDR and On Screen Display of flight battery voltage, pilot name and flight time. This is a fantastic development meaning you don't need a separate system for OSD to keep track of your battery voltage. However you do need to connect an extra wire from the battery + lead to the camera.

See my FPV playlist for reviews.

Any of these three are my favourites for fast flying wings, because of the voltage OSD and easier to view 4:3 aspect ratio at high speed.

Runcam Swift mini - Banggood link

This is a smaller version of the Runcam Swift without the OSD, designed for mounting in smaller spaces.

All of the above cameras can be powered by 2S to 4S batteries or 5 to 17 volts. Some other cameras can only take 5V. You must read the specs to determine what your camera requires.

Coming next - FPV transmitters, receivers and antennas

What cameras do I use?

This would be the most frequently asked question on my YouTube channel, so it merits a more detailed explanation.

For onboard footage I use a Mobius C2 purchased from Ebay seller eletoponline365  (Recommended seller on the RCGroups Mobius thread)
It's fairly basic with no image stabilisation and maximum res of 1080 30P but the image quality is very pleasing and the audio is the best of all flat form action cams (that I have tested). The Runcam 2 and Foxeer Legend 1 may be slightly sharper and offer higher res, but the results from the Mobius just look and sound better in my opinion. I also use this Mobius for audio recording when I'm flying FPV and need to narrate. I set up Mode 2 to be WAV Audio only recording. Initially I used the smaller 808 #16 key chain camera which did a good job but was limited to 720 resolution.

For hatcam footage and narration while flying I use a Mobius A (narrower field of view lens) This gives a closer view of the plane in the air without being too magnified. I have modded the microphone to be external and enclosed in a very effective wind sock. This means I can narrate a flight in strong wind and still have decent voice quality.

For a tripod mounted camera out in the field and "talking to camera" reviews I use an SJCAM M20 for it's nice contrast and sharp lens. I use it on 1080 30P which gives a slightly narrower field of view than the full fisheye. It also renders skin tones smoothly too which is a bonus for my ageing weather beaten face.

For close-up cut away shots I use a Canon S100 compact camera. It does a decent job but struggles with auto focus accuracy occasionally.

Audio recording for the indoor reviews is on a Zoom H1 audio recorder with Clippy lapel microphone from Micbooster in UK. That usually works well but has started letting me down with fuzzy recordings and scratchy connection interference lately. I'm now trying a Rode smartLav+ mic with my iPhone as the recorder and that sounds promising. Occasionally I will clean up the sound using the free Audacity program.

For editing I use iMovie on a Retina display 27" iMac. That's all I need for my quick and dirty Youtube videos.

I have tested many GoPro style action cams, and there are some good and some not so good options. My first action cam was a  GoPro 2 which I loved at the time, then a GoPro 3+ Silver which was a waste of money with poor focus and green colour cast. The first "post GoPro" action cam I tried was the SJCAM M20, and that prompted me to throw the GoPro 3 in a drawer and stop using my Nikon D7000 DSLR for video.

I divide the Action cams into 3 categories:

TOP QUALITY
The SJCAM SJ7 and ThiEYE T5e give the best video image quality with great sharpness and natural smooth colours and tones. But the audio on both of these cameras is not perfect, a bit muddy and ever so slightly out of sync with the picture.

MID LEVEL
The SJCAM M20, SJ5000 and SJ6 fit in this category with sharp video and bright colours. However they produce slightly posterised tones and compression artefacts in some situations. The Eken V8s also just makes it into this level with nice features but slightly less sharpness in the video.

CHEAP LEVEL
These cameras are cheap and work fine but cheaper lenses and electronics compromise image quality more than I am happy with, like the Andoer AN5000, Hawkeye Firefly 7S and Tomtop 4K action cam.

Reviews on all of these cameras can be found in this Action Cam playlist 

DIY Wing incidence meter

Here is my simple home made wing incidence meter. Used to determine the correct mounting angle for wings.

There is much debate about the correct angle of incidence required for efficient flight but a good starting point is to have the horizontal stabiliser and wing both at zero angle, then adjustments can be made after flight tests.

A4 sized plans - download and print for your own use.

Video explaining how to use the Newton Incidence meter

(You can buy a proper one made by Robart)

Eachine VR D2 FPV goggles

Banggood sent these goggles to me for review. I needed to add 2 x plus 4 close-up glasses before I could focus on the screen. I really like the diversity receiver with antennas supplies. One clover leaf and one patch antenna. And I love the built in DVR.

BANGGOOD purchase link

Here are the recorded video sizes with examples, and the review video with some flight footage.
(Images are not exact scaled sizes - limited by Blogger image display options)

4:3 camera - VGA recording 640 x 480 (4:3)

4:3 camera - D1 recording 720 x 480 (3:2)

4:3 camera - HD recording 1280 x 720 (16:9)

Mobius 16:9 camera - VGA recording 640 x 480 (4:3)

Mobius 16:9 camera - D1 recording 720 x 480 (3:2)

Mobius 16:9 camera - HD recording 1280 x 720 (16:9)

Review video on YouTube