Sunday, 22 September 2019

Best Cheap FPV gear

Here are my tips for the best cheap FPV gear.  Perfect for entry level or budget constrained pilots, but this gear will still be useful as your FPV requirements progress.

All In One camera and Video transmitter (AIO)

These camera / VTx combos are the simplest way to convert a plane to FPV. They are light and inexpensive and easy to swap from plane to plane.

The down sides are:
- The camera will not be the best quality, with lower dynamic range and large fisheye distortion.
- The range may not be as great as a more expensive Video Transmitter.
AOI VTx power output ranges from 25m to 200mW, giving range of maybe 100m up to many hundreds of meters.
- Voltage input is usually 3.5 to 5V. This means you cant run them straight from your flight battery. Best option for cleanest FPV video is to use a separate 1S battery for the FPV, or you can run it from the receiver or BEC.

Eachine TX02 200mW is my current recommendation - Eachine TX02 Banggood

FPV Goggles / screen

Recommending goggles is more difficult.

- Proper two screen goggles like Fatsharks, Skyzones and Aomway Commanders are very expensive, so I'll discount them for this discussion.
- Single screen box goggles are much cheaper but will not suit everyone. I need +1.0 close-up glasses for reading and I find that I cannot focus on the screen with most box goggles. I have modded some by glueing close-up lenses into the box enclosure.
- FPV screens by themselves can be a good solution but they are often more expensive than the box goggles.

Eachine EV800 goggles combine a detachable screen with goggles mount, so I think these are the best cheap option. The screen part can be mounted on a tripod or directly on your transmitter, and it includes the video receiver, battery and antenna. They also come with good quality antennas.



Eachine EV800 is the cheapest option with single clover leaf antenna - Eachine EV800 Banggood 











Eachine EV800D has clover leaf and patch antennas for greater range, and a DVR for recording the FPV feed - Eachine EV800D Banggood












Eachine EV800 screen on transmitter


Eachine EV800 review




Wednesday, 7 August 2019

iNav CLI dumps

Here is a link to all my iNav CLI dump text files for various boards and models
Andrew's iNav CLI files

Feel free to download them to try on your model.

Included boards and models:
AIR3             Ranger 1600
F405-Wing   E-Sky Eagles, Ranger 2000, Talon GT
F411-Wing   Dart XL
F411-WSE   C1 Chaser
F722-Wing   E-Sky Eagles, Ranger G2






Monday, 1 July 2019

Collection of Fixed Wing iNAV tips

This page will record any clever Fixed Wing iNAV tips I pick up over time.

Most of these tips come from
Facebook iNav Fixed Wing Group
Pawel Spychalski's YouTube Channel
iNav WIKI
and some very helpful YouTube subscribers.

1. Transmitter Trims (Pawel)
Trims should not be used with iNav flight control boards, don't touch them.
In fact you can disable them totally
In the Taranis Flight Modes screen change all the trim values on the default flight mode FM0 from (: 0) to (- -)
The trims will disappear from the transmitter screen and no longer be active  The trim switches now can be setup as normal switches for other uses. Which is quite useful because it's easy to run out of normal mode switches on transmitters like the QX7.

2. Only need one model setup (Stewie - UAVFutures)
Programming setup in your transmitter is identical for all iNav models. Wings, planes and even quads need the same 4 channels and mode switches. So you only actually need one iNav Model in your transmitter. Using the D16 protocol (not ACCESS) you can bind as many receivers as you need to this one OpenTX model if you set the receiver number to 00.
You can have all the extra functions like flaps and pan/tilt programmed in and just not use them on models that don't require them.

3. Forget about Angle and Horizon Modes (Pawel)
Well, maybe forget about them as commonly used flight mode.
I never use Angle as an actual flight mode, because you have to hold the stick at the angle you want the plane to maintain. The board has to be perfectly aligned to maintain altitude in these modes. It's a self-level mode, which might appeal to beginners, but to me it feels like you have to fight the board to make the plane fly where you want.
Angle Mode is necessary to initially setup the board alignment (mainly pitch degrees) and is automatically activated with the GPS modes. That's why when you select one of the GPS modes, before satellites are acquired, Angle Mode will be activated.
Angle is also useful on the bench to check that the control surfaces move in the correct direction for stabilisation.

If you want your plane to fly level without stick input use Altitude Hold. That mode uses GPS to maintain level flight and Angle Mode for stabilisation. Or even Acro mode will hold the current attitude.

I usually launch in Acro or Manual mode, fly around the field in Acro, go for an FPV cruise in Alt Hold, then use RTH to come back from a long way out.

4. PIFF (PID) Tuning (Wiki, Pawel)
Increase FF (D) until control surface movement in Acro (or Angle) is 90% of Manual Mode
This will give you all the control surface movement you need while saving some for stabilisation.
One of the biggest problems in a new iNav build is that you start with much less pitch and roll control  in Acro and Angle compared to Manual. I have been caught a few times with insufficient pitch control to get over trees while testing stabilised modes. This is because the Airplane preset (in the Presets page) puts the FF at 15, which is usually way too low. The default PIDS are are a better starting point in my opinion.

My FF ends up at 50 to 100 depending on the model. D and I terms are less important for fixed wing. Mine seem to end up around D=7 and I=10 but I'll do some further PIFF testing to confirm.

Autotune attempts to do these adjustments for you, but doesn't always get it right. I prefer to set them in the field using the  iNAV OSD Menu. Access the OSD Menu by using the Enter OSD Menu Stick Command. You can make all the adjustments using your transmitter sticks.

UPDATE 10 Sept 2019: Pawel's latest tuning tips from this video.

1. Work out your roll pitch and yaw rates (degrees per second) by doing full stick rolls, loops and rudder turns, in manual mode. 
Example - If a full stick loop takes 2 seconds then the pitch rate is 180dps
Enter these rates into the Rates section of the PID Tuning page
Average rates are Roll - 250, Pitch - 150, Yaw - 90 (Ignore yaw when you don't have rudder)

2. PIFF Values
Change P to ZERO (Actually I think about 5 feels better)
Change I to 7 (around 6 to 8 and never more than 10)
Use AutoTune to set FF value (or increase FF to get 90% throws in ACRO)
Change Gyro LPF Cutoff to 20

3. CLI
Try set fw_iterm_limit_stick_position = 0.25 (Stick position where Acro changes to Manual. Default is 0.50) for a more natural and in control feeling, with stabilisation when sticks are near the centre.

5. Check List before your first flight

On the bench and hooked up to your computer

1. iNav Configurator Receiver screen - Ail, Ele, Thr and Rud values must increase when you move the transmitter sticks up and to the right. This means the stabilisation will work in the correct direction. If a channel value decreases instead of increasing, reverse the weight in your transmitter mixing.

2. Check that values range from 1000 to 2000 when you give full movement to the sticks. Adjust end points in your transmitter mixing if the range is out. I have to use -97 to +97 on my Taranis channel end points.

3. Check control surface movement using the transmitter sticks. If a servo is moving in the wrong direction go to the Servo screen in iNav Configurator and click Reverse for that servo.

4. Check that your Modes switches are working as expected and have no modes selected with all switches UP. With nothing selected the plane will be in ACRO Mode (also called Rate Mode, but will show in the OSD as AIR)

Outside or at the flying field

5. Check that the GPS is working and acquires more than 6 satellites. You will not be able to arm the board otherwise. Motor will not be active until the board is armed.

If all the above checks out you will be good to go. Time to be brave and throw that plane in the air.

Start in Manual Mode and fly up to a safe height, switch Manual off when you're flying calmly to see how ACRO mode performs. Be prepared to switch back to Manual if something unexpected happens.

Check other modes as your confidence builds.

6. Save your FPV OSD layout
Rather than having to setup the OSD again for every new iNav build you can copy the relevant CLI entries from a previous build, and save them as a text file. Then you can paste them into the CLI for the new build.

Type "Diff" into the CLI then hit Return
Copy all the lines starting with "# osd_layout" and save them in another text file.

osd_layout 0 lines refer to the Default layout
osd_layout 1 lines refer to Alternative layout 1
osd_layout 2 lines refer to Alternative layout 2
osd_layout 3 lines refer to Alternative layout 3

I have a text file with Default and Alt layout 1 saved and available to paste into each new setup.

Here are my OSD layouts at the moment. 
Default layout has Distance to Home and Trip distance included, but not in Alternative Layout 1 




7. Trim the Board Alignment in the field using Stick Functions
To get the plane flying level in Angle Mode you usually need to adjust the Pitch Degrees in the iNav configurator Configuration Screen. Rather than connecting to a computer you can do this using your transmitter sticks.

Have a look at the Mode 2 Stick Functions picture above.
If your plane descends when you switch to Angle Mode you need to add Pitch Degrees to the board alignment. Trim Acc Backwards is the stick function you will need.

With the board disarmed, push the throttle to full up and elevator to full down.
Watch the fast flashing LED on the board (Matek F405 Wing) and notice that it will start flashing slowly. One flash equals about 1/3rd of a degree of Pitch Degrees, so 10 flashes will trim by 3 degrees.

Fly again and adjust as required.
If the plane pitches up in Angle Mode try a few degrees of Trim Acc Forwards. Same for left and right.

My planes seem to need about +4.5 Pitch Degrees.

8. Default Mode is RATE
If you have no modes selected you are actually in RATE Mode, not MANUAL.
I use RATE Mode 90% of the time for general flying around.

From the iNav fixed wing WIKI:

Default flight mode ( No mode selected ) The default flight mode does not self level the aircraft around the roll and the pitch axes. That is, the aircraft does not level on its own if you center the pitch and roll sticks on the radio. Rather, they work just like the yaw axis: the rate of rotation of each axis is controlled directly by the related stick on the radio, and by leaving them centered the flight controller will just try to keep the aircraft in whatever orientation it's in. This default mode is called "Rate" mode, also sometime called "Acro" (from "acrobatic") and is active whenever no auto-leveled mode is enabled. 

More tips coming as I find them






Wednesday, 26 June 2019

Sky Hawk V2 Twin Fin Tail

I'm not convinced about the value of V and A tail configurations. They may serve practical purposes but seem to reduce yaw stability, and even pitch stability in turbulent wind.

So to try and improve the performance of the Sky Hawk I changed to a twin fin configuration.

Once I sorted out a twitchy elevator servo the results were very good.






Twin fins dimensions
150mm high
200mm long
50mm top

The forward extensions add strength and may help to organise the flow across the horizontal stabiliser.



Horizontal stabiliser is made from the old A-Tail halves, just cut off and glued together flat, with 20mm x 6mm depron added to the leading edge for extra area.








The wing foam flexes a bit around the boom mounts (shown by the icy pole sticks) so I may add some stiffening there






Flights with the new twin tail mod



Sunday, 23 June 2019

Sky Hawk V2 Mods



This excellent 960mm wingspan A-Tail can be set up as a twin motor or a single pusher.

I really like it's size and adaptability, small enough for easy handling, but has heaps of internal space for big batteries and flight control boards. Very similar size and performance to the Talon GT



However there are a few things that can be improved.
It's a bit lacking in yaw stability, which basically means it wiggles in any wind, mainly due to the A-Tail being too small. I have added more tail area using 6mm depron which has reduced the wiggle.

The battery bay cover is flat, meaning thicker batteries will not fit. I'm using a 3000 4S which just fits, but a domed cover would allow room for Li-Ion bundles.

For the moment, to create more battery space I have cut off the nose tab and made a tape hinge for the cover




The twin motor set up is very cool and makes for a very fast plane with a sweet twin motor sound, but it's less efficient than a single pusher setup. I changed to a single 2212 980kV SunnySky motor with a 9 x 6" prop running on 3000mAH 4S. It cruises at under 4A and has heaps of extra power for fast fun. Suprisingly the weight dropped by 10g changing from twins on a 2200mAH 3S to single pusher on a 3000 mAH 4S.

I have also sliced off the boxy FPV camera mount under the nose for less drag and to reduce grass and mud entering the nose.

Flying weight - 700g without FPV and FCB
850g with all the gear.

Banggood - Sky Hawk V2 PNP / KIT 

Single motor maiden


I'm adding a Matek F411 Wing flight control board running iNav 2.1 (June 2019) with a Runcam Eagle camera and Eachine 5.8GHz 200mW VTx.

Strange behavior and crash video



Monday, 3 June 2019

Smeg Head 1060mm Canard Pusher



This cruising FPV canard pusher is inspired by the Experimental Airlines APD

The original APD uses elevon mixing and a fixed canard, but I wanted to test ailerons and a separate elevator with a central fin.







Here is the Canard Center of Gravity calculator I used to get the balance right (after the maiden)

Maiden flight video



Build overview, mods and follow follow up flight


Carboard Box version

Tuesday, 28 May 2019

RSSI for iNav - X8R L9R XM+

RSSI (Received Signal Strength Indication) is a measure of the RC signal strength between the RC transmitter and model.

Having RSSI as one of the OSD (On Screen Display) items in your FPV feed means you can see the signal strength as you are flying.





According to this excellent RSSI setup video by Droneracer101 there are 5 different ways to configure your receiver, transmitter and flight control board to enable RSSI for your OSD. He is demonstrating with Betaflight but the same setups work for iNav.

This post is just my interpretation of Droneracer101's instructions that relate to my three types of SBUS receivers.

1. X8R, X6R and X4RSB Telemetry receivers
The X series receivers transmit RSSI to your transmitter by default. You can use this value as an Input for a spare channel, which is transmitted back to the receiver / FCB.

On your Taranis

In the INPUTS page create a new input

I chose I-01 and renamed it I-RSI  but it can be any input.









Change Source to RSSI
Change Scale to 100dB












In the Mixer page create a new mix for a spare channel (eg. Ch 11 but can be any spare channel)











Change Source to I-RSI (I-01)
Change Weight to 200
Change Offset to -100

This adjusts the RSSI value to a meaningful number in the OSD








Using iNav configurator


Configuration page - Turn Analogue RSSI Off

Receiver page - change the RSSI channel to Ch11

OSD page - enable RSSI and position it where you want on the screen


2. XM+ SBUS receiver
Digital RSSI on SBUS Ch 8 or Ch 16 from receiver to flight control board.
Requires the specific firmware upgrade for the XM+ receiver.

XM+ RSSI firmware upgrade and OSD setup video

Once you have installed the RSSI firmware, follow the iNav Configurator instructions above but choose Ch 8 or Ch 16 depending on your firmware choice.

Ch 8 or Ch 16 must be spare in your Taranis.

3. L9R long range non-telemetry receiver. Analogue RSSI
Analogue RSSI via direct connection. This will only be possible if the FCB supports Analogue RSSI by providing a solder pad or pin, and the receiver provides an Analogue RSSI pin.

Matek F405 Wing and F722 Wing boards support Analogue RSSI. F411 Wing board requires MATEKF411_RSSI firmware to allow RSSI on the STI pin (Thanks for the update Samantha)

Connect the RSSI pin on the L9R receiver to the RSSI pin on the FCB. Only the signal wire is needed.

Configuration page - Turn Analogue RSSI On

Trouble shooting
If you are having problems getting the OSD information to show up in your FPV feed the issue may be your camera, TV standard choice or ground wire connection. 

Try swapping to a different camera. Some FPV cameras will not play nicely with iNav OSD and flight control boards.

Make sure you are consistent with your PAL or NTSC choices for camera, video transmitter and iNav OSD.

Make sure your camera and video transmitter share a ground connection.