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FPV GPS Guided Kraken Build. Wiring help for RXSR-FC Omnibus F4 Fireworks V2.

#1
Hello All,
I'm trying to set up a GPS guided Kraken with FPV using the FrSky RXSR-FC Omnibus F4 Fireworks V2 Flight controller. I'm fairly new to this and have never attempted anything this complex before so please excuse any incorrect terminology or stupid questions.

This FC has a built in PCB, OSD, Barometer, hall current sensor and gyro. It's built for quads but supports Betaflight so I thought it would be fun to try and make it work as a Autopilot for a plane. In betaflight I should be able (hopefully) to remap two of the motors to Servo's to control the plane (M1 and M3). However as the Servo won't take the voltage from the battery so I'm powering it off a 5v rail (not sure if this will work). Also I've read sometime you have to do it in certain pairs so I might need to do M3 and M4 as servo's.
I did up the below wiring diagram to show how I think it should all be soldered together but I'm not really sure if this is even possible let alone feasible.
If it isn't possible to run the Servo's off the motor pads I may be able to use an SBus decoder to add 3 servo's in but I'd rather save this as I'd like to add retracts and a pan tilt for the camera (to link into head tracking) later.
The components I've chosen are in the diagram and listed. I'd like to record the on board footage but I'm not 100% sold on using the Mobius mini. I'm powering it off the 5V_Bec as it can't handle any higher voltage.
I've attached the FC board layout, my wiring diagram (which induces the GPS and camera/VTX) and specs sheet for the RXSR-FC Omnibus F4 Fireworks V2. My Transmitter is a FrSky Taranis x9d+.
If any of my components are wrong, it's wired incorrectly or if this whole idea won't work please let me know. Thanks for any help!!!




Board Top.png







Board SPECS.png
Wiring diagram.png
 
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Merv

Well-known member
#2
Your setup looks good to me. I’m not sure if the quad software will work. Is it capable of fixed wing?
It’s always a good idea to use a smoke stopper whe you first power up a new build.
 
#3
Thanks for the tip, I didn't know about smoke stoppers, I'll definitely cook one up. Betaflight should be capable of controlling a fixed wing delta plane as long as I can get the servo's showing up correctly.
 

ElectriSean

Eternal Student
Mentor
#4
I wouldn't recommend powering the servos from the FC's BEC, it's pretty small and if overloaded could cause your Rx or FC to brown out. Use an external one or one from an ESC.

Betaflight is capable of being configured for a wing, but if you want to do GPS stuff you are better off running iNav.
 

evranch

Well-known member
#5
Wiring looks good, I agree with Sean that using an external BEC for your servos is better, especially since you are powering camera and VTx already off the board. It also keeps noise out of your FC. Servos can kick back noise into the power circuit when they are moving. It's a good idea to clamp them with zener diodes, but a better idea to run them off their own BEC.

Looks like a neat little board. I've never tried to use a quad FC for fixed wing, interesting setup with two of the motor outputs switched to servos. If the software supports it, I don't see why not! I only have experience with Ardupilot, I run a Pixhawk myself.
 
#6
Thanks for the input. My current ESC's don't have a bec so I'll look into rigging one up. I'd presume this would be the same for the s.bus decoder power as well correct?
Yeah I was using betaflight as its preloaded on the FC and now has return to home ability but for anything more complex like way pointing I'll need to change to inav or adrupilot. If I get this working I'll post pics and if it crashes and burns I'll post pics as well haha
 
#9
Sorry, also I wasn't planning to use s.bus servos due to their price. With the decoder you can hook 4 standard servos up to the s.bus
 

ElectriSean

Eternal Student
Mentor
#10
You connect the servos signal wire to the FC motor outputs as in your diagram. The FC gets the SBUS signal from the Rx and splits it into channels, then the mixer settings in the configurator determine what does what. In the case of a delta wing like the kraken, you select a flying wing mixer profile and all of the elevon mixing is taken care of by the FC.

I will mention again how much better I think iNav is for a wing than Betaflight, especially with a GPS. There are many tutorials for iNav wing setups that will teach you a ton and probably save your plane :) Betaflight is capable of wing stuff, but really zero development has been done for years in that regard. For that reason, very few people use it for wings, and pretty much nobody makes tutorials.
 
#11
You connect the servos signal wire to the FC motor outputs as in your diagram. The FC gets the SBUS signal from the Rx and splits it into channels, then the mixer settings in the configurator determine what does what. In the case of a delta wing like the kraken, you select a flying wing mixer profile and all of the elevon mixing is taken care of by the FC.

I will mention again how much better I think iNav is for a wing than Betaflight, especially with a GPS. There are many tutorials for iNav wing setups that will teach you a ton and probably save your plane :) Betaflight is capable of wing stuff, but really zero development has been done for years in that regard. For that reason, very few people use it for wings, and pretty much nobody makes tutorials.
Cheers, I'll load INAV forware immediately when I get it. I'll also order a few external ubecs (3amp 6g) that I can add straight to the battery which should solve the pdb 5v Bec issue. Would straight to the battery be better then onto the motor power pads be better here? Less interference?
 

evranch

Well-known member
#12
An auxiliary SBUS decoder does not use any significant power, but it's convenient just to plug the servos directly into it. So you might as well power it off the BEC to save some wiring effort.

If you say you can control your elevons from the FC via the SBUS output, then it must not be a direct SBUS pass through, but that the FC calculates that SBUS output. Making a wild deduction, I would say it only operates on SBUS and probably has an internal SBUS decoder for the 4 motor channels, so you should be able to pick and mix the channels however you like.

Edit: you posted while I was typing! It doesn't really matter where you take it from as long as it's not on the load side of your internal BEC. Going off the motor power pads will let you include your servo power in your mAh consumed reading, giving you slightly more accurate readings.
 
#13
An auxiliary SBUS decoder does not use any significant power, but it's convenient just to plug the servos directly into it. So you might as well power it off the BEC to save some wiring effort.

If you say you can control your elevons from the FC via the SBUS output, then it must not be a direct SBUS pass through, but that the FC calculates that SBUS output. Making a wild deduction, I would say it only operates on SBUS and probably has an internal SBUS decoder for the 4 motor channels, so you should be able to pick and mix the channels however you like.

Edit: you posted while I was typing! It doesn't really matter where you take it from as long as it's not on the load side of your internal BEC. Going off the motor power pads will let you include your servo power in your mAh consumed reading, giving you slightly more accurate readings.
Cheers that's a great idea about keeping it in the amp reading. I'll have to play around with it to see if I can find that SBus decoder feature. If that can be adjusted that would be fun. I think I will need to start simple with this so I can problem solve each problem as it comes up so I can have some idea what's causing the issue.
 
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ElectriSean

Eternal Student
Mentor
#14
If you say you can control your elevons from the FC via the SBUS output, then it must not be a direct SBUS pass through, but that the FC calculates that SBUS output. Making a wild deduction, I would say it only operates on SBUS and probably has an internal SBUS decoder for the 4 motor channels, so you should be able to pick and mix the channels however you like.
You are correct, but it is more general than that. The FC takes any RC input (PWM, CPPM, SBUS or any serial protocol), mixes it and outputs signals. The outputs can be servos, motors or anything that can be controlled via PWM. You can also choose to pass channel signals directly through. There are mixer profiles for all types of multirotor and fixed wing setups.
 

kilroy07

Well-known member
#15
Very cool, this is what I am planning for my Kraken build!!
I'll be using the Matek F405-wing controller though....
INAV is a little over whelming at first, at least for me...

Will be watching your progress!!
Good Luck! (y)(y)
 
#16
You are correct, but it is more general than that. The FC takes any RC input (PWM, CPPM, SBUS or any serial protocol), mixes it and outputs signals. The outputs can be servos, motors or anything that can be controlled via PWM. You can also choose to pass channel signals directly through. There are mixer profiles for all types of multirotor and fixed wing setups.
Excellent, I'll have a good play about in the settings long before I solder anything. Would the correct Inav firmware be the fireworksv2? There is also omnibus f4 and frsky f4 so I want to be sure.
 
#17
Very cool, this is what I am planning for my Kraken build!!
I'll be using the Matek F405-wing controller though....
INAV is a little over whelming at first, at least for me...

Will be watching your progress!!
Good Luck! (y)(y)
Cheers, hopefully it all works. Let me know how yours goes.