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Jan 25, 2019, 09:42 AM
Registered User
DroneSK's Avatar
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How to put together the right electronic system?


Hello,

I am trying to convert an RC airframe (FMS SkyTrainer 182) into an unmanned system for research purpose. I'd greatly appreciate some help and suggestions regarding the identification of necessary components and their integration.

So far, I've acquired the following:

1. FMS SkyTrainer 182



I am not the guy in the picture. It's just a picture from the internet. This airframe seems to be sized rightly for me to have the space for all the onboards electronics.

2. PixHawk PX4 Autopilot



This came with a GPS module and has built in Digital Gyros(2), 1 Magnetometer and 1 Digital Barometer

3. Futaba T6EX Radio Transmitter/Controller



The annoying thing about this one is that I can't seem to find the little receiver that's supposed to come with this. I will keep looking but if I can't, I may have to order one.

I figured that I'd also have to get a PX4-compatible airspeed sensor as that autopilot has no way of measuring the airspeed. If it won't be too expensive, I'd also like to use a telemetry system to have access to the flight data in real time. I have never put together a system like this and such feeling a bit intimidated. Especially about the wiring and integration of all these electronics.

Any help/suggestion/questions are most welcome.
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Jan 26, 2019, 10:23 PM
Purdue Engineering
Rocketman1092's Avatar
Hi there,

The Pixhawk is definitely a great way to get into autonomous flight, and that seems like an appropriate airframe for it. I'd recommend checking out the Arduplane wiki, which is pretty thorough and has guides for pretty much every aspect of setup and configuration. http://ardupilot.org/plane/docs/arduplane-setup.html

SiK radios are the usual choice for telemetry. There are plenty on the market and they're all more or less the same. Here's a set that's inexpensive and has the right connectors for your version of the Pixhawk: https://hobbyking.com/en_us/hkpilot-...v2-915mhz.html

Same goes for airspeed sensors. You don't absolutely need one, but it helps to improve performance especially in windy conditions when your ground speed and airspeed might be pretty different. https://hobbyking.com/en_us/pixhawk-...itot-tube.html

There are 'newer' options than the above, but most are moving to JST-GH connectors as found on newer versions of the Pixhawk. So finding or making adapter cables might make those more trouble than worth. Don't worry though - your Pixhawk isn't obsolete and can still run the latest Arduplane firmware.
Jan 27, 2019, 07:32 PM
ultra cheap pilot
ican3d's Avatar
Follow the Ardupilot based build schematics here: https://www.supermotoxl.com/fpvuav-m...ght-3-v5-960mm It pretty much have the same flight control and characteristic as your 182.
Jan 30, 2019, 05:39 AM
Registered User
DroneSK's Avatar
Thread OP
Hello Rocketman!

Thanks so much for the response. I fell ill so couldn't respond back in time.

Quote:
Originally Posted by Rocketman1092

The Pixhawk is definitely a great way to get into autonomous flight, and that seems like an appropriate airframe for it. I'd recommend checking out the Arduplane wiki, which is pretty thorough and has guides for pretty much every aspect of setup and configuration. http://ardupilot.org/plane/docs/arduplane-setup.html
I work with Matlab/Simulink and PixHawk offers some tools for that(click here to see). I am not sure if those tools still work just fine with Matlab/Simulink if I use Arduplane software instead of what PixHawk offers.

I have been looking at both PX4 and Ardupilot's wiki though.

Quote:
Originally Posted by Rocketman1092
SiK radios are the usual choice for telemetry. There are plenty on the market and they're all more or less the same. Here's a set that's inexpensive and has the right connectors for your version of the Pixhawk: https://hobbyking.com/en_us/hkpilot-...v2-915mhz.html
What a coincidence! I've been looking at the UK version of the same thing I believe.

The part that I wasn't sure about was how to integrate this telemetry set with the Futaba transmitter I showed in the original post. Would you happen to know anything about that?

Quote:
Originally Posted by Rocketman1092
Same goes for airspeed sensors. You don't absolutely need one, but it helps to improve performance especially in windy conditions when your ground speed and airspeed might be pretty different. https://hobbyking.com/en_us/pixhawk-...itot-tube.html
I think the Airspeed sensors are a must for me as I don't have any means of knowing the actual airspeed. I wouldn't have bothered at all if it was a quadcopter or something but as a fixed-wing platform, it'd be of great help to have that. Not to mention, having actual data on the airspeed will help me with getting more accurate results for the things I will investigate. Also, here in the UK, it is never not windy.

Quote:
Originally Posted by Rocketman1092
There are 'newer' options than the above, but most are moving to JST-GH connectors as found on newer versions of the Pixhawk. So finding or making adapter cables might make those more trouble than worth. Don't worry though - your Pixhawk isn't obsolete and can still run the latest Arduplane firmware.
That's good to know. I was planning on using PixHawks own flight software for the sake of better integration between all the different things I'm having to make work in unison.
Jan 30, 2019, 01:31 PM
Purdue Engineering
Rocketman1092's Avatar
Typically the telemetry is independent of R/C. You'd connect and use your Futaba transmitter and receiver as normal, while the telemetry radios provide a two-way link between the autopilot and a PC or tablet for live data, mission planning, parameter adjustment, etc.

There are ways to combine the telemetry with the R/C transmitter, such as Craft & Theory's Flight Deck system. However, this only works on FrSky transmitters and can't quite do everything that the little telemetry radios can anyways. http://www.craftandtheoryllc.com/fli...t-port-serial/

If you're looking to have telemetry at a glance and don't want to worry about bringing a laptop to the field, connecting one of the telemetry radios to an Android phone running QGroundControl and attaching that to your transmitter would be a good approach. There are some 3D printed mount designs for this such thing floating around.
Feb 05, 2019, 09:56 AM
Registered User
DroneSK's Avatar
Thread OP
Quote:
Originally Posted by Rocketman1092
Typically the telemetry is independent of R/C. You'd connect and use your Futaba transmitter and receiver as normal, while the telemetry radios provide a two-way link between the autopilot and a PC or tablet for live data, mission planning, parameter adjustment, etc.

There are ways to combine the telemetry with the R/C transmitter, such as Craft & Theory's Flight Deck system. However, this only works on FrSky transmitters and can't quite do everything that the little telemetry radios can anyways. http://www.craftandtheoryllc.com/fli...t-port-serial/

If you're looking to have telemetry at a glance and don't want to worry about bringing a laptop to the field, connecting one of the telemetry radios to an Android phone running QGroundControl and attaching that to your transmitter would be a good approach. There are some 3D printed mount designs for this such thing floating around.
Hey Rocketman!

Thanks for sharing all that.

I have decided to go with the 500mW 3DR Telemetry Kit V2 .

I am now trying to workout how to power the servos (FMS-091, 4.8-6.0 volts) properly. Pixhawk 4 comes with a Power Management Board which one can use to connect to to servos :



I will be using a 11.1 V 2200mAh 25C Lithium Polymer battery. The aircraft I bought already comes with a Predator ESC 40A. This is how it's set up inside the aircraft:



Of course no receivers are connected to it yet. What is confusing me is that if you checkout the ESC, it says that it has a 5.5 volts 3A BEC. Is that something built into the ESC? Can I even think about using that for the servos?
Feb 05, 2019, 10:07 PM
Purdue Engineering
Rocketman1092's Avatar
Yes, that BEC is built into the ESC and you can use it to power servos. The general rule of thumb is that it's safe to power up to four small servos with a built-in BEC. Anything more than that and a standalone dedicated BEC would be a better bet.
Feb 07, 2019, 10:10 AM
Registered User
DroneSK's Avatar
Thread OP
Quote:
Originally Posted by Rocketman1092
Yes, that BEC is built into the ESC and you can use it to power servos. The general rule of thumb is that it's safe to power up to four small servos with a built-in BEC. Anything more than that and a standalone dedicated BEC would be a better bet.
Thanks for the advice

I am trying to figure out how to connect all the servos to both the Pixhawk 4 and the RC-Receiver.

If I use a receiver (Futaba T6EX FASST compatible) that comes with an S-Bus, wouldn't that work? For example, this one (click here).

I want to be able to control it using both the Pixhawk and RC-Transmitter. Although I'm not sure if that's something reserved for some special type of servos and won't work with my FMS-091 servos that are pre-installed.
Feb 16, 2019, 11:30 PM
Purdue Engineering
Rocketman1092's Avatar
You'll connect the receiver's S.Bus output to the Pixhawk's RC input, which will automatically detect that S.Bus is the correct protocol. The servos get connected to the Pixhawk's PWM outputs, as in the photo you posted earlier. No particular type of servo is needed and the pre-installed ones should work just fine.

Switching control between the R/C transmitter and flight controller is done using the Pixhawk's flight modes, which you'll assign a spare switch on the transmitter to toggle. For example, in "Manual" mode the Pixhawk will pass all controls directly from the transmitter to the servos (while applying trims or end point adjustments if needed) and you'll fly the plane exactly as if the flight controller wasn't there at all. In "Auto" mode, the Pixhawk has full control of the aircraft and it'll obey a pre-planned mission unless you switch back to a different mode. There are also a few modes in between, like the stability-assisted "Stabilize" and "Fly-By-Wire" modes, the circling "Loiter" mode, and "Return to Launch".

Again, I strongly recommend reading through the Ardupilot wiki. It goes over all of these topics in pretty good detail.
Feb 17, 2019, 05:22 AM
Registered User
DroneSK's Avatar
Thread OP
Quote:
Originally Posted by Rocketman1092
You'll connect the receiver's S.Bus output to the Pixhawk's RC input, which will automatically detect that S.Bus is the correct protocol. The servos get connected to the Pixhawk's PWM outputs, as in the photo you posted earlier. No particular type of servo is needed and the pre-installed ones should work just fine.

Switching control between the R/C transmitter and flight controller is done using the Pixhawk's flight modes, which you'll assign a spare switch on the transmitter to toggle. For example, in "Manual" mode the Pixhawk will pass all controls directly from the transmitter to the servos (while applying trims or end point adjustments if needed) and you'll fly the plane exactly as if the flight controller wasn't there at all. In "Auto" mode, the Pixhawk has full control of the aircraft and it'll obey a pre-planned mission unless you switch back to a different mode. There are also a few modes in between, like the stability-assisted "Stabilize" and "Fly-By-Wire" modes, the circling "Loiter" mode, and "Return to Launch".
That's good to know because that's exactly how I am trying to do things.

Quote:
Originally Posted by Rocketman1092
Again, I strongly recommend reading through the Ardupilot wiki. It goes over all of these topics in pretty good detail.
I have planned on using PX4 instead of Ardupilot. As a result, I'm mostly going through the documentation for PX4.


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