Building an FPV Quad on ArduPilot 2.7

J

Jasseji

Member
Hello,

I am trying to calculate a good set to put together around the Naza V2 platform.

Here are the parts i came up with (starting from scratch):
- Q450 V3 Glass Fiber Quadcopter Frame 450mm - Integrated PCB Version
- DJI Naza-M V2 w/ GPS
- NTM 800kv Motors x4 with Accessory Pack and Motor Mounts
- HobbyKing 30A ESC x4
- 10x5E Props
- Multistar 5200mAh 4S Battery

As Control/FPV i would use:
- Turnigy 9x Radio with Rx Module
- Skyzone FPV Plug-and-Play set with Camera included
- 7" Monitor mounted on the Radio
- Some 11.4v Battery to power the monitor/video Rx and Radio

Future upgrade:
- DJI iPad Ground Station
- GoPro Camera with Gimbal (somehow controlled via the Turnigy 9x - dont know how yet)

Any comments on this ?
I came up to some 1700g total weight, i also know the NTM Motors might have issues with bearings but that should be a "start set", later on i plan to change the Frame to a TBS Discovery with CF tubes and replace the motors with ~600kv and larger props
 
Everything looks good, but a couple of recommendations:

ESCs - go with something that has SimonK firmware since it is programmed with signalling specifically for multirotors. Check out the Afro ESCs if you're getting everything from HobbyKing.

TX/RX - The 9x seems like a great deal, but some people on this forum and a lot or people elsewhere have a lot of complaints about it, including me. With stock firmware, mine would send half throttle for a couple of seconds every time it powered on (I had no idea until troubleshooting later). Needless to say, one time I forgot to disarm the board when I was doing some testing inside of the house with the props on (a big no-no) and when I realized I forgot to do something and turned the tx back on - my quad shot into the ceiling like a rocket taking off and busted into a lot of pieces. Later on, I flashed the 9x with er9x firmware (which is great), but the gimbals on the sticks wore out very quickly after a few more flights and it was pretty much useless. At this point, the tx would only recognize throttle if I moved the stick very slowly and sometimes wouldn't throttle down when I needed it to quickly. Plus, in order to flash it, I had to buy a separate board (smarty parts - or I could have build an adapter myself) as well as having to do some other mods (which cost way more) - although I think now it comes with an AVRasp or whatever header for flashing. Anyway, I'd highly recommend the 9XR, which is a similar radio for a similar price. Then get a USB AVRasp adapter so you can flash it with er9x (it has a header for that). It doesn't come with a tx/rx module though, but I'd recommend something from FrSKY for both. They make nice modules and they aren't too expensive. This setup would only cost you $30 or so more, but it's way worth it. Anyway - investing in your tx from the start is never a bad idea because it's the one thing you'll use for all your models as you upgrade - or you could always sell it easily later if you quit the hobby since it stays on the ground and doesn't get beat up like your flying parts. Also - they sell replacement parts, including gimbals for the 9XR.

I've owned a lot of NTM motors and have never had much of an issue with them unless they'd been in a crash. I've replaced both shafts and bearings on some of them (crashed ones that didn't have bent housings) and it wasn't too bad of a job.
 
:)

Thanks for the reply ;)

Actually now i have changed my setup a bit - rather will go with ArduPilot (i was reading about it a few years ago and it didnt have that much features back then) with 433Mhz telemetry radios

Also i got another motor recommendation so i will go for that instead (same price if you calculate the NTMwith accessory pack+mounts, better power).

As for the Turnigy, i have owned one before, was using it for a "normal" Heli - was quite good and i kinda liked it.

Also the tx is for me just optional for the initial setups - plan to do the most flying from the ground station - if i ever decide i like to fly better with a Radio, i will invest in a Futaba 12ch or something like that ;)

ESC's i already have so will use them for now (i got it from a guy who ordered for some friends but one of them didnt pay him so he kept them lying around).
 
Sounds like you have a good plan - and using what you have is always a good idea in my opinion, rather than shelling out dollars for something slightly better! Let us know if you run into any trouble and we'll see if we can help.
 
Just one quick question in addition: 750kv motors and 10" props will be fine ?
i dont really understand the relations here 100%, i want to achieve a balance between flight time and maneuverability including a GoPro and 2D Gimbal

Higher kv motors would require smaller props and have better maneuverability/handling but shorter flight times ?
Lover kv motors would require bigger props but raise flight time (lowering the handling and wind stability).

I am limited to 10" props for now, should i go as low with the kv on the motors as possible ?
What will be the impact of having even lower kv motors but keeping the 10" props (cant get larger props due to the frame size, i have the frame already so wont buy another one for now).

Did anybody make such tests regaring lift capacity/flight time/handling when switching motors with different kv but keeping prop size ?
I am looking at an option with a single 5200mAh 14.8v 4S battery
 
Nobody really understands the relationship between kv and prop size 100% without doing a bunch of math that not many people are capable of (I'm sure not)! There are a bunch of ways to figure out what works though.

A lot of motors being sold are displayed with prop test results, giving you thrust results based on that motor with various prop sizes and battery voltage (based on number of cells). Example:

http://hobbyking.com/hobbyking/stor...00W_Brushless_Motor_short_shaft_version_.html

Scroll down on that page to see data for that motor.

The loose concept is as you stated: bigger props, more cells, lower KV = more stable / smaller props, less cells, higher KV = more agile and/or better maneuverability.

This is a good theory to start thinking about things, but there are way too many other things to think about to make this a solid way of making your selection. Most people will say that if you can't find enough test data about specific combos (with exact motors, not just KV ratings) - and you're not in a position to buy several different combos to test yourself, to just follow a proven power system based on someone else's build. This is exactly what I've done for all of my builds since I don't have any shame in just copying what's proven, and I don't have the time to tinker too much with different combos. There are a lot of people spending a lot of time figuring these things out, so I figure there's no sense in me reinventing the wheel.

There is more and more test data out there though as the market matures though, so rather than simply copying, it's becoming a lot easier to pick your own combo based on data without testing yourself. One good source is:

http://www.flybrushless.com/

You can select by prop or motor and see any test data people have posted there. For some combos, there is quite a bit of info and for others, there's nothing.

You can also play with flgiht times using this calculator based on some of those test results:

http://multicopter.forestblue.nl/lipo_need_calculator.html

You can also put your numbers into ecalc and shift them around to see if you can get better results with another setup, although I'm not 100% sure anyone understands ecalc completely, so it can be a challenge.

These are some decent overviews on picking motors, etc.:


http://blog.oscarliang.net/how-to-choose-motor-and-propeller-for-quadcopter/

Also - I just found this in a google search, so I'm not sure how great it is, but it looks very promising:

http://flitetest.com/articles/choosing-multicopter-motors

I'll look at that more today.
 
There is a ton of info to digest! Thorough understanding comes with time, but then people are constantly pushing the envelope, so there is even more info being generated about new stuff than one can keep up with! Plus, most of us are DIY guys and not physicists, so there's not a hell of a lot of scientific info out there that everyone agrees on. It's mostly trial and error and then opinion.
 
stupid question - how to power the OSD, video Tx and camera if i use a 4S battery ? just adding a 12V 2.5A BEC between battery and camera/Tx will do ?
 
I played with the numbers in ecalc and through theorycrafting (and some questions asked) came up with an optimal configuration of Turnigy 935kv motors with 9x4.7 props - that should allow the copter to hover with a 4S 5000mAh battery for 20+ minutes or some 13-14min "Mixed" flying.

Hover throttle it shows me at 35%, the power might be a bit too high but i want to carry some stuff around and still have quick response times.

I also went with your suggestion about the TX/Rx ;)

Now only have to wait for delivery :P
 
Jasseji said:
stupid question - how to power the OSD, video Tx and camera if i use a 4S battery ? just adding a 12V 2.5A BEC between battery and camera/Tx will do ?
Click to expand...

Most people will use a small battery for this. For my on-board FPV equipment, I run a 350mAh zippy compact 3S (25C) from Hobby King.

Sounds like you've got everything else worked out. Can't wait to see how the build goes!
 
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