Quad Configuration and Flight Controller Questions

[Bill_in_TR]

Hi everyone. First post on these forums. I am in the early stages of research on building a quad. I have a couple of what are probably really basic questions right now. I did a search and cannot really find answers to my specific questions. They may be there somewhere but I cannot find them so my apologies if I am being repetitious. I am mainly interested in a quad for flying around the yard and mostly playing around. Perhaps later on I might want to do a little photography but nothing sophisticated. I would like something big enough to be reasonably controllable if there is some light wind so I am thinking something 450 sized.

First of all I am trying to get an idea of the difference between x quad and + quad configurations. I have come to the conclusion that it is primarily a difference in motor rotation/location but I cannot find a definition of which is which and what are the reasons for going one way or the other.

Next I am trying to decide on a flight controller. I want to stay under $50 and there seems to be a fair number of options in that price range. But my problem is I am not a Windows or Mac guy. My computers are Linux based. I am trying to find a controller that has decent Linux support for any tuning interface and for any firmware updates that might need to be done.

As I go along I am sure I will have more questions but so far I am finding out quite a bit just lurking and reading. Thanks for any help anyone can give me.

Bill

 

[.jon]

X-quads look better

OpenPilot CC3D from Hobby King (approved manufacturer) fits well in your stated budget, is a great basic controller board with configuration software for linux. I use it on Xubuntu, along with the OpenTx Companion to configure the Taranis.

 

[FlyGirl]

X-quads look better

OpenPilot CC3D from Hobby King (approved manufacturer) fits well in your stated budget, is a great basic controller board with configuration software for linux. I use it on Xubuntu, along with the OpenTx Companion to configure the Taranis.

Can't comment on the controller and Linux but I agree with Jon, X looks better. LOL! It is also better if you will be carrying a camera as the props are more out of the way....

 

[Bill_in_TR]

OK. Well pardon my ignorance but in what way do x quads look better? I am only familiar with one shape for a four rotor aircraft and that is with the arms perpendicular to each other. Which means to me that a + and an x shape are pretty much the same depending on what perspective you view them from. And then there is the question about direction of motor rotation. Do quads all have motors wired so that alternating motors rotate in opposite directions. I thought some had motors wired so that two adjacent motors rotate the same way. If my understanding is correct what are the advantages and disadvantages of each?

As far as the CC3D controller is concerned my understanding is that it does not support GPS should I choose to add it later. I also did not think it supported altitude and heading hold with a barometer and compass.

Bill

 

[FlyGirl]

OK. Well pardon my ignorance but in what way do x quads look better? I am only familiar with one shape for a four rotor aircraft and that is with the arms perpendicular to each other. Which means to me that a + and an x shape are pretty much the same depending on what perspective you view them from. And then there is the question about direction of motor rotation. Do quads all have motors wired so that alternating motors rotate in opposite directions. I thought some had motors wired so that two adjacent motors rotate the same way. If my understanding is correct what are the advantages and disadvantages of each?

As far as the CC3D controller is concerned my understanding is that it does not support GPS should I choose to add it later. I also did not think it supported altitude and heading hold with a barometer and compass.

Bill

We were kidding somewhat about it looking better... Just a personal preference. A quad in plus configuration flies with one arm forward and the X flies with no arm facing forward. See this picture....

Forward flight would be towards the top of your screen. You can also see the rotation of the motors here....

 

[Bill_in_TR]

I must have taken my dumb pills this morning by accident. I look at those drawings and the only difference I see is that on quad is turned 45 degrees in relation to the other. Motor rotation seems the same, controller board orientation is the same and the arms are perpendicular to each other in both. So why is one flying with an arm forward and the other flying with no arms forward? And is there no such thing as a configuration where adjacent motors rotate in the same direction?

Bill

 

[FlyGirl]

I must have taken my dumb pills this morning by accident. I look at those drawings and the only difference I see is that on quad is turned 45 degrees in relation to the other. Motor rotation seems the same, controller board orientation is the same and the arms are perpendicular to each other in both. So why is one flying with an arm forward and the other flying with no arms forward? And is there no such thing as a configuration where adjacent motors rotate in the same direction?

Bill

Yep! Very true! The only difference is the way they fly through the air. However, controller orientation as far as placement on the quad is different. All controllers have a side that needs to be pointed in the forward flight direction so if you are flying it as a "+" the forward side of the controller will point at the front arm whereas with an "X" it will point at the open space between the front two arms. As for why one flies with an arm forward and one with the arms pointed 45 degrees away, it's purely a matter of how you want it to look in the air. The ONLY advantage that I know of is when using a camera on the quad it is advantageous to have it flying in an "X" configuration so there won't be an arm sticking out in front on your videos. And I don't know of any quad that has adjacent motors spinning the same direction... Hope that helps!

 

[Gary_In_PHX]

I can't commrnt on the adjacent motots, but the configurations shown are built the same. The difference is which way the copter sees as the front. "X" places the rotors on either side of a forward facing camera and its field of view forming an "X" with the frame arms when facing forward.

While "+" has a rotor sitting at the forward centerline of the craft making a "+" shape when the craft is facing forward.

Sent from my phone using pixie dust and magic unicorn farts.

 

[Bill_in_TR]

OK. I thought I had seen a diagram in a thread somewhere that showed a motor rotation with two motors in the front rotating in the same direction (CW) and the two motors in the rear rotating in the same direction but opposite the front (CCW). Mybe I was hallucinating. Now I need to try and figure out what I want to use as a flight controller. Just looking at the Witespy web site alone there seem to be so many choices it is almost ridiculous and quite a few of them fit into my price range/budget. But it isn't always clear, at least not to a newb like myself, what sort of programming interfaces are used with each and do they run on Linux. I will continue to research them.

Bill

 

[.jon]

As far as the CC3D controller is concerned my understanding is that it does not support GPS should I choose to add it later. I also did not think it supported altitude and heading hold with a barometer and compass.

Bill

That is correct, it has no baro or compass, it does support a GPS but with limited functionality.

OpenPilot Revolution is their GPS FC.

What FCs in your price range support GPS and come with baro?

 

[Bill_in_TR]

I would have to go back and look at the web sites I have been researching but there were a couple on witespy and another site. I don't expect to get the gps in that price range. I would just like to know that I can add it at some point if I want. I saw more than one multi wii controllers on witespy that already had barometer and compass and were in my price range. There was also at least one that had barometer but not compass in that price range that supports later addition of gps. I am just not sure whether they have an interface that will run on Linux. I have sent an email inquiring but have not heard back yet.

Bill

 

[.jon]

Yeah, well, you choose what you like but my experience so far is that this hobby involves countless of web orders from various shops around the world, and one thing I'd try to avoid is ordering from shops with questionable reputations and return policies. Waiting for weeks for a component only to find it's wrong or faulty, and then not getting any contact with the seller sounds like a nightmare.

Furthermore FC is the heart and brain of your multi. I wanted a reasonably priced FC with strong community support, good docs and tuning process (and linux GCS) and went for OpenPilot, which is a very well maintained open source project, and not a sprawling mess of different board and firmware versions with very little testing, no central support and poor or non-existent documentation. If you have difficulties finding out any info on the firm & software in the first place, it might be impossible to troubleshoot something later.

There are several other choices for tried and tested boards with wide user bases and good support.

Paying a little bit more for the FC makes sense to me, it's a component that you can easily transfer to other projects and very unlikely to break in crashes... and is by far more important than anything else on board.

 

[Bill_in_TR]

jon, I understand exactly what you are trying to advocate. I am in the beginning stages of my research into building a quad. I have a lot to learn. But I also have a limited budget. I have visited several different web sites all of which I have seen recommeded by people both here and on other forums. I don't think I am looking at locations that have a bad reputation. What I have been finding out so far is that it is difficult to get beginner questions answered. I do as much searching as I can to avoid being repetitious. Perhaps my budget is unrealistic. If so then maybe I will have to abandon the notion of trying to get into quads. I am doing this for fun only not any serious application so I think I can get away with less than high end components. But I know to also avoid the other end of the price spectrum. There are at least a couple of boards that do not have barometer or compass that have fairly widespread use that are well within my budget. I would just like to try for something that has barometer and compass and the ability to add gps later maybe. There seems to be some stuff out there. But I need to find out what sort of programming interface is supported.

You made very valid points but when you said "there are other choices" you made no suggestion whatsoever. Perhaps the only suggestions you had were well beyond what I was willing to spend. If so then as I said I would have to stay out of the multirotor game. If you could suggest a couple of web sites I could look at that you felt were reliable that would also be useful information.

Bill

 

[.jon]

Well, you are right that the options I had in mind would stretch your budget as what comes to the hardware.

However, the APM (Ardupilot Mega) firmware runs on various different cards with the features you want, and that is mature, tried and tested open source code, and the config/setup/mission planner software is cross-platform, linux included. Several vendors manufacture cards made for APM, check out Hobby King and RCTimer for example. It seems that they are close to 50ish or so?

Good info thread on APM:

http://www.********.com/forums/showthread.php?t=1820773 <- EDIT: why is ******** censored? What is this?

It's a very interesting and big project.

Google around for info which APM-compatible card has good experiences, and also whether the shop you mentioned has gathered positive experiences.

 

[FlyGirl]

That website (from what I understand) was censoring posts from this website so references to that website are no longer allowed. "Bartman" who owns this site can fill you in better if need be but that's what I understood as the issue...

 

[.jon]

That website (from what I understand) was censoring posts from this website so references to that website are no longer allowed. "Bartman" who owns this site can fill you in better if need be but that's what I understood as the issue...

Ah, drama reaching even such nice hobbies as these. Unfortunate.

Anyway, APM 2.5/2.6 board would be my recommendation Bill, it's being phased out by the much more expensive Pixhawk and won't get any more new features, but it has more than enough of them already, and they work.

 

[Bill_in_TR]

jon, appreciate the suggestion but a bit of searching indicates the pricing on that board to be over $100. That far exceeds my budget. I can be a little flexible and realize I might have to slip a little above my $40 target. But right now it seems that there are multiwii boards out there that have a good reputation that are available that I can afford.

Bill

 

[.jon]

jon, appreciate the suggestion but a bit of searching indicates the pricing on that board to be over $100. That far exceeds my budget. I can be a little flexible and realize I might have to slip a little above my $40 target. But right now it seems that there are multiwii boards out there that have a good reputation that are available that I can afford.

Bill

Which board? I just suggested the firmware Here's one board for 39 usd.

http://witespyquad.gostorego.com/flight-controllers/readytoflyer-2-5-287.html

Anyway, good luck with multiwii!

 

[Bill_in_TR]

The witespy web site is one of the places I have been doing a lot of my researching. They have several different boards that fit nicely in my price range. To be honest I had not paid that particular one close attention so thanks for pointing it out. I got the impression that you were not a big fan of the witespy web site from comments you made about waiting weeks to receive an order. Perhaps I misinterpreted. Two of the boards I looked at there were the Multiwii Pro Mini and the Sparky. I will give the one you suggested a closer look. I have not yet received a reply to my info request from witespy. I know it says at the top of the page to wait a couple of days but it has been three days now and no response whatsoever. It makes me a little skeptical. But his work seems to have a good reputation and he has a big selection of boards that are affordable for me.

 

[.jon]

The witespy web site is one of the places I have been doing a lot of my researching. They have several different boards that fit nicely in my price range. To be honest I had not paid that particular one close attention so thanks for pointing it out. I got the impression that you were not a big fan of the witespy web site from comments you made about waiting weeks to receive an order. Perhaps I misinterpreted. Two of the boards I looked at there were the Multiwii Pro Mini and the Sparky. I will give the one you suggested a closer look. I have not yet received a reply to my info request from witespy. I know it says at the top of the page to wait a couple of days but it has been three days now and no response whatsoever. It makes me a little skeptical. But his work seems to have a good reputation and he has a big selection of boards that are affordable for me.

I don't have personal experience with his business, but I've read a lot of problems people have had with delivery times of their orders from him. He is a one-man company and overworked, and communication seems to be an issue. However, like you said the actual product quality is apparently good, and prices are excellent.