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Old Apr 08, 2012, 07:55 AM
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Building a quad - flight control

Hey there,

I'm a software developer, with some experience in electronics. As such, building a quad copter seemed like a nice and fun challenge to me.

Instead of buying a standard control board, like the KK, I want to design one myself.

Right now, I have a digital compass, an 3-axis accelerometer and a gyro to play with on my desk. I can talk to these components more or less now, but that's not the issue here.

I'm trying to plan ahead a little, trying to figure out what to order, so that it arrives just before I start needing it.

TX/RX portion

I currently only have an Turnigy X9 remote on the way from Hong Kong, as a next step. I plan to hook it up to an atmega, which in turn is hooked up to my PC via serial (FTDI). That would allow me to work out how these receivers work, but I have a few questions about that in advance:

QUESTION 1: What is the voltage requirement for the 8(?) channel receiver that comes with the Turnigy X9? And can I hook that up to a DC adapter safely?

QUESTION 2: What voltage levels can I expect from the 8 (channel) outputs?


Motors

The next step would probably getting some motors and ESCs.

Now I've been reading up on these, but I have to confess that it gets confusing to see so many makes and modes in the various shops...

Basically, this is what I think is important for my quad, ordered from most important, to least:

- should be able to carry camera equipment, realtime video would be very nice
- relatively silent operation
- long battery life

I guess to operate as silent as possible, the RPM of the motors should be relatively low, and the props relatively larges to be able to lift the weight.

HK has a (very limited) selection of motors which are especially made for quads. The "NX-4005-650kv Brushless Quadcopter Motor" seems nice... but... are they really better than "normal" brushless motors?

QUESTION 3: Anyone has any experience with the before mentioned motor, or has another good suggestion?


ESCs

When getting motors, one also needs ESCs of course. And as I'm not planning to build these myself, I have a few questions about the readily available ones

QUESTION 4: As for ESCs, say a given motor is rated as 20A, should you go for a 20A ESC, or go for one with a slightly higher value to be safe?

QUESTION 5: I've seen "ESC programming cards", but are there required? Or are there other (better?) ways to configure an ESC.

QUESTION 6: Are all programming cards compatible with all ESCs (or at least compatible with all ESCs of the same brand?)

QUESTION 7: What "protocol" do ESCs talk? Or do you simply manipulate the voltage to them to control the motors?


Batteries

Ultimately, the thing has to fly of course. So I will need batteries...

There are the LiPo's, but also the newer LiFe's. I was leaning a bit more towards the LiFe's, as they seem to perform better than LiPo's. Number of channels will depend to the type of motor used, I presume. So I'll get back to that when I picked my motors.

The thing that worries me most, however, is the charger. I'm a bit spooked by the exploding / burning LiPo's movies, so I want to be sure that my charger is a good one .

Problem is, I can't tell a good one from a bad one ;-)

I have been looking at this one, the IMAXB6-AC Charger. I like it for two reasons:
- seems to be a good one (??)
- had a build in power supply, so all I need it the proper EURO connector to stick it in a wall outlet.

QUESTION 8: Any thoughts on the IMAX B6-AX? Or other suggestions? (I also would love to know why)


Various bits an bolts and connectors

Like with any hobby, there is a certain amount of bolts and connectors that is used frequently, and/or isn't included standard with e.g. motors / ESCs...

QUESTION 9: What are the best things to have "on stock"?



Well, I'll probably have a ton more questions in the future. But I'll leave it at this for this first post :-).

Thanks for reading this far, I'm looking forward to your suggestions and help!

Kind regards,
Michel.
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Old Apr 08, 2012, 08:05 AM
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Spain
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so many questions...

Thttp://www.rcgroups.com/forums/showthread.php?t=1097355

search option in that link will probably answer many of them.
Saludos,
Jose
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Old Apr 08, 2012, 08:05 AM
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I think in 2012 you might want to look at something other than "atmega" and "FTDI".
I suggest picking up a STM32-DISCOVERY or Olimexino or at least something that isn't using an obsolete processor.

RX = 5V will work.
It outputs 5V, too.

Most of your questions can be answered by reading the megalink sticky thread.
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Old Apr 08, 2012, 08:08 AM
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Quote:
Originally Posted by timecop View Post
I think in 2012 you might want to look at something other than "atmega" and "FTDI".
I suggest picking up a STM32-DISCOVERY or Olimexino or at least something that isn't using an obsolete processor.

RX = 5V will work.
It outputs 5V, too.

Most of your questions can be answered by reading the megalink sticky thread.
The servo signal output from many receivers is 3.3 to 3.6 volts, depending on what the processor runs at.
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Old Apr 08, 2012, 08:22 AM
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David Jenkins's Avatar
United Kingdom, England, Ipswich
Joined Aug 2011
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Quote:
Originally Posted by MichelCV View Post
Batteries

Ultimately, the thing has to fly of course. So I will need batteries...

There are the LiPo's, but also the newer LiFe's. I was leaning a bit more towards the LiFe's, as they seem to perform better than LiPo's.
Michel,

Don't get confused by LiFe batteries - half of my batteries are LiFe, and I think they're great for the sort of flying I do, but they don't perform better than LiPos!

You can do a search on LiFe in rcgroups, but the pluses and minuses are:

+ They are far safer than LiPo - but LiPo are safe enough if you get a decent charger and use your intelligence when using and charging. I like being able to put them on the charger and walking away to do other things while they charge, which you must never do with LiPo.
+ You can leave them charged without damage, and you can discharge them too far occasionally without much harm.
+ You can charge them at high rates without damage, where LiPos like to be charged at moderate rates (depending on the quality of the LiPo).
- They are heavier and bigger than LiPo for a given amount of energy. This isn't a problem if you have a decent excess of power, although lightness is always good in an airframe.
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Old Apr 08, 2012, 08:28 AM
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Quote:
Originally Posted by Doblao View Post
Thttp://www.rcgroups.com/forums/showthread.php?t=1097355
Darn, I started out with ge "Be safe" thread on that page... Those are some scary injuries... Didn't realize how much power is in these things...

Thanks for the link, I have a lot of reading to do ;-)
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Old Apr 08, 2012, 08:38 AM
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Joined Jun 2004
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Welcome to R/C.
Tons of questions that re simply too much to answer all at once. It might be a good idea to buy a frame and some ready made electronics and start with that. Starting from scratch is very difficult and frustrating.

Since you have a 9x on the way you might want to check out this: http://9xforums.com/wiki
Also, you might want to look into the open source software that are available like multiwii, ardupilot, ardupirates etc...
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Old Apr 08, 2012, 09:11 AM
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I thought it would be cool to design and build my own 700mm frame and camera mount out of pure CF. Its done now but I just wished I bought one from HK for 20 bucks or what ever. Seems like you have a lot of questions that are very basic, you may want to try a quad thats basically ready to go, learn from that. Make your board later. Good luck! I sure need it...
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