1)i have a 20 amp red brick..if im ordering other 3 avionic 20 amps will the quad work fine?
2)i have no idea how to program controllers... is it easy to use an arduino as a controller? also i need to use sensors so which has the most open sources?(flight controllers)
3)plz send me a link to thread with explains how to calculate auw

http://www.rcindia.org/multirotors/tutorial-how-to-build-multirotor-from-scratch/

1) It would be better to use same ESC's, different esc's have different features and settings and you cannot predict exactly if they would work together until and unless you try it for yourself.

2)You can use arduino nano with a 6dof IMU, and use multiwii firmware. I would not say its easy,its something of an intermediate level. Something to get you started.
https://www.scoutuav.com/2011/12/13/low-cost-arduino-based-auto-stabilizing-system/

3)I dont think there are formulas to calculate AUW per se.The thumb rule is AUW has to be less than half of total thrust generated by the motors. The lesser the AUW, more thrust you will have for flight. I usually select the motors first, and accordingly add things. Most of the websites displays weight of components so it helps a lot.

Its always better to select ESCs and motors of same ratings as well as same brands. Different brands have different operations and features. It is not at all advisable to use different escs since the way they'll response is not known. Also, a slight difference could topple your quad, break props, or even hurt you. BTW, please don't mind me asking, which sensors you are planning to use and what for?

plz don't get me crazy..read at your own risk

I have an arduino uno,, yet to learn how to code it, played with some very basic curcuits but i thought that i can attach infrared sensors to make it a flying autonomous robot within a campus and thermal cams to detect people hiding behind bushes (as in fiction movies) and light sensors to automatically switch on leds when its dark, and many more (don't wanna disclose them)

Well i know i wont be able to do all these stuffs in a blink of an eye.. the best idea will be to design a quad 1st

Its going to cost you a lot if you want thermal cams(not talking about infrared night vision cameras). Similarly infrared sensors have been used for obstacle detection and avoidance but there is no firmware yet that can do fully autonomous flight inside closed spaces. You would need to implement some sort of indoor global positioning system to achieve fully autonomous flight.
APM 2.5/6 is an arduino atmega 2560 based FC which has reached its maximum limit with all the features currently available in its latest firmware, so dont think you can achieve all this with arduino uno, you will need more processing power.

Two videos that will give you a fair idea on the possibilities with multirotors if you havent seen them yet.



Its not crazy,possibilities are unlimited; but the time,effort and investment involved is too high & not to forget the vast amount of reading/learning/research you need to do. Best of luck with your project 

thanks, well i've seen both of the ted talks previously

 
its a metal frame 500mm auw(just for frame) is 350-450gms...
best electronics?
further suggestions are welcome

pls ignore the 1st pic.. i'm trying to remove it but can't..accidently attached it...

well any suggestions for my to be quad?

will a little dent and a very little disbalance affect flight??

Hmm, Heavy
By the time you will attach the Motor mounts, Centre plates, Landing skids, it will be almost 500-600gms.
Better use Aluminium booms with nuts and bolts.

Do you need a stable quad or an agile quad?
Less KV Motor goes with  Larger prop = Stable and more efficient
Higher KV Motor goes with Smaller prop = Agile but less efficient


Best would be to stick with the most common specs. i.e. 3 Cell LiPo, 900-1200 KV motor and 8-10inch prop

Little dent = No Issues
Disbalance... Please explain what kind of disbalance are you talking about. Is it disbalance in weight, disbalance in angle of arm or disbalance in height of an arm?

thats what i thought.. but i'm afraid ...will that work? are we supposed to be very precise while making quad frame?? or little flaws are manageable??

in angle.. but thats very little and one cannot figure it out in a minute... but some people told me to go for aluminium rods available at hardware stores

Yep, Precision is very well required. Why not use a Frame Kit instead?
I mean you very well can save   by using the above iron frame but then you will have to spend much more on electronics so as to be able to lift a heavy quad.
Also, these frames does get damaged pretty easily in case of crashes. Nylon frames on the other hand can take a lot of abuse.

A slight disbalance in angle should only create slight issues. Not much.
If you need a perfectly stable quad and if you use a KK2.X FCB instead then you might be able to overcome this issues.

i wanted to make something diy... but seems aluminium will be a better option

Aluminium booms certainly would be a lot better than Iron booms

Use an old TV antenna , the aluminium is of good quality and ideal for
quad arms

my new frame...looks good na got it done for 45 bucks

might be 250gms.... electronics suggestions?

What is used to attach the ply boards to the PVC Pipes?
Looks like nails!!!

And what's the wheelbase on it?

yup..nails...

yet to make wheelbase

Nails are not enough. You need something stronger. Replace them with Nuts and Bolts
Rough measurement of the wheelbase would be enough (and required to figure out the electronics)

Just measure length from the end of one arm to the end of the diagonally opposite arm. That should give us a fair amount of idea.

450mm