Hi,
    Am about to work on an Agricultural Spraying Quad. Initially I was thinking to build a quad that should lift spray of  around 5 ltrs. But the cost is not fitting any where near my actual budget. So I decided to scale down the capacity. Now I thinking to build something that should carry around 2-3 ltrs of spray. So the AUW will be somewhere around 8 kgs. I was thinking to use Pixhawk 2.1 as FC. But there are several doubts in my mind. Is it good to go with 2.1 or the older version is good enough? My problem is I need to use an Open source firmware for this purpose hence cannot think about DJI products. Also if I want to increase the payload in future, the same FC should do the job. Since 2.1 is quite expensive especially after including the gps, am thinking that is it worth? Also there are doubts regarding the gps, weather I should go with GNSS or RTK. Other setup includes 340kv T-Motors, 60a T-Motor esc, 22in props, Tarot 960 frame and 22000mah battery. If somebody have a better configuration than this, then please let me know. Also thought about Sunnysky motors, but am not getting enough confidence over T-Motors. So please help me in deciding the right configuration along with the FC. Thanks n Regards.

And yes the battery is 6s considering the cost and the weight as well. Regards.

https://discuss.ardupilot.org/t/zigzag-mode-for-copter-3-7/33717
If ur budget allows, go for 2.1

Thanks, you mean it's better than pixhawk standard. And what gps is better gnss or rtk?

Sure, it has redundant sensors, internal dampening etc.
CUAV is also a good brand to consider.
Personally I haven't used, but if you are serious, rtk might be better.
Have you used ecalc ? .It will give an idea about props,motors, AUW etc
Best wishes for ur project.

Thanks for the help. I havent used Ecalc yet but from my past experience I ve an approximate idea of what esc n props I should go with, in fact these are the minimum for a relatively smooth operation. But as you ve suggested I ll use ecalc values as well. Will also look into CUAV. Meanwhile if you come across anything that ll help in my build project then please let me Know. Regards.

Sure, happy to help.

Have a look at this. Ask the seller for its weight .(will help in calculating AUW)

https://www.aliexpress.com/item/DIY-Agricultural-drone-spray-system-accs-nozzle-Water-pump-Buck-module-Pump-governor-Adapter-Water-pipes/32764637764.html?spm=a2g0s.8937460.0.0.6ebb2e0eaWx0UN

Hi, And while buying from aliexpress, avoid sellers who don't reply fast and promptly.
Ask them to declare the package as parts & accessories.
Avoid the words drone, quaddcopter etc on the package !.

What crop do you have in mind ?
2-3 ltrs spray fluid is not going to be enough for any meaningful pest control or foliar application.

For a reference point a normal manual sprayer used by farmers and by us in plantations contains
14 ltrs .

Rather than choosing a flight controller ... First get your payload and application parameters
correct.

Hi, I agree with you. But like I ve mentioned that earlier that my budget doesnt allows me to go for a bigger capacity. My target is grapes n Pomegranate. And we are targeting small fields and also we ve grapes n pomegranates fields that are divided into an Acre or two coz of various reasons. So my initial thought was to go with 5 litr tank, but like I said the cost is out of my budget.. So as a pilot project I am thinking to go with a 3 ltr capacity, and since we are covering a small area at one point of time, hence refueling the tank again is a thing I ve to adjust with. Please give me some valuable inputs from you Sir. Regards.

firstly - grapes - its not going to work because they grow all over the vines and your drone will spray a fine mist
which will only settle on the top surface - not reach the bunches growing underneath.

drone spraying will only work for crops which grow on a flat surface - eg rice and not tomatoes.

I have never seen a pomegranate tree so no idea.

secondly consider the economics of manual spray to cover one acre

one daily wage - rs 400/- to hire a man who can easily spray one acre daily
one manual spray machine - 3000 /-  (one time investment)
protective clothing for spray - 2000 /- (one time investment)

that is basically it ! - chemical etc.. will be required in drone spraying also.

So for about Rs 500 / - you will be able to cover one acre , with targeted spray and very little wastage.
Can your drone match the costs ?

Third ... consider the hazard liability of aerial spray.  You will be spraying toxic agrochemicals . The slightest breeze
will cause these to drift to nearby habitats and water bodies .  Should such a case occur - you will have cows and goats
dying.

In conclusion - agricultural drones may have the "glam" factor - but as a practical tool they are useless.
Do not waste your hard earned money.

Hi, The idea itself is to create mist rather than just spray. And there are different layouts of grape yards, in mine its a Y layout also called Telephone layout, so I ve space to move the bird within two rows. Also its the same layout for Pomegranate. And sir this is not just for my personal use. Its a funded project and they want me to help me in designing the quad and also testing in my own field. Usually we ve the same layouts in our area and ours is a grape growing land. So basically I ll not be shelling out any money from my pocket but also I ll not be charging anything for the development. I agree with you on the point that its a fancy idea but they want it and that too within the sanctioned budget. My gain is that I ll ve an opportunity to study and understand and also learn these kind of heavy birds. The interesting part is that those guys for whom the amount was sanctioned ve left the project and are out of city for jobs. Now the college has the money,  but they ve to spend it in order to get funds for future projects. And there is a procurement process involved so the college cannot simply use the fund for any other purpose. Also they ve to have a working/semi working model to showcase. Thats where I came into the picture, and I am finding an opportunity here to implement this project by effectively utilizing the sanctioned amount and coming up with a thing that should work. So all these efforts ll give the college their project and me some knowledge. Believe me once the project is complete I ll be no where in the picture, there are other people who are already ready to take the Credit .   

i 'm trying to make a hexa,.
need help for better tuning & setup for stable flight;
configuration like F550 frame,Pixhawk 2.4.8 Fc with stock gps module.
1000kv motor,1045 prop,30amps bl heli opto esc,3000 mah lipo.

Pls guide me or suggest for for best setup for my hexacopter.

This setup is good enough but i still suggest you to go with a little lower kv motor like 800-850 or 900. Also more importantly it depends upon your payload, pm me i ll try to help you out.

Yes..sir..pls suggest me for best stable tuning for my Hexacopter..I've already tried with latest version of mission planner.

@miginstruments

I am working on a pilot project with 4kg AUW (to be increased later) and have done extensive research. Even I've written a path algorithm to spray the pesticide on the field and tested it on Ardupilot + SITL.

Now my main problem is to import the required hardware. Since I am new to this thing, I am not aware of trustworthy exporters or sellers. From your post, it seems you are also using Ardupilot.

Lets collaborate and exchange the experience, Mate!!