I am a mostly retired farmer with some experience in building farm machinery including air seeders, grain conveyors, grain drying aeration and the like. I have also played with quad copters  for a number of years including a DJI 2+ for crop inspections. I am interested in building a flying boom type agriculture sprayer that could apply fungicide to flowering canola and wheat.  The idea is to use the boom or tube, about 4.75 inches inside diameter  for the frame and also contain the fungicide. It would fly maybe 6 to 12 inches above the crop at a speed of maybe 10 mph with propellers all along the tube creating a down draft to help disperse the chemical into the canopy of the crop getting excellent penetration . Most fields around here are 1 half mile long and to go back and forth I would need about 7 lbs. of product for every foot of sprayer. As an example 20 feet of sprayer times 7 lbs. per foot would be 140 lb. of product in the tube. A back and forth trip of 1 mile at 10 mph with a turn around and some hover time would take 8 minutes. That would be the right time to change batteries and a refill. The supply trailer would be a low flat bed unit with the bottom housing the water tank and the sprayer homing in on top  after each run. On the farm we have an RTK GPS signal that could be used.

Now the benefits, less chemical used, having very accurate coverage with very little drift and applying during night time when bees and the like are at home. There are meany more benefits like no pilot on board.

Now is this feasible?  If so, what would make it work? The technology today is almost endless with ultra sonic perception, GPS, compass, altitude, way points, 3D FPV and the like.   . What would the cost to build and maintain be? An airplane here cost from 7 to 10 dollars an acre. Would like to start with 1000 acres each year.

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Bill-

I do not know where you are located, but in the USA you will most likely be limited to a 55lb all up weight if you want to operate under part 107. That being said, for a 140lb payload you are realistically looking at something the size of a small manned helicopter (Robinson R22 or similar).

I developed a large X8 and sprayer system for dispensing pheremone based pesticides here in California last year. The vehicle itself with a 1 gallon tank system weighs about 50 lbs, and can fly for approx. 30 minutes with that payload. I also developed a boom system to compliment the tank. For the products that were being used, only a very small amount was needed to achieve coverage (approx. .9 oz/acre).

For our application, 1 gallon of product would cover a very large area, so we were simply limited by flight time. We also found that strategically placing the nozzles under the rotors allowed for the products to be evenly distributed inside the canopy.

Overall I think that there is a potential in your application, it might be worth seeing if you could get the same effectiveness out of a concentrated product, and thus reduce the amount of product needed to be carried on each flight. Feel free to contact me brian at rmd-systems dot com if you have any questions, I would be happy to share my experiences.

Thanks

-Brian

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hi Brian. excellent build you got there bro. just one question, how do you know if the tank is empty?



Brian Riskas said:

Bill-

I do not know where you are located, but in the USA you will most likely be limited to a 55lb all up weight if you want to operate under part 107. That being said, for a 140lb payload you are realistically looking at something the size of a small manned helicopter (Robinson R22 or similar).

I developed a large X8 and sprayer system for dispensing pheremone based pesticides here in California last year. The vehicle itself with a 1 gallon tank system weighs about 50 lbs, and can fly for approx. 30 minutes with that payload. I also developed a boom system to compliment the tank. For the products that were being used, only a very small amount was needed to achieve coverage (approx. .9 oz/acre).

For our application, 1 gallon of product would cover a very large area, so we were simply limited by flight time. We also found that strategically placing the nozzles under the rotors allowed for the products to be evenly distributed inside the canopy.

Overall I think that there is a potential in your application, it might be worth seeing if you could get the same effectiveness out of a concentrated product, and thus reduce the amount of product needed to be carried on each flight. Feel free to contact me brian at rmd-systems dot com if you have any questions, I would be happy to share my experiences.

Thanks

-Brian

Paul-

Thanks for the compliments, we are really happy with how this vehicle has been performing.To answer your questions:

Depending on the application, there are a few ways we can tell if the tank is empty. The pressure tank carries an external gas bottle, which allows the tank to be at a constant pressure during the whole flight, regardless of the liquid level in the tank.

When spraying row crops, we set the pressure to a setpoint (usually around 40psi) and then calculate the amount of time it will take to empty the tank based on the nozzle selected. We then use a timer during the flight to know when the tank is empty. Obviously not high tech, but it seems to work ok.

When doing spot spraying, we set up the tank to be triggered by the camera trigger on the pixhawk. This allows us to alter the 'shutter duration' and control the shot size from the tank. For example, when spraying for certain invasive grasses, we desire a shot size of approx. 7 fl-oz. We set the camera trigger for 1 second, and adjust the pressure to match the nozzle. This gives us approx. 16 shots per tank (each shot is logged in a KMZ file from mission planner).

Also, we have a small FPV camera attached to the vehicle that lets us see the nozzle. When the nozzle starts sputtering, we know that we are out!

Let me know if you have any questions.

Thanks

-Brian


Brian, 

       I appreciate your reply and thank you very much for sharing your expert knowledge,it is very informative and a huge help for people like me who are new into this thing.
        The reason i was asking that question is because i am planning to build a sprayer UAV myself. I have done a lot of reading and research of all that is needed to built an effective and efficient agricultural drone. Your post about your experience in building the x8 was one of my favourite. 
        My design is generic compared to yours. Just a dc pump connected to a palstic tank. But i got stuck in this, triggering the UAV to RTL if the liquid in the tank reach a certain level. I could not find the answer despite scouring the internet and wiki for information. 
        My idea is to install a float switch inside the tank and maybe hook up the connection in one of the aux ports of the pixhawk. And have the FC read the pwm values of the switch with out using a companion computer. Hopefully it is possible because i dont want to use an onboard computer as i know nothing about coding. I would like to build a spraying system just like yours but that is way beyond my capability. 
      
        Anyway, thanks for the reply. If you and your talented team is interested in figuring this out, please keep me updated. 😊
Regards, 
Paul

Brian Riskas said:

Paul-

Thanks for the compliments, we are really happy with how this vehicle has been performing.To answer your questions:

Depending on the application, there are a few ways we can tell if the tank is empty. The pressure tank carries an external gas bottle, which allows the tank to be at a constant pressure during the whole flight, regardless of the liquid level in the tank.

When spraying row crops, we set the pressure to a setpoint (usually around 40psi) and then calculate the amount of time it will take to empty the tank based on the nozzle selected. We then use a timer during the flight to know when the tank is empty. Obviously not high tech, but it seems to work ok.

When doing spot spraying, we set up the tank to be triggered by the camera trigger on the pixhawk. This allows us to alter the 'shutter duration' and control the shot size from the tank. For example, when spraying for certain invasive grasses, we desire a shot size of approx. 7 fl-oz. We set the camera trigger for 1 second, and adjust the pressure to match the nozzle. This gives us approx. 16 shots per tank (each shot is logged in a KMZ file from mission planner).

Also, we have a small FPV camera attached to the vehicle that lets us see the nozzle. When the nozzle starts sputtering, we know that we are out!

Let me know if you have any questions.

Thanks

-Brian

Paul-

I am glad you liked the post about building the X8! There is nothing wrong with a submerged sump pump setup, I looked at that option when I was building the tank. The customer liked the idea of a pressure vessel with less moving parts, and it turns out to be a lighter setup when all is said and done. Plus, with the pump you have the additional electrical load on the battery, which lowers the flight time (can be significant depending on the pump).

To answer your question, I think that you are on the right path using a float switch inside the tank. You may want to baffle the inside of the tank as well, as we found that the fluid slosh can cause some stability issues with even a large multicopter (our Tarot T18 test mule (x8 18" props) would get a little wild without the tank baffling).

I will do a little reading on passing through a PWM signal to the pixhawk. I know that you can trigger RTL from the channel 7 or channel 8 optional feature (configured on mission planner), it would seem that you would need to configure one of those channels to RTL in mission planner, and then see if there is a way to throw the PWM 'high' on the right channel by triggering the float in the tank. I need to look into it more, but at first glance it seems possible without a companion computer.

Sounds like an interesting project, let me know if I can help in any way. By the way, we do sell the vehicle and tank system, as well as provide the tank for sale by itself (if you are interested). Feel free to drop me an email (brian at rmd-systems.com) if you have any questions.

Thanks

-Brian

Hi Brian,

Did you use the sprayer option in mission planner to control your sprayer? I'm having trouble with it... it says to set RC_Function# to 22... but I don't see that doing anything. Any advice?

Thanks!

-Ben



Brian Riskas said:

Bill-

I do not know where you are located, but in the USA you will most likely be limited to a 55lb all up weight if you want to operate under part 107. That being said, for a 140lb payload you are realistically looking at something the size of a small manned helicopter (Robinson R22 or similar).

I developed a large X8 and sprayer system for dispensing pheremone based pesticides here in California last year. The vehicle itself with a 1 gallon tank system weighs about 50 lbs, and can fly for approx. 30 minutes with that payload. I also developed a boom system to compliment the tank. For the products that were being used, only a very small amount was needed to achieve coverage (approx. .9 oz/acre).

For our application, 1 gallon of product would cover a very large area, so we were simply limited by flight time. We also found that strategically placing the nozzles under the rotors allowed for the products to be evenly distributed inside the canopy.

Overall I think that there is a potential in your application, it might be worth seeing if you could get the same effectiveness out of a concentrated product, and thus reduce the amount of product needed to be carried on each flight. Feel free to contact me brian at rmd-systems dot com if you have any questions, I would be happy to share my experiences.

Thanks

-Brian

Ben-

My sprayer system has no pump, instead my system uses a pressurized gas cylinder with a solenoid valve. I have a custom driver circuit that opens the solenoid valve when triggered by a voltage. In my case, I use channel 7 optional set to camera trigger, which outputs a 3.3v signal on the pixhawk's output rail. I use that voltage to trigger the sprayer tank.

With this setup, triggering the tank is the exact same as triggering the camera in mission planner. I have full control over the tank in the manual modes, as well as the automated modes (guided and auto). The tank system is pressure compensated, so the output rate is the same regardless of the level in the tank. As long as the speed of the vehicle stays relatively constant, the coverage rate remains constant as well.

Thanks

-Brian



Ben Despain said:

Hi Brian,

Did you use the sprayer option in mission planner to control your sprayer? I'm having trouble with it... it says to set RC_Function# to 22... but I don't see that doing anything. Any advice?

Thanks!

-Ben



Brian Riskas said:

Bill-

I do not know where you are located, but in the USA you will most likely be limited to a 55lb all up weight if you want to operate under part 107. That being said, for a 140lb payload you are realistically looking at something the size of a small manned helicopter (Robinson R22 or similar).

I developed a large X8 and sprayer system for dispensing pheremone based pesticides here in California last year. The vehicle itself with a 1 gallon tank system weighs about 50 lbs, and can fly for approx. 30 minutes with that payload. I also developed a boom system to compliment the tank. For the products that were being used, only a very small amount was needed to achieve coverage (approx. .9 oz/acre).

For our application, 1 gallon of product would cover a very large area, so we were simply limited by flight time. We also found that strategically placing the nozzles under the rotors allowed for the products to be evenly distributed inside the canopy.

Overall I think that there is a potential in your application, it might be worth seeing if you could get the same effectiveness out of a concentrated product, and thus reduce the amount of product needed to be carried on each flight. Feel free to contact me brian at rmd-systems dot com if you have any questions, I would be happy to share my experiences.

Thanks

-Brian

Ah, yes, that's the original way I had mine built (funny, very similar... I used a pump to pressurize a bladder, and then had the spray inside another bladder inside a bucket, then had a servo actuated valve open up at each gps camera trigger, the pump/bladder would just maintain a specified pressure inside the bucket as spray was evacuated), but my needs shifted recently from GPS coord camera triggering to variable output according to the speed of the UAV.  The only thing GPS is needed for now is to maintain the path and turn the system on or off depending on whether the UAV is inside the spray zone or just en route.

So, basically, I'm trying to get Randy's implementation working: http://ardupilot.org/copter/docs/sprayer.html.

-Ben

I've reached out to Randy a few times, but haven't heard from him yet.


Ben Despain said:

Ah, yes, that's the original way I had mine built (funny, very similar... I used a pump to pressurize a bladder, and then had the spray inside another bladder inside a bucket, then had a servo actuated valve open up at each gps camera trigger, the pump/bladder would just maintain a specified pressure inside the bucket as spray was evacuated), but my needs shifted recently from GPS coord camera triggering to variable output according to the speed of the UAV.  The only thing GPS is needed for now is to maintain the path and turn the system on or off depending on whether the UAV is inside the spray zone or just en route.

So, basically, I'm trying to get Randy's implementation working: http://ardupilot.org/copter/docs/sprayer.html.

-Ben

Hi
I'm excited about your project, and I am developing a spraying drone using Pixhawk controller. Hope can exchange exp and knowledge about designing spraying process with you. And I'm also interested in your farm machines like air seeder, and grain conveyor. Can you share some their information with me? My email is lekhanhlinhbker@gmail.com. Thank you a lot.

Hi,

      I am too starting to build a pesticide sprayer with a 5L spray tank. I am about to build a Quad not X8 or Octo. I was thinking to use Tarot X4 960mm frame, replace the retracting landing gear with a fixed one. And connect a 5L tank with 2 sprayers. The tank comes as a unit along with a motor and two sprayers. Now the problem starts from here. What motor and esc should I use? Which Flight controller? And Battery. Here are some points I would like to mention. T-Motor 370Kv or Tarot or Sunnysky? Pix Hawk that was I thinking but any better option ll also help me out. Battery in India are very expensive, since they come under Dangerous goods hence draw a huge Custom duty. They also require special license/permission to import in India. So I am left with LHS who ve to charge a hefty amount considering the above problems. Also high capacity batteries like a 22V 20000mah are very rarely a available. So guys please help me out in deciding the configuration and help me building this craft. Thanks in Advance.

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