I created an autonomous intelligent ag sprayer drone that identifies and sprays only the wild blackberries (weeds) in my prairie grass. It worked surprisingly well and could be copied for other applications. This video will show you how it's built.
Note - This is version 1 - it works but the system to identify weeds is a bit of a clooge. Version 2 is forthcoming and will use a raspberry pi zero 2 to do onboard image processing and will work much better - I recommend going that route, raspberry pi zero 2's should be back in stock in the summer of 2023.

Landing Pad and Battery Swap Station Video:    • DIY automated drone battery swap, lan...  

Electrical schematic: https://drive.google.com/file/d/1o7SM...
Tensor Flow code:
webcamCapture.py - https://drive.google.com/file/d/1-QmJ...
sprayerLoop_captureOnly.py - https://drive.google.com/file/d/1grrT...
BuildModel.py - https://drive.google.com/file/d/1VQ3s...
PredictImage.py - https://drive.google.com/file/d/1BX-I...
listener_mpScriptsTab.py - https://drive.google.com/file/d/1ZCnA...
sprayerLoop.py - https://drive.google.com/file/d/1_t9U...
Bill of Materials - Drone ($1035 USD as of 2/23, version 2 camera system)
Drone
1 s500 frame - $48 (https://www.amazon.com/gp/product/B01...)
4 30A ESC - $40 (https://www.amazon.com/Readytosky-Ele...)
4 920kV drone motors - $40 (https://www.amazon.com/gp/product/B09...)
1 2 pair drone props - $14
1 cube orange, 1 here 3+ GPS, 1 900MHz radio - $679 (https://irlock.com/collections/combos...)
This is a huge portion of the total cost, and cheaper pixhawk autopilots and radios exist, but I tried them without much success
1 tf-mini (lidar) - $50 (https://irlock.com/collections/rangef...)
1 4s 5200 mAH lipo - $49 (https://www.amazon.com/Zeee-Battery-5...
adhesive velcro - $5
Sprayer:
1 L298N Motor Controller - $7 (https://www.amazon.com/Qunqi-Controll...)
1 12V and 5V DC buck converter (adjustable) - $12 (https://www.amazon.com/dp/B01MQGMOKI?...)
1 Sprayer Pump - $10 (https://www.amazon.com/gp/product/B07...)
1 Nozzle - $8 (https://www.amazon.com/Hourleey-Misti...)
1 Nozzle tubing - $8 (https://www.amazon.com/REDTRON-Distri...)
5' section of 1/2" PVC, 6 90 degree connectors, 4 T connectors, silicon, 1/4" inside diameter tubing - $25 (tank/landing gear)

Version 1 Camera System -
*NOTE I don't recommend buying version 1. Version 2 will be WAY better and cheaper. Just wait for raspberri pi to be back in stock*
1 Runcam swift 2 FPV Camera - $28 (https://usa.banggood.com/RunCam-Swift...)
1 eachine 5.8GHz Video Transmitter TX805S - $35 (https://usa.banggood.com/Eachine-TX80...)
1 eachine ROTG02 5.8GHz receiver w/ USB - $31 (https://www.banggood.com/Eachine-ROTG...)

Version 2 Camera System -
1 Raspberri Pi Zero 2 - $15 - (https://www.raspberrypi.com/products/...)
1 Raspberri Pi Camera 2 - $25 - (https://www.raspberrypi.com/products/...)