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It should be obvious that crops require water — usually a lot of it. But due to droughts or simple arid conditions, many farmers struggle to provide their crops with adequate water. To further exacerbate the problem, it isn’t always obvious when crops aren’t receiving sufficient water. Aerial thermal imagine surveys can provide valuable information on water stress, but they’re expensive and add to the climate change problem. That’s why Florian Ellsäßer developed this affordable, open source device to measure crop water stress.
Aerial surveys are able to provide information on the health of crops through thermal imaging. Infrared (IR) thermal cameras reveal physical indications of plant health that aren’t visible to the naked human eye. If a plant is receiving adequate water, evaporation cools its surfaces. If it isn’t, the plant’s surfaces become hot and that is perceivable with an IR thermal camera. Ellsäßer’s Crop Water Stress Sensor provides the same utility as an aerial survey, but in a localized area with inexpensive off-the-shelf components.
The device contains a small infrared camera mounted to the top of a mast. The camera points down at a portion of the crop and monitors the surface temperatures of the visible plants. Ellsäßer’s algorithm, which runs on an ESP32 development board, analyzes the thermal video feed and generates a corresponding crop water stress index (CWSI). The CWSI ranges from 0 to 1, with 1 indicating extreme water stress. The device displays the current CWSI and recent history on a GUI interface on a 3.2” 320x240 resolution TFT LCD screen. WS2812B individually addressable RGB LEDs act as additional status indicators and a real-time clock (RTC) keeps track of time for the data logging.
Because this device is meant for use in agricultural fields that don’t have power outlets and batteries are inconvenient for long term use, it receives power from a small solar panel. The components mount to a 3D-printable frame, which fits into an IP65-rated enclosure to protect the electronic components from the elements. Ellsäßer says that the current iteration of the device costs 168€ to 213€ to build (depending on the price one pays for the 3D-printed parts).
Ellsäßer already tested this prototype and it seems to be working well. His next step is to refine the design to make it practical and the most important new future will be LoRaWAN. That will let the device communicate over long distances with a central hub, so a farmer could check multiple Crop Water Stress Sensors at once without needing to walk from one to the next.
This project may not be as sexy as some of the others we feature here on Hackster, but it is has the potential to be very useful in the real world.