Optical Soil Moisture Meter

A unique moisture meter that can play an integral part in Precision Agriculture and the infiltration of water in Civil Infrastructure.

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Traditionally, resistivity or capacitance are used to measure soil moisture. Open source moisture sensors that everyone uses with Arduinos are based on electrical resistance measurements. First, they are known to rust very fast. Second, conductivity in soils is very sensitive to ionic concentrations, or amount of salts for example. The goal of this project is to explore optical methods to measure moisture in soils, or can be used in concrete infrastructures, such as measuring stress on the infiltration of water on re-bar.

Traditionally the resistance and capacitance is used to measure the humidity in the soil. Open Source humidity sensors work with the Arduino micro controller. The soil conductivity is sensitive to ionic concentrations of salts, or the concentration of salts.

The Market for Precision Agriculture is expected to grow at 12.5% over the next 6 years, to a 4.5 billion dollar industry. Only 5% of Agricultural Professionals in the United States employ a moisture sensor. Professionals that employ moisture sensors enjoy a reduction of anywhere between 40%-70% of water usage due to irrigation activities. We protect our innovations it with Creative Commons, Share and Share alike, which prevents anyone from closing this innovation, we are able to maximize value by easily putting it to the hands of as many people as possible. With climate change, we are experience a rapid increase in meteorological volatility, where there is going to be a higher probability of droughts. Agricultural Professionals will need tools to help them employ limited fresh water resources, while reducing waste, and preserving this precious resource.

The Optical Soil Moisture Meter is the only, optical fiber sensor, besides Fiber Braggs that can be employed in the analysis of moisture content in soils. Our sensor is alot cheaper to produce, as we are just essentially scoring the cladding of a PMMA fiber, compared to scoring the interior of a glass fiber. Our fiber is Open Source and can be produced a lot cheaper, than the conventional Fiber Bragg. Anyone with a rudimentary knowledge of electronics can easily produce it

Here is the methodology in the preparation of the PMMA fiber.

This our first trial.

  • 1 × PMMA 1mm diameter optical fiber This is a polymer optical fiber
  • 1 × LED The light source. Any visible LED works.
  • 1 × Phototransistor This is the light detector
  • 1 × Arduino Nano Microcontroller used to control the LED and read the phototransistor
  • 1 × Optical connector (LED) Used to couple the LED to the PMMA optical fiber

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Bruce Merlo wrote 08/17/2015 at 20:39 point

This project is still in prototyping stage. 

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