The Water Regulator An automated soil sensor project by Karna Agrawal

The BeginningI am an avid gardener and manage my own vegetable garden. In a garden, one has to repeatedly water the plants manually which is time consuming and tedious. This process is dependent on estimates and experience. I was looking for a system that could automatically regulate the soil water content by correctly estimating the rate of water loss. In addition, it would also measure the pH and total dissolved solids (TDS) to check the fertility of the soil.

InternshipDuring my summer internship, I had modified a steel making machine to automatically measure lengths of steel bars. I realized that a similar approach could work in my garden also. I would have to change the measuring device but the rest of the process could be controlled similarly and automated.I already had drip irrigation installed in my garden. I needed to measure the water content and control water supply through controller and solenoid valves.

Stage 1 : ResearchFirst, I clearly visualized the product and its functions. The sensor should measure the amount of water that the soil needs, and automatically provide it to the soil, thus conserving manual labor. The sensor should also indicate the quality of soil through an indicator.My primary source of research was the Internet. I noticed that some rudimentary sensors were available but they weren’t automated, while those that were automated were expensive. I decided to start from square one.I discovered that the pH and TDS (Total Dissolved Solids) of soil was a good indicator of its quality, and thus a pH and TDS meter would be required.

Stage 1: ResearchI approached an agricultural engineer, Mr Naran Fuletra. He guided me through the science required to build the device and encouraged me through the entire process.I further learned that various factors contribute to determine the required level of water. The most important ones are evaporation rate, humidity, temperature, rain level and transpiration rate. Therefore, a sensor which measures these factors would be needed. The water-regulator I envision will consist of two parts: one which measures the water requirement (station) and one which regulates the water supply (water meter).

Necessary Equipment I decided I would need the following equipment to build the station:

Pan evapometer: Measures the evaporation rate.Tensiometer: Measures the transpiration rate.Temperature sensor: Measures the temperature in the soil.Rain Gauge: Measures the rainfall amount in a day.pH meter: Measures the pH of the soil.

 

Station Equipment

Stage 2: Making Of The Station

I procured the necessary sensors and meters and installed them in my garden.The garden was separated into two zones with different crops, aubergine and tomato.In this stage, I will be taking manual readings from the various sensors for a week every month and calculating the water requirement through an equation. I will record the readings in an Excel sheet.Equation: Water requirement= (.75*evaporation rate + transpiration rate – rain level)* Area

Stage 3: Regulating the Water Supply

I attached a controller and a water meter to the drip irrigation. These devices control valves in the water supply, and regulate the water as well. I plan to connect them to a router, so that they can be accessed online as well. Once I have the readings from the station, I can use it to regulate the water supply online, leading to partial automation. The next stage includes complete automation of the process.

Controller and Water Supply

Stage 4: Automation of Process

The regulator consists of two parts: the supply and the measurement. I will automate the supply through online access but will take the measurements from the meters manually.Next, I will work on automating the measurements from the meters and gauges. For example, the evapometer and rain gauge can be automated through a water level sensor. This will ensure that the complete process is automated and zero labor is required.Thereafter, I want to integrate all these soil measuring meters into a single device.