Volumetric measurement controlling irrigation

Discussion in 'Sensors & Remote Controls' started by top_gun_de, Jan 17, 2020.

  1. top_gun_de

    top_gun_de LawnSite Member
    from Germany
    Messages: 28


    I know most people prefer a fixed schedule plus a rain sensor. Still, from a gardening perspective it's best to wait just before the wilting pint and then refill up to capacity.

    i just finished my winter project: A volumetric soil moisture sensor with electronics that allow me to monitor the soil moisture via smartphone and also automatically control my irrigation clock.

    The sensor is a commercial Truebner SMT50 sensor that measures volumetric water content in a volume of about 0.25 gallons of soil together with soil temperature. Keep in mind: Volumetric water content is not saturation. 100% volumetric water is imside a swimming pool. A saturates sandy soil is around 15-18% volumetric water content, and the wilting point is around 4-5%.

    The sensor gets buried in the root zone, it is strapped to a small computer that gathers data and sends the data to a house automation server via wi-fi. Moisture data is sent to the server every hour, this should allow the sender to work on just 1 set of batteries per season. Watching moisture data in real-time is pointless. It would be like watching paint dry.

    The house server controls a relay that is connected to the sensor input of a regular irrigation clock. In spring, it will meet my Hunter PHC-1200 that will handle it like a regular Hunter soil-clik.



    Sensor open:


    Sensor closed: (It comes with 30ft of wire, so there is a lot of flexibility to mount the sender)


    This is what I see on my phone:


    One week of moisture and temperature data. It's winter in nothern Germany, almost no evapotranspiration). The temperature is in °Centigrade.


    This is the simple code on the server that locks/unlocks the Hydrawise controller based on koisture data. It runs each morning at 3:30am, the PHC-1200 is scheduled for 4:00am.


    And the relay that is connected to the PHC sensor input.


    The relay has four seperate channels, it can also switch the well pump and switch a fertigation pump, but that's an idea for the coming years. Shelly makes a very small 1-ch model that would even fit into the housing of a Hunter Pro-HC.

    This is nerd stuff: programming the sender, a ESP8266 microcomputer.


    Thisis what I see in the Hydrawise dashboard:


    the code for the sender and for the house automation server is available freely for anybody who is interested:


    i know this is no screw-in solution that an irrigation technician deploys in a few minutes, but it's smarter than a soil-clik.
    Last edited: Jan 17, 2020
    Crazy 4 grass likes this.

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