Simple Soil Dryness Detector Circuit

Important thing for plant growth and life is water for proper plant hydration we need to pour water regularly and when soil get dry. Here is the simple soil dryness detector circuit to help you to identify the dryness of water in your plant soil or where ever needed.




This circuit employs two NPN transistors as switch and a buzzer element to produce beep sound when there is no water on soil. we can use insulation removed copper wires as sensor here or you can use conducting material nail as a moisture detecting sensor.

Circuit Diagram

Components Require

  1. Battery 9V
  2. Regulator IC 7805
  3. Conducting Copper wire (or) nail
  4. Variable Resistor 100KΩ
  5. Resistors 1KΩ, 560Ω
  6. Transistor BC547 (NPN) = 2
  7. LED Red, Green each one
  8. Buzzer

Construction & Working

Start with the Soil moisture detector to construct this circuit, Here we have used two insulation removed copper wires as a detector you can use two nails also and you need to put those detectors in the soil up to your detection range. Don’t put copper wire or nails too near it may come to contact each other.

9V battery supply is regulated by the Regulator IC 7805 and applied to the two transistor switches and to the soil moisture detector setup (sensor). Another terminal from sensor is applied to the Q1 transistor base here you can vary the sensitivity level by using RV1. When there is moisture in the soil then Q1 becomes turn ON due to the positive supply flow through sensor to base, if the soil being dry then Q1 stays in turn OFF position and all bias through Q1 collector flows to Q2 Base terminal and Q2 gets turn ON and makes buzzer to produce beep sound. Here Green LED indicates enough moisture on the soil and Red LED indicates dryness on the soil.




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