Plant Moisture Meter by IC 741

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Stick the metal probes into a freshly watered plant and adjust R5 for a mid-scale meter deflection. The meter will monitor the soil wetness and the meter will indicate whether it is to moist or to dry. This circuit uses a dual power supply which could be created by two 9 volt batteries.

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Source : http://home.maine.rr.com/randylinscott/nov20.htm

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