Soil Moisture Sensor

Monday, November 1, 2010 by darco
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This is an experimental capacitive soil moisture sensor I am working on. Just thought I would share.

MoistureSensor_CloseUp

OldMoistureSensor_Schematic

MoistureSensor

These images are actually a little old, but I don't feel like making new ones. The new revision uses a slightly different mechanism for measuring capacitance that should be more accurate.

I'm using capacitance to measure the moisture instead of resistance because it allows me to void having any metal directly touch the soil. Resistive moisture sensors are not practical for semi-permanent use due to electrode corrosion. This moisture sensor should work indefinitely with no corrosion.

Assuming it will work at all, that is. We shall see.

I plan to have several of these daisy-chained around my yard. At the end of the chain will be a solar-powered wireless micro-controller unit which will allow me to read any of the sensors from the wireless home automation network I'm building. The goal is to use the moisture information to help the irrigation system know when it should water less than it normally would.

My hobby is complicated.