For those of you out there applying your circuitry skills for gardening and yo need a bunch of moisture-sensing soil sensors, you might want to try making your own moisture-sensing soil sensors from nails, and plaster of Paris.
According to the author, this is how the soil sensor works:
As water is added to the problem more electrons can pass between the probes effectively reducing the amount of resistance between the problem to the point when it is fully saturated where the probe has virtually zero resistance. By using this range of values you can determine the amount of water than exists in your soil.
Rather fantastic isn’t it? I think this certainly can be applied to many hydroponics applications too.
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