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Soil moisture fail

Home automationPosted by fredrik.wiberg8@gmail.com Mon, May 09, 2016 08:48:39
The soil moisture sensor I used for my Plant Monitoring was a huge fail. I used a cheap sensor from china that didn't seem to handle water so well!! The conductive foil has deteriated!
The new solution is a lot simpler. 2 wirer soldered to two nails.
Seem to work just fine.


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Posted by Steve Thu, May 18, 2017 01:26:17

Forgot to add, I use the nails approach, and they fail after a while for the same reason. Using the alternate polarity, cycled power approach makes for a longer lasting solution using the nails as well.

Posted by Steve Thu, May 18, 2017 01:24:38

The foil fails because of electrolysis, the chemical reaction facilitated by the flow of electrons between plates whilst measuring. There's a couple of ways around this. You can prolong the life by only powering the probe briefly while measuring and de-powering it in between. That has some effect. Additionally, power it in reverse direction each measure cycle - that is make the left pin positive for one measure then next alternate measure make the right pin positive. Advanced systems use a small alternating current rather than DC, but the method of reversing polarity each measure cycle makes a significant difference.