I've been trying to find a decent probe for detecting the "dryness" of a soil sample. Testing different probes in different soils, the best I have come up with is slim piece of wood sandwiched between a pair of aluminum plates, courtesy of a coke can. Long term, wood has issues, but it absorbs the moisture and registers a consistent resistance change. Pure metal based probes are hit and miss. Loose soils sometimes don't even register. Wood rots, metals corrodes, sponges and foams didn't work (at least the ones I tried), and even good old red pottery didn't work well (with the coke can sandwich. surprised a bit about that one). A bit curious if anyone has gone down a similar path.

Basic project was an on demand hydroponic watering system. Design works, but the piece of wood thing seems short term (or perhaps genius, like HP print cartridges .

Thanks,

Paul

 

well, you still didn't try capacitive approach

 

well, you still didn't try capacitive approach...

...and therein lies your solution...

 

Looks a bit more complicated, but would be an excuse to use one of my digisparks.

Paul