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Long moisture sensors for irrigation

Posted: Thu Jan 03, 2019 3:01 pm
by oldjake
Hi all

For my next project, I want to set up an irrigation system for some large-ish planters that my other half has ordered. Each planter is about 1.5m long, 45cm wide and 35cm deep. I've seen lots of tiny little sensors about 6cm long that look like they're aimed at pots but `I don't think this will be any good for these planters as the top will dry out quicker than the bottom and it's likely to over water them.

Does anyone have any recommendations for sensors that could be used in this sort of container?

I guess the alternative would be to bury them deep in the soil but I'm not sure that would be a good idea unless the electronics is protected.

Re: Long moisture sensors for irrigation

Posted: Thu Jan 03, 2019 4:09 pm
by PhatFil
with a lot of flux its possible to solder capillary ss tube to the prongs of the basic arduino style soil moisture sensor which can both extend the depth that they can sense but also resist the inevitable corrosion that will be hastened by sticking an anode and cathode in a salt solution.

these sensors will have a limited life.. there are alternative sensors which use capacitance to detect the volume of moisture in the surrounding soil, as these do not rely on conductivity you can sleeve then and pot the electric components/contacts and bury as deep as you like..

iirc there is a product available via Tindie called the 'chirp' that uses spi or i2c for coms?? ... re-sensor/ add some nail varnish and some heatshrink and you could waterproof the pcb for deeper depths imho.

Another example of this type of sensor used with a pi..(not one to bury tho..)

Re: Long moisture sensors for irrigation

Posted: Thu Jan 03, 2019 10:13 pm
by oldjake
Thank you for that very in-depth reply! I'll have a good read and hopefully have something to keep me busy. I've just finished my latest project (ambient lighting for the TV) and need something to get my teeth into.