Moisture Module


Can this Moisture Module SMSTR-GM-326 be used to monitor soil humidity on big farms so it can automatically activate water irrigators ?

I mean, it will be buried on the ground and connected to a data reader. Does it support heavy environments like this ?

I think i’ll need some plastic casing to protect it , leaving only the terminals outside. Does GHI sell this casing ?

Any recommendations ?


We do not sell plastic but we do have consulting services and can customize our circuits to fit in any plastic enclosure of your choice.

What is great about Gadgeteer is that it is very low cost to try out and prototype and from there we (or you) can customize a solution to fit your exact needs.

Welcome to the community.

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@ brunoaduarte - This module will work to suite your needs, however, there are a few factors you need to account for, and make any adjustments needed to collected data. Certain soil conditions such as pH level, mineral impurities as well as nutrient solutions can alter the moisture reading with any module of this design. Even a heavy rain that flushes the soil can cause a reduction in conductivity causing low or even dry readings.

For full production you may benefit from Gypsum sensors, Time domain transmission or even heat dissipation sensors.

See this link: Soil moisture sensor - Wikipedia

I’ve used a number of the moisture models and while they do work great, they measure resistance and as mentioned there are a ton of factors which can influence resistance (such as over fertilizing, oooops). They will corrode after time (this one was in constant service for six months), but certainly they are an excellent starting point and if you or anyone else comes across other suitable moisture models or related sensors I’d love to hear about them.

I haven’t personally tried this yet, but it is something that looks very promising.

I don’t know how the sensor module works, but I suspect that it’s simply two copper pads, and they’re powering one side and have the other side connected to the A/D converter. If so, this isn’t an optimal design, because having the current travel in one way will cause the corrosion you’re seeing.

There is a better way, see this answer to an electronics stackexchange question:

@ goefroi. According the blurb on this page it is not susceptible to corrosion.

I might give one of these a try as my low cost Seeed unit is already badly corroded and I need something that can be left in the plants all the time.

Sure, that looks like an ideal solution. I was only speculating that it might not need to be much more complex than a couple bits of nichrome wire and a few resistors…

BTW, Vegetronix is a local company here. I’d heard of them before, but I have no experience with their products.

@ godefroi you have my attention. @ Dave McLaughlin I thinking I might have to get one as well to test it out. Soil sensors as well as water sensors are always an interest.

The only issue is that it is quoting me $42 for shipping. More than the cost of the sensor itself. :frowning:

$30 to ship it here. Perhaps need to see if its available somewhere closer with cheaper shipping.