Feasibility: Arduino monitor moisture sensor to turn on/off 24v DC power supply?

Looking for thoughts on feasibility of using an Arduino and connecting a moisture sensor (similar in function to a thermistor where the resistance varies based on moisture content) that will activate a 24v AC power feed to a lawn sprinkler solenoid to supply water to a garden when moisture content is below target.

This sound like a feasible project for an Arduido board? Anyone know of similar projects I can reference? Also trying to find source for moisture sensor.

Any thoughts would be appreciated.



I think I found my answer: Arduino Project Hub: Arduino Soil Moisture Sensor Tutorial Sorry all... I should have searched project hub first.

I am developing exactly the same project right now using the Wemos D1 mini and a solar battery charger.
Jint- the sensor in the tutorial you found is crap. The probes oxidize quickly.

Instead, use a capacitive probe like this

SteveMann - Thanks for the info on both the alternate sensor and the Wemos D1 Mini. Will take a look at both.

This was the sensor I was considering: SparkFun Soil Moisture Sensor It looks similar to the one in the tutorial as well. High probability it’s crap too.

Keep me posted on your progress… I’d love to hear how it’s going.


The Sparkfun probe is crap. Any moisture probe with metal to soil contact will corrode and require frequent cleaning. The capacitive probe does not have any metal parts in contact with the soil.

A little piece of advice when you do use the resistive sensor (I agree the capacitive is much better!): don't leave it powered on. Power it up only for the time you measure, then switch it off again. The voltage applied to is will greatly accelerate the oxidation of the metal!

Na, let it powered and use copper electrodes - stainless steel is so boring. This would be a interesting experiment :slight_smile:

For sure your plant will end up in interesting colours! (probably blue)

Feasible yes but you need quality soil moisture sensors. Installation is critical.

You may also want to install 2 sensors (one lower than the other).