DIY - Arduino plant projects

Measuring soil humidity: Capacitive Soil Moisture Sensor

Capacitive Soil Moisture Sensor v1.2

This kind of soil moisture sensors are sold under the name of Capacitive Soil Moisture Sensor v1.2. They present free corrosion prove, and so, they are highly more durable and offer a longer service life. Also, they are really cheap (from 0.50$)

How capacitive moisture soil sensor work?
Capacitive Soil Moisture Sensor v.1.2 for Arduino watering plant projects.
Capacitive Soil Moisture Sensor v.12

Capacitive soil moisture sensors measure electrical conductivity of the soil using dielectric materials, and because of this design the prove is corrosion free comparing to the most common resistive soil humidity sensors covered on this post.

Durability, accuracy and reliability:

They certainly present larger durability, higher accuracy and reliability comparing to the first resistive moisture soil sensor that we’ve covered on the other post. But this design as it is presents some major flaws due to the limited waterproof protection of the pins and electronics of the sensor.


The exposed pins and connection of the head of the sensor are prone to corrosion and malfunctioning on wet environments, so they will not last for very long. Encapsulated solutions of this sensors may come to the retail market soon, meanwhile, resistive soil sensors with encapsulated solutions may offer better long-term capabilities.

Alternatives to direct soil moisture sensor monitoring

Alternative feasible options to soil moisture sensors on traditional soils use two concepts: air relative humidity nearby soil and soil weight. Reliable sensors of air relative humidity can be placed nearby soil and get an approximated measure of relative soil humidity, this will only work for certain cultives and specially on shallow pots, it may be a yet simple but powerful solution to not very water demanding plants like succulents.

Monitoring the weight of the soil or the plant pot as a measure of how many water is trapped within the soil may be on of the most simple solution for conventional watering systems. If we know how much the soil weight on dry state making a few test we can build a weight scale from dry soil to flooded soil, and so, we can know exactly when it is time for watering and the state of the soil.

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