A True Soil Moisture Sensor: SHT20

June 28, 2019

1. Most so-called "Plant-Hydration-Kit" in the market

There're soooooo many companies designed kits called "Plant-Hydration-Kit", such as the https://www.smart-prototyping.com/Zio-Plant-Hydration-Kit-v1, but the most significant feature is that they all have a “soil moisture sensor” in their product/kit... Like this:

Or this:

But, I want to ask all these vendors, do you have used this kind of module really, to test the soil moisture sensors, while try to watering them?
What I have tested for this kind of "soil moisture sensor" is ugly bad……

1. The sensor output bad... The output data either high, or low, or unstable... For example, in the air, it can be 100, while a finger touches 500, while in dry soil 300, if a little water touched, 500. It changes a lot depends on how deep you dig it into the soil...

2. No water-poof… It is impossible that you can avoid some water touch them, and the whole board got useless, and even short the VCC to GND… Burn the whole system. This is a high risk even this “Plant-Hydration-Kit” a kit for Maker.

2. SHT20 Soil Temperature and humidity Sensor

So, in a real watering kit, an industry leaves soil moisture sensor is necessary. Which I suggest the SHT20 Soil Temperature/ humidity Sensor.

It’s output stable, and water-proof.

I tested the module with Maduino, with the library of SHT20. Connect it to Maduino with A4/A5, and the VCC/GND:

In the air, the output humidity and temperature really good:

And then insert it into the soil, in 10s, the output data get stable, and reliable, no matter how deep you dip it into the soil:

The output:

I try to put some water around the sensor, the output data changes Continuously, without any jumping… Which is reasonable.

The metal case also proofs waters in, which ensures the soil moisture sensor works OK with rain:

The soil moisture sensor works well in the rain…~ this makes the kit a really working smart plant watering kit…

A True Soil Moisture Sensor: SHT20