Capacitive sensor module

Capacitive moisture sensor module

This is the first project I'm publishing.   07/2025

It is a moisture sensor with a anologic output for arduino, other MCU with analog pin, logic circuit and more.

How to use :

There are 3 connectors, 2 for the probe (same connections) and 1 for alimentation and output

• 1 JST-XH 2.54mm - 2P -> To have a connection compatibility with the resistive probe
• 1 Terminal block 5.08mm - 2P -> For easily connection. If you don't have a probe with JST connector, you can also use 2 steel nails/screw about 5-10 cm
• 1 Terminal block 5.08mm - 3P -> GND-OUT-VCC

Specifications  :

• 3 to 15V (depend of yours capacitor)
• The maximum voltage of output is ≃ 1 V udder VCC when the probe is not used (dry). For exemple : VCC = 5 V -> OUT ≃ 4V
• If the ground is dry the voltage is high and if the ground is wet the voltage is low

Remarks

When I test the module, I noticed a delay about 60 sec of stabilisation when you put the probe in a wet ground, the voltage decrease like a exponential function. I had put a 750k for R3 instead of 1M like other schematics to have a quick reaction but this phenomenon is still present.

You can isolate the connector to avoid external interference.

This project is directly inspired from Capacitive soil moisture sensor V1.2. The detailed operation and schematic is here .

I'm not a native English speaker, be kind.