A. Description
 

1  This is simple moisture sensor to be used to detect moisture of soil. When the soil is lacking water, the sensor will output high voltage, else it will low voltage. Now you can build an automatic watering system for your garden. 
2 Adjustable Sensitivity （Please refer to the photo, the blue color screw）
3 Working voltage 3.3V-5V
4 Dual output, easy calculation digital and analog output for high accuracy。
5 With screw holes for easy installation
6 Small PCB size：3cm * 1.6cm
7 Power indicator（red）and digital output indicator（green）
8 More stable compare to LM393 IC

B Interfacing description（4 wires）
1 VCC  Connect to 3.3V-5V
2 GND  Connect to GND
3 DO   Digital Output（0 and 1）
4 AO   Analog Output 

C How to Use?

1. Soil moisture module is most sensitive to the ambient humidity is generally used to detect the moisture content of the soil
2. Modules in the soil moisture to reach the threshold value is set, the the DO port output high, when the soil humidity exceeds the threshold value is set, the module D0 output goes low.
3. The small board digital output D0 can be connected directly with the microcontroller microcontroller to detect high and low, to detect soil moisture;
4. Small board digital output DO  can directly drive  relay module or the buzzer module, which can form a soil moisture alarm equipment;
5. Small board analog output AO and AD module connected through the AD converter, you can get more accurate values ​​of soil moisture;

What are included?

As shown soil moisture detection module 

1. the testing board and
2. the soil moisture probe sensor
3. 20cm 5 digital cables