Soil Moisture Sensor YL-69 Hygrometer w/ HC-38 Module Board LM393

A soil moisture sensor can read the amount of moisture present in the soil surrounding it. It's a low tech sensor, but ideal for monitoring an urban garden, or your pet plant's water level. This is a must have tool for a connected garden! This sensor uses the two probes to pass current through the soil, and then it reads that resistance to get the moisture level. More water makes the soil conduct electricity more easily (less resistance), while dry soil conducts electricity poorly (more resistance).

It will be helpful to remind you to water your indoor plants or to monitor the soil moisture in your garden. The IO Expansion Shield is the perfect shield to connect this sensor to Arduino.

Soil moisture sensor uses Immersion Gold which protects the nickel from oxidation. Electroless nickel immersion gold (ENIG) has several advantages over more conventional (and cheaper) surface platings such as HASL (solder), including excellent surface planarity (particularly helpful for PCB's with large BGA packages), good oxidation resistance, and usability for untreated contact surfaces such as membrane switches and contact points.

Specification

• Operating voltage: DC 3.3V - 5V
• Output voltage signal: 0 ~ 4.2V
• Current: 35mA
• LED: Power indicator (Red) and Digital switching output indicator (Green)
• Size: 60 x 20 x 5mm

Pin definition:

• VCC external 3.3V-5V
• GND external GND
• DO digital output interface (0 and 1)
• AO analog output interface (0 ~ 4.2V)

Connect soil moisture with an Arduino

Upload the following code in your Arduino IDE and watch it in serial monitor.

Sample Code
/*
 # Example code for the moisture sensor
 # Connect the sensor to the A0 (Analog 0) pin on the Arduino board
 # the sensor value description
 # 0 ~300 dry soil
 # 300~700 humid soil
 # 700~950 in water
*/ 

void setup(){
 Serial.begin(57600);
}

void loop(){
 Serial.print("Moisture Sensor Value:");
 Serial.println(analogRead(0));
 delay(100);
}

Video Demonstration: