Project42.Soil Moisture Sensor
==============================

Description
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The soil moisture sensor or the hygrometer is usually used to detect the humidity 
of the soil. So, it is perfect to build an automatic watering system or to monitor 
the soil moisture of your plants.

The sensor is set up by two pieces: the electronic board (at the right), and the 
probe with two pads, that detects the water content (at the left).

The sensor has a built-in potentiometer for sensitivity adjustment of the digital 
output (D0), a power LED and a digital output LED, as you can see in the following 
figure.

Specification
--------------


Connect
--------
.. image:: /img/connect/42_bb.png

Code
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.. code-block:: c

    int rainPin = A0;
    int ledPin = 13;

    // you can adjust the threshold value
    int thresholdValue = 800;

    void setup(){
    pinMode(rainPin, INPUT);
    pinMode(ledPin, OUTPUT);  // Set the LED pin as the output mode
    Serial.begin(9600);
    }

    void loop() {
    // read the input on analog pin 0:
    int sensorValue = analogRead(rainPin);
    Serial.print(sensorValue);

    if(sensorValue < thresholdValue){
        Serial.println(" - Doesn't need watering");
        digitalWrite(ledPin, LOW);  // If you don't need to water, turn off the LED
    } else {
        Serial.println(" - Time to water your plant");
        // If you need to water, flash the LED quickly
        for(int i = 0; i < 5; i++){
        digitalWrite(ledPin, HIGH); 
        delay(100);                 
        digitalWrite(ledPin, LOW);   
        delay(100);                 
        }
        digitalWrite(ledPin, LOW);
    }
    delay(500);  //
    }

Whenever the soil is short of water, the LED on the Arduino will flash five times
continuously, and it will output "Time to water your plant" in the serial monitor.

If there is no shortage of water, the LED will not light up


Phenomenon
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.. image:: /img/phenomenon/42.jpg