Capacitive Soil Sensor Code Question

Projects Programming
1

I have the following capacitive soil sensor.

const int AirValue = 520;   //you need to replace this value with Value_1
const int WaterValue = 260;  //you need to replace this value with Value_2
int intervals = (AirValue - WaterValue)/3;   
int soilMoistureValue = 0;
void setup() {
  Serial.begin(9600); // open serial port, set the baud rate to 9600 bps
}
void loop() {
soilMoistureValue = analogRead(A0);  //put Sensor insert into soil
if(soilMoistureValue > WaterValue && soilMoistureValue < (WaterValue + intervals))
{
  Serial.println("Very Wet");
}
else if(soilMoistureValue > (WaterValue + intervals) && soilMoistureValue < (AirValue - intervals))
{
  Serial.println("Wet");
}
else if(soilMoistureValue < AirValue && soilMoistureValue > (AirValue - intervals))
{
  Serial.println("Dry");
}
delay(100);
}

Basically we need to calibrate the sensor by entering the dry and wet value, which is done by analogRead. Pardon my math, but I have trouble understanding the following

int intervals = (AirValue - WaterValue)/3;

Could someone explain the above equation. Why do we have to deduct, then divide by 3?

2

Because you're dividing the total range into 3 sub-ranges: "Very Wet", "Wet", Dry".

3

I figured it out, they are just basically dividing it into 3 segments, dry, wet and water. Each 1/3 is a value of 90. The confusion was they rounded off the value of "interval"(86) to 90 without mentioning it, and posted the results on their website. Now it makes sense.

4

gfvalvo thanks, I just realised. The problem is they rounded off results on their website, which confused me.