soil_moisture.c

soil_moisture.c

#define voltageFlipPin1 6
#define voltageFlipPin2 7
#define voltageFlipPin3 4
#define voltageFlipPin4 5
#define sensorPin A1
#define SENSOR_PIN_SOIL_VIN A2
#define SENSOR_PIN_TEMP A0
#define NUM_READS 10

int flipTimer = 500;
int Vin = 5;
float R1 = 4700;
float R2 = 0;
float buffer = 0;
float Vout = 0;

void setup() {
  Serial.begin(9600);
  pinMode(voltageFlipPin1, OUTPUT);
  pinMode(voltageFlipPin2, OUTPUT);
  pinMode(voltageFlipPin3, OUTPUT);
  pinMode(voltageFlipPin4, OUTPUT);
  pinMode(sensorPin, INPUT);
  pinMode(SENSOR_PIN_SOIL_VIN, INPUT);
  pinMode(SENSOR_PIN_TEMP, INPUT);
  delay(200);
}


void setSensorPolarity(boolean flip) {
  if (flip) {
    digitalWrite(voltageFlipPin1, HIGH);
    digitalWrite(voltageFlipPin2, LOW);
  } else {
    digitalWrite(voltageFlipPin1, LOW);
    digitalWrite(voltageFlipPin2, HIGH);
  }
}

void setSoilSensorOff() {
    digitalWrite(voltageFlipPin1, LOW);
    digitalWrite(voltageFlipPin2, LOW);
}

void setSensorPolarityTemp(boolean flip) {
  if (flip) {
    digitalWrite(voltageFlipPin3, HIGH);
    digitalWrite(voltageFlipPin4, LOW);
  } else {
    digitalWrite(voltageFlipPin3, LOW);
    digitalWrite(voltageFlipPin4, HIGH);
  }
}


void loop() {

  //

  delay(1000);
  int sum = 0;
  int val1 = 0;
  float avg = 0.0;

  int vin = 0;
  int sum_vin = 0;
  float avg_vin = 0.0;
  
  float vout = 0.0;

  bool flip = true; 
  // Soil measurements with a Watermark 200SS
  // With a 10000ohm resistor totally saturated reads at 1.23V
  // Note there is about a 1.8% variation in the reading per degree C (or 1% for 1F - http://www.irrometer.com/faq.html#reads0)
  setSensorPolarity(flip);
  // We need about 500ms as warm up for the sensor with voltage applied
  delay(500);
  for (int i = 0; i < NUM_READS; i++) {
    val1 = analogRead(sensorPin);
    Serial.print(val1);
    Serial.print(", ");
    sum += val1;

    vin = analogRead(SENSOR_PIN_SOIL_VIN);
    sum_vin += vin;
    
    if (flip) {
      flip = false;
    } else {
      flip = true;
    }
    setSensorPolarity(flip);
    delay(500);
  }
  /*
  setSensorPolarity(false);
  // We need about 500ms as warm up for the sensor with voltage applied
  delay(500);
  for (int i = 0; i < NUM_READS; i++) {
    val1 = analogRead(sensorPin);
    Serial.print(val1);
    Serial.print(", ");
    vin = analogRead(SENSOR_PIN_SOIL_VIN);
    sum += val1;
    sum_vin += vin;
    delay(50);
  }
  */
  setSoilSensorOff();
  
  avg = sum / (NUM_READS);

  Serial.println();
  Serial.print("Soil Moisture: ");
  Serial.print(avg);
  avg_vin = (sum_vin / NUM_READS) * (5.0 / 1023);
  Serial.print(" , avg_vin: ");
  Serial.print(avg_vin);
  // TODO fix the avg_vin reading
  vout = (4.99 / 1023) * avg;
  Serial.print(" , vout: ");
  Serial.print(vout);
  // TODO this needs to be adjusted for temp
  vout = mapfloat(vout, 0, 2.6, 0, 100);
  Serial.print(" , moisture (%): ");
  Serial.print(vout);

  // Temp measurements using a Davis IC6470 resistive temp sensor
  // Calibrated against a certified thermometer
  // 87C water 1V
  // Frozen water 0.8C 4.25v
  // TODO from spec resistance 10-20C is 19.8kohm to 12.5Kohm so prob should use a 15kohm resistor, currently 4.7kohm
  sum = 0;
  setSensorPolarityTemp(true);
  // We need about 500ms as warm up for the sensor with voltage applied
  delay(500);
  Serial.println();
  Serial.print("Temp: ");
  for (int i = 0; i < NUM_READS; i++) {
    val1 = analogRead(SENSOR_PIN_TEMP);
    sum += val1;
    delay(10);
  }
  setSensorPolarityTemp(false);
  avg = sum / NUM_READS;
  Serial.print(avg);
  // TODO fix the avg_vin reading
  vout = (4.98 / 1023) * avg;
  Serial.print(" , vout: ");
  Serial.print(vout);
  // Get a temp reading in Celcius
  float temp = 0.0;
  temp = mapfloat(vout, 1.0, 4.25, 87, 0.8);
  Serial.print(" , temp (C): ");
  Serial.print(temp);

  Serial.println();
  delay(1000);
}


float mapfloat(float x, float in_min, float in_max, float out_min, float out_max)
{
 return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}