Leaf Wetness

[epierre]

@AWI your sketch has 3 sensors ? do you use a special wiring or you just get through high and low ?

The sketch on soil humidity does this but with two pins to make kind of AC current, but it needs also some gypsum to protect the electrodes.

. Leaf wetness is not immersed by nature hopefully ;-)

[AWI]

@epierre It has 3 sensors with copper wiring. It switches the polarity of the voltage divider (1 Mohm in series with the "sensor") and measures the voltage over the sensor. Actualy it is a moisture alarm for a sensitive wooden floor.

and I learned something today :smirk:
"Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O"

[epierre]

@AWI You can call it also "Plaster of Paris" ;-)

When immersed you need to protect it whatever you do : http://vanderleevineyard.com/1/category/vinduino/1.html

[epierre]

@awi going back to you above sketch, what is your wiring ?

#define MoistureHighPin 3
#define MoistureLowPin 4
#define Moisture1ReadPin A1
#define Moisture2ReadPin A2
#define Moisture3ReadPin A3

[epierre]

Hello,

I guess it is the same as Vinduino :

with their test code:

// This program tests 3 soil sensor inputs and prints bias caused by galvanic effects
// Copyright (C) 2015, Reinier van der Lee
// www.vanderleevineyard.com


// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

#include <math.h>       // Conversion equation from resistance to %


// Setting up format for reading 3 soil sensors
#define NUM_READS 10    // Number of sensor reads for filtering
long buffer[NUM_READS];
int index;

typedef struct {        // Structure to be used in percentage and resistance values matrix to be filtered (have to be in pairs)
  int moisture;
  long resistance;
} values;


const long knownResistor = 1500;  // Constant value of known resistor in Ohms

int supplyVoltage;                // Measured supply voltage
int sensorVoltage;                // Measured sensor voltage

values valueOf[NUM_READS];        // Calculated moisture percentages and resistances to be sorted and filtered


int i;                            // Simple index variable


void setup() {
  // initialize serial communications at 9600 bps:
  Serial.begin(115200); 
    

  // initialize the digital pins as an output.
  // Pin 6,7 is for sensor 1
  pinMode(6, OUTPUT);    
  pinMode(7, OUTPUT); 
 
  
}

void loop() {
  
 

measure(1,6,7,1);
Serial.print ("\t");
Serial.println (average());
long read1 = average();

measure(1,7,6,0);
Serial.print ("\t");
Serial.println (average());
long read2= average();

long sensor1 = (read1 + read2)/2;

Serial.print ("resistance bias =" );
Serial.println (read1-read2);
Serial.print ("sensor bias compensated value = ");
Serial.println (sensor1);
Serial.println ();

 delay (3000);

}

void measure (int sensor, int phase_b, int phase_a, int analog_input)
{
 
  // read sensor, filter, and calculate resistance value
  // Noise filter: median filter

  for (i=0; i<NUM_READS; i++) {

    // Read 1 pair of voltage values
    digitalWrite(phase_a, HIGH);                 // set the voltage supply on
    delayMicroseconds(25);
    supplyVoltage = analogRead(analog_input);   // read the supply voltage
    delayMicroseconds(25);
    digitalWrite(phase_a, LOW);                  // set the voltage supply off 
    delay(1);
     
    digitalWrite(phase_b, HIGH);                 // set the voltage supply on
    delayMicroseconds(25);
    sensorVoltage = analogRead(analog_input);   // read the sensor voltage
    delayMicroseconds(25);
    digitalWrite(phase_b, LOW);                  // set the voltage supply off 

    // Calculate resistance
    // the 0.5 add-term is used to round to the nearest integer
    // Tip: no need to transform 0-1023 voltage value to 0-5 range, due to following fraction
    long resistance = (knownResistor * (supplyVoltage - sensorVoltage ) / sensorVoltage)-457 ;
    
    delay(1); 
    addReading(resistance);
    Serial.print (resistance); 
    Serial.print ("\t");
  }
  }
  


// Averaging algorithm
void addReading(long resistance){
  buffer[index] = resistance;
  index++;
  if (index >= NUM_READS) index = 0;
}

long average(){
  long sum = 0;
  for (int i = 0; i < NUM_READS; i++){
    sum += buffer[i];
  }
  return (long)(sum / NUM_READS);
}

and my hall of fame and shame of sensors I've tried :