Leaf Wetness

Sparkman

@elisavetgrig As I mentioned a few posts ago and how it's shown in the diagram on that link, is that you only need one resistor. The leaf wetness sensor becomes the other resistor in the circuit. In your last diagram, you have both the terminals of the wetness sensor connected to ground. Think of the wetness sensor as a resistor, with each of the terminals representing one leg of a regular resistor.

Cheers
Al

elisavetgrig

OK... So I need only one resister... I think that "Scheme 2" is closer to the solution... images ofs.jpg

5546dug

@epierre how is the gold plating holding out on the sensor?
Is there pitting and would you'd recommend this over the style in the store?
How is the battery life with this setup?

Thanks

epierre

Hello,

gold plating is a must have for outdoor.

I am now regarding to have something more robust in time , I'm waiting for a light with movement with solar pannel to modify it for it.

AWI

In the case described there is a constant battery drain when there is "wetness" (moisture) on the sensor. This also implies an electrolytic process which takes care of eroding your sensor. No matter if you use gold plating or not.

To avoid both you can supply the sensor during measurement only -and- reverse te polarity each time.

An example ketch which takes care of measuring three moisture sensors which relies on this principle.

(the actual measurement is in the "ReadMoistureValues()" routine)

/*
 PROJECT: MySensors / Floor moisture sensor - measures moisture
 PROGRAMMER: AWI
 DATE: june 7, 2015/ last update: june 9, 2015
 FILE: AWI_FloorMoisture.ino
 LICENSE: Public domain

 Hardware: tbd .- ATmega328p board w/ NRF24l01
	and MySensors 1.4

	(later: Temp & Humidity - HTU21)
	
	
Special:
	program with Arduino Pro 3.3V 8Mhz
	
SUMMARY:
	Moisture by analog read a polarity switching voltage divider between (high/ low)
 Remarks:
	Fixed node-id
*/

#include <SPI.h>
#include <MySensor.h>
#include <Wire.h> 								// I2C

#define batteryVoltagePin A0
#define MoistureHighPin 3
#define MoistureLowPin 4
#define Moisture1ReadPin A1
#define Moisture2ReadPin A2
#define Moisture3ReadPin A3
#define BuzzerPin 5
#define LedPin 6

// MySensors Child ID's
#define MOISTURE1_CHILD_ID 5					// Moisture 1
#define MOISTURE2_CHILD_ID 6					// Moisture 2
#define MOISTURE3_CHILD_ID 7					// Moisture 3
// #define MOISTURE4_CHILD_ID 8					// Moisture 4

// MySensors messages 
MyMessage moisturePercentageMsg1(MOISTURE1_CHILD_ID, V_HUM);	// Percentage
MyMessage moisturePercentageMsg2(MOISTURE2_CHILD_ID, V_HUM);	// Percentage
MyMessage moisturePercentageMsg3(MOISTURE3_CHILD_ID, V_HUM);	// Percentage

// MySensors instantiate 
MySensor gw(9,10); 								// board, 3.3v (pin default 9,10)

// Reference values for ADC and Battery measurements
const float VccMin        = 1.0*3.5;    // Minimum expected Vcc level, in Volts. Example for 1 rechargeable lithium-ion.
const float VccMax        = 1.0*4.2;    // Maximum expected Vcc level, in Volts. 
float VccReference = 3.3 ;				// voltage reference for measurement (=vcc)
unsigned long SLEEP_TIME = 60000;  		//  10 sec sleep time between reads (seconds * 1000 milliseconds)

// **** class for Moisture measurement *****
// attaches an analog input to a data structure for measurements
// 			measures % of full scale voltage and scales the range of actual values
// 			stores current/ min & max values for the sensor
class MoistureSense
{
public:
	// Create an instance of MoistureSense and initialize (digital & input pin and reference values)
  MoistureSense(uint8_t ReadPin, int LowValue, int HighValue) ; 		// attach to pin and init
  void ReadHigh();								// Read moisture if positive
  void ReadLow();								// Read moisture with polarity inverted
  // average the low/ high readings ang get the moisture percent value
  uint8_t MoisturePercent();
  void ResetMinMax();							// reset min & max values

protected:
  uint8_t _ReadPin ; 							// Hardware Analog Pin number
  int _CurMoisture, _MaxMoisture, _MinMoisture, _Low, _High, _HighValue, _LowValue ;
  uint8_t _curState; 
  };

// to create an instance of MoistureSense and initialize (input pin and reference values)
MoistureSense::MoistureSense(uint8_t ReadPin, int LowValue, int HighValue) {		// attach to pins and init
	_ReadPin = ReadPin;
	_LowValue = LowValue;
	_HighValue = HighValue;
	_CurMoisture = _MaxMoisture = _MinMoisture = NULL ;	// min & max in percent
  }
void MoistureSense::ReadHigh()
 // Read moisture with high polarity (in relation to Gnd)
{
	_High = analogRead(_ReadPin);
}
void MoistureSense::ReadLow()
 // Read moisture with low polarity (in relation to Vcc)
{
	_Low = 1024 - analogRead(_ReadPin);
}
void MoistureSense::ResetMinMax()
 // Reset min & max values
{
	_MinMoisture = _MaxMoisture = _CurMoisture;
}
uint8_t MoistureSense::MoisturePercent()
// average the low/ high readings ang get the moisture percent value
{
	uint8_t reading = constrain(map((_Low + _High)/2, _LowValue, _HighValue, 0, 100),0,100);	// average map to the 0-100% range
	_MinMoisture = min(reading, _MinMoisture);	// set min and max values
	_MaxMoisture = max(reading, _MaxMoisture);
}

// Instantiate moisture sensor objects
MoistureSense Moisture1(Moisture1ReadPin, 0, 1024); 
MoistureSense Moisture2(Moisture2ReadPin, 0, 1024); 
MoistureSense Moisture3(Moisture3ReadPin, 0, 1024); 

void setup(){
  	// MySensors setup (baud 115200)
	gw.begin(NULL, 21);  // fixed node 21, (final: connected to repeater 3 (living))"
	// Send the sketch version information to the gateway and Controller
	gw.sendSketchInfo("AWI FloorMoisture 21", "1.0");
	gw.present(MOISTURE1_CHILD_ID, S_HUM);			// Present Moisture sensors as humidity
	gw.present(MOISTURE2_CHILD_ID, S_HUM);			// Present Moisture sensors as humidity
	gw.present(MOISTURE3_CHILD_ID, S_HUM);			// Present Moisture sensors as humidity

	Serial.print("AWI Moisture Started ");
	pinMode(BuzzerPin,OUTPUT);						// Setup intermittent buzzer & light
	pinMode(LedPin,OUTPUT);
}

void loop(){
//
	Serial.println("Moisture Percentages");
	ReadMoistureValues();
	gw.send(moisturePercentageMsg1.set(Moisture1.MoisturePercent())); // MySensors Send (V) 
	gw.send(moisturePercentageMsg2.set(Moisture2.MoisturePercent())); // MySensors Send (V) 
	gw.send(moisturePercentageMsg3.set(Moisture3.MoisturePercent())); // MySensors Send (V) 
	gw.sendBatteryLevel(batteryPercentage());
	// show local alarm if moisture > 20%
	if ((Moisture1.MoisturePercent()>20) || (Moisture2.MoisturePercent()>20) || 
		(Moisture3.MoisturePercent()>20) || (batteryPercentage() < 10))
	{
		MoistureAlarm();
	}
	gw.sleep(SLEEP_TIME);							// low power for sleep time
}

unsigned ReadMoistureValues()
// read all moisturevalues
{
	pinMode(MoistureLowPin, OUTPUT);				// first set all pins to measurement(non floating) mode
	pinMode(MoistureHighPin, OUTPUT);
	digitalWrite(MoistureLowPin, LOW); 				// Set polarity on voltage divider high and read the values
	digitalWrite(MoistureHighPin, HIGH); delayMicroseconds(100);
	Moisture1.ReadLow(); delayMicroseconds(100);
	Moisture2.ReadLow(); delayMicroseconds(100);
	Moisture3.ReadLow(); delayMicroseconds(100);
	digitalWrite(MoistureLowPin, HIGH);				// reverse polarity on voltage divider and read values
	digitalWrite(MoistureHighPin, LOW); delayMicroseconds(100);
	Moisture1.ReadHigh(); delayMicroseconds(100);
	Moisture2.ReadHigh(); delayMicroseconds(100);
	Moisture3.ReadHigh(); delayMicroseconds(100);
	pinMode(MoistureLowPin, INPUT);					// reset pins to floating, to avoid power leakage
	pinMode(MoistureHighPin, INPUT);
	Serial.print("Moist1: ");
	Serial.print(Moisture1.MoisturePercent());
	Serial.print(" , Moist2: ");
	Serial.print(Moisture2.MoisturePercent());
	Serial.print(" , Moist3: ");
	Serial.print(Moisture3.MoisturePercent());
	Serial.println();
 }

unsigned MoistureAlarm()
// If moisturelevel to high, sound & show local alarm
{
	digitalWrite(MoistureLowPin, HIGH);
	digitalWrite(MoistureHighPin, HIGH); 
	delay(100);										// sound & light for 100ms, uses a lot of power, so no no need for power down
	digitalWrite(MoistureLowPin, LOW);	
	digitalWrite(MoistureHighPin, LOW);
}

// get Battery Voltage & charge current
// assumes a balanced voltage divider on Battery and uses the Vcc as reference (3.3V in this case)
// Parameters:
// - VccMin = minimum battery voltage
// - VccMax = maximum battery voltage
// - VccReference = reference voltage for ADC
uint8_t batteryPercentage()
{
	float batteryVoltage = ((float)analogRead(batteryVoltagePin)* VccReference/1024) * 2;	// actual voltage is double
	Serial.print("Batt: ");
	Serial.print(batteryVoltage);
	Serial.print("V ; ");
	return(constrain(map(batteryVoltage, VccMin, VccMax, 0, 100),0,100));	// and map to the 0-100% range
}

hek

This is a great idea to get less erosion!

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 :

Leaf Wetness

15

11.7k

11.2k

113.1k