SoilMoistSensor.ino

/*
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <[email protected]>
 * Copyright (C) 2013-2019 Sensnology AB
 * Full contributor list: https://github.com/mysensors/MySensors/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * DESCRIPTION
 *
 * Arduino soil moisture based on gypsum sensor/resistive sensor to avoid electric catalyse in soil
 *  Required to interface the sensor: 2 * 4.7kOhm + 2 * 1N4148
 *
 * Gypsum sensor and calibration:
 *  DIY: See http://vanderleevineyard.com/1/category/vinduino/1.html
 *  Built: Davis / Watermark 200SS
 *      http://www.cooking-hacks.com/watermark-soil-moisture-sensor?_bksrc=item2item&_bkloc=product
 *      http://www.irrometer.com/pdf/supportmaterial/sensors/voltage-WM-chart.pdf
 *      cb (centibar) http://www.irrometer.com/basics.html
 *          0-10 Saturated Soil. Occurs for a day or two after irrigation
 *          10-20 Soil is adequately wet (except coarse sands which are drying out at this range)
 *          30-60 Usual range to irrigate or water (except heavy clay soils).
 *          60-100 Usual range to irrigate heavy clay soils
 *          100-200 Soil is becoming dangerously dry for maximum production. Proceed with caution.
 *
 * Connection:
 * D6, D7: alternative powering to avoid sensor degradation
 * A0, A1: alternative resistance measuring
 *
 *  Based on:
 *  "Vinduino" portable soil moisture sensor code V3.00
 *   Date December 31, 2012
 *   Reinier van der Lee and Theodore Kaskalis
 *   www.vanderleevineyard.com
 * Contributor: epierre
 */
 
// 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.
 
// Enable debug prints to serial monitor
#define MY_DEBUG
 
// Enable and select radio type attached
#define MY_RADIO_RF24
//#define MY_RADIO_NRF5_ESB
//#define MY_RADIO_RFM69
//#define MY_RADIO_RFM95
 
#include <math.h>       // Conversion equation from resistance to %
#include <MySensors.h>
 
// Setting up format for reading 3 soil sensors
#define NUM_READS (int)10    // Number of sensor reads for filtering
#define CHILD_ID 0
 
MyMessage msg(CHILD_ID, V_LEVEL);
uint32_t SLEEP_TIME = 30000; // Sleep time between reads (in milliseconds)
 
long buffer[NUM_READS];
int idx;
 
typedef struct {
    int moisture; 
    long resistance; 
} values;
 
const long knownResistor = 4700;  // 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 the digital pins as an output.
    // Pin 6,7 is for sensor 1
    // initialize the digital pin as an output.
    // Pin 6 is sense resistor voltage supply 1
    pinMode(6, OUTPUT);
 
    // initialize the digital pin as an output.
    // Pin 7 is sense resistor voltage supply 2
    pinMode(7, OUTPUT);
}
 
void presentation()
{
    sendSketchInfo("Soil Moisture Sensor Reverse Polarity", "1.0");
    present(CHILD_ID, S_MOISTURE);
}
 
void loop()
{
 
    measure(6,7,1);
    Serial.print ("\t");
    Serial.println (average());
    long read1 = average();
 
    measure(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 ();
 
    //send back the values
    send(msg.set((int32_t)ceil(sensor1)));
    // delay until next measurement (msec)
    sleep(SLEEP_TIME);
}
 
void measure (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) ;
 
        delay(1);
        addReading(resistance);
        Serial.print (resistance);
        Serial.print ("\t");
    }
}
 
 
 
// Averaging algorithm
void addReading(long resistance)
{
    buffer[idx] = resistance;
    idx++;
    if (idx >= NUM_READS) {
        idx = 0;
    }
}
 
long average()
{
    long sum = 0;
    for (int cnt = 0; cnt < NUM_READS; cnt++) {
        sum += buffer[cnt];
    }
    return (long)(sum / NUM_READS);
}