AgriSensor : Arduino-Based Sensor for Agriculture

Hardware Requirement

• Arduino Nano
• Soil Humidity Moisture Detection Sensor
• DHT11/DHT21/DHT22 etc. Temperature & Humidity sensors
• Photocell

Arduino sketch

// Hardware requirement
// Soil http://dx.com/p/soil-humidity-moisture-detection-sensor-module-blue-black-white-200142
// DHT http://dx.com/p/arduino-digital-temperature-humidity-sensor-module-121350
// Photocell https://www.sparkfun.com/products/9088

#include "DHT.h"

int SOIL_DIGITAL_PIN=2;
int SOIL_ANALOG_PIN=A0;  

int LIGHT_ANALOG_PIN=A1;

int DHT_PIN=4;

#define DHT_TYPE DHT11   // DHT 11 
//#define DHT_TYPE DHT22   // DHT 22  (AM2302)
//#define DHT_TYPE DHT21   // DHT 21 (AM2301)

// Connect middle pin of the sensor breadout to +5V
// Connect pin S of the sensor to whatever your DHTPIN is
// Connect pin - (on the right) of the sensor to GROUND

DHT dht(DHT_PIN, DHT_TYPE);

void setup() {
  Serial.begin(9600);
 
  pinMode(SOIL_DIGITAL_PIN, INPUT);
 
  dht.begin();
}

void loop() {

    Serial.print("/soil/humidity ");
    Serial.print(map(analogRead(SOIL_ANALOG_PIN),200,1023,100,0));
//    Serial.print("/soil/alert ");
//    Serial.println(digitalRead(SOIL_DIGITAL_PIN));
    Serial.println();

  delay(1000);

  int lightSensorValue = analogRead(LIGHT_ANALOG_PIN);
  Serial.print("/light/intensity ");
  Serial.print(map(lightSensorValue,0,1023,10,0));
  Serial.println();

  delay(1000);

  float humidity = dht.readHumidity();
  float temperature = dht.readTemperature();

  // check if returns are valid, if they are NaN (not a number) then something went wrong!
  if (isnan(humidity) || isnan(temperature)) {
    Serial.println("/error DHT");
  } else {
    Serial.print("/air/humidity ");
    Serial.print(humidity);
    Serial.println();
    Serial.print("/air/temperature ");
    Serial.print(temperature);
    Serial.println();
    Serial.print("/air/dewpoint ");
    Serial.print(dewPoint(temperature, humidity));
    Serial.println();
  }
  
  delay(1000); 
}


// from http://arduino-info.wikispaces.com/DHT11-Humidity-TempSensor


/*-----( Declare User-written Functions )-----*/
//
//Celsius to Fahrenheit conversion
double Fahrenheit(double celsius)
{
        return 1.8 * celsius + 32;
}

//Celsius to Kelvin conversion
double Kelvin(double celsius)
{
        return celsius + 273.15;
}

// dewPoint function NOAA
// reference: http://wahiduddin.net/calc/density_algorithms.htm 
double dewPoint(double celsius, double humidity)
{
        double A0= 373.15/(273.15 + celsius);
        double SUM = -7.90298 * (A0-1);
        SUM += 5.02808 * log10(A0);
        SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
        SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
        SUM += log10(1013.246);
        double VP = pow(10, SUM-3) * humidity;
        double T = log(VP/0.61078);   // temp var
        return (241.88 * T) / (17.558-T);
}

// delta max = 0.6544 wrt dewPoint()
// 5x faster than dewPoint()
// reference: http://en.wikipedia.org/wiki/Dew_point
double dewPointFast(double celsius, double humidity)
{
        double a = 17.271;
        double b = 237.7;
        double temp = (a * celsius) / (b + celsius) + log(humidity/100);
        double Td = (b * temp) / (a - temp);
        return Td;
}

Python script on host

BROKER=test.mosquitto.org
python agrisensor.py $BROKER

            
#!/usr/bin/python
#
# simple app to read topic and value strings from serial port (arduino board)
# and publish via MQTT
#
# uses the Python MQTT client from the Mosquitto project
# http://mosquitto.org
#
# Didier Donsez, 2013
# initially from Andy Piper http://andypiper.co.uk
# 2011/09/15

import serial
import mosquitto
import os
import sys

broker=sys.argv[1]
#broker = "10.0.1.3"
#broker = "test.mosquitto.org"
port = 1883

# serialdev = '/dev/ttyACM0'
serialdev = '/dev/tty.usbserial-A400DNT0'

topicPrefix="sensor/123456789"

#MQTT callbacks

def on_connect(mosq, obj, rc):
    if rc == 0:
        print("Connected successfully.")
    else:
        raise Exception


def on_disconnect(mosq, obj, rc):
    print("Disconnected successfully.")


def on_publish(mosq, obj, mid):
    print("Message "+str(mid)+" published.")


def on_subscribe(mosq, obj, mid, qos_list):
    print("Subscribe with mid "+str(mid)+" received.")


def on_unsubscribe(mosq, obj, mid):
    print("Unsubscribe with mid "+str(mid)+" received.")


def on_message(mosq, obj, msg):
    print("Message received on topic "+msg.topic+" with QoS "+str(msg.qos)+" and payload "+msg.payload)


#called on exit
#close serial, disconnect MQTT
def cleanup():
    print "Ending and cleaning up"
    ser.close()
    mqttc.disconnect()

try:
    print "Connecting... ", serialdev
    #connect to serial port
    ser = serial.Serial(serialdev, 9600, timeout=20)
except:
    print "Failed to connect serial"
    #unable to continue with no serial input
    raise SystemExit


try:
    ser.flushInput()
    #create an mqtt client
    mypid = os.getpid()
    client_uniq = "arduino_pub_"+str(mypid)
    mqttc = mosquitto.Mosquitto(client_uniq)

    #attach MQTT callbacks
    mqttc.on_connect = on_connect
    mqttc.on_disconnect = on_disconnect
    mqttc.on_publish = on_publish
    mqttc.on_subscribe = on_subscribe
    mqttc.on_unsubscribe = on_unsubscribe
    #mqttc.on_message = on_message

    #connect to broker
    mqttc.connect(broker, port, 60)

    #remain connected to broker
    #read data from serial and publish
    while mqttc.loop() == 0:
        line = ser.readline()
        #split line as it contains topic and value
        list = line.split(" ")
        #second list element is value

        topic = list[0].rstrip()
        if topic.startswith('/'):        
            value = list[1].rstrip()
            print(topic + " is " + value)
            mqttc.publish(topicPrefix + topic, value)
            
        pass


# handle list index error (i.e. assume no data received)
except (IndexError):
    print "No data received within serial timeout period"
    cleanup()
# handle app closure
except (KeyboardInterrupt):
    print "Interrupt received"
    cleanup()
except (RuntimeError):
    print "uh-oh! time to die"
    cleanup()