Agri IoT :: Prototype 2 : Overview & Sensor


With prototype 2 of Agri IoT, attempt is to proceed further by creating a sensor node that collects more types of data and last much longer on battery. Pro mini 3,3v 8Mhz is selected because of its small form, low power consumption and NRF24L01+ will work with it on 2 AA batteries. Mysensors v2.0 API is used to build and connect the blocks.  Prototype 2 sensor node setup is covered in this article, rest is in Agri IoT :: Prototype 2 : Gateway & Controller 

Prototype 1 is covered in below articles,

  1. Agri IoT :: Prototype 1 : Overview
  2. Agri IoT :: Prototype 1 : Sensor
  3. Agri IoT :: Prototype 1 : Gateway
  4. Agri IoT :: Prototype 1 : Controller

Objective ::

Sensor node should,

  • Be able to collect the soil moisture data, humidity, temperature and luminescence
  • Send the collected data via RF network to gateway.
  • Be battery operated.

Components ::

  • Arduino pro mini 3.3v 8Mhz
  • NRF24L01+
  • CP2102 USB to TTL Serial
  • Soil Moisture sensor
  • LDR
  • DHT11
  • 10K resistor
  • Copper enameled wire
  • Perforated PCB Board 3 x 2 Inches
  • 2 AA batteries

How to ::

Idea is to power each sensor in the node with one of the Arduino digital out, this would be a first step in the long journey to save power.  Sensors would be powered on data collected and powered off.




Quick and dirty pcb setup :

Multi Sensor node
Multi Sensor node


Connect the arduino via Mini usb cable. Make sure you select the right options as mentioned here

Upload the sketch to sensor node.

#define MY_DEBUG // enabling debug
#define MY_NODE_ID 1 // node id 
#define MY_RADIO_NRF24 // enabling support for NRF radio module
#define CHILD_ID_MOIST 1 // Moisture sensor id
#define CHILD_ID_LIGHT 2 // Light sensor id
#define CHILD_ID_TEMP 3 // Temp sensor id
#define CHILD_ID_HUM 4 // Humidity sensor id
#define MOIST_SENS 2
#define LIGHT_SENS 3
#define HUM_SENS 4
#define VAL_MOIST A0
#define VAL_LIGHT A1
#define DIGITAL_HUM 8
#include <MySensors.h>
#include <SPI.h>
#include <DHT.h>
#define DHTTYPE DHT11 

MyMessage msgMoist(CHILD_ID_MOIST, V_LEVEL); // constructing the msg
MyMessage msgHum(CHILD_ID_HUM, V_HUM);
MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);

void setup()

void presentation()
 present(CHILD_ID_MOIST, S_MOISTURE); // presenting the sensor 
 present(CHILD_ID_HUM, S_HUM); 
 present(CHILD_ID_TEMP, S_TEMP); 
 sendSketchInfo("SoilSensor", "0.1"); //meta data 

void loop()
 digitalWrite(MOIST_SENS, HIGH);
 int moisture = analogRead(VAL_MOIST); //measuring the moisture 
 digitalWrite(MOIST_SENS, LOW); 
 send(msgMoist.set(moisture)); // sending the data 

 digitalWrite(LIGHT_SENS, HIGH);
 int light = analogRead(VAL_LIGHT); //measuring the moisture 
 digitalWrite(LIGHT_SENS, LOW); 
 send(msgLux.set(light)); // sending the data 
 digitalWrite(HUM_SENS, HIGH); 
 delay(1000); // delay to get Humidity sensor ready to read data
 float humidity = dht.readHumidity(); //measuring the humidity 
 float temperature = dht.readTemperature(); //measuring the temperature 
 digitalWrite(HUM_SENS, LOW); 
 send(msgHum.set(humidity,1)); // sending the data 
 send(msgTemp.set(temperature,1)); // sending the data
 sleep(300000); // sleeping for 5 minutes

Testing & Troubleshooting::

Use Arduino IDE serial monitor and set the baud rate to 115200.  You can find sensor node related debug output there.

Reference ::

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