4.2 Coding

Program :

For programming the ESP8266 NodeMCU module, only the DHT11 sensor library is used as external library. The moisture sensor gives analog output which can be read through the ESP8266 NodeMCU analog pin A0. Since the NodeMCU cannot give output voltage greater than 3.3V from its GPIO so we are using a relay module to drive the 5V motor pump. Also the Moisture sensor and DHT11 sensor is powered from external 5V power supply.

Since we are using the ThingSpeak Server, the API Key is necessary in order to communicate with server.

Complete Code:

#include
#include
String apiKey = “X5AQ3EGIKMBYW31H”; // Enter your Write API key here
const char* server = “api.thingspeak.com”;
const char *ssid = “CircuitLoop”; // Enter your WiFi Name
const char *pass = “circuitdigest101”; // Enter your WiFi Password
#define DHTPIN D3 // GPIO Pin where the dht11 is connected
DHT dht(DHTPIN, DHT11);
WiFiClient client;
const int moisturePin = A0; // moisteure sensor pin
const int motorPin = D0;
unsigned long interval = 10000;
unsigned long previousMillis = 0;
unsigned long interval1 = 1000;
unsigned long previousMillis1 = 0;
float moisturePercentage; //moisture reading
float h; // humidity reading
float t; //temperature reading
void setup()
{
Serial.begin(115200);
delay(10);
pinMode(motorPin, OUTPUT);
digitalWrite(motorPin, LOW); // keep motor off initally
dht.begin();
Serial.println(“Connecting to “);
Serial.println(ssid);
WiFi.begin(ssid, pass);
while (WiFi.status() != WL_CONNECTED)
{ delay(500);
Serial.print(“.”); // print … till not connected
}
Serial.println(“”);
Serial.println(“WiFi connected”);
}
void loop()
{
unsigned long currentMillis = millis(); // grab current time
h = dht.readHumidity(); // read humiduty
t = dht.readTemperature(); // read temperature
if (isnan(h) || isnan(t))
{ Serial.println(“Failed to read from DHT sensor!”);
return;}
moisturePercentage = ( 100.00 – ( (analogRead(moisturePin) / 1023.00) * 100.00 ) );
if ((unsigned long)(currentMillis – previousMillis1) >= interval1) {
Serial.print(“Soil Moisture is = “);
Serial.print(moisturePercentage);
Serial.println(“%”);
previousMillis1 = millis();
}
if (moisturePercentage < 50) {
digitalWrite(motorPin, HIGH); } // tun on motor

if (moisturePercentage > 50 && moisturePercentage < 55) {
digitalWrite(motorPin, HIGH); } //turn on motor pump
if (moisturePercentage > 56) {
digitalWrite(motorPin, LOW); } // turn off mottor
if ((unsigned long)(currentMillis – previousMillis) >= interval) {
sendThingspeak(); //send data to thing speak
previousMillis = millis();
client.stop(); }
}
void sendThingspeak() {
if (client.connect(server, 80))
{
String postStr = apiKey; // add api key in the postStr string
postStr += “&field1=”;
postStr += String(moisturePercentage); // add mositure readin
postStr += “&field2=”;
postStr += String(t); // add tempr readin
postStr += “&field3=”;
postStr += String(h); // add humidity readin
postStr += “\r\n\r\n”;
client.print(“POST /update HTTP/1.1\n”);
client.print(“Host: api.thingspeak.com\n”);
client.print(“Connection: close\n”);
client.print(“X-THINGSPEAKAPIKEY: ” + apiKey + “\n”);
client.print(“Content-Type: application/x-www-form-urlencoded\n”);
client.print(“Content-Length: “);
client.print(postStr.length()); //send lenght of the string
client.print(“\n\n”);
client.print(postStr); // send complete string
Serial.print(“Moisture Percentage: “);
Serial.print(moisturePercentage);
Serial.print(“%. Temperature: “);
Serial.print(t);
Serial.print(” C, Humidity: “);
Serial.print(h);
Serial.println(“%. Sent to Thingspeak.”);
}
}

Demonstration :