Here is the code for the irrigation controller with only one pump:
/*
* This is a sketch for turning on a water pump
* when a dryness threshold is met. It uses serial
* communication with a sensor station to check to see
* what the current humidity level is. It then turns on
* a pump to water the plants.
*/
int rxLed = 13;
int redLed = 3;
int pumpPin = 8;
int inByte = -1;
char inString[6];
int stringPos = 0;
void setup() {
Serial.begin(9600);
pinMode(redLed, OUTPUT);
pinMode(pumpPin, OUTPUT);
pinMode(rxLed, OUTPUT);
}
void loop() {
if (Serial.available()) {
// turn on RX LED whenever reading data
digitalWrite(rxLed, HIGH);
handleSerial();
}
else {
// turn off the led when not reading data
digitalWrite(rxLed, LOW);
}
}
void checkPump(int sensorVal){
if (sensorVal < 500) {
digitalWrite(redLed, HIGH);
digitalWrite(pumpPin, LOW);
} else {
digitalWrite(redLed, LOW);
digitalWrite(pumpPin, HIGH);
}
}
void handleSerial() {
inByte = Serial.read();
// save only ASCII numeric characters (ASCII 0 - 9):
if ((inByte >= '0') && (inByte <= '9')) {
inString[stringPos] = inByte;
stringPos++;
}
// if you get an * (end of message),
// then convert what you have to an integer:
if (inByte == '*') {
// convert string to number
int humidity = atoi(inString);
// see if the pump needs to be turned on
checkPump(humidity);
// put zeros in the array
for (int c = 0; c < stringPos; c++) {
inString[c] = 0;
}
// reset the string pointer:
stringPos = 0;
}
}
And here is the code for the sensor station:
/*
* A Garden Sensor Station
* Sends the moisture sensor reading via serial communication.
*/
int moistureSensor = 0;
// to show communication
int txLed = 13;
int moistureVal;
void setup() {
Serial.begin(9600);
pinMode(txLed, OUTPUT);
}
void loop() {
// Get sensor reading and send it.
moistureVal = analogRead(moistureSensor);
digitalWrite(txLed, HIGH);
Serial.print(moistureVal, DEC);
Serial.print('*'); // end of message marker
digitalWrite(txLed, LOW);
delay(2000); // wait
}
I see some possible benefits to having the sensor station just transmit to the irrigation controller whether or not the irrigation controller should turn on, but one of the disadvantages that I see with that is that you now have all the irrigation logic spread across all the sensor stations. So, the choice I made was to make the sensor stations "dumb" and the irrigation controller "smart". If I want to make changes to the irrigation amount, timing, sensitivity, etc. I just have to go to one micro-controller.
Next up: getting the whole thing in place and watering some real plants!
