Arduino code my Dad wrote to automate his greenhouse lamps

greenhouse.ino

int lightPin0 = 0;
int lightPin1 = 1;
int relayPin = 2;
int night = 1000;
int sunny = 8000;
float filter = 0.0;

void setup() {
  pinMode(relayPin,OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int r0 = analogRead(lightPin0);
  int reading  = analogRead(lightPin1);
  // first order filter
  filter = filter*0.9 + r0;
  
  Serial.print("Raw ");
  Serial.print(reading);
  Serial.print("  Filtered ");
  Serial.print(filter);
  Serial.print("  Secondary ");
  Serial.println(r0);
  
  if (filter < night || filter > sunny) {
    digitalWrite(relayPin, LOW);
  }
  else {
    digitalWrite(relayPin, HIGH);
  }
  delay (1000);
}

Richard,

Here’s the entirety of my Arduino program. The print statements are just diagnostics one can view while it runs. Rather lacking in comments.

Two photo resistors as inputs, with a resistor each to make a voltage divider. One binary output that then drives a relay. Araldite on the bottom of the relay to insulate the 240V!

Dad

He wants to stop his seedlings from getting leggy so switches on lamps when the sky is gloomy