temperature-monitor (1).txt

// Pin definitions
const int SENSOR_PIN = A0;    // Analog input pin for LM335AH
const int SIGNAL_PIN = 13;    // Output signal pin (using onboard LED)

// Temperature threshold (37°F = 275.93K)
const float TEMP_THRESHOLD_K = 275.93;

// Time threshold (2 minutes in milliseconds)
const unsigned long TIME_THRESHOLD = 120000;

// Variables for temperature monitoring
unsigned long coldStartTime = 0;
bool isColdCondition = false;
bool isSignalActive = false;

// LM335AH calibration constants
const float REFERENCE_VOLTAGE = 5.0;
const float SENSOR_CALIBRATION = 10.0;  // mV/°K

void setup() {
  // Initialize pins
  pinMode(SENSOR_PIN, INPUT);
  pinMode(SIGNAL_PIN, OUTPUT);
  digitalWrite(SIGNAL_PIN, LOW);
  
  // Initialize serial communication for debugging
  Serial.begin(9600);
  Serial.println("Temperature Monitor Initialized");
}

void loop() {
  // Read temperature from LM335AH
  float tempK = readTemperature();
  float tempF = (tempK - 273.15) * 9.0/5.0 + 32.0;
  
  // Print current temperature (for debugging)
  Serial.print("Temperature: ");
  Serial.print(tempF);
  Serial.println("°F");
  
  // Check if temperature is below threshold
  if (tempF < 37.0) {
    if (!isColdCondition) {
      // Start timing when temperature first drops below threshold
      isColdCondition = true;
      coldStartTime = millis();
      Serial.println("Cold condition detected - starting timer");
    }
    else {
      // Check if cold condition has persisted long enough
      unsigned long timeInCold = millis() - coldStartTime;
      
      if (timeInCold >= TIME_THRESHOLD && !isSignalActive) {
        // Activate signal after 2 minutes of cold
        digitalWrite(SIGNAL_PIN, HIGH);
        isSignalActive = true;
        Serial.println("Temperature below 37°F for 2 minutes - Signal activated!");
      }
      
      if (isSignalActive) {
        Serial.print("Cold condition maintained for: ");
        Serial.print(timeInCold / 1000);
        Serial.println(" seconds");
      }
    }
  }
  else {
    // Reset monitoring if temperature rises above threshold
    if (isColdCondition) {
      isColdCondition = false;
      isSignalActive = false;
      digitalWrite(SIGNAL_PIN, LOW);
      Serial.println("Temperature rose above threshold - Monitoring reset");
    }
  }
  
  // Small delay to prevent excessive readings
  delay(1000);
}

float readTemperature() {
  // Read analog value
  int sensorValue = analogRead(SENSOR_PIN);
  
  // Convert analog reading to voltage
  float voltage = (sensorValue * REFERENCE_VOLTAGE) / 1024.0;
  
  // Convert voltage to Kelvin
  // LM335AH outputs 10mV/°K
  float temperatureK = (voltage * 100.0);  // Convert V to K
  
  return temperatureK;
}