"CORO METER" (... the unique infra red thermometer)

#include <Wire.h>
#include <LiquidCrystal.h>
LiquidCrystal lcd (2,3,4,5,6,7);

#define trigPin 11
#define echoPin 12
#define redLight 8
#define blueLight 10
#define greenLight 9
#define buzzerPin 13
char degree = 223; 

long duration, distance;
float objtemp,ambtemp;

// Declaring pins...

#define THERMOPILE A0
#define THERMISTOR A1

// Declaring constants for the thermistor calculations...

const float a = -412.6;
const float b = 140.41;
const float c = 0.00764;
const float d = -0.0000000000000000625;
const float e = -0.00000000000000000000000115;

// Declaring constants for the thermopile calculation...

const float k = 0.004313; 
const float delta = 2.468;

const float reftemp = 25; // 25 degree Celsius used as reference temperature
const float shiftv = 0.6; // Degree of shift for thermopile voltage for negative V values in range
const float verr = 0.6;  // voltage error introduced to thermopile by circuit

void setup() 
{
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
  lcd.begin(16,2);
  lcd.setCursor(0,0);
  lcd.print("IR THERMOMETER");             
  lcd.setCursor(2,1);
  lcd.print("( CORO METER )");
  delay(2000);
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Made in Nigeria");
  lcd.setCursor(0,1);
  lcd.print("by: EVATRONICS");
  delay(2000);
  lcd.clear();
}

void loop() 
{
  measureTemperature();
  checkDistance();
   
  if(distance<=60)
  {     
    if(objtemp<38)
    {
      digitalWrite(greenLight,LOW);
      digitalWrite(blueLight,HIGH);
      lcd.setCursor(0,0);
      lcd.print("Temp: ");
      lcd.print(objtemp);
      lcd.print(degree);
      lcd.print("C");
      lcd.setCursor(2,1);
      lcd.print("YOU'RE OKAY.");
      delay(2000);
      lcd.clear();
      lcd.setCursor(3,0);
      lcd.print("STAY SAFE");
      lcd.setCursor(6,1);
      lcd.print("BYE !");
      delay(2000);
      digitalWrite(blueLight,LOW);
      lcd.clear();
    }   

    if(objtemp>=38)
    {
      digitalWrite(greenLight,LOW);
      digitalWrite(blueLight,LOW);
      digitalWrite(redLight,HIGH);
      digitalWrite(buzzerPin,HIGH);
      lcd.clear();
      lcd.setCursor(0,0); 
      lcd.print("Temp: ");
      lcd.print(objtemp);
      lcd.print(degree);
      lcd.print("C");
      lcd.setCursor(0,1);
      lcd.print("HIGH TEMPERATURE");
      delay(2000);
      lcd.clear();
      lcd.setCursor(3,0);
      lcd.print("CALL NCDC: ");
      lcd.setCursor(2,1);
      lcd.print("080097000010");
      delay(2000);
      digitalWrite(buzzerPin,LOW);
      digitalWrite(buzzerPin,LOW);
    }
  }
  else
  {
    digitalWrite(redLight,LOW);  
    digitalWrite(blueLight,LOW);
    digitalWrite(greenLight,LOW);
    lcd.setCursor(1,0);
    lcd.print("SHOW YOUR FACE");
    lcd.setCursor(0,1);
    lcd.print("COME A BIT CLOSE");
    delay(2000);
    lcd.clear();
  }
}  

float measureTemperature()
{
  float thermopileValue = analogRead(THERMOPILE);
  float thermistorValue = analogRead(THERMISTOR);
  
  // Working out thermistor temperature from reading...
  
  float v1 = (thermistorValue / 1024) * 5; // Reading is fraction of source voltage, which is 5v.
  float r = -(v1*1000)/(v1-5); // Getting resistance...
  ambtemp = a + b * sqrt(1+c*r) + d*pow(r,5) + e*pow(r,7); // getting ambient temp...
  
  float comp = k * (pow(ambtemp,4-delta)-pow(reftemp,4-delta));  //calculating equivalent thermopile voltage for ambient temperature...
  
  // Calculate the thermopile temperature...
  
  float v2 = (thermopileValue / 1024) * 5 + comp - verr - shiftv; // Calculating thermopile voltage...
  objtemp = pow((v2+k*pow(ambtemp,4-delta))/k, 1/(4-delta)); // Calculating object temperature...
  
  Serial.print("thermopile value = ");
  Serial.println(thermopileValue);
  Serial.print("thermistor value = ");
  Serial.println(thermistorValue);
  Serial.print("ambient temp = ");
  Serial.println(ambtemp);
  Serial.print("object temp = ");
  Serial.println(objtemp);
  Serial.println();
}

double checkDistance()
{
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = (duration/2) / 29.1;
}