====== Thermometer ======

**//The Circuit://**
{{:hpc0:thermometer.jpg?nolink|}}

**//The Code://**

<code c>
  1 /**********************************************************************                                     
  2 * Filename    : Thermometer.cpp
  3 * Description : DIY Thermometer
  4 * Author      : www.freenove.com
  5 * modification: 2020/03/09
  6 **********************************************************************/
  7 #include <wiringPi.h>
  8 #include <stdio.h>
  9 #include <math.h>
 10 #include <ADCDevice.hpp>
 11  
 12 ADCDevice *adc;                                                // Define an ADC Device class object
 13  
 14 int main(void){
 15     adc = new ADCDevice();
 16     int   adcValue;                                            //get input from hardware
 17     float voltage;                                             //stores the voltage
 18     float Rt;                                                  //stores the resistance of thermistor
 19     float tempK;                                               //Temp in Kelvin
 20     float tempC;                                               //Temp in Celsius
 21     printf("Program is starting ... \n");
 22  
 23     if(adc->detectI2C(0x48)){                                  //Is it the pcf8591
 24         delete adc;                                            //Empty previous hardware
 25         adc = new PCF8591();                                   //Set the hardware
 26     }
 27     else if(adc->detectI2C(0x4b)){                             //Is it the ads7830
 28         delete adc;                                            //Empty previous hardware
 29         adc = new ADS7830();                                   //Set the hardware
 30     }
 31     else{
 32         printf("No correct I2C address found, \n"
 33         "Please use command 'i2cdetect -y 1' to check the I2C address! \n"
 34         "Program Exit. \n");
 35         return -1;
 36     }
 37     printf("Program is starting ... \n");
 38     while(1){
 39         adcValue = adc->analogRead(0);                         //read analog value A0 pin    
 40         voltage  = (float)adcValue / 255.0 * 3.3;              //calculate voltage    
 41         Rt       = 10 * voltage / (3.3 - voltage);             //calculate resistance value of thermistor
 42         tempK    = 1/(1/(273.15 + 25) + log(Rt/10)/3950.0);    //calculate temperature (Kelvin)
 43         tempC    = tempK -273.15;                              //calculate temperature (Celsius)
 44         printf("ADC value : %d  ,\tVoltage : %.2fV, \tTemperature : %.2fC\n",adcValue,voltage,tempC);
 45         delay(100);
 46     }
 47     return 0;
 48 }
</code>

This project has the same setup as [[hpc0:nightlamp|Nightlamp]] and [[hpc0:softlight|Softlight]] with the difference being that this project uses a thermistor to detect how much voltage should be running through the circuit. So when the program runs the thermistor will detect the temperature and with that change its resistance. This resistance will tell us how hot it is and how much voltage is going through the system. As for the code I aligned the comments, added comments to the conditional, and I moved all the variable declarations to be outside the loop.