Project tutorial
SD Card Temperature Data Logger

SD Card Temperature Data Logger © GPL3+

In this project, I am going to demonstrate to you how to log data from LM35 temperature sensor values to an SD card and store it as CSV.

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About this project

In this project, I am going to demonstrate to you how to log data from LM35 temperature sensor values to an SD card and store it as CSV file, with the help of the idIoTware shield.

Temp:

We are using LM35 temperature sensor to monitor the temperature. The idIoTware shield has a built in, on board, LM35 sensor.

  • The sensor has a sensitivity of 10mV / oC.
  • We use a reciprocal conversion factor, that is 100 oC/V.
  • The output voltage varies linearly with temperature.
  • The general equation used to convert output analog voltage (Vout) to temperature is:
  • Temperature ( oC) = Vout * (100 oC/V)
  • So if Vout is 0.5V , then, Temperature = 50oC

However on the idIoTware shield, the LM35, temperature sensor is wired such that with a higher temperature we get a higher Analog Voltage on PIn A0.

Working

This example shows how to log data from LM35 temperature sensor to an SD card using the SD library.

SD Card Temperature Logger

In this example we have created a CSV file with the temperature values every one minute for 15 minutes. This interval rate and duration is configurable. If there is existing file, then it will create new file with different name.

Configuring Idiotware Shield

Once we upload the code in Arduino, you need to test the temperature sensor data on the serial monitor. It's time to keep the device in some place where you want to collect the temperature data for day or even month!

Once you copy the csv file from sd card.you can plot the temperature graph using excel software.

No more connecting leds to breadboard and messy wiring. With the idIoTware shield the sky's the limit.

Code

data_loggerArduino
/*
  SD card temperature logger
 This example shows how to log data from LM35 temperature sensor
 to an SD card using the SdFat library.
 In this example we have created a CSV file with the temperature values
 every one minute for 15 minutes. This interval rate and duration is configurable.
 If there is existing file, then it will create new file with different name.
 
  
 The circuit:
 * LM35 sensor on analog pin A3
 * SD card attached to SPI bus as follows:
 ** MOSI - pin 11
 ** MISO - pin 12
 ** CLK - pin 13
 ** CS - pin 4
 */

#include <SPI.h>
#include <SdFat.h>
SdFat sd;
const uint8_t chipSelect = 6;

//const int chipSelect = 4;   //cs pin of SD card shield
int tempPin = A3;      // LM 35 is connected to A3 pin.
int buzzerPin = A2;    // buzzer is connected to A2 pin

File dataFile;   // the logging file
char filename[] = "Temp000.CSV";
float tempInCelcius;
float tempInFarenheit;
unsigned long time=0;
int samplingTime = 10;  //this variable is interval(in Seconds) at which you want to log the data to SD card.
int duration = 15;     //this variable is duration(in Minutes) which is the total time for which you want to log data.


void setup() 
    {
      // Open serial communications and wait for port to open:
      Serial.begin(9600);
      while (!Serial)
          {
            ; // wait for serial port to connect. Needed for native USB port only
          }

      Serial.print("Initializing SD card...");

     // see if the card is present and can be initialized:
     if (!sd.begin(chipSelect))  
        { sd.initErrorHalt();
          Serial.println("Card failed, or not present");
          // don't do anything more:
          return;
        }
     Serial.println("card initialized.");

     // create a new file
     for(unsigned int i = 0; i < 1000; i++) 
        {
          filename[4] = i/100 + '0';
          filename[5] = ((i%100)/10) + '0';
          filename[6] = i%10 + '0';
          if(! sd.exists(filename)) 
            {
              // only open a new file if it doesn't exist
              dataFile = sd.open(filename, FILE_WRITE);
              break;  // leave the loop!
            }
        }

      if(! dataFile) 
        { //alert user
          Serial.println("couldnt create file");
          int alertAlarm1[] = { 1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,
                           1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,};
          int noteDurations[] = { 5,5,5,5,5,5,5,5,5,5,5,
                                  5,5,5,5,5,5,5,5,5,5,5 };
          for (int thisNote = 0; thisNote < 20; thisNote++) 
             {
               // Duration = 1 second / note type
               // e.g. quarter note = 1000 / 4, eighth note = 1000/8, etc.
               int noteDuration = 2500 / noteDurations[thisNote];
               tone(A2,alertAlarm1[thisNote], noteDuration);
               //pause for the note's duration plus 100 ms:
               delay(noteDuration + 100);
             }
        }

     Serial.print("Logging to: ");
     Serial.println(filename);
     
     dataFile = sd.open(filename, FILE_WRITE);
     // if the file is available, write to it:
     if (dataFile) 
       { 
         dataFile.print("Logging Temperature for ");
         dataFile.print(duration);
         dataFile.print(" minutes at interval of ");
         dataFile.print(samplingTime);
         dataFile.println(" seconds.");
         
         dataFile.close();
       }
      // check availble space on SD Card
      uint32_t freeKB = sd.vol()->freeClusterCount();
      freeKB *= sd.vol()->blocksPerCluster()/2;
      Serial.print("Free space KB: ");
      Serial.println(freeKB);
      uint32_t freeMB= freeKB/1024;
      Serial.print("Free space in MB: ");
      Serial.println(freeMB); 
      
      if(freeKB <= 500)
        {
          Serial.println("LOW SPACE!!!");
          int alertAlarm2[] = { 1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,
                               1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,1000,1000};
          int noteDurations[] = { 15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,
                                  15,15,15,15,15,15,15,15,15,15,15,15,15,15,15  };
          for (int thisNote = 0; thisNote < 20; thisNote++) 
             {
               // Duration = 1 second / note type
               // e.g. quarter note = 1000 / 4, eighth note = 1000/8, etc.
               int noteDuration = 2500 / noteDurations[thisNote];
               tone(A2,alertAlarm2[thisNote], noteDuration);
               //pause for the note's duration plus 50 ms:
               delay(noteDuration + 50);
             }
        }
     duration *= 60;   //convert durartion in minutes to seconds   
   }

void loop() 
    {
      dataSamples();    // here we are logging data at interval of 1 minute for 15 mintutes, i.e, 15 samples.
                            // if you want to save data for 2 hours then simply multiply 2 by 60 which will give 
                            // you value of 120 minutes then use 120 as second parameter.
    }

// this method will log data to SD card at particular interval and for paricular duration
int dataSamples()
   { 
     // here we are logging data at interval of 1 minute for 15 mintutes, i.e, 15 samples.
     // if you want to save data for 2 hours then simply multiply 2 by 60 which will give 
     // you value of 120 minutes then change the varible duration to 120. 

      tempInCelcius = ( 5.0 * analogRead(tempPin) * 100.0) / 1024.0;
      
      // uncomment following line to get temperature values in Farehniet
      //tempInFarenheit = ((tempC*9)/5) + 32;            //convert celcius to farenheit
      
      unsigned long  elapsedTime = millis()/1000;   // this variable will keep track of elapsed time
      while(((millis()/1000)-elapsedTime) < 1);    // this loop will do nothing until a second has passed 
      time++;                                       //increment time after each second.
 
      if((duration >= time) && (time % samplingTime == 0))
        {
          LogToSDcard();  //Log to SD using commands under void LogToSD()  
          // print to the serial port too:              
          Serial.print("Temperature: ");
          Serial.print(tempInCelcius);
          Serial.print(char(176)); 
          Serial.println("C");     
        }
           
   }
   
void LogToSDcard()
   {
     // open the file. note that only one file can be open at a time,
     // so you have to close this one before opening another.
     dataFile = sd.open(filename, FILE_WRITE);
     // if the file is available, write to it:
     if (dataFile) 
       { 
         dataFile.print(tempInCelcius);   
         dataFile.println("°C");
         dataFile.println(",");
         dataFile.close();
         
     // to print temperature values in Farehniet uncomment following code.    
         
      /*  dataFile.print(tempInFarenheit);
         dataFile.print("°C");
         dataFile.println(",");
         dataFile.close();   */
       } 
  
      //if the file isn't open, pop up an error:
     else 
        {
          Serial.println("error opening datalog.txt");
          delay(2000);
        }
   }   
 

Schematics

idiotware-shield

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