Arduino Nano send wrong value!!

Projects Programming
1

Hi,

i want to developp a wireless-voc sensor-system. I used tgs2602, arduino Nano and Xbee Pro S1.
This is my arduino-code:

int value ;       
const int gasSensor = A0;

void setup() {

  Serial.begin(9600);

   }

void loop() {
 


  int value = analogRead (gasSensor);



  float volt = (value/1023.0)*5.0 ;    // Rechne die von ADC ausgegebenen Werten in Volt um
  float Rs1 = 10*(5-volt)/volt;        //Rechne den Widerstandswert
  //Serial.print("40B7DEF1");            // Sensorname
  //Serial.print("\t");                  // Tabulator

  
  // Kalibrierungsarray der Länge N = 17
 float Rs [17] = {57.84260516,  2.200081335,  1.606762875,  1.178596714,  0.944910617,  0.865628395,  0.764262648,  0.687566798,  0.626992561,  0.567101091,  0.544815465,  0.496850952,  0.474860336,  0.474860336,  0.442046642,  0.423905489,  0.402219139};
 float ppmValue [17] = {0,  5,  10,  15,  20,  24,  28.25,  32.5,  37.75,  43.25,  48.75,  53.25,  57.75,  62.50,  67.50,  75.5,  77.5};
 
     
if (Rs1 >= Rs [0])
{
    float ppm = ppmValue [0];
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println(ppm);  
    delay(30000);
} 
  // Interpolation: ppm [0;5]
 
  if ( Rs[1] < Rs1 && Rs1 < Rs[0]){

    float ppm = ppmValue [0] + ((-Rs1 + Rs [0])/(Rs[0] - Rs [1] ))*(ppmValue [1] - ppmValue[0]);
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm);  
    delay(30000);
}
// Interpolation: ppm [5;10]
  else if ( Rs[2] < Rs1 && Rs1 < Rs[1]){
   
   float ppm = ppmValue [1] + ((-Rs1 + Rs [1])/(Rs[1] - Rs [2] ))*(ppmValue [2] - ppmValue[1]);
    
    //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  } 
  
  // Interpolation: ppm [10;15]
  else if ( Rs[3] < Rs1 && Rs1 < Rs[2]){
   
    float ppm = ppmValue [2] + ((-Rs1 + Rs [2])/(Rs[2] - Rs [3] ))*(ppmValue [3] - ppmValue[2]);
    
    //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  }
    // Interpolation: ppm [15;24]
  else  if ( Rs[4] < Rs1 && Rs1 < Rs[3]){
   
 float ppm = ppmValue [3] + ((-Rs1 + Rs [3])/(Rs[3] - Rs [4] ))*(ppmValue [4] - ppmValue[3]);
   
    //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  }
  
  // Interpolation: ppm [24;28.25]
  
 else if ( Rs[5] < Rs1 && Rs1 < Rs[4]){
   
   float ppm = ppmValue [4] + ((-Rs1 + Rs [4])/(Rs[4] - Rs [5] ))*(ppmValue [5] - ppmValue[4]);
  
  //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  }
  
   // Interpolation: ppm [28.25;32.5]
   else  if ( Rs[6] < Rs1 && Rs1 < Rs[5]){
   
  float  ppm = ppmValue [5] + ((-Rs1 + Rs [5])/(Rs[5] - Rs [6] ))*(ppmValue [6] - ppmValue[5]);
     
     //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
   }
   
  // Interpolation: ppm [32.5;37.75]
else  if ( Rs[7] < Rs1 && Rs1 < Rs[6]){
   
  float  ppm = ppmValue [6] + ((-Rs1 + Rs [6])/(Rs[6] - Rs [7] ))*(ppmValue [7] - ppmValue[6]);
   
   //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  }
  
  // Interpolation: ppm [37.75;43.25]
  else  if ( Rs[8] < Rs1 && Rs1 < Rs[7]){
   
  float  ppm = ppmValue [7] + ((-Rs1 + Rs [7])/(Rs[7] - Rs [8] ))*(ppmValue [8] - ppmValue[7]);
     
     //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  }
  
  // Interpolation: ppm [43.25;48.75]
  else if ( Rs[9] < Rs1 && Rs1 < Rs[8]){
   
   float ppm = ppmValue [8] + ((-Rs1 + Rs [8])/(Rs[8] - Rs [9] ))*(ppmValue [9] - ppmValue[8]);
     
     //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);    
  }
   // Interpolation: ppm [48.75;53.25]
  else  if ( Rs[10] < Rs1 && Rs1 < Rs[9]){
   
  float  ppm = ppmValue [9] + ((-Rs1 + Rs [9])/(Rs[9] - Rs [10] ))*(ppmValue [10] - ppmValue[9]); 
  
  //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  }
  
 // Interpolation: ppm [53.25;57.75]
 else  if ( Rs[11] < Rs1 && Rs1 < Rs[10]){
   
   float ppm = ppmValue [10] + ((-Rs1 + Rs [10])/(Rs[10] - Rs [11] ))*(ppmValue [11] - ppmValue[10]); 
  
  //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  }
 
  // Interpolation: ppm [57.75;62.5] 
 else if ( Rs[12] < Rs1 && Rs1 < Rs[11]){
   
  float  ppm = ppmValue [11] + ((-Rs1 + Rs [11])/(Rs[11] - Rs [12] ))*(ppmValue [12] - ppmValue[11]); 
  
  //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  }
 
  // Interpolation: ppm [62.5;67.5]
  
 else  if ( Rs[13] < Rs1 && Rs1 < Rs[12]){
   
  float  ppm = ppmValue [12] + ((-Rs1 + Rs [12])/(Rs[12] - Rs [13] ))*(ppmValue [13] - ppmValue[12]); 
  
  //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  }
  
   // Interpolation: ppm [67.5;75.5]
 else  if ( Rs[14] < Rs1 && Rs1 < Rs[13]){
   
   float ppm = ppmValue [13] + ((-Rs1 + Rs [13])/(Rs[13] - Rs [14] ))*(ppmValue [14] - ppmValue[13]); 
  
  //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  }

 // Interpolation: ppm [75.5;77.5]

else    if( Rs[15] < Rs1 && Rs1 < Rs[14]){
   
   float ppm = ppmValue [14] + ((-Rs1 + Rs [14])/(Rs[14] - Rs [15] ))*(ppmValue [15] - ppmValue[14]); 
  
  //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);
  }
  
  else    if( Rs[16] < Rs1 && Rs1 < Rs[15]){
   
   float ppm = ppmValue [15] + ((-Rs1 + Rs [15])/(Rs[15] - Rs [16] ))*(ppmValue [16] - ppmValue[15]); 
  
  //PPM Ausgabe
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm); 
    delay(30000);}

    else    if (Rs1 >= Rs [16])
{
    float ppm = ppmValue [16];
  
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm);  
    delay(30000);
} 
  
   else    if (Rs1 < Rs [16])
{
    float ppm = 80;
  
    //Serial.print ("ppm: ");
    Serial.print("1");            // Sensorname
    Serial.print("\t");                  // Tabulator

    Serial.println (ppm);  
    delay(30000);    
} 
delay(3000);    
  }

I don´t know what i´m doing wrong, but the values i´m getting are all wrong. It seems that this value aren´t from the analogpin.
Can someone help me?

Thanks

2

but the values i´m getting are all wrong

But the values that you get and the values you expect are some kind of secret?

What do your debug prints tell you?

3

Let me summarize your post:

I was expecting something, but I got something else.

Can anyone explain this?

4

Your code also needs to be refactored; it's at least 140 200 lines too long.

5

Hi AWO,
Hi Nick,

Thanks for the answers.

Sorry, i forgot to tell exactly the values i´m getting.

The values i´m getting are 3,0ppm, 3,2ppm....., it doesn´t really change at all.
I check the value from the analogpin and it seems to be alright. (this analogvalue change when i approach an alcohol recipient from the sensor). But the converted value i´m reading at the serial port are wrong.

i will also try to reduce my code ::slight_smile:

thanks

6

There's a famous axiom in computing "Garbage in, garbage out".

You need to find out what's going in to your algorithm.

7

Hi,
it works!! i made it.

Thanks a lot!!