Control multiple relays with thermistors

Projects General Guidance
1

I am trying to program my arduino to detect the thermistor resistance from 4 heated seats and then have the arduino power off the relay associated with each thermistor, with the way the code is currently the relays will activate or deactivate when they sense a certain resistance on either of the 4 analog inputs when i only want the associated relay to be activated with its thermistor. Any help would be appreciated.

/****************************************/
#include <math.h>
/****************************************/
const int relayPin1 = 8;
const int ThermistorPin1 = A0;
const int relayPin2 = 9;
const int ThermistorPin2 = A1;
const int relayPin3 = 10;
const int ThermistorPin3 = A2;
const int relayPin4 = 11;
const int ThermistorPin4 = A3;
double Thermistor(int RawADC) {
 double Temp;
 Temp = log(10000.0*((1023.0/RawADC-1))); 
 Temp = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp ))* Temp );
 Temp = Temp - 273.15;          
 Temp = (Temp * 9.0)/ 5.0 + 32.0; 
 return Temp;
}
/****************************************/
void setup() {
  Serial.begin(9600);
  pinMode(relayPin1, OUTPUT);
  pinMode(relayPin2, OUTPUT);
  pinMode(relayPin3, OUTPUT);
  pinMode(relayPin4, OUTPUT);
}
void loop() {             
  int val1; 
  int val2; 
  int val3;
  int val4;              
  double temp1; 
  double temp2;
  double temp3;
  double temp4;           
  val1=analogRead(ThermistorPin1);      
  temp1=Thermistor(val1);  
  val2=analogRead(ThermistorPin2);      
  temp2=Thermistor(val2);
  val3=analogRead(ThermistorPin3);      
  temp3=Thermistor(val3);
  val4=analogRead(ThermistorPin4);      
  temp4=Thermistor(val4); 
  Serial.print("Temperature = ");
  Serial.print(temp1);   
  Serial.println(" F");
  if (temp1 >= 107){
    digitalWrite(relayPin1, LOW);
  }
  if (temp1 <= 107){
    digitalWrite(relayPin1, HIGH);
  }
  if (temp2 >= 107){
    digitalWrite(relayPin2, LOW);
  }
  if (temp2 <= 107){
    digitalWrite(relayPin2, HIGH);
  }
  if (temp3 >= 107){
    digitalWrite(relayPin3, LOW);
  }
  if (temp3 <= 107){
    digitalWrite(relayPin3, HIGH);
  }
  if (temp4 >= 107){
    digitalWrite(relayPin4, LOW);
  }
  if (temp4 <= 107){
    digitalWrite(relayPin4, HIGH);
  }
  delay(1000);            
}
2

the relays will activate or deactivate when they sense a certain resistance on either [any?] of the 4 analog inputs

(Presumably "either" means "any" of the 4?)

How do you know that?: you're only printing temp1.

3

I forgot to remove the serial print as i did not use it, i actually went and connected the relays and thermistors to the arduino and all of the relays would activate off of one thermistor when it should have only activated one relay.

4

I'd put serial prints back in, to print all the raw values and all the temperatures.

There's a school of thought that each analog pin should be read twice in succession, first value being discarded:

analogRead(A0);
myVal=analogRead(A0);
5

You should have some hysteresis (deadband) between cut on and cut off points to keep the relays from constantly switching:

  if (temp1 >= 107){
    digitalWrite(relayPin1, LOW);
  }
  if (temp1 <= 105){
    digitalWrite(relayPin1, HIGH);

How are the relay coils powered? If from the Arduino 5V pin, that could cause a power glitch and make a relay that was near it's switch point go on or off prematurely.

6

12Stepper:
There's a school of thought that each analog pin should be read twice in succession, first value being discarded:

analogRead(A0);

myVal=analogRead(A0);

If the first analogRead is not used, the compiler may "optimize" it away, just double the second statement:

myVal=analogRead(A0);
myVal=analogRead(A0);
7

That sounds good to me, ill add thise entries as well cause ya id prefer them not constantly switching. The relay module is powered by the 5v power supply which the arduino is also powered by. I will also add 12Stepper suggestion for the double value.