Other Parts Discussed in Thread: ENERGIA
I am trying the basic thermistor program using my launchpad and I am having trouble using the log() function. When I take the log() of the variable I received an error. I then used logf() of the variable and the program compiled and downloaded to the board but the value was incorrect. What am I doing wrong here?
int Vo_raw;
float R1 = 10000;
float logR2, R_t, T, Vo_volt;
float c1 = 1.12924e-03, c2 = 2.34108e-04, c3 = 0.87755e-07;
void setup() {
pinMode(23, INPUT);
Serial.begin(9600);
}
void loop() {
Vo_raw = analogRead(23);//V_out signal from board
Vo_volt = Vo_raw * 3.3/4096; //convert from signal to volts
R_t = (3.3*R1)/Vo_volt - R1 ; //voltage divider equation to determine resistance
logR2 = logf(Vo_volt); //take log of voltage
T = (1.0 / (c1 + c2*logR2 + c3*logR2*logR2*logR2)); //thermistor equation
T = T - 273.15; //celsius to kelvin
T = (T * 9.0)/ 5.0 + 32.0; //kelvin to F
Serial.print("log(Resist): ");
Serial.print(logR2);
Serial.print("; Temp: ");
Serial.print(T);
Serial.print("; Resistance: ");
Serial.print(R_t);
Serial.print("; Volts: ");
Serial.println(Vo_volt);
delay(1000);
}
