Just wanted to share for those that might be interested - didn't see something like this in my immediate searches...
Code is beta...working excellent so far, though.
https://www.youtube.com/watch?v=Ff-VO6j2OTM
Supplies:Any Arduino with PWM output and Analog input
Thermistor
Resistor that matches thermistor resistance value (100 Ohm in this example)
Fan with PWM input (PFC1212DE)
Thermistor reading dictates fan speed.
// Measured thermistor and received 80k at 80 degrees, so guessed it's a 100k
// Voltage divider resistor was then selected as 100k ohm
// (Ground) ---- (10k-Resistor) -------|------- (Thermistor) ---- (+5v)
// |
// Analog Pin 0
int ThermistorPin = 0;
int Vo;
float R1 = 10000;
float logR2, R2, T;
float c1 = 1.009249522e-03, c2 = 2.378405444e-04, c3 = 2.019202697e-07;
int PWMpin=3;
int x=3500; // Initial X value. Higher value decreases total fan speed, lower increases.
int y=0;
void setup() {
Serial.begin(9600);
}
void loop() {
Vo = analogRead(ThermistorPin);
R2 = R1 * (1023.0 / (float)Vo - 1.0);
logR2 = log(R2);
T = (1.0 / (c1 + c2*logR2 + c3*logR2*logR2*logR2));
T = T - 273.15;
T = (T * 9.0)/ 5.0 + 32.0;
Serial.print("Temperature: ");
Serial.print(T);
Serial.println(" F");
// Trial and error settings to drive a PFC1212DE-F00 FAN using PWM Pin 3 from Arduino
// Fan is wired to power source
// Arduino shares ground with GND from fan power source
// Arduino PWMpin connects to yellow PWM pin from fan
for(y = 0; y < 2500; y++) { // Temperature sampling rate, 2500 is about 10 second sample
digitalWrite(PWMpin, HIGH);
delayMicroseconds(x);
digitalWrite(PWMpin, LOW);
delayMicroseconds(4000-x); // Total PWM time 4000 microseconds - X value
if (T>=60 && T<=69){
x=3950;
} else if (T>=70 && T<=79){
x=3700;
} else if (T>=80 && T<=89){
x=3500;
} else if (T>=90 && T<=99){
x=2000;
} else if (T>=100){
x=10;
}
}
}
