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77 lines
2.2 KiB
77 lines
2.2 KiB
// normal delay() won't work anymore because we are changing Timer1 behavior
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// Adds delay_ms and delay_us functions
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#include <util/delay.h>
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// Clock at 8MHz
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#define F_CPU 8000000 // This is used by delay.h library
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word VentPin = 1;
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word DetPin = A0;
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float PWM = 50; // takes values from 0 to 100
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float PWM9, PWM8, PWM7, PWM6, PWM5, PWM4, PWM3, PWM2, PWM1;
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// Thermistor
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int Vo;
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int DeltaT = 10; // shift curve up/down
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float R1 = 13000;
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float logR2, R2, T;
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float c1 = 1.009249522e-03, c2 = 2.378405444e-04, c3 = 2.019202697e-07;
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// Boot up delay countdown to keep the fan spinning initially
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int countdown = 10000; //Microseconds to delay
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void setup() {
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//Serial.begin(115200);
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TCCR0A = _BV(COM0B1) | _BV(WGM01) | _BV(WGM00);
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TCCR0B = _BV(WGM02) | _BV(CS01);
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// Set TOP and initialize duty cycle to zero(0)
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OCR0A = 40; // TOP - DO NOT CHANGE, SETS PWM PULSE RATE
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OCR0B = 30; // duty cycle for Pin 1(PB1) - generates 1 500nS pulse even when 0
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pinMode(VentPin, OUTPUT);
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pinMode(DetPin, INPUT);
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}
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void loop() {
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// Thermistor data acquisition
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Vo = analogRead(DetPin);
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R2 = R1 * (1023.0 / (float)Vo - 1.00);
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logR2 = log(R2);
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T = (1.00 / (c1 + c2*logR2 + c3*logR2*logR2*logR2));
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T = T - 273.15;
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// End of temperature measurement
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// PWM control Logic
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if (T < 30) {
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// this next if is necessary to trick BIOS into thinking it xontrols the fan at boot
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if (countdown > 0) {
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countdown--;
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delayMicroseconds(100);
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PWM = 50;
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}
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else if (T < 15 && countdown <= 0) {
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PWM = 0; // stop the fan if the machine is critically cold
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}
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else {
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PWM = 25; // minimum fan speed while operating normally
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}
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}
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else if (T >= 30+DeltaT && T < 40+DeltaT) {
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PWM = 2*T - (35+2*DeltaT); // first part of the fan curve
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}
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else if (T >= 40+DeltaT) {
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PWM = 5*T - (155+5*DeltaT); // second, steepest, part of the curve
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}
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// these variables are used to average the value over 10 cycles before sending it to the fan
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PWM9 = PWM8,
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PWM8 = PWM7;
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PWM7 = PWM6;
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PWM6 = PWM5;
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PWM5 = PWM4;
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PWM4 = PWM3;
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PWM3 = PWM2;
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PWM2 = PWM1;
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PWM1 = PWM;
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OCR0B = (PWM9+PWM8+PWM7+PWM6+PWM5+PWM4+PWM3+PWM2+PWM1+PWM)/30; // average and send value to timer
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}
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