// This a test program, no warranties are implied or given. PWM Mercedes ext temp sensor V1
// Use, copy any modify this test program any way you want, at your own risk. Then test, test, test
// It reads a extermal 10K thermister temperature probe and controls a Mercedes PMW module/fan.
// fan: 90% duty = full, 20% = min, 10% = off, no PWM = full Freq = 11Hz, PWM signal is 5 volt, Temps in Centigrade
#include <PWM.h>
/*----------------------- User adjustable variables and preferences section ---------------------------------*/
// FYI a PWM duty ranges from 0 to 255. Set desired temperature range below
const int tempForFanStartup = 98; // target low temp. below this temperature, the fan will be off
const int tempForFanOnFull = 110; // target High temp. above this temperature, the fan will be on at full power
const int A_C_Start_temp = 100; // Als de A/C aan staat gaat de Ventilator vanaf 80 °C draaien

// adjust these for PWN to for fan off, fan start and fan full on
const int fanDutyOff = 63; // Duty Cycle for 25% ( Off Fan Speed ( 10% of 255 )
const int fanOnFullDuty = 229; // Duty Cycle for 90% ( Full Fan Speed ( 90% of 255 )

/*----------------------- end of User adjustable variables and preferences -----------------------------------*/
const int fanPwmOutPin = 9; // Arduino forces this pin to 0 or 5 volts.
const int tempSensorPin = A0; // Pin to read analog voltage from the temp sensor.
const int AC_ClutchPin = A1; // Pin to A/C Clutch via 1K/10K Voltage Devider

int pwmDuty;

void setup() { /* ++++++++++++++++++ Setup is run once when the arduino boots ++++++++++++++++++++++++++*/
Serial.begin(9600); // set up serial port for 115200 baud (optional)
InitTimersSafe(); // set pwm frequency to 11 Hz for mercedes module pwm
SetPinFrequency(fanPwmOutPin, 11); // set pwm frequency to 11 Hz for mercedes module
analogReference (EXTERNAL); // note, this is using the 3.3 volt supply as the analog reference for more accuracy.
} // end setup


void loop() { /* ++++++++++++++++++ Main Loop, continuously loops forever ++++++++++++++++++++++++++++*/
int tempReading = get_temperature_sensor(); // read and translate the temp sensor

if (analogRead(AC_ClutchPin) > 20 ) { // A/C is on
// When the A/C Clutch is On, Voltage > .32V at Analog Input ( is ~ 1.4V when A/C is On )
if (tempReading < tempForFanStartup) {
tempReading = A_C_Start_temp; // Override NTC Temp Sensor Reading with A/C On & Engine Cold
}
}

if (tempReading < tempForFanStartup) {
pwmDuty = 25; // Engine Cold & No A/C, Turn Fan Off with 10% duty
} else { // Calculate PWM Duty Cycle
pwmDuty = calculate_PWM_duty(tempReading); // calculate the needed pwm
}

pwmWrite(fanPwmOutPin, pwmDuty); // send PWM to output pin

Serial.print("Temperatuur Radiateur = "); Serial.print(tempReading); Serial.println(" °C ");
Serial.print("PWM Duty Cycle = "); Serial.println(pwmDuty);
delay(1000);
} // end main loop


int calculate_PWM_duty(int currTemp) { /* ++++++++ subroutine to calculate and set PWM duty cycle ++++++++++++++*/
int duty = map(currTemp, tempForFanStartup, tempForFanOnFull, fanDutyOff, fanOnFullDuty ); // calc PWM Duty
int contrainedDuty = constrain(duty, fanDutyOff, fanOnFullDuty ); // PWM duty is never allowed ouside of min or max duties
return(contrainedDuty);
} // end calculate_PWM_duty


int get_temperature_sensor() {/* +++++ returns temp for extermal 10K thermister temperature probe ++++++++++*/
float R0 = 10000; // The base resistance of the NTC sensor used. 10K with a 4000 Beta.
float Beta = 4000; // The Beta of the sensor used. Very commonly available
int tmp = analogRead(tempSensorPin); // read temperature sensor (range 0 to 1023)
float r = ((1023.0*R0)/(float)tmp)-R0; // for a 10K thermister with a beta of 4000
tmp = (int) (Beta/log(r/0.09919) - 273.15 + .499); // for a 10K thermister with a beta of 4000
return(tmp);
} // end get_temperature_sensor