#ifndef _EC_H_ #define _EC_H_ #include bool ec_flag_measurement_available=false; #define EC_ADC_UNAVAILABLE 0 #define EC_UNAVAILABLE -1 #define EC_PIN_RELAY_PROBE 27 //#define EC_PIN_ADC 4 #define EC_ADS_CHANNEL 0 #define EC_PIN_FREQ 5 #define EC_PWM_CH 0 #define EC_RESOLUTION 8 #define EC_FREQUENCY 5000 #define EC_CALIB_ARRAY_SIZE 128 uint16_t ec_calib_array[EC_CALIB_ARRAY_SIZE]; uint16_t ec_calib_array_pos=0; #define EC_CALIB_READ_INTERVAL 250 //interval of reading adc value inside a measurement #define EC_ARRAY_SIZE 256 uint16_t ec_array[EC_ARRAY_SIZE]; uint16_t ec_array_pos=EC_ARRAY_SIZE; unsigned long last_measurement_ec=0; #define EC_MEASUREMENT_INTERVAL 30000 //complete filtered measurement every x ms //One filtered measurement takes EC_READ_INTERVAL*EC_ARRAY_SIZE*4 #define EC_READ_INTERVAL 10 //interval of reading adc value inside a measurement. one reading takes about 9-10ms #define EC_RELAY_SWITCH_SETTLETIME 500 //time until voltage of ec circuit has settled //const uint16_t ec_centerADCvalue=9026; //adc value when probe resistance is equal to the range resistor (mean of both) //Range Resistor is two parallel 1k2 = 600 Ohm unsigned long ec_last_change_relay=0; //millis of last relay change enum ECState{IDLE,MEASURE}; ECState ecstate=IDLE; float ec_adc; float ec_adc_adjusted; //adjusted for reference resistor float ec_calib_adc; float ec; //ec value after adjustment for reference (at current temperature) float ec25; //ec value but temperature adjusted for 25 degC float ec_tempadjust_alpa=0.02; float ec_reference_adc=6016.88; //adc reference value for the calibration resistor measurement. //EC short circuit adc value: 17497, 17861.4 (for connection resistance testing) //EC open circuit adc value: 738, 730, 737.27 //x^0*p[0] + ... + x^n*p[n] //float ec_calibration_polynom[]={691.5992624638029,-1.4015367296761692,0.0008513503472324141,-2.2140576823179093e-07,2.8962580780180067e-11,-1.8577565383307114e-15,4.7162479484903865e-20}; //float ec_calibration_polynom[]={1033.928052655456,-3.8909104921922895,0.005627541436014758,-4.103988840997024e-06,1.7231981870816133e-09,-4.433707707721975e-13,7.203892111369395e-17,-7.406549810844244e-21,4.667420606439905e-25,-1.6439457516812463e-29,2.477292190335455e-34}; //20220505 float ec_calibration_polynom[]={-323.68589929771457,0.5836096440900665,-0.000279737392438965,5.98673062873e-08,-5.4460235093798435e-12,1.8535134644431135e-16}; //20230509 //float ec_calibration_polynom[]={212.6826331524675,-0.6043878865263305,0.000571551634082491,-1.827897106718841e-07,2.682337041246909e-11,-1.8368511021965982e-15,4.8269168538877025e-20}; //20230509 manuell float ec_calibration_linearize_below_adc=6500; //use linear approximation below this adc value. 0=disable float ec_calibration_linear_lowADC=746; //x0 float ec_calibration_linear_lowEC=0; //y0 bool ec_measurementReady(); void ec_startMeasurement(); void ec_setRange(uint8_t range); void ec_connectProbe(bool); void ec_releaseRelay(); float ec_getECfromADC(float adc); float ec_calculateEC25(float pEC,float pTemp); void ec_setup() { ledcSetup(EC_PWM_CH, EC_FREQUENCY, EC_RESOLUTION); ledcAttachPin(EC_PIN_FREQ, EC_PWM_CH); ledcWrite(EC_PWM_CH, 127); //50% duty cycle pinMode(EC_PIN_RELAY_PROBE,OUTPUT); //LOW=Calibration/idle, HIGH=Probe connected ec_releaseRelay(); } void ec_loop(unsigned long loopmillis) { static unsigned long last_read_ec=0; switch (ecstate) { case IDLE: if (loopmillis>last_measurement_ec+EC_MEASUREMENT_INTERVAL && ecstate==IDLE) { //start measurement if idle last_measurement_ec=loopmillis; ec_startMeasurement(); ec_connectProbe(true); ecstate=MEASURE; } break; case MEASURE: if (ec_measurementReady()) { ec_releaseRelay(); ec_adc=getMean(ec_array,EC_ARRAY_SIZE); if (isValueArrayOK(ec_calib_array,EC_CALIB_ARRAY_SIZE,EC_ADC_UNAVAILABLE)){ ec_calib_adc=getMean(ec_calib_array,EC_CALIB_ARRAY_SIZE); ec_adc_adjusted=mapf(ec_adc,0,ec_calib_adc,0,ec_reference_adc); ec=ec_getECfromADC(ec_adc_adjusted); ec25=ec_calculateEC25(ec,tempC_reservoir); }else{ ec_calib_adc=EC_ADC_UNAVAILABLE; ec_adc_adjusted=EC_ADC_UNAVAILABLE; ec=EC_UNAVAILABLE; ec25=EC_UNAVAILABLE; } ec_flag_measurement_available=true; ecstate=IDLE; } break; } if (ec_array_poslast_read_ec+EC_READ_INTERVAL) { //take reading into array last_read_ec=loopmillis; if (loopmillis>ec_last_change_relay+EC_RELAY_SWITCH_SETTLETIME) { //values have settled uint16_t value = ADS.readADC(EC_ADS_CHANNEL); ec_array[ec_array_pos]=value; ec_array_pos++; } } }else{ //measurement not running, then take calibration readings if (loopmillis>last_read_ec+EC_CALIB_READ_INTERVAL) { //take reading into array last_read_ec=loopmillis; if (loopmillis>ec_last_change_relay+EC_RELAY_SWITCH_SETTLETIME) { //values have settled uint16_t value = ADS.readADC(EC_ADS_CHANNEL); ec_calib_array[ec_calib_array_pos]=value; ec_calib_array_pos++; ec_calib_array_pos%=EC_CALIB_ARRAY_SIZE; } } } } void ec_startMeasurement() { ec_array_pos=0; } bool ec_measurementReady(){ if (ec_array_pos>=EC_ARRAY_SIZE) { //reached end of both arrays return true; }else{ return false; } } void ec_connectProbe(bool relay) { bool val=digitalRead(EC_PIN_RELAY_PROBE); if (val!=relay) { //write only if different digitalWrite(EC_PIN_RELAY_PROBE,relay); ec_last_change_relay=millis(); } } void ec_releaseRelay() { digitalWrite(EC_PIN_RELAY_PROBE,LOW); ec_last_change_relay=millis(); } float ec_getECfromADC(float adc) { uint8_t polynom_order=sizeof(ec_calibration_polynom) / sizeof(ec_calibration_polynom[0]); double _ec=0; if (adc>=ec_calibration_linearize_below_adc) { //adc is in range where polynomial approximation fits well for (uint8_t i=0;i