122 lines
4.0 KiB
C++
122 lines
4.0 KiB
C++
/*
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* TipThermoModel.cpp
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*
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* Created on: 7 Oct 2019
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* Author: ralim
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*/
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#include "TipThermoModel.h"
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#include "Settings.h"
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#include "hardware.h"
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/*
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* The hardware is laid out as a non-inverting op-amp
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* There is a pullup of 39k(TS100) from the +ve input to 3.9V (1M pulup on TS100)
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*
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* The simplest case to model this, is to ignore the pullup resistors influence, and assume that its influence is mostly constant
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* -> Tip resistance *does* change with temp, but this should be much less than the rest of the system.
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*
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* When a thermocouple is equal temperature at both sides (hot and cold junction), then the output should be 0uV
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* Therefore, by measuring the uV when both are equal, the measured reading is the offset value.
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* This is a mix of the pull-up resistor, combined with tip manufacturing differences.
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*
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* All of the thermocouple readings are based on this expired patent
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* - > https://patents.google.com/patent/US6087631A/en
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*
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* This was bought to my attention by <Kuba Sztandera>
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*/
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// TIP_GAIN = TIP_GAIN/1000 == uV per deg C constant of the tip
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#ifdef MODEL_TS100
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#define OP_AMP_Rf 750*1000 /*750 Kilo-ohms -> From schematic, R1*/
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#define OP_AMP_Rin 2370 /*2.37 Kilo-ohms -> From schematic, R2*/
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#define TIP_GAIN 405
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#else
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#define OP_AMP_Rf 180*1000 /*180 Kilo-ohms -> From schematic, R6*/
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#define OP_AMP_Rin 2000 /*2.0 Kilo-ohms -> From schematic, R3*/
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#define TIP_GAIN 115
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#endif
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#define op_amp_gain_stage (1+(OP_AMP_Rf/OP_AMP_Rin))
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uint32_t TipThermoModel::convertTipRawADCTouV(uint16_t rawADC) {
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// This takes the raw ADC samples, converts these to uV
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// Then divides this down by the gain to convert to the uV on the input to the op-amp (A+B terminals)
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// Then remove the calibration value that is stored as a tip offset
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uint32_t vddRailmVX10 = 33000; //TODO use ADC Vref to calculate this
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// 4096 * 8 readings for full scale
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// Convert the input ADC reading back into mV times 10 format.
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uint32_t rawInputmVX10 = (rawADC * vddRailmVX10) / (4096 * 8);
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uint32_t valueuV = rawInputmVX10 * 100; // shift into uV
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//Now to divide this down by the gain
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valueuV = (valueuV) / op_amp_gain_stage;
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//Remove uV tipOffset
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if (valueuV >= systemSettings.CalibrationOffset)
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valueuV -= systemSettings.CalibrationOffset;
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else
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valueuV = 0;
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return valueuV;
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}
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uint32_t TipThermoModel::convertTipRawADCToDegC(uint16_t rawADC) {
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return convertuVToDegC(convertTipRawADCTouV(rawADC));
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}
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uint32_t TipThermoModel::convertTipRawADCToDegF(uint16_t rawADC) {
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return convertuVToDegF(convertTipRawADCTouV(rawADC));
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}
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//Table that is designed to be walked to find the best sample for the lookup
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//Extrapolate between two points
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// [x1, y1] = point 1
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// [x2, y2] = point 2
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// x = input value
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// output is x's extrapolated y value
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int32_t LinearInterpolate(int32_t x1, int32_t y1, int32_t x2, int32_t y2,
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int32_t x) {
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return y1 + (((((x - x1) * 1000) / (x2 - x1)) * (y2 - y1))) / 1000;
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}
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uint32_t TipThermoModel::convertuVToDegC(uint32_t tipuVDelta) {
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//based on new measurements, tip is quite linear at 24.9uV per deg C = 2.49 per 0.1C
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//
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tipuVDelta *= TIP_GAIN;
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tipuVDelta /= 10000;
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return tipuVDelta;
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}
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uint32_t TipThermoModel::convertuVToDegF(uint32_t tipuVDelta) {
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tipuVDelta *= TIP_GAIN;
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tipuVDelta /= 1000;
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return ((tipuVDelta * 9) / 50) + 32;
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//(Y °C × 9/5) + 32 =Y°F
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}
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uint32_t TipThermoModel::convertCtoF(uint32_t degC) {
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//(Y °C × 9/5) + 32 =Y°F
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return 32 + ((degC * 9) / 5);
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}
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uint32_t TipThermoModel::convertFtoC(uint32_t degF) {
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//(Y°F − 32) × 5/9 = Y°C
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if (degF < 32)
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return 0;
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return ((degF - 32) * 5) / 9;
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}
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uint32_t TipThermoModel::getTipInC(bool sampleNow) {
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uint32_t currentTipTempInC = TipThermoModel::convertTipRawADCToDegC(
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getTipRawTemp(sampleNow));
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currentTipTempInC += getHandleTemperature() / 10; //Add handle offset
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return currentTipTempInC;
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}
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uint32_t TipThermoModel::getTipInF(bool sampleNow) {
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uint32_t currentTipTempInF = TipThermoModel::convertTipRawADCToDegF(
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getTipRawTemp(sampleNow));
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currentTipTempInF += convertCtoF(getHandleTemperature() / 10); //Add handle offset
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return currentTipTempInF;
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}
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