201 lines
6.5 KiB
C++
Executable File
201 lines
6.5 KiB
C++
Executable File
/*
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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 "BSP.h"
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#include "power.hpp"
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#include "../../configuration.h"
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#include "main.hpp"
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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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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; //The vreg is +-2%, but we have no higher accuracy available
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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 /= OP_AMP_GAIN_STAGE;
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if (systemSettings.CalibrationOffset) {
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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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}
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// Bias removal (Compensating for a temperature related non-linearity
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// This uses the target temperature for the tip to calculate a compensation value for temperature related bias
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// This is not entirely ideal as this means we will be wrong on heat up, but will settle to the correct value
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// This will cause us to underread on the heatup until we reach the target temp
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// Compensation (uV)== ((((80+150*(target_temp_c_x10-1000)/3000)*vddRailmVX10)/4096)*100)/GAIN
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// Reordered with Wolframalpha
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if (currentTempTargetDegC > 0) {
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uint32_t compensation = (20625 * ((currentTempTargetDegC * 10) + 600)) / 512;
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compensation /= OP_AMP_GAIN_STAGE;
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if (valueuV > compensation) {
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valueuV -= compensation;
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}
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}
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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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#ifdef ENABLED_FAHRENHEIT_SUPPORT
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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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#endif
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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, 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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const uint16_t uVtoDegC[] = { //
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//
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0, 0, //
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175, 10, //
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381, 20, //
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587, 30, //
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804, 40, //
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1005, 50, //
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1007, 60, //
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1107, 70, //
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1310, 80, //
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1522, 90, //
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1731, 100, //
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1939, 110, //
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2079, 120, //
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2265, 130, //
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2470, 140, //
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2676, 150, //
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2899, 160, //
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3081, 170, //
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3186, 180, //
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3422, 190, //
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3622, 200, //
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3830, 210, //
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4044, 220, //
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4400, 230, //
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4691, 240, //
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4989, 250, //
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5289, 260, //
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5583, 270, //
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5879, 280, //
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6075, 290, //
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6332, 300, //
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6521, 310, //
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6724, 320, //
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6929, 330, //
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7132, 340, //
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7356, 350, //
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7561, 360, //
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7774, 370, //
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7992, 380, //
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8200, 390, //
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8410, 400, //
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8626, 410, //
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8849, 420, //
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9060, 430, //
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9271, 440, //
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9531, 450, //
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9748, 460, //
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10210, 470, //
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10219, 480, //
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10429, 490, //
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10649, 500, //
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};
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uint32_t TipThermoModel::convertuVToDegC(uint32_t tipuVDelta) {
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if (tipuVDelta) {
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int noItems = sizeof(uVtoDegC) / (2 * sizeof(uint16_t));
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for (int i = 1; i < (noItems - 1); i++) {
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//If current tip temp is less than current lookup, then this current loopup is the higher point to interpolate
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if (tipuVDelta < uVtoDegC[i * 2]) {
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return LinearInterpolate(uVtoDegC[(i - 1) * 2], uVtoDegC[((i - 1) * 2) + 1], uVtoDegC[i * 2], uVtoDegC[(i * 2) + 1], tipuVDelta);
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}
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}
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return LinearInterpolate(uVtoDegC[(noItems - 2) * 2], uVtoDegC[((noItems - 2) * 2) + 1], uVtoDegC[(noItems - 1) * 2], uVtoDegC[((noItems - 1) * 2) + 1], tipuVDelta);
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}
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return 0;
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}
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#ifdef ENABLED_FAHRENHEIT_SUPPORT
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uint32_t TipThermoModel::convertuVToDegF(uint32_t tipuVDelta) {
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return convertCtoF(convertuVToDegC(tipuVDelta));
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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 (320 + ((degC * 90) / 5))/10
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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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#endif
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uint32_t TipThermoModel::getTipInC(bool sampleNow) {
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int32_t currentTipTempInC = TipThermoModel::convertTipRawADCToDegC(getTipRawTemp(sampleNow));
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currentTipTempInC += getHandleTemperature() / 10; //Add handle offset
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// Power usage indicates that our tip temp is lower than our thermocouple temp.
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// I found a number that doesn't unbalance the existing PID, causing overshoot.
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// This could be tuned in concert with PID parameters...
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currentTipTempInC -= x10WattHistory.average() / 25;
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if (currentTipTempInC < 0)
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return 0;
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return currentTipTempInC;
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}
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#ifdef ENABLED_FAHRENHEIT_SUPPORT
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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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currentTipTempInF += x10WattHistory.average() / 45; // 25 * 9 / 5, see getTipInC
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return currentTipTempInF;
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}
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#endif
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uint32_t TipThermoModel::getTipMaxInC() {
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uint32_t maximumTipTemp = TipThermoModel::convertTipRawADCToDegC(0x7FFF - (80 * 5)); //back off approx 5 deg c from ADC max
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maximumTipTemp += getHandleTemperature() / 10; //Add handle offset
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return maximumTipTemp - 1;
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}
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