95 lines
3.5 KiB
C
95 lines
3.5 KiB
C
/*max_functions.c*/
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#include"max_functions.h"
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int set_output_voltage(double setpoint_voltage, ESeries E_resistors) {
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bool solution_found = false;
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int decade_max = 6;
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int decade_min = 1;
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double R_high_resistance = 0.0;
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double R_low_resistance = 0.0;
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//start at 10k for low resistor and at minimum for high resistor
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int R_high_decade = decade_min;
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int R_low_decade = 4;
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double R_high_value = 1.00;
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double R_low_value = 1.00;
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// voltage computed from resistor configuration used to compare new result to previous optimum
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double output_voltage = 0.0;
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double output_voltage_w = 0.0;
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// set the max array index for given e series
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unsigned int e_max_values = get_E_MAX(E_resistors);
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if (e_max_values == E_NIL) {
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printf("max668_calc:max_functions:set_output_voltage: Unknown E series.\n");
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return EXIT_FAILURE;
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}
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// working variables
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int R_high_decade_w = R_high_decade;
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int R_low_decade_w = R_low_decade;
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double R_high_value_w = R_high_value;
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double R_low_value_w = R_low_value;
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/*
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* start at minimum given Rlow from datasheet and select optimal Rhigh for given Rlow and Vout.
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* do this for all possible Rlows and choose the optimal combination
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* (minimize |setpoint_voltage - output_voltage|)
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*/
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for(int i_low = R_low_decade; i_low <= 6; i_low++) {
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R_low_decade_w = i_low;
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for (int j_low = 0; j_low <= e_max_values; j_low++) {
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// in the 6th decate only examine R_low = 1M, then stop
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if ( i_low == 6 && j_low > 0 )
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break;
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// select new R_low
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R_low_value_w = E_values[E_resistors][j_low];
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R_low_resistance = R_low_value_w * exp(log(10)*R_low_decade_w);
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// calculate corresponding R_high
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R_high_resistance = R_low_resistance *((setpoint_voltage/1.25)-1);
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R_high_decade_w = floor(log10(R_high_resistance));
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R_high_value_w = round_to_E_series((R_high_resistance / exp(log(10)*R_high_decade_w)), E_resistors);
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// calculate the acchieved outputvoltage for resistor combination from the given E series
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output_voltage_w = 1.25 * ((R_high_resistance/R_low_resistance) + 1);
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// if the calculated resistance is too small or too great, ignore it
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if (R_high_decade_w > decade_max || R_high_decade_w < decade_min)
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continue;
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// if a new optimum is found -> save the values
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if (fabs(output_voltage - setpoint_voltage) > fabs(output_voltage_w - setpoint_voltage)) {
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R_high_decade = R_high_decade_w;
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R_high_value = R_high_value_w;
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R_low_decade = R_low_decade_w;
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R_low_value = R_low_value_w;
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output_voltage = output_voltage_w;
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solution_found = true;
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}
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}
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}
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// report the found optimal resistor combination in the given E series
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if (solution_found) {
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printf("Found optimal combination for R_high / R_low: \n");
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printf("R_low: %5.2fE%i ohms\n",R_low_resistance,R_low_decade);
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printf("R_high: %4.2fE%i ohms\n",R_high_resistance,R_high_decade);
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printf("Achieved output_voltage:");
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printf("V_out: %4.2f",output_voltage);
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}
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else {
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printf("max668_calc:max_functions:set_output_voltage: Unable to find valid resistance combination within given range.\n");
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return EXIT_FAILURE;
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}
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return EXIT_SUCCESS;
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}
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