/*

Calculate a Coil's Inductance for Various Number of Turns

                                                  Revision:      5-JULY-1995

This routine calculates the inductance of a single layer air core coil using
the simplified formula:

               a^2 * n^2
     L(uH) = -------------
              9a  +  10b

  where:   a = the coil radius in inches
           b = the coil length in inches
           n = the number of turns

This formula gives a good approximation of a coils ture inductance for coils
having a length (b) that is equal to or greater than 0.8 times their radius (a).

Recall also that;  Inductive Reactance = 2 pi f L
        and that;  Resonant Frequency = 1 / 2 pi sqrt(LC)



*/

#include <stdio.h>                   /* I/O definitions         */


#define     MAXLINE  80
#define     PI       3.1415926

main()


{
        float   radius, turn_width, inductance, aspect, reactance;
        float   frequency, capacitance;
        int     turns, min_turns, max_turns;
        char    filename[MAXLINE];

        FILE   *fpout;


/*   Get the various parameters that will be used for this run  */

        printf("Enter the RADIUS of the coil in inches: ");
        scanf("%f", &radius);

        printf("Enter the coil length per turn (pitch) in inches: ");
        scanf("%f", &turn_width);

        printf("Enter the Frequency (MHz) for this coil's operation: ");
        scanf("%f", &frequency);

        printf("Enter the MINimum number of turns that should be considered: ");
        scanf("%d", &min_turns);

        printf("Enter the MAXimum number of turns that should be considered: ");
        scanf("%d", &max_turns);


/*   Get the filename of the output file    */

        printf("Enter the filename of the output text file: ");
        scanf("%s", filename);

        if ((fpout = fopen(filename, "w", "rat=cr", "rfm=var")) == NULL) {
                printf("\nERROR: Can't open output file %s\n", filename);
                exit (2);
        }



/*   Now that we have all of the parameters and the output filename
     we can start the actual work                                        */

/*      In the reactance calculation the inductance in uH
        will be balanced by having the frequency in and Mhz.             */

/*      In the capacitance calculation the frequency in MHz squard and
        inductance in uH both in the denominator is balanced by the
        10^6 in the numerator to give capacitance in pF                  */

        fprintf(fpout, "\n    Coil Radius is: %6.3f inches \n", radius );
        fprintf(fpout, "    The Coil's pitch is: %6.3f inches \n", turn_width );
        fprintf(fpout, "    Coil's Operating frequency is: %6.3f MHz \n", frequency );

        fprintf(fpout, "\n                                            Inductive                 "  );
        fprintf(fpout, "\n                                            Reactance    Capacitor for"  );
        fprintf(fpout, "\n                            Ratio of the        at        Resonance at"  );

        fprintf(fpout, "\n     Coil    Inductance        Coil's     %7.3f MHz     %7.3f MHz ", frequency, frequency);

        fprintf(fpout, "\n    Turns       (uH)       Length/Radius      (Ohms)          (pF)   "   );

        fprintf(fpout, "\n    -----    ----------    -------------    ---------    ------------- " );


        for (turns = min_turns; turns <= max_turns; ++turns) {

           inductance = (radius * radius * turns * turns) /
                               ((9.0 * radius) + (10.0 * turns * turn_width));

           aspect = (turns * turn_width) / radius;

           reactance = 2 * PI * frequency * inductance;

           capacitance = 1000000.0 /
                              (4 * PI * PI * frequency * frequency * inductance);


           fprintf(fpout, "\n    %4d      %6.2f          %5.2f        %7.2f        %6.1f",
                           turns, inductance, aspect, reactance, capacitance);
       }
   }