Cardwell.bas (C) 2005 John Fields

This program plots the capacitance change and the change in frequency and wavelength
(if used in a resonant circuit) VS rotation of the plates of a Cardwell variable 
capacitor with wedge shaped plates.

The rotation of the capacitor is represented on the abscissa and varies from 0° to 180°

The capacitance is represented on the ordinate, with a range of from 0 to 1000pF

Frequency and wavelength are normalized, plotted on the linear grid, and scaled 
for convenience of display.


          SCREEN 12
          x = 65536 * 63 + 256 * 63 + 63
          PALETTE 0, x

          WINDOW (0, 0)-(800, 600)
start:    CLS


          rot = 800 / 180         '1ø = 4.44 pixels
          Cmax = 600              '600 pixels = 600pF
          ka = .014               'square inches per degree of mesh
          kd = .0482 / 180        'plate separation per degree of mesh
          cmin = 20               'unmeshed capacitance
          a = 0                   'area of plates
          d = 0                   'distance between plates
          r = 0                   'degrees of rotation
          c = 0                   'capacitance

         
          COLOR 8

          LOCATE 30, 1
          PRINT "0 deg"
          LOCATE 30, 31
          PRINT "<-----rotation----->"
          LOCATE 30, 74
          PRINT "180 deg"

          LINE (0, 0)-(800, 0)
          LINE (800, 0)-(800, 600)
          LINE (800, 600)-(0, 600)
          LINE (0, 600)-(0, 0)

          x = 60
          WHILE x < 660
          LINE (0, x)-(800, x)
          x = x + 60
          WEND

          x = 80
          WHILE x < 560
          LINE (x, 0)-(x, 540)
          x = x + 80
          WEND

          WHILE x < 880
          LINE (x, 0)-(x, 600)
          x = x + 80
          WEND

loop1:    COLOR 4                      'red
          LOCATE 1, 10
          PRINT "CAPACITANCE"
          a = ka * r
          s = .07 - (kd * r)
          c = cmin + (3.15 * a) / s
          PSET ((rot * r), c)          'plot capacitance VS rotation


          COLOR 2                      'green        
          LOCATE 2, 10
          PRINT "FREQUENCY"
          f = 2700 * (1 / (SQR(c)))
          PSET ((rot * r), f)          'plot frequency VS rotation

         
          COLOR 1                      'blue
          LOCATE 3, 10
          PRINT "WAVELENGTH"
          p = 30 * (SQR(c))
          PSET ((rot * r), p)          'plot wavelength VS rotation

          r = r + 1                    'increment rotation by 1°
          IF r > 180 THEN GOTO finish
          GOTO loop1

finish:   COLOR 8
          LOCATE 3, 34
          PRINT "Press any key to exit."

kblpa:    a$ = INKEY$
          IF a$ = "" THEN GOTO kblpa

END