Dan Perersen's

Cylinder Coil Version

Instructions for Professor Coyle: Professor Coyle is intended to be a mathematical aid in determining the inductance of a coil and the resonant frequency of a coil-capacitor tuned circuit. To Use The Coil Calculator: The coil calculator will calculate the inductance of both closewound or non-closewound or "spaced" coils. To do a closewound coil, enter the coil diameter and the desired number of turns into the appropriate places. Left-click on any of the red numbers to change their value, then press <enter>. Look at the list below the entered numbers and you will note a series of inductances and lengths paired with the gauge of wire to be used. These are the inductances and coil lengths of a closewound coil as a function of the wire guage. For example, enter a form diameter of 1.75" and 78 turns into the calculator. Now if you wanted to use #28 enamelled wire, you would need a space of 1.11" on the coil and the inductance would be 244.9 uH. The amount of wire needed is also given. A "spaced" coil is one that has a gap between turns. An example is a coil that is 1 inch long and has 8 turns of #24 wire "spaced" along the 1 inch length.There is a significant gap between turns. To calculate the inductance, enter the coil diameter, the number of turns and the coil length into the calculator. The calculated inductance will appear in blue just under the entered parameters. To Use the Resonance Calculator: Enter the known inductance and capacitance into the calculator section at the top of the page. The resonant frequency and the reactance of the L-C circuit will be given in blue immediately below. Example: You have a 40-400pF variable capacitor and a 240uH inductor and you want to find the tuning range. Enter the inductor value, press <enter>, and the highest variable capacitor value into the calculator and press <enter>. You should see a resonance of .514 MHz. Left-click on the capacitance value and now enter 40. You should now see a resonance of 1.624 MHz. In this example would be perfect for tuning the AM broadcast band.The result is a theoretical value. The actual frequency will differ slightly due to distributed capacitance and measurement tolerances.