The Turn Of The Century Electrotherapy Museum http://www.electrotherapymuseum.com Binary Based Adjustable Capacitor / Condenser for Tuning Tesla Coils I've used this method for years, and it is particularly handy when you find rare Tesla Coils embedded in wax that are unable to be measured or have unknown winding configurations to do the formulas. Rendering of assembled cap - 8.5" x 11" acetate sheets and aluminum foil. I designed these caps so that each pair of foils measured .001 mfd.  The first pair comprised the first section, .001 mfd. The next section was made from pairs, containing two sets of foils, giving a total of .002 mfd. The third section was 4 pairs yielding .004 mfd... The fourth section was 8 pairs yielding .008 mfd... The fifth section was 16 pairs yielding .016 mfd... The rest of the cap followed the same pattern until the desired maximum capacitance could be obtained - .032 mfd, .064 mfd, .128 mfd etc. One leg of the cap was connected in parallel and the other leg to knife switches in series with a long binding post representing the other leg of the cap. Depending which switches were set, according to binary numbers, the cap was adjustable from .001 mfd to the maximum (here 1.024 mfd) in .001 mfd increments in a precise and accurate manner. For all practical purposes, this concept can be carried out using .001 mfd, .002 mfd, .004 mfd,  and .008 mfd sections yielding from .001 - .015 mfd in .001 increments for smaller Tesla Coils...  or .001 mfd, .002 mfd, .004 mfd, .008, .016  mfd sections yielding from .001 - .031 mfd in .001 increments for medium Tesla Coils...  or .001 mfd, .002 mfd, .004 mfd, .008, .016, .032  mfd sections yielding from .001 - .063 mfd in .001 increments for large Tesla Coils...  Pancake Coils will require more sections to handle the lower frequencies encountered by this coil type. In this way, you have a master power supply and simply change the value of the cap quickly at will to tune any coil in your collection.  The setup is particularly suited for lectures where one supply and many coils are to be exhibited. Examples:.001 mfd .002 mfd .001 + .002 mfd = .003 mfd .004 mfd .004 + .001 mfd = .005 mfd .004 + .002 mfd = .006 mfd .004 + .002 + .001 mfd = .007 mfd .008 mfd .008 + .001 = .009 mfd .008 + .002 = .010 mfd .008 + .001 + .002 mfd = 0.011 mfd .008 + .004 = .012 mfd .008 + .004 + .001 mfd = .013 mfd .008 + .004 + .002 = .014 mfd .008 + .004 + .002 + .001 mfd = .015 mfd etc. (C) Jeff Behary, 2008