This Tesla Coil was my first attempt at making a twin coil.  My plan was to build a miniature twin coil in order to prove to myself that I had the theory down.  After building most of it one Sunday evening, and substituting parts for the yet unbuilt portion, I concluding that the experiment was a success.  After finishing it and extensive tuning, I achieved about a 12" spark between the two coils. Although this was very inefficient, it worked, and I was excited!

Specifications:
-  powered by 7.5A  0-140VAC Variac
-  12kV 60mA Neon Sign Transformer
-  safety gap
-  500pF 40kV bypass capacitors
-  .012uF primary tank capacitors (doorknob style)
-  RQ style spark gap, adjustable distance, up to 16 gaps, air cooled
-  primaries (2) are each about 2.5 turns #12 AWG wire
-  secondaries are 1.5" PVC, wound 8" tall with #28 AWG magnet wire
-  topped with copper toilet bowl floats
-  no secondary ground
-  unknown resonant frequency (as of yet)

Schematic:

I have been having a severe problem of internal secondary arcing. I have burnt the inside of one PVC tube from the top HV terminal down the inner wall of the tube to the base.  The arc was so severe that the PVC was melted and prominent branches or black char appear. The coil is now mostly repaired and fully functional.
 

This webpage originally born on 11-7-98. Last updated on 9-7-01