non-conductive mandrel or spool--ideally made of plastic or a glass rod
(be careful not to break a glass rod). Try to make the roll straight and free of lumps and wrinkles. When it's all
rolled up, secure it with plenty of tape. The author uses clear package-sealing tape for this. Now secure the
positive foil tab (assuming it's going to be for DC) to the mandrel using tape. Finally, coat the exposed ends with
an insulating product like silicone RTV.
The remaining foil connection tab may be reinforced by rolling it around a small metal dowel. A nail, or a cut-off
piece of 1/8-inch uncoated brazing rod is suggested. Apply glue to hold the assembly tog ether.
Foil tabs can be strengthened by adding "ribs" of adhesive from a hot glue gun. Similarly, the tabs can be made
tear-resistant by applying hot glue where they enter the capacitor.
Note most problems with this design come from particle contaminants that stretch a dielectric thin in spots where
they are trapped by the tightly rolled dielectric. Another trouble is inadequate edge spacing, causing arcing across
the ends. Careful planning and assembly will eliminate both headaches.
High Voltage Safety and Warning Label:
High voltage is considered any value over 500 volts AC or DC. When you attach a capacitor to
high voltage, you are multiplying its hazard many fold. There fore, experimenters must take extra precautions to avoid
painful shocks and possible electrocution. Here are a few guidelines to follow when working with high voltage:
Label your project in several location with: "Danger, High Voltage" where appropriate. Such
a warning label is provided here for you to copy (See Fig. A). Keep children, pets, and curiosity seekers away from
the apparatus. Cover all bare leads, wires, connection terminals, and possible points of contact with high voltage
putty or a cover fabricated from thick clear plastic.
Work in a dry location. Working in a damp basement of workshop courts disaster. Wear
rubber-soled boots or sneakers. Stand on a thick rubber mat.
Never put your body in a position to become a conductor. Locate your apparatus away from
appliances, metal doors and windows frames, heating ducts, vents, radiators, sinks, or water-pipes. All these items
can become a deadly ground if your body comes between them and high voltage.
Always pull the plug when working on a high voltage circuit unless you must test it. When
testing a live circuit, use the utmost caution. Keep one hand in your pocket. Use clip-on test leads that are rated
twice the voltage of the live circuit. Use a high voltage probe whenever possible--its insulating handle will help
Use NE-2 neon lamps to indicate live or stored high voltage. Bleed off the charge on
capacitors with a power resistor before performing adjustments.
Adequate ventilation must be provided for circuits that produce large amount of ozone such as Jacob's Ladders or Tesla Coils.
Copyright and credits:
This article was originally written by Anthony Charlton and the editors of "Electronics Now" and "Popular
Electronics" magazines and published by Gernsback Publishing, 1992(Gernsback Publishing is no longer in business).
Editor's note and Disclaimer:
The device carries lethal high voltage and carelessness can be dangerous to your health. Build and/or use at your own risk.
The Sentex Corporation of Cambridge Ontario, host of "Tony's Website", or Tony van Roon himself, cannot be held liable or
responsible or will accept any type of liability in any event, in case of injury or even death by building and/or using or
misuse of this device or any other high-voltage device posted on this web site. By accessing, reading, printing, or building
the unit in this article you agree to be solely responsible and agree with the above stated disclaimer.
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Copyright © 2005 - Tony van Roon
Last Updated July 24, 2010