in the center of both bottoms; when the
cans are fitted together, you should be
able to test connectivity from top to
bottom using a multimeter. Cut a
corresponding hole in the center of the
other tube end cap and assemble the
two bottom halves of the cans as shown
in Figure 10.
A solder lug is a convenient way to
make the connection to the end of the coil. After
connecting the toroid, check for connectivity from the
bottom wire of the secondary to the top of the toroid. The
resistance should be the same as the ohm value of just the
coil by itself. You can attach a wire or metal piece with
sharp edges to the top-most point on the toroid to provide
a breakout point for corona discharge if you like
(illustrated in Figure 11). If you construct the primary to
secondary geometry correctly, the corona should self-discharge without a nearby ground path.
Try attaching thin pieces of aluminum or tin
geometries that have intentionally designed sharp points
for the best corona effects. Use wire or a stiff lead
component to elevate the metal shape. The intensity of
the corona is a function of the capacitance of your toroid.
A pinwheel design using a circular array of points will
actually spin as charge leaves the sharp edges.
Constructing the
Printed Circuit Board
The parts layout for the PCB is not critical. If you mount
the 25V transformer on the base, you may want to contour
the PCB for it to fit as shown in Figure 12. The power jack
located in the lower left corner of the PCB is a parallel
connection to the 25V AC output of the transformer. It can
be used for an alternate input voltage source.
The 120V input to the transformer connects to the
circuit using a molded two-pin connector. The RF may
interfere with programming, so you may want to open the
+V supply to the coil using an optional SPST switch shown
in the schematic. This allows a programming voltage to be
present on the controller, but disables the coil output. The
C4 capacitor that connects across the coil should be
placed as close as possible to the primary. This large
capacitor can be integrated into the coil form used for the
primary. This high voltage capacitor is important and for
best operation, it should be able to withstand a minimum
of 1,600V potential.
The capacitor is constructed from metalized
polypropylene and is specially designed for horizontal
resonance circuits for color TVs and monitors. These
capacitors can be hard to find and expensive to buy, and
are best salvaged from the circuit boards of a monitor or TV.
How to Demonstrate It
A high voltaic potential will accumulate on the
capacitive structure on the end of the secondary coil. By
convention, it is usually constructed in the shape of a
; FIGURE 10.
; FIGURE 12.
; FIGURE 11.
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