Test Steps

To test the project, follow these steps:

1. Him R3 to full counterclockwise (CCW) and SI off. Insert a temporary 10-amp fuse into the holder.

2. Connect a test lead at the chassis ground and place the other end about one inch from the output lead of Tl. This is a crucial step.

3. Connect to a suitable 12-volt converter or a high-current battery. It is a good idea to moni­tor the input amps for circuit performance verification.

4. Turn the power switch SI on and note a quies­cent current of 1 amp. Slowly adjust R3 clock­wise and note a rise in the current of about 2 amps along with some corona at the output terminal. This is the low-output mode and can be used for continuous operation without overheating. Preset R4 to midrange.

Plasma arc starts at bottom of ladder and travels up the ladder elements where it expands and eventually extinguishes. Arc quickly reforms at the bottom and repeats itself.

Adjust bottom of ladder spacing so that arc reliability starts but yet does not remejn stationary Adjust top of ladder so that arc travels up to desired length before extinguishes and repeats It may lake patience and perseverance to get it right*!

1 Shape two 1/8" brass rods as shown.



Test Steps

2 Drill two 1/8" holes about 1/2" deep into EN1 enclosure as shown

3 Connect output lead of T1 to one rod andgroundleadtoother Solder or crimp for a positive secure connection.

4 Adjust bottom separation to 1/2". Separation between rods increases to about 1 to 2" at top end

Figure 17-B Final view of Jacob’s ladder project

5. Continue tuning R3 and note a very sharp rise in the current (about 7 amps) with the output coming to life. Immediately shut it down as the coil can be damaged in this mode without a suitable load such as connection to a neon or fluorescent tube.

lf you have a scope, you may short the output of Tl to ground and note the test patterns included in Figure 17-2. This verifies the oper­ation. Note that the transformer is designed to allow proper switching of ihe MOSFETs even with shoried outpui.

6. Replace the 10-amp fuse with a 5- to 7-amp value.

7. Insert a four-inch enclosure tube (EN1) into the boitom cap (CAP1). Use PVC plumber cement to seal these pieces as they must not leak the transformer oil. Do this only after

correct circuit performance has been verified as you cannoi service Tl without hacksawing the enclosure apart.

8. Fill the enclosure with oil to the lop of the Tl. It is not necessary to seal the top cap if the unit is always operated in its upright position. Note this step is not necessary for use wilh the enclosed experiments when operaied as shown.

9 Proceed to conduct the experiments as shown in figures 17-8 and 17-9. Experiment using pieces of steel wool, needles, and fluoresceni and gas-filled lamps, and observe how differ­ent materials react to the high-frequency energy. Caution: Obtain some potassium nitrate and sprinkle ii omo some steel wool. Note the pyroiechnic display. Danger: Do not use chlorates or perchlorates.

1. Carefully solder a piece of thin bus wire to the center terminal of lightbulb. This is usually iead and solders easily Caution lo not overheat.

2 Connect output lead from 11 lo this lead Bulb should be secured to top of EN1 via a small bracket or other suitable means. Use a nonconductive material

3. Use a 5", clear 100-watt "DECOR” lamp, preferably one made by Sylvenia orGE as these seem to work the best Experimant with other bulbs as you may get some interesting results

4 Do not leave this display on for long penods as high — frequency energy mey quickly puncture the thin glass envelope of these bulbs.

Figure 17-9 A poor man’s plasma globe

Table 17-1 Solid-state Tesla coil

Ref. # Qty. Description DB#

Rl, 6,7 3 10-ohm, ‘A-watt resistor (br-blk-blk)

R2 I -kilo-ohm, ‘/4-watt resistor (br-blk-red)

R3 5 kilo-ohm trimpot

R9 IO-ohm. ‘/г-watt resistor (br-blk-blk)

R8 15-ohm, 3-watt resistor (br-grn-blk)

R30 10K, 17-millimeter potentiometer

Cl 100 mfd. 25-volt vertical electrolytic capacitor

C2 4700 pfd, 50-volt polyester capacitor

C3 1000 m fd, 25-volt vertical electrolytic capacitor

C4 .1 mfd, 100-volt polyester capacitor

C5 .0033 mfd. 250-volt polypropylene capacitor

11 I ntegrated circuit driver 3525

Ql,2 2 MOSFETs IRF540

Tl Reworked flyback transformer; see Figure 17-3 FLYGRA

WR1BLK 6 feet #20 vinyl hookup wire, black


‘table 17-1 Continued

Ref. #




6 feel

#20 vinyl hookup wire, red


6 feet

#20 vinyl hookup wire, green


6 inches

#20 bus wire


PCB or perforated circuit board.1 X.1 grid



6-32 X ‘/z-inch nylon screws



6-32 X ‘/2-inch steel screws



6-32 nuts



Mica washers for Ql and Q2



6-inch nylon tie wraps


Fuse holder and 5-7 amp fuse


SPST 5-amp switch



#6 solder lugs


3/8-ineh plastic bushing


Strain relief plastic bushing


Mounting bracket, as shown in figure 17-4


Plastic channel base, as shown in Figure 17-5


2- X 2-inch thin plastic insulating sheet


3 ‘/2-inch plastic cap


4- X 3 l/2-inch schedule 40 PVC lube


Plastic cover, as shown in Figure 17-5


I — X ‘/«-inch vinyl tube for control pot, which prevents annoying burns


12-volt, 5- to 7-amp converter for main power


An advanced electrical project is an excellent display for museums or can be a fascinating and rewarding project for the serious and experienced hobbyist. Highly energetic audible and visual bolts of lightning jump into empty space, providing a spectacular effect. This can be an excellent advertising and attention-get­ting display when properly set up (see Figure 18-1).

The project is shown using basic materials but will require certain specialized parts readily available through our web site at www. amazingl. com (see Table 18-1). Expect lo spend around $400 for the spe­cial parts with the others available at a local hard­ware store. The unit utilizes dangerous high voltages and is not recommended for inexperienced person­nel. Safety is fully emphasized throughout these con­struction plans.

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