Testing the Circuit

To test the circuit, follow these steps (see Figure 19-2):

1. Set the bottom of the ladder elements to no more than 4a of an inch separation and tem­porarily short circuit the ladder elements with a clip lead. Preset the trimpots R4 and RIO to midrange (12 o’clock).

2. Connect an oscilliscope to TP1 and TP2. If you do not have a scope and your assembly is correct, you may assume the circuit is cor­rectly functioning if the following measure­ments are read.

3. Obtain a 40-watt lightbulb used as a ballast and an isolated source of 115 volts-alternating

current (VAC), preferably with a adjustable voltage transformer (variac) and a current- reading meter. A suggested circuit is described in Chapter 8 (see Figure 8-3).

Rotate R19 full clockwise (CW) and quickly adjust R4 to read a period of 40 microseconds (usee) (25 kHz). Turn R9 back full counter­clockwise (CCW).

4. Turn off the power and remove the short across the ladder elements, as directed in step

l. Turn on the power and advance R19 in a CW direction, noting an arc that forms and attempts to rise up the ladder. Switch out the ballast, noting the full action of the plasma arc rising and breaking at around 3 inches and repeating. Check that the fan is fully on and measure 12 volts-direci current (VDC) across the leads,

5. Observe the line current, noting that it rises to around 1 to 2 amps as the arc rises and breaks at the ladder top.

6. Firmly grab a metal object and contact one of the ladder elements. The unit should quickly

Testing the Circuit

Figure 19-3 Wiring diagram

shut down. Note that R4 may be adjusted CW 7. Even though the circuit is intended for contin – to increase shutdown sensitivity or to full uous use, the project as described should not

CCW to disable. The normal setting is at be left on unattended,

midrange.

Testing the Circuit

Allow access to FAULT and ADJ trimpots.

Figure 19-4 Bottom view of parts lavout

Testing the Circuit

Figure 19-Б Top view of parts layout

Table 19-1 Jacob’s ladder parts

Ref. # Rl

R2,3

R4

R5.ll

R6,7

R8

RIO

R30

R9

R19/SW1

Rx

C2

C3

C4

C8

CIO, И

C12

СЗО

Dl,2,3,4

D5

D6

D30

Qty. Description

100-ohm, ‘/4-watt resistor (br-blk-br)

2 18K, 3-watt metal oxide (mox) resistor

2K vertical trimpot

2 IK, ‘A-watt resistor (br-blk-red)

2 15-ohms, ‘/4-watt resistor (br-grn-blk)

Ю-ohm, 3-watt mox resistor

10K vertical trimpot

30-ohm, 3-watt mox resistor

lOOK, l/4-watt resistor (br-blk-yel)

IOK potentiometer and 115 VAC switch

In-rush current limiter #CL1V0

10 mfd/25-volt vertical electrolytic capacitor

.01 mfd/100-volt plastic capacitor

.1 mfd/600-volt metalized polypropylene capacitor

2 1.5 mfd/250-volt metalized polypropylene

capacitor

.0015 mfd/600-volt metalized polypropylene capacitor

.47 mfd/50-volt plastic capacitor

2 220 to 330 mfd/200-volt vertical

electrolytic capacitor

.01 mfd/1 Kv disc capacitor

100 mfd/25-vo! t vertical electrolytic capacitor

4 1N5408 1 Kv, 3-amp rectifier

1N4937 1 Kv fast-switching diode

1N914 silicon general purpose diode

1N40011-amp rectifier diode

Ref. #

IC1

Ql,2 2

SCR

Zl,2 2

PCI

THERMOl 2 SWNYLON 2

Qty.

COl

Tl

WR24

WR20

WR20KV 5 feet BASE

LADDERS 2

BLOCKS 2 FEET 4

TYE12

SCRW6 8

WASH6 2 SCRW4X1 2

SCRW8X.5 4

Description

IR2153 dual in-line package driver

IRF450 metal-oxiile-semiconductor field effect transistors (MOSFETs)

Sensitive gate silicon-controlled rectifier #EC103D

6-volt 1-watt zener diodes #IN4735

PCB and wire as shown in Figure 19-3 #PCLINE

Insulating thermo pads for Ql and Q2

6-32 X ‘/2-inch nylon screws and metal nuts

Panel-mount fuse holder and 3-amp slow-blow fuse

Three-wire #18 power cord

High-voltage ferrite switching transformer, #JACKT1

#24 red and black pieces of hookup wire

#20 red and black pieces of hookup wire

20 Kv silicon high-voltage wire

6 x 9 x ‘/4 finished plywood or Lexan, fabricated as required

18 x ‘/г x.05 stainless steel, fabricated as shown

I ‘/4 x 1 x 3/4 PVC or Teflon blocks

I X 2 wooden dowels or plastic

12-inch tie wrap tor securing Tl

#6 X 3Ai-inch blunt sheet metal screws

#6 X V2-inch washers

#4-44 X ‘/2-inch screw and nuts for attaching the assembly board

#8 X ‘/2-inch wood screws for attaching feet pieces

#6 solder lugs

This project provides a simple yet quite spectacular display of various lorms of electrical plasma (see Fig­ure 20-1). The medium used is safe, ordinary, rarefied air pumped down to a rough vacuum of approxi­mately Ч2 millimeters (which is measured in Torr, which is a measure of pressure equal to 1 millimeter of mercury). The plasma display takes on various forms from a well-defined, multivortcx swirling tor­nado to a column of orange saucer-shaped disks. Hand proximity to the container produces an interac­tive mechanism where the tornado can be controlled both in position, movement, and intensity.

Testing the Circuit

Testing the Circuit

Figure 20-1 Plasma tornado enclosure jar

The low-cost construction includes the use of a 1- gallon glass pickle jar as the plasma display vessel. A wide-mouthed jar is preferred with a brass cap that will allow the soldering of the necessary fittings. The electrical input is supplied by the high-frequency, high-voltage Tesla project described in Chapter 17. ^‘Solid-State Tesla Coil.” You will need access to a vacuum pump usually found in most high school sci­ence labs that will pump down the air. A pumped – down jar—one that is processed with a vacuum—is available from ama7ingl. c0m. Properly processed, the display will last up to a year.

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