Construction 5teps

Figure 21-3 shows the foil traces for those wanting to do their own PCB. To begin construction, follow these steps:

Construction 5teps

This view is helpful for those who want to design their own layout on a vector or perforated circuit board. Component leads may be used for most routing traces with heavier leads for the wider traces.

Figure 21-3 X-ray view showing foil traces and pads

1. Lay out and identify all the parts and pieces, and check them wilh the parts list. Note that some parts may sometimes vary in value. This

Construction 5teps

Figure 21-4 View showing parts placement on board

is acceptable as all components are 10 to 20 percent tolerant unless otherwise noted.

2. Identify the pins on the base of transformer Tl, as shown in Figure 21-4.

3. Insert components into PCB PCPF5 as shown in Figure 21 -4. Note to leave at least 4n to 4a of an inch of lead between the actual compo­

nents and the surface of the board. Also notice the polarity on C2 and the proper position of transistors Ql and Q3. Solder the connections and cut away the excess leads. Connect the Tl transformer using short pieces of bus wire and secure it to the board using some tape. Then attach the leads for B1 and B2. Note these leads are strain relieved by passing through

the holes on the foil side of the board. Solder 11-inch leads for contact pads locatcd on the enclosure tube. These may be shortened later. Check for accuracy, the quality of solder joints, potential shorts, and so on.

4 Obiain a 12- to 36-inch neon tube, NE26, as shown in Figure 21-5. Note that the neon tube is shown utilizing only one internal electrode. An external electrode consisting of a piece of metallic tape wrapped around the tube end will also work. The internal electrode approach seems to work slightly better as the input impedance of the feedpoint is obviously noureactive, now being only resistive.

Note that the assembly of the tube is beyond most hobbyists and probably should be obtained as indicated on the parts list. Solder the tube to the assembly board as shown in Figure 21-5 and secure it with some room tem­perature vulcanizing (RTV) silicon rubber. Insert a piece of plastic vinyl tubing between the tube and the PCB to protect the tube from hitting the assembly board and possibly frac­turing.

5. Connect two У-volt batteries or a 9-volt power converter. Note that batteries are connected in a parallel way to supply more current and consequently last longer.

6. You may verify the circuitry by connecting a current meter in series with the batteries and note it reading zero. Hirn the meter range down a step at a time to 50 micro-amps or the lowest range. The meter should still read zero.

Note that any current flow in this test will wear down the battery over a period of time, indicating transistor leakage or a wiring error.

The battery will drain down even if the saber is not in use.

7. Now set the meter range to read 300 to 400 milliamperes and reverse if necessary. Make contact between the pads’ and + leads.

Note that the neon tube fully ignites and the current meter indicates around 300 mil – i

liamperes. Please refer to the test points in

Figure 21-2 if you experience difficulty. These are explained in the supplementary lest points section.

8. Attempt to make contact between these points using the resistance of your finger and verify the partial ignition of the neon tube.

Dampen your finger if the skin is dry. This ver­ifies the proper operation of the electronics. A

Construction 5teps

Figure 21-5 X-rav view of handle innards

dry hand may require a tighter grip, whereas a damp hand requires only a light touch to achieve full plasma ignition.

Circuit Theory

The system utilizes a high-frequency, high-voltage plasma power source that requires only one electrode or an external capacitive electrode for input to the plasma display discharge tube (see Figure 21-2). The external capacitive effect greatly reduces the cost of producing this plasma tube, as no internal electrode or glass-to-metal seals are required. Also eliminated are any grounds or electrical returns required in con­ventional systems.

Ignition of the plasma discharge appears to occur, extending outwardly into space without a return con­nection. In actuality, high-frequency electrical cur­rents flow through the capacitive reactance of the plasma tube with the surroundings where the glass enclosure acts as the dielectric between the two. The user, by hand contact with the control pads, forms the other plate of this virtual capacitor.

The circuit consists of transistor Q3 connected as a Hartly-type oscillator where its collector is in a series

Circuit Theory

It may be necessary to reduce the value of R2 to 100k for decreasing the touch sensitivity. This will depend on humidity, skin resistance, end other factors.

Wava shape at TPC when connected to a 26” red neon tube fully lit.

It is connected to a 9-volt source and drawing 4 amps Note input was adjusted to 7 volts before display started to break from end

T1 transformer winding data

Output. 1350 turns

Primary. 10 turns

Feedback 10 turns

You may use two parallel connected 9-volt batteries for all display tubes. A 12-volt battery pack with Є AA cells may also be used for a brighter display.

Figure 21-2 Plasma lightsaber schematic

with the primary winding, PR1, of transformer Tl and is energized by batteries B1 and B2.The drive signal to its base is obtained by a feedback winding (FB) properly phased to allow oscillation to take place.

The base current is limited by resistor R4 and biased into conduction by resistor R3. Capacitor C3 speeds up the switching times. The oscillations produced are at a frequency of approximately 100 kHz. This is usu­ally determined by the resonant frequency of Tl and tank capacitor C4.

The output of Q3 is controlled via the conduc­tance of pass transistor Q2 by biasing its base with a ramp signal from transistor Ql. C2 bypasses any high-frequency switching currents to the common line of the circuit. This approach provides a positively defined state between the energized and denergized plasma, hence its lit display length.

The current through Q2 and therefore the power to Q3 is controlled by the DC ramp amplifier Ql. The Ql transistor is now controlled when a base current flows through resistor R2.This occurs when the user’s fingers simultaneously touch the two external pad contacts biasing Ql to a point dependent on the user’s contact resistance. This effect produces the variable current ramp that controls the current through pass transistor Q2, hence controlling the out­put of Q3. No off/on switch is necessary since total power is controlled by the user’s finger contact, a capacitor Cl bypasses any external signals that may cause premature operation, and R1 controls the sen­sitivity range of the necessary contact resistance for full ignition as well as linearity.

Construction

The device can be built in two parts, consisting of the display and power sections. These are easily sepa­rated for convenience should the plasma display dis­charge tube become broken or damaged. Also, we must consider the option of using display tubes with other gases, producing different colorful effects.

Tlie display section of the device can consist of a 12- to 36-inch length ot small-diameter neon or another gas tube. Only one electrode is necessary on the display lube, thus eliminating unnecessary costs. This internal gas tube is centered in a clear or colored plastic tube that serves for protection from breakage and provides a more enhanced visual effect due to its diffusive, refractive, and diffractive optical properties.

Special Note

Your display will vary over time, starting out as a wide, undefined glow with purplish and orange disks and eventually forming a defined purple tornado-like vortex extending to the length of the container. This change is due to the pressure increasing and is a func­tion of leakage and internal impurities. The system, properly processed, should be active for up to months before repumping is required.

This chapter shows how to construct a novelty product that provides a bizarre special-effect light display. It is fashioned after the Star Wars lightsaber (see Figure 21-1) and uses a recently patented phe­nomenon involving’ traveling plasma” (our patent #5,089,745). Total control of this display effect is accomplished by simple grip contract on the saber’s handle. No switch is used in any way. Energized plasma (an electrically ignited gas giving off visible light) travels up the saber, illuminating its length as it moves. The effect is greatly enhanced in darkness and is quite dramatic when properly controlled by the user. This gives the effect of a controllable length of visible light appearing to emanate from the handle of the device and continues out into space. A striking visual display now results when operated at low light levels.

Expect to spend $25 to $35 for this awesome, attention-getting display project. Instructions are detailed with all the specialized parts, the printed cir­cuit board (PCB), and the actual plasma tube avail­able from www. amazingLcom. Tlie parts list is included in Table 21-1 at the end of the chapter.

Assembly Instructions

This project will require a properly working Tesla driver, as described in Chapter 17.

Obtain a 1-gallon pickle jar or the equivalent with a brass – or tin-plated metal cap for the display con­tainer, as shown in Figures 20-2 and 20-3. The display container must have a provision for depressurizing and then being permanently sealed. Again, this metal cover of a pickle jar makes an excellent choice because a piece of copper capillary can be directly soldered to it. forming a good, vacuum-tight seal and allowing pinching off for sealing. Should the display container require repumping, the pinched capillary may be easily reopened for reconnection to the vac­uum system.

The display container may be mounted on a suit­able stand that houses the generator beneath, resem­bling a water cooler. Refer to the figures for final assembly and pump down instructions.

Assembly Instructions

Note that the penny stiffens up the thin metal cover to provide a sturdy mounting point for the capillary tubing.

Automotive Cover preparation:

vacuum hose 1. Drill a 125" hole in the center of a copper penny and in the jar cover.

2. Throughly clean the penny and cover to a bare shiny surface.

3 Obtain a propene torch and solder the tube to the penny and to the jar cover as shown. Try not to bum the jar seal. Verify that the solder completely seals this point as any leaks will prevent operation.

4. Throughly clean the jar and let it dry. Put in microwave and "nuke’1 for 30 seconds.

5. Apply vacuum grease to the jar seal and tightly screw on the cap.

6. Unit is ready to pump down.

Assembly Instructions

as this point must support the high voltage and high-frequency energy for this setup.

3. Slide copper capillary into appropriate section of vacuum hose.

4. Allow to pump down to limit of system-should be below tOO millitorrs.

5. Bleed off to.5 Ton and apply power, noting rarefied air glowing a purplish pnk.

6. Disconnect from vacuum system and pinch off section of rubber hose as shown.

7. Connect power supply output now to copper tube on cap and reapply power, noting a well-defined tornado – shaped discharge extending the full length of jar Display is visible under normal lighting but should be quite spectacular in the dark See note below

NOTE – Display may vary with temperature, proximity to other objects, grounding, and, of course, pressure of air inside. Many display variations are possible and experimentation is suggested.

Figure 20-2 Assembly and pump dam

Connection is made to copper tube by a slip fit to vacuum hose

Assembly Instructions

Jar is sealed via a small washer pinching the folded rubber hose. This method provides an excellent temporary seal that is easily removed for repumping etc.

Caution: Jar is under a high vacuum and should be placed in a meshed bag to contain flying shards of glass rf used in public.

Output from power supply can cause a moderately peinful shock or bum. It is not injurious or life threatening due to low current and high frequency.

DANGER: Jar is under a high vacuum and will implode violently if broken.

Assembly Instructions

Insulating plate-use glass or plastic. Dry wood will wor4 but might leech off energy. You may also support it on a glass mixing bowl.

Use a metal plate by grounding, ungrounding, or attaching various lengths of wire etc. for best results.

Operation

t. Place an approx. 6 x 6" piece of metal on a larger piece of glass or other insulating material.

2. Place jar as shown on metal plate. Do not ground for now

3. Verify proper operation of power supply as shown on instructions.

4. Connect up green grounding ieed to a positive earth ground. Failure to do this will result in improper operation

5. Connect output lead to copper capillary tube exiting the jar cover.

6. Rotate power control full CCW and turn on power switch.

7. Rotate power control until you get desired effect that should be a pink column of energized plasma resembling a tornado

Bnng hand near jar and note attraction of display.

This demonstrates the capacitive effect produced by proximily of two conductive objects. The high – frequency current now wants to flow between these points that form a capacitive reactance.

Hold a fluorescent lamp near the jar and note it lighting! This demonstrates the radiative effects of the energized plasma and provides an interesting science project.

If you are fortunate enough to have access to a vacuum pump, experiments with different pressures can yield some real interesting results.

Adjust power control knob for maximum display. Note a peak in adjustment.

Do not leave on for extended periods of time until you check for heating of supply and jar.

Fi g и re 20-3 Plasma tornado jar setup

Application and Operation

The display is inside a glass enclosure and resembles a tornado shape of glowing and swirling plasma. It dances and jumps to anything brought near it and is highly visible, even in normal, fluorescent lighting. This sensitivity to any external capacity creates many bizarre and seemingly striking effects. The plasma also can light up a fluorescent lamp when brought near the glass enclosure without any wires or connec­tions of any kind. This feature demonstrates the highly radiative properties of the plasma field and serves as an excellent science fair project or a unique conversation piece.

Theory of Operation

An evacuated glass comainer is sealed and pumped to.5 to 2 Torrs of pressure. A metal cap seals the con-

tainer and serves as an electrode for charging the remaining thin gas mixture. The voltage applied to the cap is at a potential of 10 to 20 thousand volts and is at a high frequency of approximately 25 kHz. The capacitive effect of the thin gas causes a current to flow, creating the plasma discharges. One may visual­ize the device in the following manner: A capacitor is formed by the conductive gas inside the container forming one plate, the glass envelope being the insu­lating dielectric and the outer air serving as the other plate. Any conducting object brought near the con­tainer now only enhances this effect and appears to draw the plasma arc to the point of contact.

The vacuum will vary along with the physical parameters of the container and can be adjusted to enhance the type of discharge desired. A pressure where the plasma discharges are most defined may be critical. Increases will create a broken, wispy effect, whereas a further decrease will broaden the discharge and eventually form striations as a series of weird, orange disks. Any weird effects are possible from changing pressure, power frequencies, and voltage.

The effect of where the conduction of a gas peaks at a certain pressure is known as the Townsend effect and becomes an important factor in the design of vacuum systems where medium – to high-voltages are encountered. The device as described does not use any gas other than the existing atmosphere rarefied by evacuation. Other colors and effects are limitless when the builder chooses to charge the unit with other gases or combinations of pressures.

Project Description

The described device is intended for display pur­poses, novelty decorations, and special effects, as well as an educational science fair project demonstrating plasma that is controlled electrically and magneti­cally. Special materials treated by a controlled plasma beam can also be realized.

Plasma is often considered lo be the fourth state of matter. It consists of atoms that are ionized and

demonstrates peculiar effects unlike the other three forms of matter.

Columns of pinkish and purplish plasma are attracted to external influences such as fingers and other objects when placed on or near the display con­tainer. These columns of plasma light span the entire length of the display container, dancing and writhing with a tornado-like effect. Balls of plasma and fingers are created and controlled by simply touching the container. This effect cannot be effectively or justifi­ably described in words and can only be appreciated when actually observed.

The device is low powered, high frequency, and high voltage, producing the necessary parameters for obtaining the described plasma effect. This generator utilizes conventional electrified circuitry, consisting of a transistor switching the ferrite core of a high-volt­age resonant transformer (similar to a TV flyback). Power for the transistors is obtained from a simple step-down transformer and rectifier combination.