Sam's Gadget FAQ

Salvaging Interesting Gadgets, Components, and Subsystems

Version 1.58 (14-Dec-06)

Copyright © 1994-2007
Samuel M. Goldwasser
--- All Rights Reserved ---

For contact info, please see the
Sci.Electronics.Repair FAQ Email Links Page.


Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:
  1. This notice is included in its entirety at the beginning.
  2. There is no charge except to cover the costs of copying.


Table of Contents

PART I - Household (Well, Sort of) Sources of Useful Gadgets

PART II - What Common Consumer Electronic Equipment and Appliances Contain



  • Back to Sam's Gadget FAQ Table of Contents.

    Preface

    Author and Copyright

    Author: Samuel M. Goldwasser

    For contact info, please see the Sci.Electronics.Repair FAQ Email Links Page.

    Copyright © 1994-2007
    All Rights Reserved

    Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:

    1.This notice is included in its entirety at the beginning.
    2.There is no charge except to cover the costs of copying.

    DISCLAIMER

    We will not be responsible for damage to equipment, your ego, blown parts, county wide power outages, spontaneously generated mini (or larger) black holes, planetary disruptions, or personal injury that may result from the use of this material.



  • Back to Sam's Gadget FAQ Table of Contents.

    Introduction

    Reducing the Clutter in Land Fills

    The purpose of this document is to prevent land fills from becoming filled. :-)

    Many dead appliances, and consumer electronic and computer equipment contain parts and subassemblies which are not only neat and interesting, but useful for various experiments and projects.

    There will be several types of information:
    1. Where to obtain a particular type of part like a powerful magnet.

    2. What dead consumer electronics, computer equipment, and appliances yield in the way of useful parts.

    3. Unconventional uses for subsystems or common replacement parts or modules from such equipment.

    Safety Considerations

    The devices, equipment, circuits, and other gadgets described in this document may be dangerous. Much of it deals with potentially lethal voltages. Getting electrocuted could ruin your whole day.

    Before thinking about experimenting with anything using or producing high voltages or connected to the AC line - even opening up a disposable camera that may have been laying around gathering dust (the capacitor can still be charged - arggh!), see the document: Safety Guidelines for High Voltage and/or Line Powered Equipment. A large percentage of equipment that is perfectly safe from the outside has dangers lurking inside. In addition to electrical dangers, there might be sharp sheet metal, wound up springs, powerful magnets, and other potential risks to your outer surface integrity like CRT implosion - just to name a few. Something that looks innocent can really ruin your entire day!

    For really high voltage equipment, also see: Tesla Coils Safety Information.

    Places to Obtain Sacrificial Equipment

    So, where do you find the equipment from which to remove parts other than your basement, your attic, or those of your relatives or friends? Consider garage, yard, tag, estate, and other sales; thrift stores (which may even have a 'free' table); junk, salvage, and surplus yards (including those run by the Department of Defense!), the town dump and other landfills if they let you take things away, trash rooms of high rise apartment complexes, the curb on pickup day, college campuses around the end of the Spring term, and any other place where perfectly good equipment gets tossed in this throw-away society!

    Of course, don't overlook high tech flea markets as well as ham and computer fests. Regular flea markets are usually overpriced (where do you think they get the stuff??) but sometimes you will be able to negotiate a great price because they have no idea of what they are selling!

    Yes, we are a strange bunch. :-)



  • Back to Sam's Gadget FAQ Table of Contents.

    Neat Magnets

    Sources of Extremely Powerful Magnets

    Two excellent sources of magnets are described below. These are at least as strong as the more well known speaker types, possibly much stronger, and generally easier to remove:

    CAUTION: Both these types are powerful and will squash flesh as they suck all the bits off of your magnetic media! I am not kidding about the part about squashed flesh - with some you actually need a small crowbar to pry the assembly apart!

    You will find that some of these magnets are painted. This provides some resistance to chipping though this material may be on the verge of flaking off or has already done so in spots. In any case, I further recommend that you add additional layers of a tough enamel (e.g., Rustoleum) or the plastic/rubber dip used to coat tool handles. Otherwise, chipping damage (at least) will result all too easily and the chips are just as powerful as the rest of the magnet.

    Additional Disclaimer: I will not be responsible when your spouse or parents come home to find the microwave or PC missing some key components and as dead as a brick!

    (From: Terry Sanford (tsanford@nf.sympatico.ca).)

    Magnets salvaged from scrapped computer drives are strong!

    PS: After WWII, strong horseshoe ex radar magnetron magnets were sold surplus for about two and sixpence each. Someone took his into a pub on way home and everyone had a great time with it until people starting checking their (then magnetic) watches. He wasn't too popular after that I can tell you!

    Other Sources of Fairly Powerful Magnets

    The following are other possibilities. However, they are not likely to be nearly as strong!

    Disassembling Loudspeakers to Get at the Magnets

    For small speakers with AlNiCo type magnets (the magnets usually look like metal cylinders), careful prying with a sturdy screwdriver will usually break the adhesive bond and/or free them from the yoke assembly. Note: Use the proper tool for the job - not your dad's prized screwdrivers!) Unlike the ceramic magnets described below, AlNiCo types are metal and quite sturdy.

    (From: Arie de Muynck (ademu@pi.net).)

    For the normal black ceramic ring shaped magnets (and likely for some Ticonal 'iron colored') the trick is: heat the complete assembly slowly using a paint-stripper gun, or in an oven (thermal, not microwave!). The glue will weaken and with a screwdriver you can SLOWLY work them loose. Protect your fingers with an old cloth. Never apply too much force, the ceramic would chip or break.

    Do not overheat them above the so-called Curie temperature or the magnet will loose it's power irreversibly. That temp depends on the material but should be way above the 120 C or so to soften the glue. If you want to experiment with this effect: use a piece of iron attracted towards a magnet, heat the iron with a flame and above a rather sharply defined temperature it will not be attracted anymore. The effect is used in some Weller soldering irons to stabilize the temp.

    Note that the force of a bare ceramic magnet is not as strong as you might expect, the magnetic lines of the large area of the ring have to be bundled and guided though iron to a narrow gap to provide a proper magnetic field.

    How do I Make a Harddrive Motor Spin?

    You are tempted - those spindle motors that are part of the same large old clunky harddrives that yield really powerful magnets look like they would be perfect in that next robotics project if only you could figure out what all those darn wires were for! The following also applies to other multiphase brushless motors lacking (usable) driver electronics including those from high-X CD and DVD drives.

    (From: Bob Weiss (bweiss@carroll.com).)

    These motors are usually brushless DC, and can be a pain to figure out. Windings are usually 3-phase wye. DC power applied to center tap of wye, and ends of windings go to output transistors/fets in the driver. Driven by 3 pulse trains 120 degrees apart. Other leads are for hall effect sensors that measure rotor position and time the drive pulses to the relative positions of the rotor magnets and stator coils. Not an easy driver to build from discretes! Some motors contain all the driver electronics, and only require +12VDC and a TTL enable signal to run. The Disc drive you took them out of will contain appropriate parts to build a controller, probably a driver chip from SGS or Sprague UCN series. Look up the chip in a databook for suggested circuitry. Best way to learn this field is reverse engineering!

    Some general info on motor construction, rewinding, and electronics can be found at Home-Built Brushless Motors and Models and RC Group Groups Discussions - Brushless ESC Designs, as well as the Web sites of major semiconductor manufacturers providing motor driver ICs.



  • Back to Sam's Gadget FAQ Table of Contents.

    High Voltage Power Supplies from Dead Equipment

    You are Surrounded by HV Equipment!

    There are a surprisingly large number of types of common consumer electronics equipment and appliances which employ high voltage in one form or another:

    CAUTION: Since these power supplies were designed for a specific purpose under specific operating conditions, their behavior when confronted with overloads or short circuits on the output will depend on their design. It may not be pretty - as in they may blow up! Take care to avoid such events and/or add suitable protection in the form of fast acting fuses and current limiting to the switching transistor.

    Note about X-rays: Improper use of these sorts of devices may result in shock or electrocution, but at least you will not be irradiated at the same time unless you connect them to a something which includes a vacuum. In order to produce measurable X-ray radiation, electrons must be accelerated to high velocity and strike a heavy metal target. A high vacuum such as in a CRT or other vacuum tube (valve) is best but there may be some X-ray production from a low pressure gas filled tube. There is virtually none in sparks or arcs at normal atmospheric pressure. However, there will be UV and ozone which are both hazardous.

    Sam's Super-Starter(tm)

    This would be called a kludge by some, a Rube Goldberg by others. But, hey, as still others would say: "If it works, use it!". The original application was for starting LARGE HeNe laser tubes but there can be many other uses.

    The entire horizontal deflection and high voltage sections of a long obsolete and lonely ASCII video display terminal were pressed into service for starting larger HeNe tubes. A source of about 12 VDC at 1.5 A is needed for power and a 555 timer based oscillator is needed to provide the fake horizontal sync:

    I guarantee that "Sam's super-starter(tm)" - or its big brother, "Sam's hyper-starter(tm)" using parts from a color TV or monitor - will start ANY HeNe tube that can possibly be started! These also make nice self contained HV sources for other experiments. :-)

    Why the Yoke is Needed to Keep the Horizontal Deflection System Happy

    If you unplug the yoke (even if there is no interlock), while the system may still work to some extent but performance will be poor. High voltage will be reduced and parts may overheat (and possibly blow up).

    (From: Jeroen Stessen (Jeroen.Stessen@philips.com).)

    Of course that doesn't work. The flyback capacitor is tuned for the presence of both inductances: line transformer and deflection coil. If you remove the deflection coil then the remaining primary transformer inductance is about 5 times as large. So, rule-of-thumb, you would have to decrease the flyback capacitor by a factor of approximate 5. But that's not all:

    Without the deflection coil, a lot less current runs through the horizontal output transistor. So, in all likelihood, it will now be overdriven. So you need to reduce the base drive. But that's not all:

    If you remove the picture tube capacitance and the deflection coil then all peak energy demand must be delivered from the primary winding of the line transformer. Even the shortest peak load will cause saturation. The parallel deflection coil will at least lend some temporary energy, and the picture tube capacitance does an even better job. A good high-voltage source without the benefit of a deflection coil is more expensive...

    If you *must* get rid of the 'ugly' deflection coil, then you may want to replace it with an equivalent 'pretty' coil. But:

    And you might want to add a discrete high-voltage capacitor. How to isolate the wiring (corona discharge!) is left as an exercise to the reader... (We pot them in convenient blocks).

    High Voltage Power Supply Module from Monitronix EZ Series Monitors

    This is a self contained module (separate from the deflection circuitry) which makes it very convenient for your HV projects.

    It is fully enclosed in an aluminum case about 1-7/8" x 6" x 5" with a 9 pin connector for the low voltage wiring and thick red wires with HV connectors - suction cup and Alden type - for the CRT 2nd anode and focus voltage respectively.

    There are 8 pins installed on the 9 pin connector of which 6 were used. I wonder if the other 2 have any function other than spacing off the G2 voltage.
    
          ___________
         /           \
        (  o3  o6  o9 |
         >            |  View of connector on case.
        (  o2  o5  o8 |
         >            |
        (  o1  o4  o7 |
         \___________/
    
    
    I assume the NCs are truly not connected to anything and simply serve as clearance for the up to 1000 V G2.

    In addition to the Focus and G2 pots, there is an unmarked adjustment accessible via a hole in the case. At first, this appeared to have no effect on any output.

    When I opened the case, 2 additional pots come into view. While I do not really know their exact function, by advancing them clockwise, the HV could be boosted significantly. With both fully clockwise, the externally accessible control will vary the HV between about 27 and 32 kVDC regulated (only HV probe meter load).



  • Back to Sam's Gadget FAQ Table of Contents.

    High Voltage Transformers

    Types of HV Transformers and Where to Get Them

    There are many types of transformers capable of generating high voltages for hobbyist type projects. Some operate from the AC line directly while others require an interrupter or solid state high frequency driver. Both neon sign and oil burner ignition transformer generally have centertapped secondaries connected to the case - which MUST be grounded (via a three wire cord and properly wired outlet) for SAFETY. Therefore, it is generally not possible to construct a totally isolated HV power supplie with these devices. Note: Ignition coils and flyback transformers can generate very high voltages but must be driven by a pulsed or high frequency drive circuit. These cannot be plugged into the wall socket directly!

    Also see the section: Driving Automotive Ignition Coils and Similar Devices.

    Basic Ignition Coil Circuit

    For a description of how an ignition coil generates high voltage and some math, see the section: Driving Automotive Ignition Coils and Similar Devices. The circuit below is about the simplest possible and easily generates 25 kV using the 12 VDC output of a surplus PC power supply:
    
                                        T1 +-------o HV Out
                           Rb       Bat ||(
             +12 o--------/\/\--------+ ||(
                                       )||( Ignition Coil
                                       )||(
                          Cp           )||(
                     +----||---+----+-+    +-+
                     |         |    |        |
                     | S1 _|_  |    +--------+
             Gnd o---+----o o--+
                        Points
    
    I was able to obtain a 1 inch spark from each button release using about 2 ohms for Rb. If you build an interrupter/buzzer or a mechanical doohickey (technical term) to operate the points, you will get a nice steady stream of fat juicy sparks. Just take care - contact with one isn't going to be an experience you will want to repeat.

    (From: Jonathan Bromley (jsebromley@brookes.ac.uk).)

    The voltage across the coil is L*dI/dt. Voltage across the coil HT winding is the same, but larger by a factor of (turns ratio) which is typically 50 to 100 in ordinary car coils.

    When the points are closed, the coil current will progressively increase because the full battery supply appears across the primary. This will incidentally put around 1kV across the secondary, not enough to jump the gaps in spark plug and distributor. The points dwell time (or the behaviour of the electronic points-substitute controller) will be such as to allow the coil current to reach some sensible value.

    When the points open, if no capacitor then current would instantaneously collapse to zero giving a very high coil voltage (huge dI/dt). But this happens JUST AT THE MOMENT THE POINTS OPEN, when the points gap is tiny. So the high coil voltage will immediately strike an arc at the points as they open. This provides a fairly low-resistance path which will be sustained as the points open further. dI/dt is therefore not so big after all, just enough to maintain the few tens of volts across the points arc. Therefore, not enough voltage on the HT winding to fire the proper spark, and all the stored energy in the coil goes into the arc at the points.

    So, the (rather small) capacitor is there to allow the coil current to continue to flow, without a big voltage appearing across the points initially. Basically this C is there to give the points time to open before the coil primary voltage reaches its peak value of a few hundred volts. The C is chosen to resonate with the L of the primary so that the peak voltage is delayed just long enough so that the points are open wide enough that the 500V primary voltage DOESN'T arc across them, but the 50*500V = 25kV secondary voltage DOES jump the plug/distributor gaps. It's therefore the breakdown voltage of the plug/distributor gap that controls the highest voltage reached across the points. Typically this will not be high enough to allow much of the coil's energy to be transferred into the capacitor. Any energy that _is_ stored in the capacitor will eventually find its way into the spark by the reverse- current mechanism that you describe - the spark current will oscillate for a while. But the oscillations are fairly heavily damped by the loss of energy into the spark.

    The story is slightly more complex in reality because of finite resistance of the coil windings and their distributed capacitance, but this simplified account is not too far from the truth.

    (From: George Nole (gnole@brisbane.dialix.com.au).)

    In the operation of the Kettering ignition system three clearly defined stages or phases can be identified.

    1. Points closed.
    2. Points open, but no gas discharge or spark has been initiated.
    3. As per (2) but discharge has occurred.

    Before proceeding with an analysis, a few notes on the ignition coil. The ignition coil is a transformer with very high leakage inductance. This because the core of the coil is not a closed magnetic circuit, but a straight piece with both ends open. The turns ratio is of the order of 100 or so. Recent measurements on a 6V coil revealed primary inductance with secondary open -no discharge- of 4mH, and with the secondary loaded -gas discharge- of 1mH. These values vary considerably from coil to coil.

    Now the analysis which you can do yourself. Don't take my word.

    1. With the points closed a current flows and energy is stored in the inductor (primary inductance).

    2. When the points open, the circuit consists of a capacitor or condenser in series with the inductor. The other terminal of the capacitor is connected to chassis, and so is the other terminal of inductor via the ignition switch and the car battery.

      This forms a series resonant circuit of finite Q with energy stored in the inductor, and will start to oscillate. The voltage across the inductor -and the capacitor- will be much higher than the voltage across the series resonant circuit and in practice it is of the order of a few hundred volts. This is important because, with a transformer ratio of -say- 100 and a secondary requirement of 20kV, the primary voltage has to be 200V.

    3. Before the oscillation can reach the first peak the gas discharge commences and the inductance changes to that of the leakage value, with a quenched oscillation continuing at a higher frequency than the frequency before the spark.

    End of analysis.

    What would happen if you tried to start the car without a condenser? If you do the experiment, please let me know the result.

    Driving Automotive Ignition Coils and Similar Devices

    From a posting on one of the sci.electronics newsgroups:
    "I have some questions about automotive ignition coils. I'm referring to the cylindrical "universal" type which has two 12 V terminals and one HV terminal in the center of the cap.

    What is the typical peak output voltage and current?

    What is the maximum average power input that such a coil can tolerate? I'm aware that the cross-sectional area of a transformer core dictates power handling capability. Judging from the skinny core in a spark coil, I'd place the maximum continuous duty input at around 50 watts. Am I in the ball park on this?

    Is there an optimum pulse rate?

    Do ignition coils employ any sort of current limiting?

    Do "high-performance" coils with 45-75kv outputs offer significant increases in output power, or just higher voltage?"

    (From: jfreitag@gsosun1.gso.uri.edu (John Freitag).)

    First, be aware that the coil does not act as a transformer as such, even so called "Hot Coils" have only a 1:100 turns ratio which would give only 1,200 volts from a transformer. If you were to energize the coil with an AC voltage like you would with a transformer this is what you would get. An automobile ignition is more properly referred to as an "induction coil" Its output voltage is defined, not by the turns ratio but rather by the differential equation:

                            V = L di/dt
    
    Where: V into an open circuit, will essentially rise until a spark jumps. When the air ionizes and the spark occurs the remaining energy in the coil sustains the spark.

    Hot coils have a heavier primary so that they can pass more current, hence a higher di/dt.

    The maximum pulse rate is determined by the time taken for the current to build when the points close (due to L it rises slowly until it reaches a steady state) and the time for the field to collapse when the points open. (the voltage to generate the spark occurs only after the points open and the field is collapsing)

    I have never thought about the power in the spark but I suppose it would be:

    P = (L di/dt)^2 / R where P is the power in watts and R is the total resistance of the coil secondary, the plug wire and the ionized spark gap. (Some Professor of EE is welcome to comment here).

    As for current limiting, many coils employ a series resistor in the primary which limits current and is shorted out during starting.

    (From: Mark Kinsler (kinsler@froggy.frognet.net).)

    I use a 12 volt battery and it works pretty well. Probably the best high voltage power supply for careless amateurs is the one I designed, which could be found on my Web page if I knew how to do schematics but I don't. But it's simple enough.

    I've been driving my old 12 V coil (bought as a replacement for the one in my Econoline but never used) through a buzzer-type interrupter made from an old relay. I put a capacitor across the contacts for good luck, and for the most part it works pretty well. It'll give me about a 1/2" spark, which is all I need for my illegal spark transmitter and the spark plug in my famous "One Stroke Engine" demonstration. However, it yields some amusing effects, to wit: blue sparks dancing around on the battery lead and the battery itself, extremely strange noises, copious production of ozone, and the occasional puff of smoke. I have the whole mess mounted inside a plastic 2-liter cola bottle. On the advice of my friend Dewey King, who restores old gas engines from oil rigs, I've purchased a Chrysler ballast resistor to put in series with the battery and thus keep the coil healthy.

    All you need to do is make a trip to the local auto junkyard:

    Buy a used but fairly viable car battery, an old-fashioned ignition coil (i.e., before electronic ignition came out in the '70's), an ignition condenser (capacitor) from out of a dead distributor, and the heaviest 12 volt spdt relay you can get from Radio Shack. DPDT is okay, too.

    1. Figure out how to connect the relay so it buzzes.

    2. Connect the capacitor across the contacts

    3. Connect the primary winding of the ignition coil in parallel with the relay coil.
    If you do this right, the relay contacts will give a pulsating current through the ignition coil primary. You'll get a several hundred Hz, 12,000 V between the secondary (the central tower of the coil) and ground. It'll give you a big surprise but it won't kill you unless you're pretty determined to do yourself in.

    I've found that only a car battery has sufficiently low internal resistance to run the thing: my big old bench power supply won't do it. So keep a trickle charger on the battery. It seems capable of giving a 3 cm or so arc depending on conditions.

    (From: Pamela Hughes (phughes@omnilinx.net).)

    I did something like that only it plugged into the wall. Don't remember the circuit but it was a 33 uF, 630 VAC mercury vapor ballast cap connected to a rectifier in a linear fashion (much like using a cap for an AC resistor only the rectifier prevented bidirectional current flow...). This was connected to an 800 V, 6 A SCR and a neon lamp for a diac in a trigger circuit. Adjusted the trigger point so the scr would fire at a certain point in the AC cycle and discharge the cap through the primary of an ignition coil. If you adjusted the trigger point right, you could get about 3" to 4" sparks. Connected that to a 40 kV TV rectifier and a cap made from a window and some aluminum foil and to a 2" spark gap. Wouldn't fire unless something was placed in the spark gap, but then it went off with a bang that would put any bug zapper to shame.

    BTW, I took the ignition coil apart, disconnected the common lead connecting the primary and secondary and then used the secondary and core for a giant sense coil for monitoring changes in magnetic fields... thing would make the volt meter jump if you brought a magnet anywhere close to it, but mostly it just fluctuated with atmospheric effects like lightning.

    (From: Pierre Joubert joubertp@icon.co.za).)

    1. Use a monostable-based circuit which gives the maximum 'on' time for current in the coil. As revs go up, many older systems produce reduced spark energy simply because the rate of rise of current in the coil prevents full current from being reached before the current has to be switched off.

    2. Use one of the coils which is designed to operate normally with a series resistance, which is conventionally bypassed during cranking to help get a better spark on the reduced battery voltage. But instead, limit the current in the coil to a safe value by setting a current limit around the switch transistor. This prevents the coil overheating (which it would if you used it without the resistor in a conventional system.

    3. Look around for the 'best' coil you can find; you might find a better match to your needs by using a coil from a different model or even make of car. If you know the R and approximate L you can model the current buildup and estimate the energy available. Generally the more energy the better, assuming that the transformation ratios of most coils are roughly the same, which was true way back when.
    (From: Scott Stephens (Scott2@mediaone.net).)

    I have characterized a 'typical' car coil, and found it rings best around 1 kHz with the steel core in, and around 8 kHz with it out (no capacitive load on secondary). As you can imagine, leakage (coupling) get worse without the core out, but Q is a little better. Q is under 10, more like around 4. The secondary is around 20 Henries (core in) and 4 H with it out, and primary is around 5 mH. Step up ratio is around 60. My thermal guestimate said continuous power should be under 300 watts in oil. Disappointing.

    Mark's Comments on High Voltage Lab Conditions

    (From: Mark Kinsler (kinsler@frognet.net).)

    So how do you make your high-voltage laboratory safe? Well, you just assume that anything you build is likely to catch fire and/or arc over, and design your lab space accordingly. Stay out of the way of capacitor strings, though when these blow up the shrapnel is generally pretty harmless. I've gotten stung by exploding carbon resistors, but again, it's no big deal if you're well away from them. In general, take the same precautions with high-voltage or high-current components that you would with small fireworks: avoid flammable environments and stay well away from them. If all else fails, take the stuff outside.

    My advisor at Mississippi State University observed that if you never damage any equipment and you don't have fairly catastrophic failures, you're probably not doing any research. That helped justify the 6" crater I blew in the concrete lab floor (a record that still stands--his crater was only 4", though there were several of them produced at once.)



  • Back to Sam's Gadget FAQ Table of Contents.

    Discharge Display Gizmos

    Plasma Globes

    A 'plasma globe' is one of those things sold at Radio Shack and gift shops which have a glass sphere containing a partial vacuum sitting on a power supply base which is a high frequency inverter. The pressure is such that the discharge tends to take place in streamers rather than as a diffuse glow. The resulting display is supposed to be neat, nifty, interesting, etc. When you place your hand(s) on the globe, the patterns of the discharge inside change.

    Recent Sci-Fi movies and TV series seem to have latched onto plasma globes as high-tech replacements for the old-fashioned Jacobs Ladder. :-) (E.g., certain episodes of "Star Trek the Next Generation" and "Star Trek Voyager".)

    One such product is called "Eye of the Storm".

    It should be possible to construct these gadgets with salvaged flyback transformers, power transistors, and a few other miscellaneous parts using a large clear light bulb - good or bad, doesn't matter - for the discharge globe (However, I don't know how good these actually are for this purpose).

    Of course, purists will insist on fabricating their own globe (and official ones can also be purchased at exorbitant prices as well).

    As far as I know, these will work with just regular air (though the expensive ones no doubt have fancy and very noble gasses!) and the vacuum is not that high so a refrigeration compressor should be fine.

    See the document: Vacuum Technology for Home-Built Gas Lasers for general information on vacuum pumps and recycled refrigeration compressors.

    However, since large clear light bulbs may also be satisfactory (though I don't which ones to recommend), there is may be no need to mess with a vacuum equipment. :-) And, of course, you have a wide selection of inexpensive types to use for experiments, and dropping one or blowing it up isn't a disaster!

    Excitation is usually from a high frequency flyback transformer based inverter producing 12 to 15 kV AC at around 10 kHz. Its HV terminal attaches to the internal (center) electrode of the globe or light bulb. The HV return is grounded. Ionization of the gas mixture results from the current flowing due to capacitive coupling through the glass.

    For a power source, either the "Simple High Voltage Generator" or "Adjustable High Voltage Power Supply" would be suitable. See the document: Sam's Schematic Collection - Various Schematics and Diagrams for circuit ideas.

    However, note that its output must be AC so there must not be any internal HV rectifier in the flyback transformer (which may be hard to find these days since most flybacks have internal rectifiers). (If a flyback with an internal rectifier is used, the globe will just charge up like a capacitor which is pretty boring after a few milliseconds!)

    (From: Don Klipstein (don@misty.com).)

    As for common gas fills, Radio Shack's "Illuma Storm" sure looks like neon and xenon. I have seen others that had neon-krypton or neon-xenon-krypton. I have seen one in a science museum that looked like plain argon. Other lightning display type things with brighter basically white sparks have xenon.

    (Portions from: Steve Quest (Squest@mariner.cris.com).)

    A $20 air conditioner repair hand-pump is fine. If the colors of plain air are not 'pretty' enough, let me recommend what is used in commercial units: a mixture of low pressure argon and neon. If you want to be extra fancy, try all the inert gasses, or a mixture of them all, helium, neon, argon, krypton, xenon, radon. :) Of course, radon may not be safe/legal, or even available. You could just toss a chunk of radium into the globe, it will generate the daughter isotope Rn(222) thus slowly, over time, enhance the color of the gas mixture. Just a thought.

    The power supply needs to be dielectrically isolated (using the glass as the dielectric), otherwise you'd have direct emission from the metal, and it would be more of a light bulb than streaks of color. Plus, people touching it would feel a tingle while the dielectrically isolated is less likely to shock. What this means is that a direct connection to the filament lead wires is not that great as you really want glass in between the driving source the center as well as the outside globe.

    If you cannot locate a suitable flyback, wind your own. Tesla-style air core transformers work. :)

    However, I would highly recommend using a commercial flyback! You just need to find one without an internal rectifier. To wind your own flyback requires several thousand turns of super fine wire in 50 to 100 nicely formed layers with the whole thing potted in Epoxy for insulation. Not a fun project.

    (From: John Drake (jdrake_deja@deja.com).)

    Here is a simple trick:

    1. Find some clear light bulbs. Burnt out ones are fine. Any size will do, from a small turn signal light for a car, to a head lamp for a car, to whatever.

    2. Attach any Tesla coil output or other low current high voltage source in the 10 to 100 kV range to one of the filament leads. Leave the other lead alone.

    3. Turn on the power and watch. Touch with your hand, if you dare. Plenty of lightning in a jar. Eventually, the lightning will poke a hole in the glass, and let the air in. Game over. Get another bulb.

    The guy who patented the plasma globe, William Parker (aka Sparks), primarily concentrated on using really interesting blends of gasses and certain frequencies of AC voltage to produce really unusual discharges. For example, it was common to see a kind where an orange lightning bolt had a white tip on it, and a control would let you change the length of the white tip. Other mixes of gasses produced lightning that had a "kinkyness" control -- you could make a bolt very twisty or very straight with a slider control. Check out U.S. Patent #4754199: Self Contained Gas Discharge Device. Suitably obscure, huh? :)

    Sparks patented his device, and overseas companies literally ripped off the patent wholesale. (Most of the $49 plasma globes you see use his exact circuit from the patent, including a couple of unnecessary parts, etc.) He was trying to get some money out of the whole thing, but I don't know if he ever did or will. Alas.

    Of course, if you are just going to make plasma globes and not sell them, you aren't necessarily violating the patents. The underlying idea was well known for a long time before Sparks patented his "globe with controls".

    If you want to make your own globes, you can make them lightning compatible by either just sucking the air out, or sucking the air out then adding gas in. Common gasses to use are argon, neon, and krypton. Helium might work (haven't tried), and it's easy to get and use; you can replace the air in the bulb with helium since it's lighter than air.

    (From: Anonymous.)

    Anyone into plasma globes will definitely want to talk their local high-school maintenance person out of burnt-out bulbs used in their fixture arrays, if they are in fact incandescent, when they are being replaced. (If they not the incandescent type, that may be even more interesting, though perhaps not for plasma globes!) The bulbs are about the size of your head and roughly 20" base-to-top and fit a "mogul" socket. Get one and you will see the potential. Still-good ones make interesting conversation pieces when lit at 120 VAC (half operating voltage) when mounted in a stable fixture. Use/make a 120 VAC 1:1 isolation transformer with insulation that can withstand the output of whatever power supply you would use with it as a plasma globe for an interesting effect.

    Lum(n)glass Lightning Plates

    There are the disk shaped displays that have random electrical discharges radiating from cente