Sam's Gadget FAQ

Salvaging Interesting Gadgets, Components, and Subsystems

Version 1.59 (10-Jun-10)

Copyright © 1994-2013
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



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    Preface

    Author and Copyright

    Author: Samuel M. Goldwasser

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

    Copyright © 1994-2013
    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.



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    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. :-)



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    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.



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    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).



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    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.)



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    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@donklipstein.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 center to edge and are sold in science/novelty stores in various styles and sizes. Unfortunately, Star Trek Voyager has latched onto these 20th century gizmos as somehow being beneficial to the Borg regeneration cycle - or perhaps they just got a good deal from some antique dealer or on the 24th century equivalent of eBay! :)

    A basic description can be found in U.S. Patent #5383295: Luminous Display Device. The abstract reads:

    "A luminous display device which includes a fused assembly of three flat members, behind the first of which a chamber partly defined by an opening in the second of said members is formed, a quantity of beads and an ionizable gas being disposed in said chamber, a source of high frequency voltage being connected to an electrode through an opening in the third of said members to form myriad discharge paths throughout said chamber."
    For the diagrams, you have to view the patent on-line. In non-patentspeak, the device consists of a sandwich of two glass plates and a spacer ring. It appears as though constructing one of these at home might be possible. A neon sign type electrode in the center of the bottom disk is fed from an RF source probably similar to the high frequency flyback based power supply used for a plasma globe. This will typically be several kV at a couple of mA, at frequency of 20 to 50 kHz or higher. There is no return electrode - the capacitance between the ionized gas and ground provides the return path. However, the physical discharge chamber will certainly more difficult to fabricate. A fairly decent vacuum is also required - the patent claims 15 microns. This requires at least a two stage mechanical pump.

    By adjusting the voltage and frequency, using gasses (other than air), phosphor type materials on the beads, colored beads and/or glass, higher or lower pressure, and other changes in drive or construction, the size, color, character, and dynamics of the resulting display to be varied over a wide range.

    I would suggest making the assembly out of a pair of pieces of plate glass (though even Lucite/Plexiglas might work - it shouldn't get hot during operation). The plates don't even need to be circular though this isn't really difficult with a glass cutter and template. The outer ring which serves to space the glass plates and also to seal the chamber may be the greatest challenge if made of glass. The space is filled with glass beads, or frit, which, in conjunction with the outer ring, also prevents the thing from imploding. Drilling the hole in the center of the bottom plate for the electrode can be done with some abrasive and a tile or glass bit.

    The patent describes a construction method that fuses the entire assembly together at high temperature. This may not be needed unless you intend to seal the device permanently (and even then, a good two-part Epoxy will likely be adequate).



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    Cheap Sources of Magnet Wire

    It has been suggested that transformers, inductors, and TV/monitor deflection coils are inexpensive or free sources of magnet wire. This may be OK for antennas or similar applications where the insulation isn't critical. However, unwinding those coils may result in damaged insulation as the wire is peeled apart since they tend to be impregnated with varnish. This makes the wire unsuitable for winding new coils. Unless, you have a way of dissolving the varnish without destroying the insulation, the risk of a random shorted turn or two (or many) buried beneath several thousand nice separate ones isn't worth it!

    However, a nice source of fine magnet wire is relays and solenoids - many have very fine wire - #40 for example - and miles of it (well thousands of feet at lest). These are very often not varnished so they unwind easily (just don't let them unwind all over your junk drawer!).



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    Ideas for Things to do with High Voltage

    (From: Robert Michaels (rrr@crush.wwnet.net).)



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    Dangerous (or Useful) Parts in a Dead Microwave Oven

    A microwave oven with its power cord cut or removed AND its high voltage capacitor safely discharged is an inanimate object. There are no particularly hazardous parts inside. Of course, heavy transformers can smash your feet and sharp sheet metal can cut flesh. And, the magnets in the magnetron may erase your diskettes or mess up the colors on your TV.

    Some may feel there is nothing of interest inside a microwave oven. I would counter that anything unfamiliar can be of immense educational value to children of all ages. With appropriate supervision, an investigation of the inside of a deceased microwave oven can be very interesting.

    However, before you cannibalize your old oven, consider that many of the parts are interchangeable and may be useful should your *new* oven ever need repair!

    For the hobbiest, there are, in fact, some useful devices inside:

    DOUBLE WARNING: Do not even think about powering the magnetron once you have removed any parts or altered anything mechanical in the oven. Dangerous microwave leakage is possible.

    Microwave Oven Transformers

    The high voltage transformers from discarded microwave ovens can be put to many useful purposes. They are LARGE and can easily handle a kW or more, And due to their construction with separate and distinct windings for the 115 VAC primary, filament, and HV, are much more easily modified compared to typical power transformers with all the windings on top of one-another.

    However, these transformers are designed with the bare minimum of copper so without a load, they still draw several amps from the power line. Therefore, they are most suitable for applications where a heavy sustained load is involved - not for that isolation transformer used mostly for testing (20 W) laptop switchmode power supplies! Figure things like arc or spot welding, battery charging, shaker table drivers, aluminum ring levitation (remember that science museum demo?), and other low voltage high current experiments. I am not recommending these for your 1 kW class A audio amp because of they are not generally rated for continuous duty and tend to hum - but you could try especially if you add some cooling.

    Note that very few microwave oven failures are due to transformer problems. And, even those that are, likely mean that the HV or filament windings are to blame - neither of which you will likely be using (unless you want the 1.5 to 2.5 kVRMS at 0.5 A or so they put out).

    Aside from the dead microwave oven(s) you may have around the house and your friends' and relatives' houses, try the local dump and repair shops - but you may have to convince them that you know what you are doing and of course be willing to haul away the entire carcass, not just the transformer!

    WARNING: The intact microwave oven transformer is extremely dangerous when powered. (When not powered, about all it can do is smash your foot.) That 1.5 to 2.5 kVRMS at 0.5 A or more is an instantly deadly combination. Take extreme care if you have any idea about using the transformer without modifications. In addition, since it is so LARGE, any windings you add are also going to be capable of high current and could quite easily end up arc welding or burning things you didn't intend!

    Assuming you are not using the HV or filament windings, the first step is to remove them. The filament winding is only 2 to 3 turns of heavy wire and easily extracted. However, the HV winding is likely to require the services of one or more of the following: a chisel, hacksaw, ax, blowtorch, heavy cutters, drill. (And, make sure your accident insurance is paid up for the required trip to the ER to stitch up your hand afterwards.)

    Once these windings are gone, there is plenty of core area to wind your own new ones.

    Using the Control Panel from Defunct Microwave Oven as an Electronic Timer

    It is usually possible to remove just the touchpad and controller board to use as a stand-alone timer with a switched output. Be careful when disconnecting the touchpanel as the printed flex cable is fragile. With many models, the touchpanel (membrane touchpad) needs to be peeled off of the front plastic panel or the entire assembly can be removed intact.

    The output will control a 10 to 15 A AC load using its built in relay or triac (though these may be mounted separately in the oven). Note that power on a microwave oven is regulated by slow pulse width modulation - order of a 30 second cycle if this matters. If it uses a triac, the triac is NOT phase angle controlled - just switched on or off.



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    The Zap in Scripto Lighters and Gas Grill Ignitors

    Some types of disposable lighters contain a piezo electric element (instead of a flint and wheel) which generates a spark to ignite the butane gas. Pressing down on the activator drives an escapement which results in a bar hitting the piezo element.

    The result is several thousand volts on demand with its output available at a couple of terminals. This can be used to trigger xenon tubes or even to start helium neon lasers (with the addition of a pair of high voltage diodes to form a charge pump). Or as a prod for small cattle, but I didn't say that. :-) For a discussion of the HeNe laser application, see the document: Sam's Laser FAQ.

    Detaching the piezo assembly only requires bending back and removing the sheet metal shroud at the top of the lighter. The entire piezo unit then just pops out.

    Gas grill ignitors are similar - and even more powerful. These are available as replacement parts at your local home center or appliance store. (Don't steal the one from the family gas grill - your dad won't be happy.) Ditto for piezo matches. Once the gas is used up in these, you're the only one who will want them anyhow. :)



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    Useful Parts in a Battery Powered Electronic Flash

    These units are found in both pocket cameras (regular 35 mm, older 110 or 126, as well as disposable 'single use' types), and external flash units. Larger, more sophisticated models will have proportionately larger components but the basic circuits are very similar.

    For information on how these things work, see the document: Sam's Strobe FAQ - Notes on the Troubleshooting and Repair of Electronic Flash Units and Strobe Lights which also includes many many sample circuits. Two popular designs from Kodak disposable camera flashes are:

    For detailed instructions on disassembling the Kodak MAX camera to safely remove the flash unit and some simple modifications, see Don's Hack Kodak MAX to Strobe Page. Details on other cameras will differ but this information should alert you as to what to avoid touching.

    WARNING: The energy storage capacitor in even the tiny flash from a disposable camera may hold a painful, if not lethal, charge for days or longer. Always remove the battery first and then make sure to check and, if necessary, safely discharge this large capacitor before touching anything!

    The major parts present in all units include:

    And, in the disposable cameras, there is likely to be a very nearly fresh Alkaline cell unless the place you obtained them from knew this and beat you to it! :)

    Automatic types will have additional components including the following:

    There will also be a variety of other small electronic components possibly including fancy microchips in TTL (Through The Lens) programmable units.

    Note: To remove individual components without destroying either the PCB or the component, you must use a proper desoldering technique. If too much heat is used for too long, I've heard that the HV winding inside the transformer may become detached which renders it useless. And, the PCB will certainly be damaged. I generally use a desoldering pump like Solda-Pullet(tm), (not the cheap short one) but this can still damage the fine PCB traces. The use of copper braid with rosin like Solder Wick(tm) may be gentler.

    Also see the document: Sam's Schematic Collection - Various Schematics and Diagrams for possible useful modifications to inverters like the one from the Kodak MAX Flash.



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    Useful Parts in a Non-Working VCR

    What can you build with it? One can never tell! :-)



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    Useful Parts in a CD, DVD, LaserDisc, or Other Optical Disc/k Device

    All of these devices are basically need to perform similar functions though the specific implementation can differ considerably. Usually, the older the equipment, the more good stuff it yields. Modern CD and DVD drives have almost everything laser and optics related in a little tiny optical pickup block which may not be easy to disassemble. However, 20 year old CD players have much larger optical assemblies with larger numbers of distinct parts. All CD players, CDROM drives, and other common optical storage devices use infra-red laser diodes usually around 780 nm. For all intents and purposes, this is invisible and they make truly lousy laser pointers. DVD players are so new that few cast-offs are available but they, at least, use visible red (635 to 650 nm) laser diodes. Really old LaserDisc players use red helium-neon lasers (actually appears orange-red, 632.8 nm) with possibly even separate focus and tracking mirrors on galvo-like devices which can be easily converted into a simple laser show. See the documents: "Notes on the Troubleshooting and Repair of CD Players and CDROM Drives" and "Notes on the Troubleshooting and Repair of Optical Disc Players and Optical Data Storage Drives" for information on how this equipment works.

    WARNING: In addition to electrical and mechanical dangers, the laser may emit levels of visible or invisible radiation that is potentially harmful to vision.

    There is much more info on their laser and optics Sam's Laser FAQ.

    Wayne's Notes on Salvaging Parts from Pioneer LaserDisc Players (From: Equinox (eso@pacific.com).)

    I have taken apart several of Pioneers old video disc units, I cannot remember the model #'s right now.

    The units I had contained the following items that I found of value and kept. Yours should be the same or similar, as all units that I took apart, internally were very similar.

    Disassemble the unit with care. Be careful if you start cutting wires, as the laser power supply has DC control voltages used to enable/disable high voltage output of the laser supply. It may also have other DC voltages used to assist in HV generation. Count the wires coming off of the board and follow and note where they go. You need to know the DC voltages on these wires.

    With care and the forethought that you are working with 110 VAC, 700 VAC and more than a kV for the laser, you can measure the voltages in, and enable/disable the safety interlock and see which line it triggers. The interlock switches (2?) were a metal tab activated switch in the back of the lid, and I think part of the latch gizmo near the front of the system had one.

    (From: Chris Hoaglin (choaglin@aol.com).)

    Inside Maxoptix magneto-optical drives, there are quite a few small mirrors, lenses, beam splitters, etc. The models I've taken apart have been the Tahiti II model. These drives also have a very nice actuator. The laser diode isn't even on the part which emits the beam against the disc, it's mounted on the frame of the drive and reflected against the disc by a mirror mounted on the bottom of the part that moves back and forth. The actuator assembly might be useful for experimentation as well, since It's very sturdy (It rides on two metal shafts and has small metal wheels which keep in contact with the shafts). It has a coil and magnet arrangement on each side. All the optics are on small removable mounts as well, so they'd be easy to put to other uses. I believe the wavelength being used is IR, but they might work for visible stuff as well.

    How and where to find them: The drive is a full height 5.25" drive. Looks a bit like an ESDI drive, except for the slot on the front to insert the MO disk, of course. A good place to look for them might be places which do data storage, or use workstations (DEC, Sun, etc.) I don't think they're used much on the PC platform.

    Also, I noticed today while reading Lasers and Optronics that several outfits are offering OEM modules which incorporate 400 nm diodes. Sooner or later people will start scrapping equipment that uses them, although probably not for a few years.



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    Useful Parts in a Laser Printer or Laser Fax

    All modern laser printers use IR diode lasers of 5 to 30 mW maximum output (or perhaps more in high performance units). Very old laser printers used helium-neon lasers but these are even rarer than HeNe laser based LaserDisc players. However, if you do find one, there will likely also be an Acousto-Optic Modulator (AOM) and driver since directly controlling HeNe lasers at high speed isn't feasible - don't neglect these very desirable components!

    I'm sure I've missed some major parts.

    See the document: "Notes on the Troubleshooting and Repair of Printers and Photocopiers" for information on how this equipment works as well as warnings and precautions with respect to the hazards of toner dust.

    WARNING: In addition to electrical and mechanical dangers, the laser may emit levels of visible or invisible radiation that is potentially harmful to vision.

    There is much more info on their laser and optics Sam's Laser FAQ.



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    Useful Parts in a Photocopier

    There are mostly similar to laser printers, above. However, instead of a laser, the light source is usually a halogen or high intensity fluorescent lamp. Most other parts are similar and similar precautions with respect to toner apply. Copiers are likely to use toner cartridges having the various components such as the photosensitive drum, toner reservoir, and developer as separate units. Thus, they are more likely to have gobs of messy toner all over the interior when you finally get your hands on them!

    Items in place of the laser of a laser printer include:

    See the section: Useful Parts in a Laser Printer or Laser FAX for more information.



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    Useful Parts in a Barcode Scanner

    The types mostly likely to show up surplus are helium-neon laser based supermarket checkout scanners that have been replaced by more modern diode laser based equipment but are probably still operational.

    Looking through the glass of the scanner, it may appear that all sorts of stuff is arranged at random. However, this is not the case. :) For more information on how barcode scanners operate, see the chapter: "Laser Instruments and Applications" in Sam's Laser FAQ.



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    Useful Parts in a Smoke Alarm

    Aside from using obvious things like the extra-strength piezo beeper and battery connector for other projects, the mostly intact smoke alarm can also serve as a detector for normally open (high to low resistance) or normally closed (low to high resistance) applications water leak/flood detectors or perimeter alarms.

    The sensor in ionization smoke detectors (which are the most common type) conduct slightly with no smoke present since the mildly radioactive source (Americium 241, an alpha emitter) ionizes a small number of O2 and N2 molecules in the air providing a slightly conductive path between two plates. When smoke is present, this current flow decreases because the smoke particles attach to and neutralize some of the ions. The increase in resistance triggers the alarm. Removing the sensor entirely and attaching to its connections would provide a means of detecting a switch opening or increase in resistance.

    The test button closes a circuit to sound the alarm and is usually very sensitive in that even a high resistance connection will work. So, this will be suitable for detecting decreases in resistance from water or other liquids between its contacts - extended appropriately of course!

    Even a smoke alarm that has surpassed it useful life and is sounding off even when there is no fire or smoke may still be useful if the ionization detector/chamber is removed.

    (From: Bob Wise.)

    I may have stumbled across a good way to put an old smoke detector to use. It seems also to be a way to add another function to existing smoke detectors.

    A standard circuit approach to make a water leak detector begins with a clothes pin and an aspirin tablet. When my washer recently overflowed the fourth or fifth time, I decided to build one. But I didn't think the audio volume in a piezoelectric alarm module from Radio Shack seemed anywhere near loud enough.

    Instead, I used alligator clips to put the sensor in parallel with the test button on an old smoke detector. The audio from these devices is perfect for a serious alarm, of course. I couldn't solder to the metal on the arm with the test button nor to the case of the sensor section that this arm contacts when pressed, but the alligator clips seem to provide sufficiently secure connections. They connect to wires that run down to our floor drain. I had a plastic clip that seemed stronger than a clothes pin and an antihistamine tablet that dissolved quickly in tests, but I discovered by accident that neither was needed. The conductivity of clean (albeit not distilled) water reliably triggers the alarm. So the two sensor wires just have to be in a dry spot that will get wet early in case of a leak. And I need to teach the family about lifting the contacts out of the water and keeping them apart to silence the alarm in case of an actual leak or someone stepping on the contacts and triggering a false alarm.

    Notice that the alarm also remains a smoke detector. We haven't impaired that function at all. (The alarm made this point very loudly while I was trying to solder the connections.)

    (From: Sam.)

    However, I'd still recommend keeping this separate since it's still possible your modifications could impair its original function, no matter how unlikely that might seem!


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