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Copyright © 1994-2007
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1.This notice is included in its entirety at the beginning.
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.
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.
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. :-)
Surplus places typically charge $3 to $6 each for one of these magnets.
Note: A few older magnetrons used AlNiCo magnet assemblies or even possibly
electromagnets which are not nearly as interesting. However, you probably
won't see any of these.
Surplus places may charge $12 or more for ONE of the magnets from a large
disk drive (there are typically 2 to 6 such magnets in a disk drive)!
I have a monolithic clump of 40 or 50 of the magnets from full height 5-1/4"
SCSI drives. I figure there is a black hole growing inside but haven't dared
to look. :) The only way I was able put the clump together with minimal
damage to flesh was by using a hard wood ramp to gently guide each new
magnet into place. I haven't figured out how I'll ever get them apart
though!
Here is a quick easy experiment to try with these powerful magnets: Slide
one such magnet over a thick aluminum plate. What do you feel? Or, let a
1/8" x 2" x 12" aluminum plate drop through the intact yoke from a Seagate
WREN series 5-1/4" full height hard drive positioner. What happens? Why?
What material might produce an even more pronounced effect? Why?
For more things to do with these neat magnets, see:
Neodymiumarium.
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!
WARNING: The toner is a possible health hazard. A good dust mask should be
used while working on these. Also, do not vacuum what remains - static can
set off a dust explosion - use wet rags or paper towels to clean up the
mess! The coating on the photosensitive drum may also be a hazardous
material.
AlNiCo magnets are not as powerful as ferrite or rare earth types and are
easily demagnetized (but just as easily remagnetized). Passing a stack
of these through the center hole of a strong ferrite magnet will increase
their strength dramatically - until they are separated from each other!
(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.
(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.
Some capacitance on the HV output may be needed as well (though the ones
I have tried were happy enough with just the stray capacitance of the
wiring). Originally, the CRT envelope provided this capacitance.
See the section: Why the Yoke is Needed to Keep the
Horizontal Deflection System Happy.
One key advantage of using predesigned circuitry is that you are less likely
to destroy power transistors and other expensive parts - and I have blown my
unfair share. :-(
See the section: Sam's Super-Starter(tm) for a specific
example of this kludge, um, err, approach for starting large HeNe laser
tubes. :-)
Since these HV generators are not combined with anything else, they are
likely to be self contained modules and very easily used by themselves.
However, available current from some of these sources is generally less than
from TVs or monitors. Details are left to the highly motivated student. :-)
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.
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:
Well, it turns out there was an unused spot on the board ready made for this
circuit (well almost, at least there was a pattern for a spare 8 pin DIP!
So, once the thing was basically working, I built the oscillator onto the
board to reduce the clutter!
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. :-)
(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).
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.
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).
Current limited means that the transformer will deliver the rated current
(Io) into a short circuit and produce the rated voltage (Vo) with no load.
In between, it is designed to produce a somewhat constant current up to a
substantial fraction of its no-load output voltage. This is somewhat
similar to being in series with a resistor equal to n*Vo/Io (where n may be
2 or 3 or more) over this range but implemented without silicon as the
magnetic design of the core and windings with no extra power dissipation.
(It isn't really this straightforward but will serve as a first
approximation.) Therefore, a short circuit on the output will not blow a
fuse or trip a breaker (though the transformer will overheat if left this
way for too long).
Sources: Your local sign shop, demolition company, or salvage yard. New:
$100 or more. Used: $5 to $50 or free.
Both iron (an actual transformer) and electronic (high frequency inverter)
types are available. The iron types are more robust and will survive
repeated abuse that may destroy the others but they are heavy.
WARNING: Though current limited, the available current from neon sign
transformers - especially the larger ones - is far into the range where
lethal consequences are likely under the wrong circumstances.
(From: Jason Freeburg (egraffiti@iname.com).)
BTW, the best name to look for in neon sign transformers is France. These
things are ruggedly built like and will take a lot of abuse without dying.
The name to avoid is Actown - their transformers are wimpy and usually don't
deliver the rated current."
Sources: Your local HVAC contractor probably for the asking as the ignition
transformers are thrown out along with old oil burners when they are
replaced. Of course, you will probably have to take the entire icky smelling
disgusting burner assembly as part of the deal. :-) However, there is will
be a nice motor and small oil pump in there as well. ;-)
WARNING: Though current limited, the available current from oil burner
ignition transformers is still more than enough to kill under the wrong
circumstances.
Sources: Dead microwave ovens (the transformer is rarely the problem). Try
your local appliance repair shop. However, you will probably have to cart
away the entire oven - but other useful parts inside. :-) See the section:
Dangerous (or Useful) Parts in a Dead Microwave Oven.
WARNING: The electrocution danger from microwave oven transformers cannot be
overemphasized. They are not current limited, and even if they were, could
be instantly lethal given the least excuse for a suitable path through your
body since the rated current is a substantial fraction of an AMP at several
thousand volts. Normally, one end of the high voltage secondary is bonded
to the core - which must be grounded for safety. However, it may be
possible to disconnect this and construct an isolated HV power supply (which
will be only marginally less dangerous).
Sources: Your 1997 Honda. Just kidding. :-) Auto repair shops or parts
stores, salvage yards.
WARNING: While unlikely to be lethal, the HV output of an ignition coil can
still result in a seriously unpleasant shock and possible collateral damage.
For many hobbyist uses, the only portion of the flyback that is important
will be the high voltage winding (and rectifier, if present). It is a
simple matter to add your own drive and feedback windings on the flyback
core. This eliminates the uncertainty of determining the number of turns
and wire size for the existing windings.
Sources: CRT based equipment tossed for failures NOT caused by a defective
flyback. However, sometimes even a bad flyback can be used for HV projects.
This will be the case if the problem is:
If you really want AC, this is an advantage! In fact, it might be
possible to deliberately short the HV rectifier where you want an AC
source by passing excessive (DC) current through it and/or violating its
PIV rating (but that may be tough as other parts are likely to fail
first!).
No one actually buys flyback transformers for experimentation!
WARNING: Flyback transformers are capable of producing shocking experiences.
However, when run at high frequencies, your first hint of bodily damage may
be via your sense of smell - from burning flesh. Keep clear!
Also see the section: Driving Automotive Ignition Coils and
Similar Devices.
I used a .1 uF, 400 V capacitor for Cp. You can try smaller capacitors (but
at least the same voltage). Too small, however, and that annoying arcing will
return and you will barely be able to light a tiny neon indicator lamp!
(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.
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.
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.
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.
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?"
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:
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.
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).)
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.
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.)
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:
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.
A basic description can be found in U.S. Patent #5383295: Luminous Display
Device. The abstract reads:
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).
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!).
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.
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.
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.
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. :)
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.
What can you build with it? One can never tell! :-)
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
All Rights Reserved
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.
Introduction
Reducing the Clutter in Land Fills
The purpose of this document is to prevent land fills from becoming filled. :-)
There will be several types of information:
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.
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!
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:
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.
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.
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:
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.
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).
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.
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.
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.
"A used neon sign transformer should not cost more than $20 or so. Find a
neon shop in your area. They usually have the used ones stacked up
somewhere and will sell cheap. The 60 mA models are usually somewhat
cheaper than the 30 mA type if you buy them used from a neon shop because
they are really too hot (e.g., provide too much current) for running neon
and they cause staining and premature burnouts. It all depends on the
particular shop you go to. I don't suggest buying new for something like
this, the performance will be the same but the price much higher. A new
15 kV, 60 mA transformer lists for about $80.
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!
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.
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.
(From: jfreitag@gsosun1.gso.uri.edu (John Freitag).)
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.
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.
(From: Scott Stephens (Scott2@mediaone.net).)
Mark's Comments on High Voltage Lab Conditions
(From: Mark Kinsler (kinsler@frognet.net).)
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.
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 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.
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!
Ideas for Things to do with High Voltage
(From: Robert Michaels (rrr@crush.wwnet.net).)
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.
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.
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 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.
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.
Useful Parts in a Non-Working VCR
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.
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.
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.
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.
Items in place of the laser of a laser printer include:
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.
The HeNe laser power supply may be a self-contained 'brick' or built onto the mainboard.
The laser diode driver circuit will be in close proximity to the laser diode itself and may be on a separate board. However, it is most likely part of the mainboard. and difficult to determine correct use without a schematic.
The components of the this part can generally be separated to use individually using a combination of brute force and solvents. For example, to remove the lens and prism from the combo in the Orien 300, a pad of tissue paper is inserted in the hole followed by a wooden dowel that just fits. A couple of whacks to the dowel with a small hammer while holding the assembly should result in the prism/lens popping free. They can then be separated by soaking in acetone.
WARNING: Acetone and its vapors are flammable and toxic.
CAUTION: Acetone will also damage many plastics including most likely, the large plastic lens, so don't let it contact that or other plastic optical components.
Unlike those in a laser printer, the mirror facets are large since they have to reflect the diffuse return beam as well as the tiny spot of the outgoing beam. They are fabricated as individual mirrors glued to a cast metal wheel type affair and are all set at slightly different angles so that each rotation of the mirror wheel results in scan lines at 3 to 6 slightly different locations depending on the number of facets.
-- end V1.58
