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--Disclaimer--
Building a
Jacob's Ladders involves high voltages and high currents can be
LETHAL and destructive. I am not responsible for any injury to
yourself, your lab, by standers or town-wide blackouts. In simplest
words, a Jacob's Ladder is extremely dangerous so be extremely
careful when building or operating one. The information provided
here is for educational purposes only - I strongly advise against
building one for yourself. ATTEMPT AT YOUR OWN RISK
Safety
The first rule
and possibly most important rule is to make sure that nothing (this
includes humans, non-humans, animals and all foreign matter) but
mainly unruly onlookers, come in contact with ANY part of your
ladder or transformer. Keeping a large distance between the
bystanders and the high Voltage is really the only SURE way of
protecting against idiots or the unaware (and also protecting you
from very angry people). People that are not familiar
with high voltage can be very curious and extremely naive. The
naive and high voltage never mix and usually result in death.
10,000 volts can jump anywhere from 1/2 inch to 1 inch over an air
gap. (the more moisture in the air the greater the distance). Neon sign
transformers are good for Jacobs Ladders but don't forget that they have current
outputs and are still very lethal.
Due to the Large electrical discharges of a Jacobs ladder, ozone is
produced so always operate in a well ventilated area. In
large amounts ozone can be a health hazard and even lethal.
When watching electrical arcs be careful not to stare to long as it
will have the same blinding affect as a welding arc. This is
mainly due to invisible UV light waves. On a final note My Jacobs
ladder produces large amounts Of Radio Frequency Interference and
electromagnetic interference which can effect televisions, phones
etc.
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A Jacobs
Ladder is A High Voltage Device that produces a climbing arc up two
electrodes made in a "V" shape. They can be made in many
shapes, sizes and at different voltages.
The Very
simplified explanation is that due to the fact that hot air rises,
so does the arc. The arc is started and the bottom of the "V"
shaped electrode, It then rises until the voltage supplied to it is
insufficient to span the gap.
If you still
want a better explanation read the following.
To understand the following, read these terms: Voltage: Electromotive force or potential,
Potential being the key word.
Current:
electrical flow.
Dielectric: Something that resists the flow of electricity
until a high enough voltage is created to pass through it. In the
case of the Jacobs Ladder, Air is the dielectric, and when the two
electrodes build
up enough voltage between them, a arc forms between them. Air is a
quite tough dielectric. A not so precise rule of thumb is that
1KVcan jump 1.1mm though a tough dielectric such as air. The Initial voltage determines the
"distance" that the arc can first "jump" across to the other electrode.
Current determines the amount of distance the arc can be
stretched after it has
connected the two electrodes. Given these to factors, To arc
the distance it takes to make a functional ladder, the voltage has
to be extremely high. Way over the point of being lethal!
NEVER TOUCH THE LADDER WHILE IN USE! ATTEMPT AT YOUR OWN RISK
Not only the
fact that hot air rises contributes to the rising arc. Hot air
does half of the work, but other affects are at play.
The reactance curve of the
transformer contributes to the effect. The transformer will easily
create an
arc across the bottom of the ladder as long as Paschen's Law will allow
it.
Once the arc is gapped the electrodes, the current flowing through the arc will
increase to the transformer's already set limit. The heat created by
the arc also
creates higher resistance. In normal circumstances the transformer would try
push
the voltage lower as current increases. Just above the arc
exists a path that the transformer can easily maintain.
To build a
Jacobs Ladder you need two major parts. A high Voltage Power
Supply and a Pair of Electrodes. For a power supply you will
need a minimum of at least 6000V AC at 20mA or better. Exact Values
are not to important. Lower voltages can work to , but are not
as spectacular or as reliably. A neon sign transformer is generally
the best way to go but you could also use an oil burner ignition
transformer or a ignition coil.
-
Oil
burner ignition transformers
can be removed from old oil burners, or can be obtained from
junkyards or other suppliers. The downside of an Oil burner
ignition transformers is that you will likely have to disassemble
the disgustingly icky oil burner dispose of the unwanted
parts . Most Typical Oil burner ignition transformers can range
from 5,000 to 10,000V AC.
-
Neon Sign Transformers
can be obtained used from lighting shops or sign shops.
These could cost you anywhere from nothing to $200.
Everything depends on size and condition. Most NST put out 7000 to
15,000VAC, current = 20 to 30 mA. When getting a neon sign
transformer try to get one with a heavy iron-core.
Electronic transformers can't quite handle the abuse.
-
Other lower powered devices
like
ignition
coils and Flyback
transformers will work too. Ignition coils can provide high
voltages and currents depending on the power fed to it, generally
these work quite well for Jacobs ladders. Flybacks generally
provide very high voltages but at low currents which sometimes is
not very good.
Step
1: Take two, quite sturdy thin metal rods. They must be strong
enough to hold themselves up without bending. For mine I used two metal
coat hangers and welding rods. They are still a bit flimsy but will do for now. Take some pliers and make the as
straight as possible and then fix them on a non conductive base. You
must have a gap between them of about half and inch (this varies from
power supply to power supply) Then bend them gradually upwards in a
"V" shape. It should be about 1 to 4 inches at the top. You
will have to tune your ladder by moving then apart until you get an
optimal arc. You must pay important attention to the
distance of the rods under the base where your "+" and "-" connect.
If they are to close they will just arc there. To solve this I put
my rods in at an angle then straitened them up. Straighten them out and
mount them on an insulated non-flammable support with a gap of about 1/2
inch at the bottom and 1 to 3 inches at the top forming a narrow tall 'V'.
This depends on your power supply and you'll need some experimenting to
get the optimum positions. Many different shapes can be constructed
but are much more difficult to build.
Your End result should look close
to this...
On the Top right we have the two
rods, on the left is the transformer
The gap between the
electrodes at the bottom of a Jacob's ladder is the most important part..
If the distance is too large the arc won't strike, too small and it
will arc across the bottom and stay there. If you cannot acquire a
high enough voltage transformer, or just want a larger stating arc, this
electrode will assist arc striking.
What it is, is simply a third electrode placed between the gap at the
bottom of the two electrodes. It can be connected to either one of the
main electrodes with two 1M ohm resistors.
These resistors have to be large ones, as if the are to small they will
melt. When power is applied to the electrodes......
The combination of high voltage at the middle electrode and the ionized
path makes the arc strike all the way across. It's quite simple in design,
but works like a charm.
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This was my Prototype Jacobs
Ladder. It was a prototype to determine whether an ignition Coil
Could drive a Ladder. The total height is about 3 1/2 feet tall
and about a foot wide (including the base). I can run it for
about 25 seconds before it gets too hot.
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