TESLA
COIL DEMONSTRATION
HOME I
have been fascinated experimenting with high voltages for long time and it has been
quite some since I had played with one of these...This past summer I decided to
built one as class demo for CIRCUITS I. This is
perfect demo to show what an electrical resonance can do...Produced
high voltage discharges are small lightning bolts essentially...
There
was a lecture on the principle of operation of the Tesla coil and a
demonstration right after that in the Circuits class on
Dec 4th, 2006 and the following week for freshmen Science of Nature Class on Dec 11th.
Here
is the clips from the demos...note the screen on the back going nuts as
the Tesla coil operates...Movie files are mp4.
This demo is with a fluorescent light...As the end of the tube touches the
discharge I feel a mild shock. Coil operates at 400 kHz which the nerve system cannot respond but
it is pulsed at 100 Hz so there is
100 Hz and its harmonics exist in the discharge signal...which is clearly noticable!
These two below are
recorded while a HeNe laser tube is sitting on top of the toroid. As you
see the laser is almost about the lase...It is a fantastic scene...
WHAT IS A TESLA COIL?
Nicola Tesla, inventor of AC power generation and distribution among others, a genius of late 19th and 20th century.
One of his most influential and famous invention was
the Tesla coil. Unlike his contemporary and rival inventor
Edison,
he was a real scientist and the unit of magnetic field intensity is named after him. 1 Tesla = 10^ Gauss.
Tesla coil is basically a high frequency resonant transformer.
With his original coils he was able to lit light bulbes miles away.
This circuit is basically the first wireless transmitter, first RADIO!
(called spark gap radio).
Although almost everybody thinks that Marconi invented the radio (he
was actually was a business man with cash...hired some engineers to
copy the experiments of others...). The real inventor of radio is
Tesla as the history is getting corrected as even the US patent office
reissued the key radio patents to Tesla right after he died.
Since over 100 years people are fascinated with the Tesla coil, it has
even cult like followers in the world...Exhibitions in science fairs
and museums are quite common. In the US there are even
companies that their main line of business is performing Tesla
coil shows in the high schools and universities to attract technically
minded students into engineering and science...
In this lecture, I will explained the operation of Tesla coil in detail followed by the demo of our Tesla coil.
Later I will put technical explanations here too...
Below is an image of our Tesla coil in operation. This is a medium size
coil, powered by 10 kV, 30 mA neon transformer...The high voltages
produced can be anywhere between hundreds of thousands of volts to a
million
volt...though maximum here is more like 500 thousand volts I
estimate...I will measure it some day...as one can imagine this is no
piece of cake...
By clicking the picture you can access the video...Tesla coil is located in the Photonics Research Lab and
it is recorded there...If you cannot access it try again later since the video file is on another server...
The toroid on the top of the tower (which is the secondary coil) acts
like about 16 pF of a capacitor and it is a part of the series resonant
circuit that is formed with the secondary coil...It gets charged to
such high voltages and the electric fields are so large that the
air surrounding the toroid gets ionized,
air molecules are stripped from their electrons! As the electrons
recombine with the atoms we see the intense blue light called corona
discharge.
The spectrum of light contains significant amount of UV actually and it
is not advisable to watch it with a naked eye long times...
Since there is about 20 % of Oxygen(O2) in the air...during the
recombination of ions significant number of Ozone (O3) is produced and
the
Ozone is not safe to inhale in large quantities since it is a higly
reactive gas. Also NOx compounds are also produced which are quite
toxic, so the Tesla coil should not operate long times without adequate
ventilation.
The blue lights at the bottom is from the multiple static spark gaps
that is used to initiate the oscillations in the primary coil
as I will explain in the lecture.
Initially
I am holding an old HeNe laser tube in my hand...Electric field is so
large that the neon atoms are excited even though they are so far away from the high voltage
discharges..as the atoms relax to ground state photons are produced
which
we see as the characteristic neon light. Later in the video
you see
that I am waving a fluoroescent light which lights up to the point
where my hand is...Fluorescent light is filled with Mercury
vapor...electric field again excites the Mercury vapor, most of the
light that comes from Mercury is UV light but the phosphor coating on
the tube converts the UV photons into visible white light...The glass
between my hand and the ionized gas inside acts like a capacitor actually....Current
continues thru my arm passes thru my body to the ground. People think I have a bad hair day!
This is a demo of wireless power transfer in essence...
In general Tesla coil is a dangerous piece of equipment...At least the high voltage of Tesla
coil do not produce any shock that can be felt since it operates at
high enough frequency (400 kHz in our case) and the human nerve system cannot respond to
frequencies that high (and I don't know any
other nerve system that can respond to it for that matter)...High voltage
discharge from a Tesla coil may not kill a person...but can give some nasty burns...
HOWEVER, if there is a discharge between the secondary and primary
(due to some physical error of placement of
cabling etc. or due to some random discharge) and at the same time
if a
person come into contact with one of the streamers, that might mean
death in a microsecond! I don't think anybody would see the white
tunnel and all in that case...
There are just too many Tesla coil related web sites as you could find
easily with a simple search...Almost all of them -except a few
knowledgeable people- have a gross mistake in their Tesla coil setups.
This mistake exists even in some Scientific publications... They
simple connect the grounds of primary and secondary of the transformer.
This is extremely dangerous. The secondary ground must be separate than
the primary as it must be a dedicated RF ground. It is not advisable to
connect that to powerline ground either. People might say well I did
and it worked...Lightly speaking, this is no different than well
I am not using my seat belt and nothing happened so far...it takes only
one accident...
Best is to use a dedicated ground installation of course...
In my case I use a piece of metal about 1m X 2m on the floor as the RF ground and it works just fine.... HOME