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Tesla Coils
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Closeup of Tesla Coil outputTesla Coils

A Tesla coil is an air cored resonant transformer. It works by matching all the components in the system so that they resonate at the same (or harmonic) frequency. The end result is that the voltage input is stepped up by a tremendous amount.

 

Example Tesla Coils

Firing Argon from the TipTesla Coils can come in many forms. These two examples are ones we have made for the DIY Devices section. The image in the right shows a battery powered tesla coil which uses an ignition coil driver to charge the tank capacitor.

Battery Powered Tesla Coil
The leftmost image show the 'Plasma Gun' which is a much smaller hand held version of the other Tesla Coil.

How a Tesla Coil Works

This image shows a simple schematic diagram of a Tesla Coil. There are numerous configurations to choose from. Using this configuration, the TC is powered from a high voltage DC source, such as a rectified output from a neon sign transformer (NST). The device operates in a cyclic manner. This means that a series of changes occur within the circuit, until it is reset and the next cycle begins.

First of all, the capacitor (C1) is charged by the power source (HVDC). When the voltage across the capacitor is high enough, the air in the spark gap (SG) breaks down and allows a current to flow. This forms an LRC (inductance/resistance/capacitance) resonant circuit until the voltage across the capacitor drops sufficiently to quench the spark gap. This all takes a fraction of a second and completes one cycle. The capacitor will then begin charging again. But what about the rest of the circuit? First of all we must understand more about the LRC circuit described above.

When the air in the spark gap breaks down, it is acting like a switch connecting the charged capacitor in parallel with the inductor or coil (L1). As the initial current flows around the LC circuit, energy from C1 is stored in a magnetic field created by L1. When the capacitor is discharged, the magnetic field will collapse. This collapsing field will cause a current to flow in the opposite direction as before, therefore recharging the capacitor. This process will then repeat, causing the current to oscillate back and forth until the energy is dissipated by losses in the circuit and the spark gap quenches. This cycle happens within the other cycle described before, i.e. every time the spark gap fires (1st cycle) the current will oscillate back and forth between C1 and L1 (2nd cycle). The frequency at which the 2nd cycle oscillates is determined by the physical values of the components. This is known as the resonant frequency. The second part of the circuit (C2 and L2) must be constructed so that its natural resonant frequency is the same as the previous part.

A Brief History of Nikola Tesla and the Tesla Coil

Nikola TeslaThe Tesla Coil (TC) was invented in 1891 by Nikola Tesla. It is one of many ingenious devices he created which have paved the way in which our technology has developed. The AC electrical grid, radio transmitters and car ignition systems we use today are derived directly from Tesla's inventions. So why have most people never heard of him? History seems to record two different versions of Tesla. One is that he was a crackpot inventor and that he made unsubstantiated claims of fantastical inventions, whereas the other version is of an under appreciated, misunderstood genius. It is the former that seems to be the official view, although it now seems as if the true Nikola Tesla was a combination of both these opinions.

Nikola Tesla was born in Smiljan, Croatia in 1856. As a small boy, Tesla had a problem where certain things could trigger visual memories and they would appear to him as if they were real. These images could persist, therefore obscuring his true vision. He learned to control these images before he matured, and could use this 'gift' to his advantage.

He had an extraordinary photographic memory, which allowed him to easily learn six languages. He used his visualization skills like we use a CAD program today. He states in his autobiography that he was able to construct machines, test their performance, and disassemble them to check for ware; All in his mind!

Tesla's LabRotating magnetic fields and resonance fascinated Tesla. He often worked continually on his inventions and theories, only sleeping for two hours per day. Tesla always eat alone and woul feel the need to measure exactly the amout of food he was about to consume. He was also obsessed with germs, and avoided touching utensils directly. It is this obsessive behavior gave people an impression that he was a 'crackpot'. It could also have led to his mental decline in his later years.

In his days of invention, Tesla came up with some astonishing ideas and devices. Often he was misunderstood by the rest of the scientific community, as is ideas were so far out from anything that they understood themselves. Tesla made claims that he could transfer energy around the globe without the use of wires, and that the energy its self could be obtained freely from the environment without the need for fuel. These ideas made him unpopular with the establishment, as such devices would reduce their political power and overall wealth. It is only more recently that some of this work is being taken seriously. There is much conspiracy theory around these subjects, but it will not be discussed here. You can learn more about the science involved by going to the physics section of this site. It is also recommended that you do further reading on Nikola Tesla if you are interested in this subject.

Nikola Tesla's invention of AC electricity is what is used to power homes today yet many people connect the name Edison with electricitys origins. Both Tesla and Edison were competing with eachother for the promotion of their ideas as the best technology. Edison was trying to promote DC electricity as the best way to power homes and went to some extreem lengths in an attempt to discredit Teslas work in order to make his own appear superior. The video shown below was filmed in 1903 when Edison electrcuted to death an elephant as a cruel stunt to try to show the danger of AC electricity.

The fact is that Teslas AC electricity is actually safer in many ways. Edison just made the current very large. Such large currents would kill regardless of AC or DC. Most of us learned about Edison at school but rarley is it mentioned what a cruel and dishonerable man he was. Tesla sought to make the world better for all, Eddison sought wealth and power. Unfortunatley money usually wins more power to change things than good will does.

Tesla FlameHow to Make a Tesla Coil

The photo on the left shows electrical discharge through a small flame on the top sphere of a homemade, battery powered Tesla Coil. The aim of this design was to get the highest voltage (or longest arcs) possible from a singe self contained unit. This coil operates from 12V or 24V SLA batteries. A pair of car ignition coils are used to provide around 20kV for charging the capacitor bank. The ignition coils are driven by a variable frequency square wave from a 555 timing chip and four large transistors (2N3055).

More Info: DIY Homemade Tesla Coil

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Questions and Comments on the Nikola Tesla and the Tesla Coil

Some comments/questions are hidden. To include them below, click here
The information provided here can not be guaranteed as accurate or correct. Always check with an alternate source before following any suggestions made here.
kennySunday, 3rd June 2007 6:36am - No.1364
I have 4 neon transformers i would like to hook the transformers up in parallel, the transformers are 9000 volt at 30 milamps this should give me 120 milamps will this work im going to run wires to the first transformer to power it then connect the primaries of the other transformers to the first transformer, then connect the secondaries together to give me 120 ma?
 
DavidSunday, 29th July 2007 6:08am - No.1519
Yes, it will work if the polarities are correct, and the output voltage of transformers are the same.
 
IMMonday, 8th October 2007 4:41am - No.1864
I am hoping to make a tesla coil, but I had heard that it is dangerous because it can spark to you and spark to the AC power supply creating a ionized trail in the air so that the 110v AC can zap you, so is it safe if you use batteries?
Are there any safety issues? If so what are they?

Thanks for your help.
 
RMCyberneticsMonday, 8th October 2007 1:44pm - No.1867
Weather or not the AC power gets in to the output arc you do not want to be toucing them EVER!
It can be 'safer' to run a TC from batteries, but it could still quite easily kill you. Any device that charges capacitors to high voltage can be instantly lethal.
This mini Tesla Coil runs from a small 12V battery. Internally there are still capacitors being charged to thousands of volts so touching the wrong part could be nasty. A bleeder resistor is usually placed across the tank capacitor so that it wont hold charge for very long after being switched off.
 
StephenWednesday, 10th October 2007 1:10pm - No.1892
Thanks for providing such a wonderful service. Could you outline in detail, the method (if there is one) of tuning a tesla coil with an oscilliscope, or point me in the right direction? I've spent several days on your website and have not run across it. The quality of your replies is the best I have found on the net thus far, great work. Steve
 
RMCyberneticsWednesday, 10th October 2007 1:18pm - No.1893
A basic Tesla coil consists of two separate LC (inductor, capacitor) circuits which are not electrically connected but are loosely coupled electromagnetically. Any LC circuit has a natural resonant frequency at which it 'prefers' to oscillate. For efficient energy transfer both LC circuits of a TC must be the same.

You can measure the frequency of an LC circuit by connecting it to the scope and applying an electrical pulse. This pulse should set the circuit ringing and you should be able to see the result on your scope.

The primary circuit is a parallel LC circuit which will give maximum reactance at it resonant frequency. The secondary coil and topload form a series LC circuit which will give minimum reactance at the resonant frequency.

If you apply a signal source across an LC circuit, you can measure the high and low points while adjusting the frequency of your source. At the resonant frequency of your LC circuit the voltage measured on the scope will be either higher or lower than at other frequencies depending upon if it is series or parallel LC.

If you know the frequency of the secondary circuit, you can set a signal generator to match this and apply it to the primary LC circuit. You can then adjust your tapping point on the primary coil until you see the signal on your scope at its maximum level.
 
der stromWednesday, 21st November 2007 1:29pm - No.2200
I'm sorry if this is the wrong category for this question. I'm not sure which one it would fit under

What would be a good frequency to run my ignition coil?

Thank you very much.
 
RMCyberneticsWednesday, 21st November 2007 9:31pm - No.2202
How about the Ignition Coil Driver page.
The frequency depends on your coil and its load so I can't really answer your question. A variable frequency source is often used so it can be tweaked until the best output is found.
 
jan keithSaturday, 24th November 2007 7:47am - No.2215
I think tesla dont wanna touch utensils because if the tesla coil is on high voltage can e produced in the metal tool he would be using he is just being safe
 
RMCyberneticsSaturday, 24th November 2007 12:52pm - No.2218
Tesla would not like to touch utensils when he was sitting in a restaurant with no high voltage devices around. It seems he suffered from a form of obsessive compulsive disorder based on the relativley new concept of germs and bacteria.
 
jan keithSunday, 25th November 2007 6:26am - No.2220
i think tesla got so much imagination that he imagined how many people touched utensils at the restaurant
and he also imagine thew germs going through his arms NO OFFENSE
 
OJ-BThursday, 6th December 2007 12:29pm - No.2308
I HAVE SEEN TESLACOIL'S IN RED ALERT AND RED ALERT2 HOW DO THEY WORK? AND WHY DO THEY NEED VAN DE GRAFGENERATOR BALL ?
 
RMCyberneticsThursday, 6th December 2007 6:33pm - No.2311
The way they work is described on this page and more info can be found by following links from this page or by just searching on Google.
The ball is not a Van De Graff generator ball but it serves a similar purpose. It acts as a small reservoir for electrical energy and it also helps control the way the arcs are formed. The ball is referred to as a 'topload' and it can be any shaped piece of metal but smooth round shapes work best.
 
Awsome High VoltageSunday, 30th December 2007 11:06pm - No.2379
does the power supply have to be DC? because there are a whole bunch of sites that dont say any thing about DC. they just connect it directly to the transformer and it seems to work
 
RMCyberneticsFriday, 4th January 2008 3:10am - No.2389
No, DC input coils are probably less common. There are many ways you can make a Tesla coil.
The coils on this site use DC because the ignition coils used for the HV source will not charge a capacitor in the same way as a mains powered transformer.
A mains powered transformer is driven by a sine wave and with enough current that it can charge a tank capacitor on each half cycle.
 
gary krasFriday, 22nd February 2008 3:43am - No.2541
Type your message here
can you use a 35kvdc, .o30uF capacitor with a 12kv neon transformer. The previous cap was a 15kvacw with a 15 kv transformer and worked well for a while then blew.
 
RMCyberneticsSaturday, 23rd February 2008 11:50am - No.2546
Sounds ok. You should always use components rated for much more voltage then you intend to apply to them.
 
EPX101Saturday, 8th March 2008 5:16am - No.2591
can i use a NAND gate pulse generator instead of a 555 timer???
 
The N3RDSaturday, 8th March 2008 4:37pm - No.2592
My friend was just about to start constructing his tesla coil, when he changed his mind because of the noise factor. How loud are they (I'm talking about one 2 feet or less in height)? Can you compare them to something? Thanks
 
RMCyberneticsMonday, 10th March 2008 11:25am - No.2603
EPX101,
Yes.

The N3RD,
The sound level is roughly proportional to the power you put into it. This Tesla Coil produced a noise level akin to that of a blender (food processor).
 
D.C. CoxThursday, 12th June 2008 6:25am - No.2813
What city and country are you located in?

direct tel number?

Attached is photo of my large Tesla coil.

D.C. Cox
 
RMCyberneticsThursday, 12th June 2008 11:53am - No.2818
Email us for those details. Nice coil!
 
gtSaturday, 14th June 2008 7:06pm - No.2828
Tesla was a genius whose ideas were stolen by the "money changers" and released at optimal time for maximum profit. To keep anyone from pointing out that Tesla was the genius behind all of it they bankrupted him then discredited him so that anyone who cites him would be considered a kook in the "established" order of things.

Look at simple things like the Ionic Breeze from Sharper Image, Cell Phones, RF toys etc.. All were the brainchild of Tesla yet there were too many ideas too quickly to make any sort of profit from. Think of how big pharma operates now, they stockpile patents then release products creating a pipeline of viability for maximum profits. The FDA testing times vs. patent expirations defines their throughput. The "money changers" run the show and will only allow us to have what they think we are able to handle so that society does not buck their authority and control.
 

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