Wireless Power? (The work of Nikola Tesla)

[Desmond108]

Nikola Tesla's work has always fascinated me.

I've always heard stories and claims of Telsa's ability to be able to wirelessly power light blubs and I always found the idea intriguing. I've been doing some research on his experiments, or rather I've been trying.

I'm finding it pretty hard to find any concrete or reliable sources on what Tesla actually managed to accomplish. I read somewhere it involved large metal plates that generated an alternating magnetic field, which makes sense, but again, I've found nothing in depth.

Basically, I suppose what I'm asking is if anyone can point me towards some more in-depth or reliable sources that discuss Tesla's experiments, specifically things regarding wireless power?

It's just something that really interests me, any help would be appreciated :)

 

[phinds]

Can't help you with a source, but good luck with that. I find the guy interesting. Have read some about him and saw a good documentary on TV. Seems he was quite the genius and his wireless power distribution worked but was utterly useless for all practical purposes involving actual distribution of any significant amount of power over any significant distance. I believe I saw a calculation somewhere that showed that you could in fact have a nationwide power grid in the US using his technology if you were willing to permanently bankrupt the entire world for its construction and maintenance (AND you were willing to give up the staggering amounts of real estate it would have taken).

 

[MATLABdude]

If you haven't already seen it, there's a timeline (with references and links) over at the Wikipedia article on wireless power:
http://en.wikipedia.org/wiki/Wireless_power#Timeline_of_wireless_power

What would've been his magnum opus, the Wardenclyffe Tower (primarily intended for worldwide radio broadcasting, but also as a longer-distance electrical transmission demonstration) ran out of money before construction was completed:
http://en.wikipedia.org/wiki/Wardenclyffe_Tower

 

[0xDEADBEEF]

I think he basically used an alternating E-Field to power light bulbs. He stood on a stage inside a giant capacitor and was playing with fluorescent tubes. You basically just need a strong E-Field at some moderately high frequency to get the gas inside the tube into motion. A cheap way that produces very little light is just using the electrical field under transmission lines: http://pruned.blogspot.com/2008/02/fluorescent-field.html

I think he also did some near field magnetic transmission. And had some large ideas that never really got realized. See. MATLABdude's link.

 

[Meizirkki]

Sorry for necroposting, but I hope some of you will find this interesting.

I've replicated some experiments of Tesla. The wireless transmission is more like single wire transmission. The other end of the secondaries of the transmitter and receiver (tesla coils) have to be connected to each other with a wire or ground (earth) connection.

My miniature pancake coils have resonant frequency of about 9 MHz each. With this frequency, close range transmission via magnetic induction is possible. With longer distances, the frequency of transmission must be increased to pi/2 times the resonant frequency of individual coil. With my coils this is roughly 14MHz, but will vary depending on the ground connection. With this higher frequency, the distance between the two coils doesn't appear to have any effect on the transmission.

Tesla's method of wireless transmission is very different from the conventional radio to which it's most often compared to. In a conventional radio the energy is radiated everywhere with only small portion of it reaching the receivers. In Tesla's radio, the energy is conserved.

I've also been playing around with joule thief circuits, which have much in common with Tesla coils. A two watt joule thief made from scrap components can "wirelessly" illuminate any fluorescent lamp. I must say it is very rewarding to experiment with electric fields. Unlike magnetic fields, they seem to work over long distances. I'm already working on constructing another set of Tesla coils for further testing of wireless transmission.

 

[Alokin_Alset]

Hy Mezirkki.

My miniature pancake coils have resonant frequency of about 9 MHz each. With this frequency, close range transmission via magnetic induction is possible. With longer distances, the frequency of transmission must be increased to pi/2 times the resonant frequency of individual coil. With my coils this is roughly 14MHz, but will vary depending on the ground connection. With this higher frequency, the distance between the two coils doesn't appear to have any effect on the transmission.

¿ How did you get the resonance frequency? I could not find any formula for pancake coils, or bifilar pancake coils on the net & any physics book.

Why did you think that for higher frequencies the distance doesn't appear to be affected?

 

[Fischer777]

Tesla coils are another method Telsa used to transmit wireless energy, although, like the radio, they tend not to be very efficient. Nonetheless, they are simple to construct if you have the time and are willing to invest in them. If your interested, here's a website I've found to be very helpful if you want to undergo your own projects: http://deepfriedneon.com/tesla_frame0.html

 

[Meizirkki]

Hy Mezirkki.

¿ How did you get the resonance frequency? I could not find any formula for pancake coils, or bifilar pancake coils on the net & any physics book.

Why did you think that for higher frequencies the distance doesn't appear to be affected?

I didn't calculate the frequency. I winded two coils as identical as possible, except for the direction of winding, and measured the frequencies of standard induction and "Tesla transmission" with my schools equipment.

At the resonant frequency of individual coil I could induce electricity from one to another with distance of <2cm. The induction would fail whenever the coils were taken more than ~2cm away from each other.

When operated at the higher frequency I could leave transmitter into my room, and walk around the house holding the receiver, it's LED's shining brightly. I set up the coils for demonstration at my school's open house day and we also measure the efficiency of the transmission. 10 ohm resistor in series with the primary coil of the transmitter had a voltage drop of ~400mV and another 10 ohm resistor in series with the receiver's primary showed a voltage drop of ~380mW. This is 95% efficiency with a distance of about 6 meters. I expect it to be much closer to 100% with better coils and proper primary circuit.

In the above test, the transmitter was powered from a function generator and all voltages were RMS measure with an oscilloscope.

I'm planning to test my new coils at distances of over 100 kilometers, but it's going to take a while because building a powerful primary circuit for the transmitter is rather difficult :/

 

[Meizirkki]

Tesla coils are another method Telsa used to transmit wireless energy, although, like the radio, they tend not to be very efficient.

[citation needed] ?

Tesla coils is exactly the way to go for efficiency.

 

[jim hardy]

10 ohm resistor in series with the primary coil of the transmitter had a voltage drop of ~400mV and another 10 ohm resistor in series with the receiver's primary showed a voltage drop of ~380mW.

were both resistors in both circuits at times of both measurements?

and i assume you meant to type: 'primary showed a voltage drop of ~380 mV.' ?

 

[Fischer777]

I am curious about these pancake coils. Where can I get information regarding them (how they work and all that stuff)?

My miniature pancake coils have resonant frequency of about 9 MHz each. With this frequency, close range transmission via magnetic induction is possible. With longer distances, the frequency of transmission must be increased to pi/2 times the resonant frequency of individual coil. With my coils this is roughly 14MHz, but will vary depending on the ground connection. With this higher frequency, the distance between the two coils doesn't appear to have any effect on the transmission.

I am not sure I understand this. How can a resonant circuit operate outside it's resonance frequency?

When operated at the higher frequency I could leave transmitter into my room, and walk around the house holding the receiver, it's LED's shining brightly. I set up the coils for demonstration at my school's open house day and we also measure the efficiency of the transmission. 10 ohm resistor in series with the primary coil of the transmitter had a voltage drop of ~400mV and another 10 ohm resistor in series with the receiver's primary showed a voltage drop of ~380mW. This is 95% efficiency with a distance of about 6 meters. I expect it to be much closer to 100% with better coils and proper primary circuit.

How is the energy being transferred from the emitter to the receiver? Is it magnetically or electrically? Do the coils have to be aimed at each other for the transfer efficiency to peak?

Forgive me for asking what are probably really silly questions. I am a freshmen electrical engineering major with absolutely no formal training in electrodynamics whatsoever.

 

[Meizirkki]

were both resistors in both circuits at times of both measurements?

and i assume you meant to type: 'primary showed a voltage drop of ~380 mV.' ?

yes to both.

 

[Meizirkki]

I am curious about these pancake coils. Where can I get information regarding them (how they work and all that stuff)?

I am not sure I understand this. How can a resonant circuit operate outside it's resonance frequency?

There appears to be two resonant frequencies. The lower is for magnetic induction and the higher for electric field induction. Tesla stated that his wave travels pi/2*c (faster than light). The resonant frequency for Tesla transmission is also pi/2 times the frequency of magnetic induction.

How is the energy being transferred from the emitter to the receiver? Is it magnetically or electrically? Do the coils have to be aimed at each other for the transfer efficiency to peak?

According to Tesla himself, his radio was not magnetic and my experiments lead to the same conclusion. The transmission is achieved with the use of resonating electric fields. This way, the receiving coils acts like a capacitor in series with the capacitance of the transmitter. Or that's what I think. I've been trying to figure this out for many months now and of all the proposed explanations this makes the most sense. Coils do not need to be pointed at each other, the position of the coils does not affect the transmission.

And please don't apologize for asking those questions. It's so hard to find reliable information of the Tesla transmission that after reading some books and browsing through hundreds of shady websites I decided that the only way to understand it is to do it myself. I encourage you to do some experiments too. :)

 

[Fischer777]

Is a Tesla pancake coil essentially the same as a Tesla coil with the windings in a flat spiral instead of in a helix, i.e. there's a primary coil of a just a few turns of thicker wire, and a secondary that's several hundred to several thousand turns of small wire (with one end grounded and the other attached to a circular or toroidal capacitor)?

 

[Meizirkki]

Is a Tesla pancake coil essentially the same as a Tesla coil with the windings in a flat spiral instead of in a helix, i.e. there's a primary coil of a just a few turns of thicker wire, and a secondary that's several hundred to several thousand turns of small wire (with one end grounded and the other attached to a circular or toroidal capacitor)?

Yup.

EDIT: [According to Tesla's patents.]

 

[jim hardy]

so in your experiments are primary and secondary connected by this "ground" ?
If so, is it a wire between the coils or rods driven into Earth near each coil?

 

[Meizirkki]

so in your experiments are primary and secondary connected by this "ground" ?
If so, is it a wire between the coils or rods driven into Earth near each coil?

The primary and secondary coils are not connected to each other in either of my coils.

Did you mean to ask whether the secondaries of the pancake coils were connected? They are connected with a wire. Tesla himself used Earth in the place of this wire, but I haven't been able to test that myself since it would need a very good RF ground, and I don't have an Earth grounding of any kind. :/ Besides, using Earth ground would be rather difficult with coils this small. The pancakes are only about 15cm in diameter.

 

[sophiecentaur]

That danged Tesla rears his head again. I wonder what the FCC would have had to say about his experiments if he'd tried to carry them out today.

Amazing that all those high powered US tech. companies never took on board his 'fantastic' schemes. They certainly missed a trick there.

Reading what people have to say about our Nicola rather puts me in mind of the old Soviet history books that their Schools taught from. Read them and you'll learn that Soviets invented pretty well everything technological since the Revolution.

 

[jim hardy]

"""Did you mean to ask whether the secondaries of the pancake coils were connected? ""

yep, that was the question..errr, should have been the question..
just trying to get a handle on your setup.

Thanks !

 

[billbaty]

Most people think that Tesla was transmitting power through the air, probably because they see the towers he built, hear that he was transmitting power and associate his operation with modern-day radio transmitting towers.

What was actually happening is he was collecting electricity at the top of the tower and transmitting it into the ground. The ground was his wire. Look at his patent for the wireless transmission of power and the tower is labeled as a "generating" device.

Look up "Art Bell's Antenna" and he accidentally stumbled upon Tesla's electrical generating capabilities. I don't have all the stats before me but Art got a continuous 350 volts from a radio tower that was about 80 ft tall and had a loop of about 1/4 mile of #2 wire.

ll the best,

billbaty

 

[sophiecentaur]

Where did the energy, reputedly, come from?

 

[Meizirkki]

It has been rumored, but afaik not verified, that Tesla collected energy from naturally occurring electric fields. Wilhelm Reich was also known to "accumulate" electric fields in his accumulators (though he always called it something cool like "force of life and sexuality").

What we do know about Tesla coils is that in a well designed coil the oscillating field becomes very large and dies off rather slow. The Q factor is incredibly high, especially when operated at the "capacitive resonance" frequency, far higher than the usual resonant frequency. At this high frequency, the electricity no longer moves along the wire but along the capacitance between each turn of the coil. There is practically no current in an ideal Tesla coil secondary, which means there are no resistive losses and no magnetic-related losses whatsoever.

In his patents, Tesla is boasting how the upper terminal of his coil can reach "many hundreds of thousands of horsepower". This is not a lie for the coil maintains it's oscillation and even with a relatively small input power, the oscillating field can reach tremendous power over time. Tesla surely didn't have a continuous input power of many hundreds of thousands of horsepower. There is much confusion about this perceived "excess energy", but I hope the above has it in a nutshell.

But if Tesla indeed managed to collect large amounts of electrical energy somehow I'm all into replicating such work. I didn't look up the Art Bell's antenna yet, but it sounds reasonable. We are surrounded by many naturally occurring and man-made fields. Art Bell's antenna could be receiving anything from Earth's ELF signals to AM radio of >250KHz.

There's also this guy who designed and built a Tesla coil alike high Q AM antenna and tuned it to resonate at the frequency of certain radio broadcast. As expected, his antenna begun oscillating and up to 30 watts of power could be received from the distant radio station.

 

[sophiecentaur]

The above terminology is a bit far fetched. Power ( "Horsepower" ) is a transfer of energy and not 'stored energy'. It is true that a resonant circuit (or a standing wave) will store energy but this has nothing to do with power. It's all about having a fairly high Q circuit. But a good receiving antenna will couple well to free space so it will not have a high Q.

This stuff about 'collecting' energy from 'naturally occurring and man-made fields' violates thermodynamics and basic conservation principles that even Nicola cannot waffle his way around. I could suggest that he was probably well enough informed to be aware of this and that it's his disciples who have over egged his claims.

Many antennae have a larger effective cross section for intercepting a passing wave than their geometrical shape would suggest (a thing wire dipole, for instance) but the power has to come from somewhere and, once beyond the local field of influene, the energy flux over the sphere will not be affected. Where this "30 Watts" is supposed to have come from is anyone's guess. What was the original transmitter power and what was the separation?

Since Tesla died, technology has progressed an awful long way. People seem to be suggesting that his ideas were, somehow, so magical that they have never been understood by anyone since. This is despite GR, Quantum Physics, String Theory, even classical EM theory and the rest. There has, somehow, to be a subset of knowledge that Tesla had - some sort of magic- that has escaped all the brilliant minds that have existed since his time. Get real chaps. If they were real and worth money then we'd have them in our homes, transport systems and weaponry.

Instead, what have we got? Fizzy sparks for school kids.

 

[billbaty]

The energy is the Earth's magnet that has been concentrated. Electricity is concentrated magnetic flux. When you put a coil of wires in front of a magnet the flux is concentrated in the individual strands of wire. Tesla's tower, or Art Bell's, essentially concentrates the Earth's magnetic flux into a measurable amount of electricity when it is released or grounded, that is to say released to the ground.

We all have assumed that Benjamin Franklin flew a kite in a thunderstorm and got shocked. But what really happened is that he flew a kite in broad daylight using a copper wire for a string and when a certain altitude was reached and he touched the attached key, he ground out the concentrated magnetic flux and shocked himself.

billbaty

 

[sophiecentaur]

The energy is the Earth's magnet that has been concentrated. Electricity is concentrated magnetic flux. When you put a coil of wires in front of a magnet the flux is concentrated in the individual strands of wire. Tesla's tower, or Art Bell's, essentially concentrates the Earth's magnetic flux into a measurable amount of electricity when it is released or grounded, that is to say released to the ground.

We all have assumed that Benjamin Franklin flew a kite in a thunderstorm and got shocked. But what really happened is that he flew a kite in broad daylight using a copper wire for a string and when a certain altitude was reached and he touched the attached key, he ground out the concentrated magnetic flux and shocked himself.

billbaty

"Electricity is concentrated magnetic flux" is it? "Electricity" is, in fact, a non-specific term (in Science) which is used as a general description 'to do with' Electromagnetism and the study of it. There is Electric Field, Electric Potential and many well defined quantities - but not 'Electricity'. If you want to 'get energy' from something then you have to put energy in or there needs to be a change of some sort. This is basic stuff that has proved itself to be reliable and consistent enough to 'put a man on the Moon' and 'give us the Internet'. The standard theory could be said to have pretty much justified itself in most practical applications. If you want to propose a better theory then you had better start on a massive body of work and not just give assurances about things that happened in the dim past.
It's interesting that you quote Benjamin Franklin and not an experimenter of more recent times. Were you there to see "what really happened" and could you quote some figures to indicate just how much energy is available in this way? If it really were as you say it is, why don't we all have towers over all our houses to supply our energy needs? It's so wasteful to be burning all that gas and oil when towers could do the job. Set up a company and see if it makes you any money - based on results.

Actually, what you are proposing is outside the terms of Physics Forums in that it does not involve any peer- reviewed ideas.

 

[Meizirkki]

This stuff about 'collecting' energy from 'naturally occurring and man-made fields' violates thermodynamics and basic conservation principles that even Nicola cannot waffle his way around. I could suggest that he was probably well enough informed to be aware of this and that it's his disciples who have over egged his claims.

Why and how exactly does anything I suggested violate the laws of thermodynamics and basic conservation principles? My point was that whatever these "collectors" may be, they don't create energy but receive it from an existing source. And there are lots of sources around us.

Many antennae have a larger effective cross section for intercepting a passing wave than their geometrical shape would suggest (a thing wire dipole, for instance) but the power has to come from somewhere and, once beyond the local field of influene, the energy flux over the sphere will not be affected. Where this "30 Watts" is supposed to have come from is anyone's guess. What was the original transmitter power and what was the separation?

Here's the article. Just like a receiving Tesla coil, the antenna becomes a capacitor in series with the capacitance of the transmitter.
EDIT: He also used the regenerative circuit to increase the effective area of the antenna, sorry I didn't remember that one.
EDIT2: Nevermind, the regenerative circuit was only used in first of his tests, not the 30W one you were interested in.

Since Tesla died, technology has progressed an awful long way. People seem to be suggesting that his ideas were, somehow, so magical that they have never been understood by anyone since. This is despite GR, Quantum Physics, String Theory, even classical EM theory and the rest. There has, somehow, to be a subset of knowledge that Tesla had - some sort of magic- that has escaped all the brilliant minds that have existed since his time. Get real chaps. If they were real and worth money then we'd have them in our homes, transport systems and weaponry.

Instead, what have we got? Fizzy sparks for school kids.

I don't want to upset you, but I think Nikola Tesla is the only man to ever use the planet Earth's features as crucial parts of his circuits for wireless energy transmission. That is where everyone else have gone wrong. Tesla's wireless transmission system is very real and there's no magic: just think of the Earth and the atmosphere as capacitors and it will make sense. The energy is not radiated, it is conserved.

Peace.

 

[sophiecentaur]

Your posts and the link you have exhibit the same glaring flaw. That is there are no quoted figures and no serious experimental details.
All Science and Engineering involves details and numbers. That's why it tends to work when done 'properly'.
The fact is that there is no EVIDENCE to support this nonsense.
You either have to believe that there were successful results from the original work and they have been deliberately suppressed (conspiracy) or that no Scientist has had sufficient ability to take it to a successful commercial conclusion (cockup).
Else you could just admit to yourself that it's all moonshine.

That link is no more than a rather garbled version of a straightforward EM textbook. But with one thing missing - solid theory.

 

[Meizirkki]

I've provided details of my last experiment and given a reasonable explanation of how the transmission works, which obeys all laws of the prevalent physics. And once again I'm told that the tesla transmission is nonsense.

You have all the right to not believe what you haven't seen with you own eyes, but please keep it to yourself. It isn't very good science to come over and tell an experimenter he's wrong just because what he does isn't in the book.

And by the way, please don't take the link against me here. Whatever the author has written is his opinion, not mine. I agree with the idea of a resonant receiver becoming part of the transmitter circuit, but I don't have enough knownledge to comment on anything else he might have said.

 

[jim hardy]

i repeat, at first glance resonance looks a lot like energy creation but in reality it's energy storage.

Q being ratio of energy stored to energy dissipated per cycle,

a substantial amount of energy is expected in a high Q system that's gently excited at its resonsnt frequency.
But the energy came from the excitation source , in tiny little bits one cycle at a time..
That's why soldiers marching across a bridge break step.

If you ever lived with a Piano, you've heard individual strings come and go in sympathetic vibration with sounds in the room. Room sounds are the excitation source and each individual string is a high Q resonator.

I'm still waiting for a "Free Energy" experimenter to identify the source of excitation more specifically than "Earth's magnetic field" .. and not holding my breath on that one.

But i find your 14mhz transmission experiment producing 380 mv across ten ohms interesting.
That sure is one heck of a directional antenna pair!


old jim

 

[sophiecentaur]

I've provided details of my last experiment and given a reasonable explanation of how the transmission works, which obeys all laws of the prevalent physics. And once again I'm told that the tesla transmission is nonsense.

You have all the right to not believe what you haven't seen with you own eyes, but please keep it to yourself. It isn't very good science to come over and tell an experimenter he's wrong just because what he does isn't in the book.

And by the way, please don't take the link against me here. Whatever the author has written is his opinion, not mine. I agree with the idea of a resonant receiver becoming part of the transmitter circuit, but I don't have enough knownledge to comment on anything else he might have said.

I am "taking the link against" you because you brought it into the argument. You have used it as evidence and I am debunking that particular piece of evidence.

Your experimental results show that it is possible to get coupling between two circuits (a pretty common thing). In fact you have not given a 'reasonable explanation' for the results because they need to be analysed properly. And the results, in fact, tell you very little.

I question that your claim of 95% efficiency. To prove that, you need to be looking at Power and not just a voltage across a resistor. You can only use Current or Volts as a measure of efficiency if the impedances are the same. (A transformer can appear to be a fantastic amplifier if you don't obey the rules). Are you aware of what Jim is telling you about resonance?
What is the output power of your signal generator and the actual power delivered to your LEDs? It may be quite hard to determine this, actually.

You mention a School. I sincerely hope you are giving any students a balanced view of their Science and not taking them down strange, alternative paths. Young people are easily lead and the Tesla legend could be dangerously attractive.