witricity legality?
 

I seriously want my team to do this next year but im sure about how legal it would be based on this and last years rules.
witricity is basically the cordless transmission of power. By using coils that resonate on the same frequency one will pick up the power that the other is broadcasting(no signals are being sent only electromagnetic waves), using this with victors it think would make a very sweet crap drive, but im not sure if it would be legal via this and last years rules.

thanks for the help
cody

Re: witricity legality?
 

Not to rain on your parade, but FIRST's rules are the least of your concerns. Physics and the FCC will stomp this many times over.

1) The drive train uses a lot of energy.
2) RF transmission is lossy.
3) The energy that leaks out will affect other systems.

Do you have any examples of this "witricity" as you call it? I'd be interested to see their numbers.

Cool idea though.

Re: witricity legality?
 

Regardless of legality this doesnt seem like a great idea. Two things that come to mind would be the interference of magnetic fields and electronics. Also based on the wikipedia article the efficiency is not very good, researchers needed two 24in coils and only tansmitted at 40% efficiency, not great for battery life.

Re: witricity legality?
 

witricity which using resonating magnetic coils was proved possible my mit last year by using it to light a 60watt light bulb 2m away. With stuff blocking directing line of sight

also Tessala (can't spell) using witricity to transmit massive voltages over great distances, one example is that in a eletrical field you can light flourencent lights with out plugging them in.

the laws of physics allow this to work, but im not sure if the metal frame would interfere. Also other eletronics can work in a witricity feild if they don't opperate on the same frequency they will not conduct the current. Which is why you make sure that the cycles of the field is very high (10megahertz or higher).

MIT tested this device, there was 40% power loss in transmission. If we weren't going for speed this could be viable i think. You know for a engineering award.

Re: witricity legality?
 

You could also just build your own slip rings to transmit the power to the motors in the crab drive. It would most likely be a lot simpler.

Re: witricity legality?
 

Rather than planning this as a power transmission method for a FIRST robot drivetrain, where robustness and reliability are paramount, this sounds like a great science fair project.

If you do your research and start building prototypes and testing them now then you will not only have a good science fair project, but... if you can move more than 40 amps through the ether with minimal losses, then you will have something that your team can check against the FRC rules for legality.

Just keep in mind, however, that transmitting current is quite different from transmitting voltage. Also keep in mind that when a CIM is drawing 40amps at 10 volts, that is 400 watts of power. If you have a 40% power loss then you have 160 watts of heat showing up somewhere. Any compact, lightweight system is going to start getting really hot, really fast.

So if you are interested in this system, study it. Research it. Test it. And should you get it to the stage where you can use it in an FRC robot, then worry about what the FRC rules are. Even if it doesn't work for FRC, it will still be a very cool science fair project.

Jason

Re: witricity legality?
 

That would probably be legal, however would be difficult to do as stated in the other posts.
Another way which might be easier but probably illegal is to make a microwave transmitter to beam microwave frequencies to a reciever. The reciever is usually a rectenna, which converts microwave to electricity. It could be relativley efficient also.
However, that could be extremley dangerous and illegal in the competion. Other methods that would be safer are also availiable like laser beaming.
One may actually be able to replicate experiments such as this one
http://youtube.com/watch?v=4BxV_48Sjj4

Anyway, I hope that helped.

Amir M.

Re: witricity legality?
 

I see no FIRST rule that would prevent the use of Witricity.

That being said, you still have a lot of things to overcome
1> Matching resonators for transmission and reception. Any impedence mismatch will greatly reduce your transmission efficiency.
2> Each device would need a separate frequency to transmit power.
3> You would need to make sure you do not induce any current in any robot frame on the field, to do so would break FIRSTs rules.
4> You would need to make sure you do not interfere with any signals on the field.
5> Power losses would limit your robot and multiple transmitters in series (Battery to dist block, dist block to Victors, Victors to motors, etc) would cut your power even more.

While I think your idea is novel, and would win you an engineering award, I don't think it would provide a viable robot on the field.

Re: witricity legality?
 

<3 the typo (=

as previously said, i dont think your idea is exactly feasable. It could potentially win you an award, but youll probably be impeded by rules, physics, losses, etc.

Something also tells me that transmitting 400W of power with EM radiation is a really bad idea...

Re: witricity legality?
 

I too am looking forward to seeing a sweet crap drive! :)

Seriously, Take a shot at energizing a sensor or two (a few tenths of a watt) that are on the extremities of your robot.

Then, maybe graduate to energizing a coprocessor out on one of those extremities.

You can graduate to transmiting serious power after successfully getting a few watts to coprocessor. Along the way you can navigate the safety and other rules.

Blake

Re: witricity legality?
 

Good science fair project, poor (due to rules) way of powering a FRC robot.

Edit: I misread the original post, and thought they were talking about 'sending' additional power to the robot from the pits/stands/etc.

Re: witricity legality?
 

From what I can tell, they are not proposing to use this system to generate power, but to transmit power (presumably from the 12v battery). I don't think there's anything illegal about it, but... why, exactly, do you (the original poster) need it? Not that that's ever a good reason not to try something new, but there seem to be some disadvantages to this system...

Re: witricity legality?
 

Oh, ok. That makes much more sense, and powering sensors with it would definitely be a useful application. I wonder if you'd have to get FCC clearance to run such a device, since it uses the airwaves.

Re: witricity legality?
 

I think it maybe illegal per <R53>

This would certainly be a custom circuit and it is directly altering pathways to the speed controller (or sensors or anything else).

Re: witricity legality?
 

Induction is cool for short distance low current applications... but I don't think it would work very well (excluding rules) for running a robot. Tesla devoted a lot of his work to wireless energy transmission, and never really got anything that was very efficient over much of an appreciable distance, plus when he tried to market some of his more long-range methods of transmitting large amounts of energy to the U.S., they were deemed unsafe.

But don't mistake me about him... nothing against Tesla. He did a TON of work with EMF that we use all the time today, it's just that long range energy transmission never really worked out for him (or anyone else for that matter).

Also, let's say the frequency you were using for transmission was somewhere up in the microwave spectrum, and let's assume your transmission in 100% efficient (it wouldn't be, it decays at the square of the distance your antenna is from your source, but just for fun). Also, let's say you want to run four CIM motors at up to 40A. 40A*12V= 480W, 480W*4motors=1.92kW.

As much fun as a 2kW microwave sounds, I don't think I want to be anywhere near it (unless lead shielding was provided for the operator stations). :yikes:

Fun idea though...

q

Re: witricity legality?
 

From an engineering viewpoint, it's not a very good idea....wires work so well for carrying electric current. Wireless signal transmission makes sense because the information is what is important, not the power being used by the transmitter. Wireless transmission of power itself is not a very good idea, because it is very inefficient compared to wires (I think the inverse square law has something to do with it?)

It would be fun to experiment with, and as suggested low power applications such as powering custom sensor circuits would be a more suitable application than the drive system, also more likely to be meet the rules.

Re: witricity legality?
 

A couple things to note...

You'll need a way to convert the DC of the battery to AC in the transmitting coil. Not hard to do, but it'll hurt the efficiency. You also have to match the resonant frequencies of the transmitting and receiving coils, and match the frequency of the DC to AC inverter to those. A little harder to do, but still possible, with patience and a little research.

The power is transmitted much like it is between the two windings of a transformer - the changing magnetic field generated by the transmitting resonator passes through the receiving resonator and generates a voltage there. The difference is that the magnetic field is not in the least bit confined, which is what the ferrite core of a transformer does. What'll happen is that that changing magnetic field you generate will induce currents in every loop of metal within its range, particularly the robot chassis, manipulator, neighboring robots, metal field elements, belt buckles, tools in the pit, hoop-shaped body piercings, whatever happens to be around. It can really wreak havoc on your electronics. Plus, metals get hot really fast when you induce currents in them. And, the more power you try to transmit, the greater the volume the magnetic field takes up, so more things draw power away from your transmitter.

Then, at the receiving end of the power transmission system, you'll need to rectify the AC back to DC. If you're going to run a sensor with it, you'll need to regulate the supply.

Hang on...if you run a sensor this way, you'll have to get the data back to the RC...with a wire, since other radios on the robot are prohibited.

In short, assuming this might by some stretch be legal, then trying this on a robot will at best waste power, and at worst cause enough heating in the chassis (large current in a thin piece of metal) to catch something on fire. Hmmmm, maybe that could be your science project - ignite a sheet of paper wirelessly.

BTW, one problem with Tesla's demonstration with the fluorescent tube is that there was no easy way to confine the volume which the fields operated in - if your neighbor's transmitter was on, your lights were on. It still needed quite a lot of work to be practical.

It sounds like something really cool to tinker with, and pretty inexpensive, but there's a lot that's got to happen before it's practical and safe for use on a robot. Have fun with it.

- Steve

Re: witricity legality?
 

i don't believe that the energy that is lost in the 40% transmission lose is lost to the frame i think that the energy is lost just to space

also the energy from the robot will stil come from the battery no an out side place.


i agree with you that this would be a very sweet science experment (to bad im to old for our counties science fair). but i think this would be the spirt of first to try to put one of these things on a robot

Re: witricity legality?
 

I decided to look into what this year's rules have to say. I found one "debatable" against:I say this is debatable only because the rule is referring to wireless communication, not necessarily energy transfer.

However, it may also be legal:I think, if you made adequate provision for isolating the frame and a wired communication to the RC, you might be able to convince the GDC to allow it. However, I also think they would be more likely to not allow it.

Re: witricity legality?
 

good point it my be legal and possible but in terms of power use, it looks very impossible in practice.

Re: witricity legality?
 

It is most definitely illegal to make a custom circuit to convert the DC power provided by the battery into AC power require for inductance. While in theory DC induction could work the coils quickly become magnetically saturated and therefore not useable. Because you can not provide a source of AC power on the robot (or a custom inverter to convert the battery power) you can not use such a method to power your robot.

Now let's talk about eddy currents. The M.I.T. experiments you cite did not involve numerous large metal objects such as robots. The large magnetic fields involved in transmitting electricity wirelessly will create millions of small whirling currents in an AL frame causing it to heat and sapping energy from the motors. It's an amazing and innovative idea, but it will be several years before it reaches fruition.

Re: witricity legality?
 

Please provide the rule which would disallow a custom circuit (inverter) that would change DC to a very specific AC frequency. I do not believe you will find one.

Re: witricity legality?
 

There is plenty of energy lost to free space, because the magnetic coupling between the two coils is inefficient. That'll put an upper limit of about 60% on your efficiency considering only the coils.

In addition to that, the stray magnetic fields (of which there will be plenty) will pass through parts of the frame, and those fields will generate currents in anything that's made from a decent electrical conductor, like aluminum or steel. This is not speculation on my part, it's solidly grounded in electromagnetic theory. In fact, it's the same effect that makes your desired power transfer work - the changing magnetic field inducing a current in the metallic wire of the second coil - but it's the stray magnetic field acting somewhere you don't want it to.

I don't think there's anything in FIRST rules prohibiting converting DC to AC, but transmitting it to another point through the air violates the FIRST-only radio rules.

- Steve

Re: witricity legality?
 

JamesBrown already provided it.

<R64> even keeps you from doing it in order to transmit a signal (as opposed to transmitting power).

Re: witricity legality?
 

Just to verify from real life experience, we use AC in one process on our robot this year and have never had any trouble with it in any of our inspections.

-q

Re: witricity legality?
 

Q,

That's wired, though, and not deliberately wireless?

- Steve

Re: witricity legality?
 

As you probably know, we have a data display on the back of our robot. At midwest, the display would go out a lot because the battery voltage often went low when loads were put on it (i.e. traction motors) causing the display to go dim/out. Since the second half of the boilermaker regional, you may have noticed the display now very rarely blanks or dims now.

We put a circuit in line with the power supply to the rear display that takes in the DC voltage from the battery, and runs that into a switching transistor that flips on and off at about 15KHz, generating AC. This high frequency AC goes into one side of a transformer, and comes our the other side at a high voltage. This high voltage is then rectified using diodes, and regulated back down to a (very very clean and stable) 12 volts, while the input can vary anywhere from about 6.0vdc to 18vdc.

If you have any further questions, just come over to our pit in atlanta and ask for Q.

-q

Re: witricity legality?
 

one debate that is poping up every page that i would like to settle is that witricity is not
radio waves
anykind of standard electromagnetic wave (radio, micro, infared, light, UV, Xray, gamma)
it will not be used to control robot
it will not interfere with body
it will not heat up body
the power for the coils will be from the battery not external.

i hope this clears up any future comfusion

Re: witricity legality?
 

Uhhhh... can you tell me which of those is not a 'standard electromagnetic wave'?

Even wires transmit electromagnetic waves... they (wires) just provide a strong suggestion for which way the electrons should go.

-q

Re: witricity legality?
 

Q,
I didn't know about the display, but I follow exactly what you've done and it sounds like you've got a really slick solution to your problem. Nicely done...nice high frequency means small caps at the rectifier output and not a lot of ripple. Probably a lot cheaper and surely more educational than buying a switching power supply. I'll try to stop by when I get a chance.

- Steve

Re: witricity legality?
 

That violates <R53> as I read it. You might successfully argue that it's a non-functional decoration and thus not part of the "robot control system", but it looks to me like it's still covered by the "other sensors or circuits" phrase.

Re: witricity legality?
 

I would venture that "altering the power pathways" essentially means that nothing is supposed to go in between the breaker panels and the Victors/Spikes/RC, or between the Victors/Spikes and the motors. What Qbranch describes doesn't sound like it's altering the path to some circuit... the supply/display combo IS the circuit. I can't understand how <R53> could be read to outlaw this... there are plenty of custom circuits teams have used that derive power from the 12VDC system, but end up using something other than 12VDC at the end.

Re: witricity legality?
 

From this post I will assume that witricity is magic not electromagnetic induction.

Everything I know about electromagnetic induction indicates that using two inducting coils would both interfere with and heat the body of the frame. Take any high school physics book and look up eddy currents. The principle is essentially that any piece of metal contains hundreds of conducting loops which will all form currents when in the presence of a changing magnetic field. Such loops will generate heat and suck power from the desired application. You will notice that there was no nearby metal in the M.I.T. test and that the only barrier used was a WOODEN BOARD.

Re: witricity legality?
 

ok ok we won't use it.

Re: witricity legality?
 

Well... three regional inspections, from three different inspectors, in three different cities think different. :]

Re: witricity legality?
 

There are various rules that may come into play on this one. Solenoid actuators and transmitting devices other than the radio modems and a specific signaling device for the hybrid mode are specifically prohibited under current rules. And as Alan has pointed out, R53 most certainly applies. As to some of the previous posts, Tesla coils included, all are fairly lossy devices and/or require rather large electromagnetic fields to operate. Although cool and an interesting way of supplying power to rotating mechanisms, they are likely just too inefficient for use on a robot. Please check into the 60 watt light bulb and look closely at the power input required to light the bulb.
BTW, the circuit used to keep the display from blanking for the Kilobytes is considered a custom circuit and does follow the robot rules in that is specifically does not control any motors or actuators on the robot and thus follows R53. In a similar fashion, the power supply that some teams use to power decorations like the CCFL tubes also modifies the power supply but does not connect to any control on the robot.

Re: witricity legality?
 

ok people!

Re: witricity legality?
 

Ok, I have had a chance to do a little research on the experiment and this is what I found. The stated efficiency is about 40% and the team claims that they will be able to develop a commercial system that will meet FCC safety standards. The demonstrated system ran at 10 MHz.
A few things came to mind while I was reading some of the articles. 10 Mhz is already used for a variety of very important wireless governmental services such as WWV time standards and GPS synchronization signals. Just above this frequency is an amateur radio band that shares the spectrum with other services. So there is more to consider than just safety issues.
As far as use on a robot, this system is being developed for delivery of power and has no provision for tranmsission of control signals, although there are other devices that do that very well. In the future this might be a pretty cool thing to have on the robot if certain other problems are addressed. Keep thinking, we might see this someday.

Re: witricity legality?
 

Sounds like you got the message...but that won't stop everyone else from discussing it to death! :)

Re: witricity legality?
 

y'know i think it would be great to use but it is decades ahead of time. I will try to build a prototype of it over the summer if it works then you will hear the post.

all i need alot of eletrical stuff...

Re: witricity legality?
 

Don't forget that RF heating of body parts is a well established fact. Start reading about RF and coupled circuits before you jump in. If the numbers can be believed, to deliver 60 watts at the light bulb at 40% efficiency, then the transmitter had to be able to deliver at least 150 watts to begin with. That is 50% higher power than the transmitters many ham operators use to communicate around the world. Interference is something that you will find brings the FCC knocking on your door.

Re: witricity legality?
 

could be a very interesting conversation.

"I was trying to apply pioneering technology to a robot to give us a competive edge in FIRST, with a new type of wireless crab drive."
"Well your disrupting ICBM guidance."
"Sorry."

it wouldn't work like that. Anyways i think the current is magentic not radio, so i don't think that it will interfere. Also when Popsci (Popular Science) ran an article on Witricity they said that it does not interfere with the human body. But i will have safety glasses on anyways.

Re: witricity legality?
 

i believe this article should clear up any confusion about witricity.

there you go

Re: witricity legality?
 

this is the important part...


now can we have a more informed talk about this crap.... (not crab).

Re: witricity legality?
 

Radio is EM, as is light, x-rays, gamma rays etc, the only difference is frequency.

Do you know what issue of PopSci the article was in, I don't remember reading it but I would like to. Also PopSci is not always the best resource.

Re: witricity legality?
 

Ah, to be young and still know everything.

Electricity and magnetism are two inseparable components of electromagnetism. A changing magnetic field creates an electric field, and a changing electric field creates a magnetic field. That's how induction coils work to transfer power through empty space.

At a frequency of 10 MHz, it is radio by definition.

Re: witricity legality?
 

did anybody read the massive post i quoted from wiki!?!?!?!?!?!?!



[quote][Ah, to be young and still know everything/QUOTE]
i hear that to much but i do understand electromagentic theory. i did get side tracked see i read the quote from wiki....

Re: witricity legality?
 

Yes, I read it, actually I read it before I posted the first time in this thread.

10Mhz is radio as Alan said, specifically it is in the range referred to as High Frequency Radio, here is some information about the range. http://en.wikipedia.org/wiki/High_frequency

Re: witricity legality?
 

Shadow,
(what is your real name?) As posted above, RF communication is an electromagnetic signal. Two coils spaced apart are capable of coupling energy but it is unlikely that interference or body absorption would not occur. This is how transformers actually function. If you think about current in a coil of wire producing a magnetic field similar to a bar magnet you can imagine the field produced by this device. The FCC limits and licenses devices used to transmit energy under part 15...
TITLE 47--TELECOMMUNICATION CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION PART 15--RADIO FREQUENCY DEVICES--Table of Contents Subpart C--Intentional Radiators Sec. 15.209 Radiated emission limits; general requirements.
The table contained there (http://frwebgate.access.gpo.gov/cgi-...00&TYP E=TEXT) does not copy well but essentially it requires that unlicensed operation must be below 30 microvolts/meter at 30 meters from the radiator. Most hams naturally consider that transmitters in the milliwatt range (much less than one watt) satisfy non-licensed devices. In that the experimental device was described as transmitting 150 watts, in general it would have needed to be licensed even if only an experimental one.

Re: witricity legality?
 

The odd/nifty/novel thing about what's being called WiTricity here is that it's strictly a "near field" thing. There is no traditional radiative field; as the Wikipedia quote says, it involves "evanescant waves" which fall off exponentially with distance. I haven't seen rigorous mathematical details of the setup, but there are references to the receiving coil having to be within a quarter wave of the transmitter. At 10 MHz, 30 meters is one wavelength. It might be far enough for the field strength to be sufficiently low to not need a license.

But evanescent waves are still EM, and they still interact with any conductors within range -- and in doing so, they can scatter the energy so that it does radiate. Shadow has apparently picked up on a comment that the connection between the tuned coils is "mostly magnetic" and thus infers that it isn't radio, but fails to recognize that all the energy that is not transferred between the coils is going to interact with metal, ionic liquids, human flesh, etc. in the same way as any other RF energy.

Re: witricity legality?
 

Unfortunately, building custom connectors are not legal. Our swerve drive is limited to 8 rotations (on each wheel) and we looked into such connectors, but they cost upwards of $400

Re: witricity legality?
 

Depending on how you actually design and implement it, they are legal if they make it through the electrical flowchart of legality.

Re: witricity legality?
 

Alan - This is aimed at the Wikipedia article, not at you.

There ain't no such thing as a special kind of EM "wave" that is any more or less evanescent than any other in a vacuum.

In Earth's atmosphere, at some frequencies, EM fields are somewhat strongly affected by dust, moisture, ions, (buildings,) etc. At other frequencies, not so much.

But, as for any EM field being more more or less "evanescent" than any other field, and/or getting any other special exemption from Maxwell's equations - I don't think so. Over macroscopic distances all EM fields obey those equations.

Blake

Re: witricity legality?
 

ok lets do something easier...


screw witricity lets get the darn robot to go warp 9 how many lines could we cross in hybrid then
and would a warp core be legal on a robot?
seriously i will have to meet someone in atlanta so that they can explain there arguement. i think i just don't understand what is being said. (which you have figured out)

apperantly im wrong so im just gonna shutup and not even try to do anything like this....

by the way its cody

Re: witricity legality?
 

To play the devils advocate I believe that the key word here is macroscopic. I've been doing my best to research what the M.I.T. team has done and it seems that the entire goal of the project is the tap into field before it propagates. Although there is little regarding the topic out in the public domain I believe the concept behind witricity is this. If you look at a graphical representation of an EM wave you will notice that it consists of electrical and magnetic fields at right angles to each other as predicted by Maxwell's equations. If during the first quarter was a device were to tap into the magnetic field converting its energy back into an electrical current (which would have to occur during the first quarter wave as noted by researchers) then the field would not propagate nearly as far simply because much of its energy is being picked up by the second coil.

This may be complete nonsense; I'm only a teenager and will probably be flame, but so be it. In a few weeks I'll be traveling to M.I.T.'s prefrosh weekend so I'll attempt to arrange a meeting with the professor who developed the concept and gain a better understanding in that way.

Re: witricity legality?
 

Exaclty right. That's the way the judges interpreted it in (specific example) Buckeye. I'm sure that everybody's ok with what we did since the interesting concept to get the messy varying system voltage to something useful for consistent display intensity was part of what intrigued judges for the GM Industrial Design award about our display.

-q

Re: witricity legality?
 

Look it up. It's more of a standing wave than a "traveling" one. Here's a reasonably comprehensive explanation:

http://www.andrew.cmu.edu/user/dcpri...nt%20waves.htm

The resonant coil in the 10 MHz system confines the waves in the same way as does total internal reflection in an optical system.

Re: witricity legality?
 

I'll dig into this some more, and I may wind up eating more crow than I care to (I thought the term evanescent was being used in a layman's sense).

Most of the descriptions I read for this power transfer method smell very strongly of BS. I suspect that this is because well-meaning authors are mangling the real physics involved.

For example, in one I see an assertion that a coil fills the space around it with a non-radiative magnetic field. Something has to be wrong with that statement. It is almost certainly is an ill-formed sentence that is either wrong or lacking essential context.

This paper, http://www.sciencemag.org/cgi/rapidp...ref&siteid=sci , written by Marin Soljačić, does not appear to suffer from those oversimplified statements (nor does it refer to evanescent waves, non-radiating magnetic fields, etc.).

Blake

Re: witricity legality?
 

Having read the two above articles I believe I owe quite the apology to shadow. I too found the language of many witricity articles to resonate of pseudoscience and hence was quite dismissive. Perhaps what is most interesting about the above article is that they observed a radiated power of only 5W (concluding remarks above paper) which would make such a device (if properly resonating) fairly safe.

Re: witricity legality?
 

Cody,
Don't stop thinking or learning and don't listen to any of us, find out for yourself.
Thanks to the other contributors of this thread for the article links. The more important of course, is the one by Soljačić. Now that I see the experimental apparatus it is easy to see the mechanics of what is taking place. I disagree with his method, however. He measures his input power at 400 watts (wall) and determines output power by the brillance of the light bulb. All things being equal I call that 15% max. I would much rather see electrical power measurements in terms of current and voltage at both input and output.
The way I see this experiment, a small loop is used to excite a self resonant and unloaded coil at 9.9 MHz. (As pointed out in the article, current at the ends of the coils is zero, but any ham radio antenna enthusiast could have pointed that out, but it has nothing to do with the experiment.) That coil ought to be able to produce a rather intense magneic field. Another self resonant coil in line with the magnetic field ought to also reinforce the first magnetic field and this reinforced field is then able to induce current flow in an adjacent conductor. However, as any of us can realize, any body in or near any of the coils will affect the self resonance of the coils, thereby affecting the coupling efficiency and the energy transfer. Likewise, ferrous material in the magnetic pathway will also alter significantly the energy transfer. What makes this experiment unique is that it is undertaken at a frequency which is conducive to self resonance in easily formed coils at room distances of 1 to two meters. I believe the distance used in the experiment allows for two variables to be satisfied. One is that the two coils have minimal interaction at self resonance while simultaneously achieving a reasonable power transfer due to proximity of the two coils. I believe Maxwell's equations should give a reasonable prediciton of the power transfer in this experiment. As to the device being non-radiating, I don't see how it would be possible to not have significant radiation and therefore produce both interference and possible exposure problems. If we make the rash assumption that the oscillator is at least 50% efficient, then it is easy to assume the remaing lost power is radiated. If all these assumptions are correct, I make that radiated power at about 50 watts.

Re: witricity legality?
 

I'd like to apologize for my rather... short post about feasibility. As an RF Engineer Apprentice, I'd like to let you know that this sort of stuff is actually a lot of fun.

This specific experiment might not be feasible, but there is a lot of other cool stuff to do in this vein. RFID is a very very similar principle. Take a look!

Re: witricity legality?
 

Hmm, lots of info in this thread and a neat idea.

Keep in mind that the power curves of most FRC motors extend upwards to at least ~150watts. If power out = (efficiency) * power in, where efficiency is less than 100%, then it takes more than 150watts of power to make the motors run. Add in the efficiency of the witricity system and you're faced with coming up with a way to power 5-6 60 watt lightbulbs at once instead of just one.

I'm not going to tell you it's impossible, because actually I think it is. Is it practical in FRC with your drive train, compressor, and other possible motors running? That's what experimentation is for, so I don't know. It's hard to say if the battery output could keep up for a full 2:15. Even with the '07 or '08 rules, the GDC may have accomodations in the rules to make it legal in '09 (but don't get your hopes up).

Re: witricity legality?
 

You are correct, WiTricity is physically possible. however, probably incredibly destructive. Look at the nature of electricity and plasma. Plasmas (this includes fire and electricity) Plasmas in their nature are designed to destroy everything they get into contact with. The amount of energy require to transfer electrical potential is incredibly powerful, and can destroy not only human cells, but electrical circuits. everything in the path of these waves will be instantly destroyed. You can essentially kiss all of your electronic components good bye. And no, these cheap little electronic devices aren't made to withstand such a destructive force. Hope this clears up any notion to use such an experimental procedure.

Re: witricity legality?
 

I need to correct a little here:

1> Witricity is RF, which is the transfer of electricity (electrons) through a medium in a specific frequency band. It is not conversion of that electricity (electrons) into plasma (charged ions).
2> Plasma is not inherently destructive. There are many factors that go into what plasma does. Energy levels, frequency, material being affected, etc. I use plasma all the time in surface treating applications where I work.
3> RF (like Witricity) is also not inherently distructive. You have RF going through you everyday. Cell phones, WiFi, Radio (including the RC radio), RADAR all use RF. There's also natural RF generators (our sun is a good example).

Now I'm not saying that Witricity would not be destructive. Properly implemented and controlled it could be very useful and nondestructive. The key is an understanding of the effects that the fields will have on the local enviroment and nearby objects. And "those cheap little electronic devices" ... you'd be surprised how much RF they can handle (at specific frequencies).

Re: witricity legality?
 

Daniel,
One small correction, we are talking about electromagnetic energy in a certain frequency band.

Re: witricity legality?
 

You are correct.

I don't generally differentiate between electromagnetic energy and electrcity because any movement of electricity within a medium creates a magnetic field (so for me it's an assumed thing).

Again, you are correct.

Re: witricity legality?
 

I havnt looked into this one bit, but does any one know where the power loss comes from?

After a quick wiki search...

It seems as if this technology is similar to transformers. either steup up or step down, so if the coils were identical, then theres no ups or downs but a direct transfer of energy via electromagnetic field. So...this makes me think that the 40% efficiency @ 7feet away conducted by MIT could have been more efficient if the two coils were close to one another....similar to a transformer. Is the high frequency necessary? I can feel the 60Hz "buzz" from my desk lamp if I put a metal object close to the base of the lamp. It doesnt seem to be affecting anything.....I will try a simple coil test right after I publish my post, Ill repost with the results form my Mastercraft Multimeter.


BRB!

Re: witricity legality?
 

Okay, so I see why they dropped the Witricity. As far as I can see, I didnt get any voltage, but I did get some current, 130mA was the average. As soon as I moved about 2cm awway I was down to only 20ma....Not a very good power supply... thats the end of that..

Re: witricity legality?
 

June,
There are a variety of places where the power is lost. Turning RF into an effective field is tough enough but then you add to that the power that is lost by not coupling all of that field to the receiving coil. The inefficient coupling between the coils due to a lack of focus of the field and the varying load on the receiving coil all add up as well. Certainly placing the coils closer together would help. The RF is used to make the coils small and light enough to be a practical demo. Lower frequencies would work but the coils become significantly larger for the same efficiency.