Introduction: High-Range Wireless Power

Build a Wireless Power Transmission system that can power a light bulb or charge a phone from up to 2 feet away! This uses a resonant coil system to send magnetic fields from a transmitting coil to a receiving coil.

We used this as a demo during a sermon on Maxwell's Four Great Equations at our church! Check it out at:

https://youtu.be/-rgUhBGO_pY

Step 1: Things You'll Need

  • 18 gauge magnetic wire. Note that you can't use regular wire, you have to use magnetic wire (which has a very thin enamel insulation on it). One example is available on Amazon here:

    http://www.amazon.com/gp/product/B00BJMVK02

  • A 6W (or less) AC/DC 12V Dimmable LED light bulb. One example is here:

    http://www.amazon.com/Original-Warranty-Dimmable-R...

  • 1uF capacitors (not electrolytics, must be non-polarized). You have some choices here. If you build a low power version, you can get 250V 1uF capacitors from Radio Shack or Frys. If you want to build a high power version, you will need to get special 560V capacitors from Digikey.
  • 0.47uF Capacitor (not electrolytics, must be non-polarized)
  • Some kind of power amplifier. We used a 450W HI-FI power amp. You could use anything from that down to a PC speaker. The power more you use, the more range you'll get out of it.
  • Solder & Solder iron. Wire cutters
  • A piece of plywood and some small nails (used for winding coils)
  • Black Electrical tape
  • Measuring tape & ruler
  • Insulated wire
  • Hammer
  • Audio source with variable frequency and amplitude that generate an 8khz sine tone. It's easy to use a PC, Laptop or phone with freely available tone generation software and connect to the headphone jack. I used a Mac with this software:

    https://code.google.com/p/audiotools/downloads/det...
    Or you could use this software for a PC:
    You could also use a function generator if you have one (expensive piece of test equipment)

NTE Capacitor Part List (for the low power version). You can get these parts at Frys.

3 x 1uF 50V capacitor, NTE CML105M50 (to attach to the light bulb and the small coil)

1 x 0.47uF 50V capacitor, NTE CML474M50 (to attach to the light bulb & small coil in parallel with 1uF caps)

1 x 1uF 250V capacitor, NTE MLR105K250 (to attach to the big coil)

Digikey Order (for the high power version)

Attached is a Digikey Part List that you can use for the higher powered version. These capacitors go up to 560V, which allows you to use a ~500W amplifier, and get up almost two feet of range. The attached version only includes the bare minimum parts. As long as you're making a Digikey order, order some extras in case you make a mistake or blow one up (that's particularly true of the TVS protection diodes, which I smoked several times).

Step 2: Make the Coil Winder

In order to wind the coils, you need a frame to wind them around.

On a piece of plywood, you need to use a compass to draw out a precise 20 cm circle and a precise 40 cm circle.

Hammer nails evenly spaced around the circle. For the 20 cm circle, I used around 12 nails and for the 40 cm circle, I used around 16. At one spot in the circle, you'll want to make an entry point that will hold the wire while your beginning the first winding. At that spot, hammer another nail close to one nail, then another a couple inches away.

Step 3: Wind the 40cm Coil With 20 Turns and the 20cm Coil With 15 Turns

You'll first make a few loops with the wire on the outside nail to anchor the wire, then start the loop around the coil. Make sure you leave a lot of extra wire at the beginning and end of the coil. Leave 3 feet to be safe (you'll need this to hook up to electronics).

It's surprisingly hard to keep track of the number of windings. Use a friend to help you.

Make the windings REALLY tight. If you end up with loose windings, the coil will be a mess.

It's really hard to keep the windings in order (especially if you use 18 guage wire, 24 wire gauge is easier to handle but has a lot more loss). So you'll need a few people to help you hold it down as you wind it.

After you finish the turns, you'll want to twist the inlet wire & outlet wire to hold the coil steady. Then tape the coil with electrical tape in several spots.

When you're done with this step you should have two coils, one coil with a 20cm diameter and 15 turns and one coil with a 40cm diameter and 20 turns. The coils should be wound tightly, and secured with tape. You should be able to pick them up and handle them easily without them falling apart or unwinding.

Step 4: Add the Lightbulb & Electronics to the 20cm Coil

Next, you're going to attach the light bulb to the small coil. You need to solder three 1uf (1 microfarad, or said different way 1,000nF) and one 0.47uF (said a different way, 470nF) capacitors to the light bulb posts. That's a total of 3.47uF (capacitors add up in parallel). If you're doing the high power version, you should also solder a 20V bidirectional TVS diode between the light bulb posts as protection against overvoltage.

After you solder the capacitors, you need to twist the ends of the coil wire all the way across the center of the coil. The wire is stiff enough to support the light bulb. After you twist the wire all the way across the diameter, you're going to just cut the ends of the wire and leave them open.

Then you'll place the light bulb in the center of the twisted wire. You'll pull apart the twists, so that each wire touches one terminal of the lightbulb. Then you scrape off the wire enamel with a knife and then solder the cleaned wire to the light bulb posts. Make sure you use rosin core solder. You might want to add extra rosin, which will help clean the bits of enamel.

Step 5: Attach the 40cm Coil to the Electronics.

Next you'll need to connect the 40cm coil to a 1uF capacitor. Shown here is the high power version, where I've connected 10x 0.1uF capacitors in parallel to make one 1uF capacitor (capacitors in parallel add up). The capacitor goes between the coil and the power amplifier positive output. The other side of the coil goes directly to the power amplifier GND.

Step 6: Connect a Sine Wave Source to a Power Amp and Try It Out!

The last step is create a sine wave. You can download a function generator app on your phone or laptop or desktop. You'll want to experiment to find the best frequency of operation.

You connect your sine source to the audio power amp, and then connect the audio poweramp to the 40cm coil and 1uF capacitor, and then everything should work!

If you use a high power audio amp (100W or greater), BE CAREFUL! It can generate very high voltages in excess of +/-500V. I tested with a high voltage scope to ensure I wasn't going to blow up the capacitors. It's also easy to get shocked if you touch an exposed lead.

Also, if you use a high power audio amp, you can't get the 20cm coil too close to the 40cm coil. If they are too close, the TVS diode or LED light bulb will burn up due to excessive power.

Step 7: Create the Wireless Phone Charger

You can easily modify the circuit to charge a phone. I built a second 20cm coil and then added all of the circuitry. The same 3.47uF capacitor and TVS diode is used. That's followed by a bridge rectifier (Comchip P/N: CDBHM240L-HF), followed by a 5V linear regulator (Fairchild LM7805CT), followed by a 47uF tantalum capacitor. With a high power amplifier, the circuit can easily charge your phone from a distance of a foot and a half!

Step 8: The Results

The measured voltage versus distance curves are attached.

Design Measurements, and comparison to simulation & theory

40cm Coil

  • Main coil = 0.2m radius, 0.4m diameter. 18 gauge wire 20 windings
  • Theoretical resistance = 20.95e-3*(2*pi*0.2*20+0.29*2) = 0.5387 ohms
  • Actual resistance = 0.609 ohms. Variance from theory: +13%
  • Simulated Inductance = 0.435mH Actual Inductance: 0.49mH. Variance from simulation: +12%

20cm Coil

  • Receive coil = 0.1m radius 0.2m diameter 18 guage wire 15 windings
  • Theoretical resistance = (2*pi*0.1*15+0.29*2)*0.0209 = 0.2091
  • Actual Resistance = 0.2490. Variance from simulation: +19%

  • Simulated Inductance = 0.105mH. Actual Inductance = 0.1186mH. Variance from simulation: +12%

Step 9: Simulation, Optimization & Discussion

How we simulated the design

We simulated and optimized the design in a 2-D mangetostatic simulator, and with SPICE.

We used the free 2-D mangetostatic simulator called Infolytica. You can download for free here:

http://www.infolytica.com/en/products/trial/magnet...

We used the free SPICE simulator called LTSPICE. You can download it here:

http://www.linear.com/designtools/software/

Design files for both simulators are attached.

Discussion

This design uses resonant magnetostatic power transmission. The audio power amp produces an electric current that flows through the transmitting coil and generates an oscillating magnetic field. That magnetic field is received by the receiving coil, and turned into an electric field. In theory, we could do that without any components (i.e. no capacitors). However, the efficiency is extremely low. We initially wanted to make a simpler design that used only the coils and no other components, however, the power efficiency was so poor it couldn't turn on the LED. So we moved to a resonant system. The capacitor that we added resonates at one particularly frequency (in this case about 8kHz). At all other frequencies the circuit is extremely inefficient, but at the exact resonant frequency it becomes very efficient. The inductor and capacitor act like a transformer of sorts. On the transmitting coil, we put in a small voltage and a high current (10Vrms and 15Arms). That ends up producing >400Vrms across the capacitor, but at a much lower current. That's the magic of resonant circuits! Resonant circuits are quantified by the "Q factor". In the 40cm diameter transmitter coil, the measured Q factor is about 40, meaning that's pretty efficient.

We simulated & optimized the coil with Infolytica's 2-D magneto static simulator. That simulator gave us a simulated inductance for each coil, and the mutual inductance between the two coils.

Magnetic Simulated Values:

  • Transmitting Coil = 4.35mH
  • Receiving Coil = 0.105mH
  • Mutual Inductance = 9.87uH. K=6.87e-3 (with the coils separated by 0.2m)

We then took those numbers and fed them into SPICE to simulate the electrical characteristics.

You can download the simulation files attached, and try to make your optimizations and measurements!

Also attached are field plots, that show the magnetic field produced by the coils. It's interesting that even though we're putting in a lot of power, the absolute fields are pretty small (in the milliTesla range). That's because the fields are spread out over a large surface area. So if you add up (integrate) the magnetic field over the large surface area, it would be substantial. But at any given point in the volume it's tiny. As a side note, this is why transformers use iron cores, so that the magnetic field gets concentrated in one area.

Comments

author
GabrielC115 (author)2016-09-25

Hello, AWESOME INSTRUCTABLE, can i ask how you get the formulas? thanks:)

author
Laral (author)2016-04-12

What a fantastic Instructable. I viewed the video. What a wild church! Teaching Maxwell's equations and demoing them in action! Why didn't my church teach that? :)

author
billy_kolb (author)Laral2016-04-12

Some churches are busy proving that God made the universe only a few 1000 years ago.

author
Laral (author)billy_kolb2016-04-12

Exactly. Despite all the scientific evidence to the contrary. That is precisely what makes this particular church quite progressive by allowing one of its members to actually teach science, albeit with a religious slant.

author
jimmie.c.boswell (author)Laral2016-04-13

their teaching technology, not science here. technology is the art, of putting scientific principals to use.

author
Laral (author)jimmie.c.boswell2016-04-13

Well, when I studied Maxwell's equations, it was part of a physics major curriculum. Doesn't get any more 'science' than that… As for technology, this is a demonstration of Tesla's idea of wireless power transmission, which was soundly based on Maxwell's equations, at a time when none of the players in the nascent wireless industry even knew about them, let alone understood them.

author
jimmie.c.boswell (author)Laral2016-04-14

studying what scientists have already done, does not make you a scientist. scientists, are the ones with the original never before done or thought of ideas. they, are the forerunners of all technology and scientific education.

author

stfu jimmie- you are stupid

author

well according to your stupid opinion, i take that as a compliment.

author
_soapy_ (author)jimmie.c.boswell2016-04-15

That's the worst job description of a scientist ever.

An inventor comes up with new things, & an engineer fixes existing things. But the boundaries blur. And both can be scientists.

You know what we can people who keep trying to find ways around relativity, Maxwell's equations, how things create "free" electricity, etc when they've not learned what things are and how they work properly? Cranks. Eccentrics. And that's at best.

Science is discovery. But if you don't learn what's already known, you'll never get far. You have to stand on the shoulders of giants to see further.

author
jimmie.c.boswell (author)_soapy_2016-04-19

sorry but technology, is the application of known scientific principals. and inventors, and engineers, are designers of technology. repair technologist, and technicians are the ones who fix and or assemble things for engineers. scientist are the discoverers, of things that were not known before.

very few scientists, are also engineers, designers, and engineering technicians like Tesla.

as far as relativity goes, that is a scientific family rivalry matter. and the only possible way, around relativity is the fraction left over from Einstein's equation. and technically speaking, it would not be circumventing the equation.

and as far as, free energy goes. it has always been so far, way to expensive or fraudulent. since we seem, to limited to less than unity. thus is the basis for the search, for greater efficiency. such as with Edison, is we know it works but how can we improve it?

author
jimmie.c.boswell (author)_soapy_2016-04-19

sorry but technology, is the application of known scientific principals. and inventors, and engineers, are designers of technology. repair technologist, and technicians are the ones who fix and or assemble things for engineers. scientist are the discoverers, of things that were not known before.

very few scientists, are also engineers, designers, and engineering technicians like Tesla.

as far as relativity goes, that is a scientific family rivalry matter. and the only possible way, around relativity is the fraction left over from Einstein's equation. and technically speaking, it would not be circumventing the equation.

and as far as, free energy goes. it has always been so far, way to expensive or fraudulent. since we seem, to limited to less than unity. thus is the basis for the search, for greater efficiency. such as with Edison, is we know it works but how can we improve it?

author
Laral (author)jimmie.c.boswell2016-04-14

Yup, and clearly YOU are no scientist…

author
jimmie.c.boswell (author)Laral2016-04-14

you really should have more proof than mental magic, to support your accusation.

but you still could call, DOE Dept. of Public Relations, and inquire if i ever worked for them at The Solar Energy Research Institute, and Rocky Flats Thermonuclear Weapons Facility. even though i, have been retired since 2000.

author
jimmie.c.boswell (author)Laral2016-04-14

studying what scientists have already done, does not make you a scientist. scientists, are the ones with the original never before done or thought of ideas. they, are the forerunners of all technology and scientific education.

author

actually that would be, 5774 years just again at this point. those who run even in large circles, always come back to the beginning.

author
jimmie.c.boswell (author)Laral2016-04-13

there is, the church of science. i, live right next to one across the alley.

author
Laral (author)2016-04-12

I'm curious. How did you arrive at 8kHz?

author
jimmie.c.boswell (author)Laral2016-04-14

Fr = 1/the square root of LC.

author
Laral (author)jimmie.c.boswell2016-04-15

This does not answer the question, which is WHY the author CHOSE 8kHz.

author
jimmie.c.boswell (author)Laral2016-04-19

because of the trade off of frequency and power curve, of the audio amp used. higher frequency, transmits more efficiently than lower frequency.

and to be able to use, a higher frequency would require a much more expensive audio amp. obviously this is the audio power amp, they had available.

author
Lord_Forbes (author)2016-04-18

You would seem to have the best church ever... where I'm from, they just call that "class".

author
Lord_Forbes (author)2016-04-18

You would seem to have the best church ever... where I'm from, they just call that "class".

author
crackHacker (author)2016-04-16

So whats the current output? At 5V for a phone you shouldnt go over 2.1A

author
wwijanarko (author)crackHacker2016-04-17

most 7805 regulators are limited to 1 Amp maximum, more than that and it will produce a lots of heat. You will need to install a heatsink for the regulator to stop it from getting damaged. More complicated circuit is needed to charge a 2.1 Amps device.

author
LoknathS (author)2016-04-17

awesom one ,,,any idea about its efficeincy

author
jliberman13 (author)2016-04-12

Instead of using some sort of computer to generate an audio sine wave, maybe you could use an LC circuit. They're fairly simple and you could have a self contained system. Thoughts on that?

author

well this is an LC circuit, which you could make an oscillator out of using power mosfets. and the resonant frequency, would be around 8khz.

author

I mean using an LC as the signal source for the audio amp. You wouldn't need a phone or computer then, but I guess that makes it harder to tune the coil too.

author

why would you need, even the audio amp? if you, designed this like a MOPA. since the coil and capacitor, form a simple tuned oscillator circuit as is. which is already tuned, for somewhere around 8khz resonant frequency. using a power mosfet, to make a simple master oscillator power amplifier should be fairly easy to do.

author

I suppose that would work too. The audio amp let's you put in any waveform though and from a low current/voltage source. You could use say an Arduino or RPi for smart control or something. Your idea is definitely simpler though if you just want something you don't need/want to tune in the future. I don't know enough electrical engineering though to say if using the transmitter coil as the inductor would totally work. Maybe the load from receiver would mess with the resonance or is that even something that can happen?

author
Laral (author)jimmie.c.boswell2016-04-15

This is the first intelligent reply you have made. I agree completely. If you tune the primary circuit and drive it with a power MOSFET, you don't need any intermediate amplification. You would get sufficient power levels directly. Tuning the secondary to the primary would be child's play.

author
Mei-MeiC (author)jliberman132016-04-12

Sure, that would work! You could also use an LM555 oscillator. But it would need to be adjustable since you need to tune it to find the ideal frequency.

author
Lardo (author)2016-04-12

Sermon on Maxwell's Four Great Equations at your church? Just what kind of church is that?

author
Mei-MeiC (author)Lardo2016-04-12

It's a pretty cool church! Check it out http://www.the-river.org

author
_soapy_ (author)Mei-MeiC2016-04-15

With a church like that you should try and find your local Makerspace! That'd probably be a bit like your heaven.

author
Mei-MeiC (author)_soapy_2016-04-15

Don't worry, we've already started a Makerspace! :)

author
Laral (author)Mei-MeiC2016-04-15

Now I get it. The church is first of all, non-denominational. Second, it is in San Jose, the heart of Silicon Valley. Third, the pastor is Asian, probably Chinese, and has 'many similarities to Master-Jedi Yoda'. That is quite an impressive combination. Kudos!

author
Dr.Bill (author)Lardo2016-04-12

The First Church Of Magic Smoke.

author
Malkaris (author)2016-04-11

Very nicely done. The I'm guessing your transmission distances aligned pretty well with 1/R^2 loss, which is exactly expected.

I often wonder what Tesla was thinking about when he wanted to transfer power like this to the world.

I can only guess that Tesla was trying to use the whole planet as the primary resonator and the only losses would be when energy was absorbed by a tuned secondary.

author
Mei-MeiC (author)Malkaris2016-04-12

This project isn't exactly 1/r^2 loss,
that is for an electromagnetic plane traveling wave radiating into a
volumetric space from a monopole. This uses magnetostatic fields (which basically just means that there are only magnetic fields involved in the transmission, whereas traveling radio waves involve both magnetic and electric fields). The
transmission curves fall off exponentially with distance. The math is a bit complex, since the two coils are interacting with each other, and you have to include the mutual inductance and resonant circuits. But the transmission curves are a good match for an exponential curve. In fact, if you want the exact values, here's the emperical curve fit:

Voltage Out/Voltage In = 0.596e^(-0.147*distance)

author
Laral (author)Mei-MeiC2016-04-15

Actually, the inverse square law strictly applies to a point source at the near field. At the far field approximation the waves are planar and have already been attenuated according to the law. This coil is a short solenoid so most of the E-M field is contained within the coil initially and does not act like a point source at all. The external field along the axis would be more planar or conical than spherical. A directional antenna. So the attenuation would not be nearly as much as with a point source. Where are you getting the idea that this is producing magnetostatic fields? That would only be the case for direct current. At near distances, the coupling between the coils would be mostly magnetic but at far distances it would be electromagnetic.

author
Carlos IvánC2 (author)Malkaris2016-04-12

That's it:

https://en.wikipedia.org/wiki/Wardenclyffe_Tower

""He theorized from these experiments that if he injected electric current into the Earth at just the right frequency he could harness what he believed was the planet's own electrical charge and cause it to resonate at a frequency that would be amplified in "standing waves" that could be tapped anywhere on the planet to run devices or, through modulation, carry a signal.""

Nothing to do with Hertzian wave transmission, as this (nice!) instructable does.

Thank you all!

author

actually i believe that he, intended to inject it into the ionosphere. to tap into the trillions of watts, contained in it. and realized the consequences, of doing this. and quickly dropped his further research, for this.

author

I agree with you.

author
Climberirw (author)Climberirw 2016-04-14

And also he wanted to get the electricity to flow through the ionosphere to be received by people around the world.

author

quite right, and this is when he lost his funding from jp morgan. cause he stated, you can't put a meter on it. even though i suspect, deep down he knew it was possible to meter it at the destination.

author
jmorpuss (author)2016-04-14

Has anybody here played around with these free energy devises, We really do swim in a sea of electrons and free energy is all around us,

https://www.youtube.com/watch?v=xR6Qait2JGY

https://hal.archives-ouvertes.fr/hal-01237948/document

author
_soapy_ (author)jmorpuss2016-04-15

Except it is rarely free. It takes energy to move them away from where they are resting. Even lightning is barely free energy, & only for a split second.

Those Russian videos where they connect to the water main? They're just rusting the water pipes faster as they drain the giant battery formed by the galvanised pipes.

And don't get me started on "burning water as fuel" - water is ash. It's already burnt.

author
jimmie.c.boswell (author)2016-04-14

obviously it means more to you, and absolutely nothing to me.

as you! really are way off the inductive topic here.

now spewing, total non-sense.

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