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prab00
12-24-2009, 01:32 PM
Hi! Can u please help me in guiding how to Convert
Radio waves(U.H.F) into D.C electrical energy of 800mAh 4.2V
please reply me with all the accessories required for
converting it and the procedures to do it....my mail address is <snip>
am under an innovative
project please help me dude......

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Papabravo
12-24-2009, 01:52 PM
The voltages and currents available at an antenna are far too small to convert into meaningful amounts of DC power. The figure that you gave, 800 mAh @ 4.2 Volts is actually a battery capacity. It means that a battery can supply 800 mA for 1 hour at 4.2V, that is 3.36 Watts for 1 hour.

Back to the antenna receiving a UHF signal, we are talking microvolts and nanoamperes. Its a fundamental proposition that you cannot convert a handfull of femtowatts on an antenna into 3.36 Watts from a battery without an external source of power.

Ain't no free lunch in this life or the next one. Sorry 'bout that, someone may have swindled you on this one.

You might also want to think about removing your email address from your post. The spambots and web crawlers will find it and unload a stinkload of spam on your inbox.

bertus
12-24-2009, 02:12 PM
Hello,

Read this article:
http://www.technologyreview.com/communications/22764/

Greetings,
Bertus

prab00
12-24-2009, 02:19 PM
The voltages and currents available at an antenna are far too small to convert into meaningful amounts of DC power. The figure that you gave, 800 mAh @ 4.2 Volts is actually a battery capacity. It means that a battery can supply 800 mA for 1 hour at 4.2V, that is 3.36 Watts for 1 hour.

Back to the antenna receiving a UHF signal, we are talking microvolts and nanoamperes. Its a fundamental proposition that you cannot convert a handfull of femtowatts on an antenna into 3.36 Watts from a battery without an external source of power.

Ain't no free lunch in this life or the next one. Sorry 'bout that, someone may have swindled you on this one.

You might also want to think about removing your email address from your post. The spambots and web crawlers will find it and unload a stinkload of spam on your inbox.
but i got this idea following.......
{First detect the UHF and convert to an electrical signal. Then use a diode to rectify it to all pos. (or all neg.). Then you can use the appropriate value capacitor to smooth from half wave rectified to a solid DC. You'll need to use some sort of regulator to get the 4.1V you want.}is it Possible dude? reply me

hgmjr
12-24-2009, 02:22 PM
I think you will find that the amount of power expended to recover the energy from the RF signals will always exceed the amount of RF energy you recover.

hgmjr

steveb
12-24-2009, 02:22 PM
Hello,

Read this article:
http://www.technologyreview.com/communications/22764/

Greetings,
Bertus

Very interesting article. Personally, I would be very surprised if they actally made a 50 mW energy harvester as a practical product.

If they do, it's going to open up a can of worms on regulation issues. People will be hoarding around wireless transmitters trying to steal energy, and the people who own the transmitters aren't going to like it.

I remember reading an article (I think it was Popular Mechanics) about a company claiming that flying cars would be practical soon. It was a front page article on a well-known magazine cover. It came out in the early 1990s and claimed these cars would be common in the 2000-2010 time frame. I laughed when I saw it.

Marketing people publish many pipedreams, but some of them do come true ... so we'll see.

EDIT: I couldn't resist going online to find the magazine cover (see attached). The idea itself is not crazy, but what made me laugh was that the article claimed that 1 decade was enough to get by all the technical and regulation issues that any layman would understand as extremely difficult issues.

Duane P Wetick
12-24-2009, 05:03 PM
We still haven't come up with a usable battery design to compete with Thomas Edisons 1903 lead acid design, and it is still being put into new cars today. In spite of Interstate Battery's all out advertising campaign, its no secret!

Regards, DPW [ Everyone's knowledge is in-complete...Albert Einstein]

prab00
12-24-2009, 05:10 PM
no dude but my question is different from what u answered?

Papabravo
12-24-2009, 05:41 PM
but i got this idea following.......
{First detect the UHF and convert to an electrical signal. Then use a diode to rectify it to all pos. (or all neg.). Then you can use the appropriate value capacitor to smooth from half wave rectified to a solid DC. You'll need to use some sort of regulator to get the 4.1V you want.}is it Possible dude? reply me
No UHF signal received on an antenna is going to be anywhere near 4.1 Volts, 4.1 microvolts maybe. So amplify it you say, but an amplifier takes power from an external source and the power you get out is always going to be less than the power that you put in.

In words of as few sylables as possible:

There is no way to extract meaningful amounts of power from a UHF signal on an antenna unless you are within a very short distance (centimeters) of the transmitter. You've been scammed, and I hope all they've taken is your pride. If they've relieved you of your hard earned shekels then you have my sympathy.

beenthere
12-24-2009, 05:45 PM
my question is different from what u answeredWell, the answer was not about energy harvesting, but did point out that not all ideas pan out.

Radio receivers typically get signal levels off the antenna in microvolts, with lower current levels. The power "available" is in the nanowatt level. RFID devices tend to be passive and use energy harvesting to make their replies, but the tranceiver is usually within a meter or two.

Expecting to get multiple volt signals at 800 ma currents is not realistic. Not at any portion of the RF spectrum, let alone UHF.

The physics building where I worked was inside the near field of a radio transmitter (89 MHz) for a couple of years. Only some optical experiments could be done, as the RF levels were very high - 1 - 2 volts. Currents were possible in the 10's of microamps. That would give a possible power of 20 microwatts. That's a long way from over 3 watts.

Papabravo
12-24-2009, 05:50 PM
@beenthere -- sail on
BTW when is the next TGYC regatta I'm itching to get my wetsuit on and take my Laser II out for a spin.

Duane P Wetick
12-24-2009, 05:53 PM
[QUOTE=prab00;198488]no dude but my question is different from what u answered?
Sorry to get side-tracked...battery technology needs improved on all sides.
Here's something to consider about energy transmission thru the air, the impedance of free space, Zo averages about about 376.73 ohms and is considered to be the ratio of the Electric field strength (E) to the Magnetic field strength (H). This says that the magnetic field strength is 377 times less than the electric field strength thru free space. So trying to electromagnetically couple 2 circuits thru free space is difficult, but not impossible. But is it practical?

Regards, DPW [ Everyone's knowledge is in-complete...Albert Einstein]

prab00
12-24-2009, 06:03 PM
No UHF signal received on an antenna is going to be anywhere near 4.1 Volts, 4.1 microvolts maybe. So amplify it you say, but an amplifier takes power from an external source and the power you get out is always going to be less than the power that you put in.

In words of as few sylables as possible:

There is no way to extract meaningful amounts of power from a UHF signal on an antenna unless you are within a very short distance (centimeters) of the transmitter. You've been scammed, and I hope all they've taken is your pride. If they've relieved you of your hard earned shekels then you have my sympathy.

is there any ways like using induction methods because radio waves are electrons right and by using transformers in the circuit can v power them up plz tell me if there is a way

prab00
12-24-2009, 06:12 PM
[QUOTE=prab00;198488]no dude but my question is different from what u answered?
Sorry to get side-tracked...battery technology needs improved on all sides.
Here's something to consider about energy transmission thru the air, the impedance of free space, Zo averages about about 376.73 ohms and is considered to be the ratio of the Electric field strength (E) to the Magnetic field strength(H). This says that the magnetic field strength is 377 times less than the electric field strength thru free space. So trying to electromagnetically couple 2 circuits thru free space is difficult, but not impossible.

Regards, DPW [ Everyone's knowledge is in-complete...Albert Einstein]

can u say me the other possible ways dude plzzz
:D

Papabravo
12-24-2009, 07:32 PM
is there any ways like using induction methods because radio waves are electrons right and by using transformers in the circuit can v power them up plz tell me if there is a way

There is no practical way to extract "free" DC power from the ambient RF energy that surrounds us all day everyday. I know that delusions are powerful and that it takes considerable effort disabuse ourselves of things we are obsessed with, but you need to channel your energies in another direction

Bill_Marsden
12-24-2009, 11:02 PM
You're hearing pretty much the same things I said in the other post before it disappeared. If there were as much radio energy as you seem to think there is I suspect we would all be dying of cancer.

Unless you live next to a powerful transmitter it isn't going to happen. I suspect the guy your stealing power from would not be happy, he went to a lot of trouble to make it, it was intended for other uses. Using it might even qualify as theft of service.

There is a form of electromagnetic radiation that is plentiful, that would be sunlight.

prab00
12-25-2009, 12:42 PM
There is no practical way to extract "free" DC power from the ambient RF energy that surrounds us all day everyday. I know that delusions are powerful and that it takes considerable effort disabuse ourselves of things we are obsessed with, but you need to channel your energies in another direction

dude..... i have head that radio waves have ionizing energy is it possible??? can we make use of that in my project suggest me........

AlexR
12-25-2009, 01:19 PM
You heard wrong! Radio waves are a form of non-ionising radiation. Ionising radiation occurs at Xray energies and above.

As everyone else has been trying to tell you, unless your reciever is very very close to the transmitter you cannot get any useful power from received radio waves.

prab00
12-25-2009, 04:57 PM
You heard wrong! Radio waves are a form of non-ionising radiation. Ionising radiation occurs at Xray energies and above.

As everyone else has been trying to tell you, unless your reciever is very very close to the transmitter you cannot get any useful power from received radio waves.

ok dude i understand your quote.......but be on the logic is it possible to convert them if it is very very close to the transmitter....now we have to find out this...and then we will decide whether is it possible at long distance or not using other technologies......

Bill_Marsden
12-25-2009, 05:46 PM
We are talking very basic well understood physics, unless you are close to the transmitter taint gonna happen.

Papabravo
12-25-2009, 06:43 PM
I recommend the following book for those who continue to persist in the free energy delusion

http://www.amazon.com/Extraordinary-Popular-Delusions-Madness-Crowds/dp/051788433X

maxpower097
12-28-2009, 02:31 PM
Just for curiosity would it be possible to use some sort of laser to transmit power over LOS distances? I'm not asking if I could do it, but could MIT do it? Or someone with millions of dollars behind them do it?

steveb
12-28-2009, 03:29 PM
Just for curiosity would it be possible to use some sort of laser to transmit power over LOS distances? I'm not asking if I could do it, but could MIT do it? Or someone with millions of dollars behind them do it?

Yes, that is something you could do, and it doesn't take millions of dollars. The problem would be eye-safety. Any laser with power over 1 mW is a serious hazzard and can blind people. There are eye-safe wavelengths that could be used, but then the cost of the laser and the optical detector goes up, and these wavelengths may be attenuated more by the atmosphere.

Papabravo
12-28-2009, 05:40 PM
The problem is not the generation of large amounts of optical power. The problem is to find a non-disipative method of converting the optical power back into something useable. A clean lens is invisible to a laser, but a dirty lens will heat up rapidly if not smoke profusely.

steveb
12-28-2009, 06:44 PM
A clean lens is invisible to a laser, but a dirty lens will heat up rapidly if not smoke profusely.

The solution here is to create a wide colimated beam for transmission. This is better for eye-safety and relieves the type of power density problems you are mentioning here. A 10-100 cm diameter beam would need to exceed 100 kW before light intensity begins burning dust and debris on a lens. Still, a clean lens is needed for good transmission. This implies a vertical orientation and/or a shroud, along with routine maintainance.

Note that a 10-100 cm beam cannot fully interact with the human eye, hence it is safer than a 1-10 mm beam. But, still the beam should not be located or directed where unsuspecting people might be hit.

Basically, the idea can work for power levels that are not too high, but it only makes sense for very specialized applications, and even then only when people will not be near the transmission path (or an accidental reflection path).

I view this method of providing system power to be a case where practical implementation constraints are even more important than the technical and cost limitations of the technology itself. Issues like weather (rain, snow, fog), safety (injuring people or animals), maintainance (cleaning lenses, reflectors and detector surfaces), really limit the cases where this approach would be preferred over more typical approaches.

Pavlo138
12-29-2009, 02:57 AM
is there any ways like using induction methods because radio waves are electrons right and by using transformers in the circuit can v power them up plz tell me if there is a way

I think I might understand were you are going with this project, and it's called wireless power transmission. However, any usable forms of power transmission have occured using magnetic coupling and not through electrical fields,(since magnetic and electrical fields are 90 out of phase with each other, one does not necessarily effect the other.) But according to Lenz's law when a conductor passes through the lines of flux of a magnetic field; a current is induced. So I'm not sure of the internal dynamic of such wireless power transmission systems, but I'm sure Lenz's law is a good start as any. Also, all forms of natural/ analog energy are recipricol in nature, not descrete as DC levels are. And yes you would end up expending more enrgy powering your amplifier circuits then what you would be generating,(law of the conservation of energy; cannot get out more then what I put in!)

Heres a good example: http://electronics.howstuffworks.com/wireless-power1.htm

and: http://www.tfcbooks.com/articles/tws8c.htm

and this one is really cool!
http://www.osti.gov/bridge/purl.cover.jsp;jsessionid=04583AD26ED43813357FA7EA 54B168F5?purl=/934452-6FyoCS/

Pavlo138
12-29-2009, 03:06 AM
and yes, radio waves are made of electrons that behave in a wave-like pattern, like light. Light is not a wave yet photons that behave in wave-like pattern.

Bill_Marsden
12-29-2009, 01:10 PM
and yes, radio waves are made of electrons that behave in a wave-like pattern, like light. Light is not a wave yet photons that behave in wave-like pattern.

Radio and light are both photons, the frequency of which is different, nothing else. Radio is not composed of electrons.

Papabravo
12-29-2009, 03:02 PM
There are "no particles in radio", just like "there is no crying in baseball".

steveb
12-29-2009, 03:19 PM
There are "no particles in radio", just like "there is no crying in baseball".

There are particles in baseball. Does this mean that there is crying in radio? ;)

Pavlo138
12-29-2009, 09:41 PM
Radio and light are both photons, the frequency of which is different, nothing else. Radio is not composed of electrons.

That makes sense, since a lot of optical laws also apply to RF wave propagation. Should have known better, since light is part of the electromagnetic spectrum anyway. Thanks Bill.

steveb
12-29-2009, 10:20 PM
... Should have known better, since light is part of the electromagnetic spectrum anyway...

You would have been correct if you said that radio waves can be created by the accelleration of electrons. This is basically how a transmitting radio antenna works. Electrons are accellerated in the conductors of the antenna, which gives rise to EM radiation.

Even light is created by electrons changing energy levels in atoms.

Anyway, electrons are worth mentioning with regards to both light and radio, but Bill is correct to point out that photons are the elementary "stuff" of electromagnetic radiation, at any frequency.

Papabravo
12-30-2009, 01:01 AM
There are particles in baseball. Does this mean that there is crying in radio? ;)
All the time when you can't break a pileup.
When Sporadic-E becomes just that
When a 10:1 SWR smokes your finals
You bet there is crying in radio!

RF is created by moving electrons in a conductor, but once the wave leaves the antenna there are no electrons and no photons either, until the wave arrives at the receiving antenna and makes the electrons in the receiving antenna start moving back and forth.

Pavlo138
12-31-2009, 12:57 AM
All the time when you can't break a pileup.
When Sporadic-E becomes just that
When a 10:1 SWR smokes your finals
You bet there is crying in radio!

RF is created by moving electrons in a conductor, but once the wave leaves the antenna there are no electrons and no photons either, until the wave arrives at the receiving antenna and makes the electrons in the receiving antenna start moving back and forth.

This is just the discussion I had today with a fellow at work, exactly how and why radio wave propagation and antennas work the way they do. And in his conclusion was that nobody really knows exactly how or why it works, but there are few models out there to help conceptualize the dynamics of it all. I was trying to better understand how RF waves are converted into electrical energy to produce an intelligence signal. My idea was that the magnetic component in the wave, the moving lines of flux, induced a current into the antenna as it passed through. But his quick and dirty answer was that the antenna could be thought of as a transducer,as you said, converting one form of energy to another. It's really interesting stuff.

Pavlo138
12-31-2009, 12:59 AM
You would have been correct if you said that radio waves can be created by the accelleration of electrons. This is basically how a transmitting radio antenna works. Electrons are accellerated in the conductors of the antenna, which gives rise to EM radiation.

Even light is created by electrons changing energy levels in atoms.

Anyway, electrons are worth mentioning with regards to both light and radio, but Bill is correct to point out that photons are the elementary "stuff" of electromagnetic radiation, at any frequency.

True, such as the luster or glint from the sun hitting a pice of metal... electrons moving between energy levels in the atom, giving off photons as they go.

Papabravo
12-31-2009, 04:57 PM
... And in his conclusion was that nobody really knows exactly how or why it works, ...
This bit of misinformation is erroneous, wrong, and most unfortuneate. I think there are quite a number of people who will agree with me.

hgmjr
12-31-2009, 07:44 PM
I too hold that harvesting the RF energy that is present all around us for use in doing useful work is impractical.

The most effective use of the RF energy around us is to turn on our radios and tune them to the stations that broadcast the content we most enjoy.

hgmjr

Pavlo138
01-01-2010, 04:50 PM
This bit of misinformation is erroneous, wrong, and most unfortuneate. I think there are quite a number of people who will agree with me.

“I think it is safe to say that no one understands quantum mechanics.”
Physicist Richard P. Feynman

I believe this was along the same lines of the point that my coworker was trying to get at. We have models to help us understand physical phenomena, such as RF, but no one really, truly understands, exactly why it works the way it does.

beenthere
01-01-2010, 08:00 PM
“I think it is safe to say that no one understands quantum mechanics.”
Physicist Richard P. Feynman

I believe this was along the same lines of the point that my coworker was trying to get at. We have models to help us understand physical phenomena, such as RF, but no one really, truly understands, exactly why it works the way it does. The framework for radio (and all of electromagnetism) was developed by a British physicist in the 1860's - http://en.wikipedia.org/wiki/James_Clerk_Maxwell

Some people might disagree with you about the level of understanding we have about RF.

Papabravo
01-01-2010, 09:53 PM
I think it is safe to say that no one understands quantum mechanics.
Physicist Richard P. Feynman

I believe this was along the same lines of the point that my coworker was trying to get at. We have models to help us understand physical phenomena, such as RF, but no one really, truly understands, exactly why it works the way it does.

If you think he was serious, then you know nothing of the man or his contributions.

Pavlo138
01-02-2010, 04:58 PM
If you think he was serious, then you know nothing of the man or his contributions.

I didn't take him literally. I understood the quote to mean that there is more to understand then what is already understood. That is also how I interpreted my friend in our discussion of antennas. If he was wrong then so be it.

Bill_Marsden
01-07-2010, 02:18 PM
Over unity comes in many forms.

A popular theme in SciFi is to have solar farms in orbit (where the sun always shines) and beam the energy down to earth as microwaves. The power density can be quite low and still be effective, but the antenna farm will cover square miles.

radiohead
01-16-2010, 10:46 AM
I think Nicola Tesla beat you to the dream of wireless electricity.
Take a look at these:
http://www.google.com/search?q=Tesla+wireless+electricity&hl=en&tbs=tl:1&tbo=u&ei=xqVRS8KaMs-l8QbSsdWlBA&sa=X&oi=timeline_result&ct=title&resnum=12&ved=0CDEQ5wIwCw

...and now a renewed interest...
http://articles.latimes.com/2009/jul/28/business/fi-wireless-electricity28

If the power companies keep raising their rates, people will find alternative ways to provide power (including thermal, solar, wind and hydro).

my 2 (might not be worth a plug nickel).

AlexR
01-16-2010, 01:24 PM
As great as Tesla was in the field of power generation, wireless distribution of electricity was not one of his brighter ideas. He never made it work nor has anyone else since, other than over very short distances and at fairly low efficiencies.

Bill_Marsden
01-18-2010, 02:36 AM
As great as Tesla was in the field of power generation, wireless distribution of electricity was not one of his brighter ideas. He never made it work nor has anyone else since, other than over very short distances and at fairly low efficiencies.

Tesla was a genius of the 1st magnitude. There have been a lot of reports that he did make it work (though I wouldn't even try to guess at the efficiency). He did make mistakes, but his successes were a lot more frequent and impressive. I wish we had more info on his theory.

With all the attention I wouldn't be surprised if it wasn't "rediscovered". There were some powerful interests in burying it at the time.

I claim nothing with certainty, I just don't think all the facts are in yet. As in the microwaves, there are other forms of broadcast energy that may be exploited.

k7elp60
01-18-2010, 03:03 AM
On way of looking at an antenna is: The antenna matches the impedance of the transmission line to the impedance of air.
Another person who claims to have gotten great amounts of electrical energy from the atmosphere was T.H. Moray. There is more written about this in book called the sea of energy.
Doing a google search for T.H. Moray gives a lot of hits.

Several years ago I built an active antenna for the AM broadcast band. This consisted of a parallel resonate circuit, RF amplifier and then a emitter follower. The antenna was a telescoping whip about 20 inchs long that was connecte to the hot side of the parallel resonate circuit. I was about 10 miles from the closest AM transmitter. I had 2 volts peak to peak amplitude on hot side of the resonate circuit at the frequency of the local AM transmitter.

On the same token I have been able to have florescent tubes illuminate in a strong RF field. This was near the transmitting antenna

The point I'm trying to make is that the magnetic field of a radio transmitter is so week at a considerable distance that to get a usuable amount of energy is not possible.

Bill_Marsden
01-18-2010, 04:27 AM
I think anyone who understands theory can differentiate between deliberately harnessing power created for the purpose vs. trying to take advantage of what is out there. Lasers and Masers make concentrated beams for the purpose, instead of omnidirectional broadcasts where the inverse square law rules.