Is this true or false

[newbee]

Hi all,

Sorry if my question is naive, i don't understand anything about electronics. That's why I joined this forum to get your help, PLEASE.

I need to know if the following project I found on You Tube is false or real. Can it really charge a Phone ?

Appreciate your help. And please do laugh at my ignorance if you want

 

[(*steve*)]

No, it's not going to work.

 

[CocaCola]

Here we go again...

 

[newbee]

Thank you *steve* .
Sorry CocaCola if "it's again" , I searched before posting but did not see an answer to my question.

God bless you both.

 

[davenn]

Newbee

hi ya and welcome to the forums

Dont feel too bad about asking, its a very common question from people with little electronics experience and because of that they get fooled by these idiots on the net that promise all sorts of miracles

As you go on in electronics and learm more about the subject, you will be able to sort out the good from the bad stuff

the reason why it wont work is that the energy available from radio waves is so minute that it wont power anything. We are talking about just a few microVolts
not even enough to make those diodes in his circuit conduct

cheers
Dave

 

[newbee]

Thank you so much Dave.

I'm glad to know there are people like you helping others not to fall for these scams.
The video I posted comes from a site that promises miracles.

Wish you good luck and all the best.

 

[Electrobrains]

I know this topic has been up before.

I don't know if I dare to write this after the more experienced guys have written their comments, but I think I disagree...

As pointed out, there is very little energy to be caught from the radio waves, but there definitely is some. And it can be used.

I did not test the YouTube circuit, but once when I have time I will do that. The function is of course not to run an LED with constant current by radio waves, but that you charge a battery, gold cap etc. and then suck out the energy at certain occasions.

This really gets interesting for very low-energy circuits (I would be interested in supplying a nano-watt Microchip uC that way).

Here you can see the latest innovation from Nokia, using this technology:
Nokia Phone Charges by Drawing Energy Out of Thin Air

Another very interesting, related technology is the more high power Wireless Battery Charging:
Wireless Charging Explained

 

[davenn]

well I wouldnt hold my breath on the first link info
its got some blatant inaccuracies

and the second link is irrelevent as it has nothing to do with what is being discussed in this thread!!
and apart from that ... there's something dangerous about that second link ....
it cause many multiple page tabs to spontanously open up ... definately screwy

Dave

 

[Electrobrains]

well I wouldnt hold my breath on the first link info
its got some inaccuracies

Hm, what blatant inaccuracies?

Concerning the second link (I had no problems), I specially wrote it's a related technology.
The main differences being the frequency and the amount of power transferred.

 

[CocaCola]

What is funny is that if you follow one of the links in the first article it takes you here...

Earlier this year, Joshua Smith at Intel and Alanson Sample at the University of Washington, in Seattle, developed a temperature-and-humidity sensor that draws its power from the signal emitted by a 1.0-megawatt TV antenna 4.1 kilometers away. This only involved generating 60 microwatts, however.

[sarcasm]Clearly the answer to our energy problems, what flaw can be found in broadcasting 1,000,000 Watts to get 0.00006 Watt...[/sarcasm]

I can also see theft of service/property lawsuits flying like crazy if you are going to arbitrarily harvest 'owned' radio transmissions without authority, someone is paying the bill to broadcast, it's not exactly 'free' energy...

 

[davenn]

yup exactly CC

unless you live pretty much right under a high power transmitter you are not going to harvest enough power to even begin to power a single LED

and also as for that first article ..... IF my microwave oven emitted enough power that it could be usefully harvested, I would be thowing it out, as obviously it would be way to dangerous to use with that much leakage!!!

Dave

 

[Electrobrains]

I suppose the useful energy is somewhat predictable.

If I remember rightly, (for simplified spheric radiation) the magnetic energy density is inversely proportional to the square of the source distance (~ 1/d^2).

About microwave ovens, a quick google search gives this information from FDA - U.S. Food and Drug Administration:

A Federal standard limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts (mW) of microwave radiation per square centimeter at approximately 2 inches from the oven surface. This limit is far below the level known to harm people.

 

[CDRIVE]

I think we have to make a point of differentiating available airborne power vs available voltage. The basic 2 requirements to make a crystal radio is an RF detector (Diode) and a Crystal earphone. Since its inception and to this date the 1N34 Germanium Diode still reigns king. Schottky diodes, even with their very low Vf, will not replace a 1N34. The reason I veered off to the 1N34 is because it has a Vf = 300mV so if the signal is not loaded there's obviously >=300mV available to forward bias the 1N34. Crystal earphones are predominantly a capacitive load and can't be replaced, even with a 1000Ohm magnetic element.

So getting back to the issue... It's power that's not available not voltage.

Chris

 

[BobK]

I have often wondered about this point, why would Shottky diodes not work in a crystal set?

Bob

 

[CDRIVE]

I have often wondered about this point, why would Shottky diodes not work in a crystal set?

Bob

Quite frankly I can't even fabricate a plausible technobable answer to this question. I do know that I've read quite a few crystal radio articles and threads where guys in the UK were begging for 1N34's because Schottkys didn't perform as well. Yes, they worked but not well.

Here's a guy that I communicated with a few years ago. He's devoted quite a bit of research time to crystal radios and the 1N34.
http://www.lessmiths.com/~kjsmith/crystal/dtest.shtml
I contacted him because I was so impressed with his wood base construction found at the bottom of the page. Seeing them really sent my mind reeling back to my childhood construction practices. I didn't have a router so mine never looked this good.

Chris

 

[(*steve*)]

One thing he seems to ignore is the capacitance of the diode. (He tests some large rectifier diodes without mention of this)

I have some low voltage shottky diodes that exhibit a very low voltage (under 0.1V in some cases) However, being rated for 19A, I think they're likely to be far too high in capacitance.

Having said that, I've not tried making a crystal radio using one.

 

[CDRIVE]

He didn't completely ignore it,as shown here.

Schottky diodes are very sensitive diodes that work excellently in crystal radios. Their construction and theory are different and I confess to not fully understanding these components. Still, from the characteristic curves, they are excellent! Again, note that you dont always get what you bargain for. Here I found what was supposed to be 1N34A's to be some sort of Schottky of unknown pedigree. The 1N5819, while having the lowest forward voltage drop, has a rather very high Junction Capacitance and will not perform well.

Chris

 

[(*steve*)]

True, he mentions it once (and I missed that). I would think that the capacitance (and by extension the switching speed) would be more important in some cases than the Vf.

Interestingly, Shottky diodes have a lot in common with cat's whisker detectors.

 

[BobK]

I did some research on my own, and it seems that some Schottky diodes do work well. The parameter that seems to matter is the Rd or the resistance of the diode at 0V. This is also related to reverse leakage current. Lower on both of these is better.

Bob

 

[CDRIVE]

True, he mentions it once (and I missed that). I would think that the capacitance (and by extension the switching speed) would be more important in some cases than the Vf.
Interestingly, Shottky diodes have a lot in common with cat's whisker detectors.

While it's true that Vf seems to be his singular focus there are links in his article that also address Rd. I also find it surprising that Cj and by extension switching speed seems not to be addressed. Maybe it's covered in some of those links. I did follow one of his links but it can make you dizzy because the links contain more links that contain more links and on and on....

I did some research on my own, and it seems that some Schottky diodes do work well. The parameter that seems to matter is the Rd or the resistance of the diode at 0V. This is also related to reverse leakage current. Lower on both of these is better.

Bob

If you found particular schottkys that make a good replacement for the 1N34 it might me helpful to others to put that info in our data sheet-parts section. maybe a thread titled 1N34 Substitute?

Chris