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Is this true or false

Discussion in 'General Electronics Discussion' started by newbee, Apr 2, 2013.

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  1. newbee

    newbee

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    Apr 2, 2013
    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
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    No, it's not going to work.
     
  3. CocaCola

    CocaCola

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    Apr 7, 2012
    Here we go again...
     
  4. newbee

    newbee

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    Apr 2, 2013
    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.
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    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
     
  6. newbee

    newbee

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    Apr 2, 2013
    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.
     
  7. Electrobrains

    Electrobrains

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    Jan 2, 2012
    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
     
  8. davenn

    davenn Moderator

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    Sep 5, 2009
    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
     
  9. Electrobrains

    Electrobrains

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    Jan 2, 2012
    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.
     
  10. CocaCola

    CocaCola

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

    [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...
     
  11. davenn

    davenn Moderator

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    Sep 5, 2009
    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
     
  12. Electrobrains

    Electrobrains

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    Jan 2, 2012
    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:
     
  13. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    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
     
  14. BobK

    BobK

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

    Bob
     
  15. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    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
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    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.
     
  17. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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

    Chris
     
  18. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    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.
     
  19. BobK

    BobK

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    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
     
  20. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    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. :confused: 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.... :eek:

    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
     
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