All of the electromagnetic power around us and how to harvest it?

Discussion in 'General Electronics Chat' started by Rolland B. Heiss, Feb 27, 2015.

  1. Rolland B. Heiss

    Thread Starter Member

    Feb 4, 2015
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    I've got a few questions that may be basic and yet all perhaps are ignorant because, due to my limited knowledge, this is most likely a given. Besides, once one asks a question the fact that they fielded it in the first place proves ignorance! :)

    Firstly a simple question. What common electronic devices you may find lying around the house have step up transformers as opposed to step down transformers?

    Secondly, is what I've read true that silicon junctions pretty much have a threshold voltage of .7 whereas germanium diode junctions have a threshold voltage around .2?

    Thirdly, if I used a step up transformer in conjunction with either silicon diodes or germanium diodes (and perhaps a few capacitors) would it be possible to harness some of the electromagnetic energy that bombards me each second as I type this and also bombards whomever may be reading this each second as well? From what I gather I need to step up with silicon diodes to a voltage over .7 as stated above and if I were using germanium diodes I'd have to step up as well but not as high. Anyone get where I'm attempting to go with this?
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    It is not just about the voltage, you have to think in terms of power. What do you hope to power up with the EM waves that are hitting your body?
     
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  3. Rolland B. Heiss

    Thread Starter Member

    Feb 4, 2015
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    Actually I'm not looking to power anything at the moment other than just getting a reading of some sort, however miniscule as proof of concept to myself. After that I want to at least find a way to build something that will be equal to a simple 1.5 volt AA battery. If I can manage that then I'll let my imagination guide me from there... whether to a dead end or perhaps something better than a dead end. I'm not figuring that all of this electromagnetic energy is going to do much in a very practical sense but I just want to see it do something! This is all part of my learning process and it is very important to start small in order to understand how things happen instead of sitting around playing video games all evening after work like some people do. I'm not one of those. ;)
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Microwave oven

    Cats whisker radio.
    (no local power required)
    Max.
     
  5. planeguy67

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    Jan 29, 2015
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    I have a few tube driven guitar amps that use step-up transformers, but that's probably not a common household item unless you have a guitarist in the house. :)
     
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  6. DC_Kid

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    Feb 25, 2008
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    and 1 million thermocouples.............. might power a house?
     
  7. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    Buy solar panels and harvest the energy from a fusion reactor 92,960,000 miles away.
     
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  8. tcmtech

    Well-Known Member

    Nov 4, 2013
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    If you build a crystal radio and tune it to the frequency of a near by radio station or other high powered local RF source you can light up LED's with it.

     
  9. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    a transformer that changes 120 volts to 12 volts
    will ALWAYS be able to take in 12 volts and change it to 120. transformers are reversable.

    inverse square law. used to calculate power vs distance from a radiating source.
     
    Last edited: Feb 28, 2015
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  10. Papabravo

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    Feb 24, 2006
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    The energy harvesting question gets asked with some regularity. Some energy can be harvested, but the process is inefficient and it produces so little power that it is hard to figure out what to do with it once you have actually gone to the trouble of collecting it.

    A typical weak signal from a distant radio station might have a power level of -110 dBm. If you are not familiar with that unit, it stands for Decibels with respect to 1 milliwatt. In this case the incoming power is 11, count 'em eleven, orders of magnitude smaller than a milliwatt. That's 10^-14 watts or 10 femtowatts. Another way to look at it is that it would take 100 billion harvesters in parallel to make a milliwatt. That's a whole lotta solderin'
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    To harvest the amount of energy that an AA cell holds you'd probably have to be sitting in the dish of a powerful radar transmitter for hours on end :). Of course, you wouldn't survive to enjoy the fruits of your labour :(.
     
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  12. Papabravo

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    Feb 24, 2006
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    The guys working the DEW line didn't have to worry about staying warm. They did have to worry about the long term effects of exposure to EM radiation.
     
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  13. DC_Kid

    Distinguished Member

    Feb 25, 2008
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    exactly. $20 of parts (and ~0.24 sq.ft of space) for crystal radio for ~100mcd of light..... economics will dictate it all. ever think when oil runs dry (when) that the world govts might start controlling solar panel technology ???
     
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  14. nsaspook

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    We'll just get oil from Titan when the earths reserves run out. :)
    http://www.nasa.gov/mission_pages/cassini/media/cassini-20080213.html
     
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  15. madsi

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    Feb 13, 2015
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  16. Papabravo

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    Won't be impotent govts, but powerful multinational conglomerates. If you look closely you may find that tomorrow has already arrived. Take Amazon for example. It is well on its way to controlling the means of information dissemination, while putting publishers and authors to the curb. On /. today I read that tech companies are pressuring the WA state legislature to spend money to increase the number of CS seats at the university. The guys and gals with CS degrees I know are scrambling around for fewer jobs that pay less because the workforce is global.

    "We have met the enemy, and he is us."
    --Pogo
    http://en.wikipedia.org/wiki/Pogo_(comic_strip)
     
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  17. GopherT

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    Nov 23, 2012
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    And Monsanto has prevented farmers from keeping seeds from last year's harvest to plant next season - how else could they sell more seeds?
     
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  18. wayneh

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    Sep 9, 2010
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    Impotent govts? Ours is becoming less impotent everyday. They've already erased our border, seized control over a large chunk of the U.S. economy, just this week seized control over the internet, and they are actively buying and banning ammunition so that the 2nd amendment won't matter anymore.
     
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  19. planeguy67

    Member

    Jan 29, 2015
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    Look at who owns a large portion of the solar power industry?

    It's the oil industry.

    They aren't dumb. Ya think when their current energy product runs out, they're just going to shrivel up and die? No, they'll simply begin selling another energy product.
     
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  20. nsaspook

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