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Need help with fet circuit

Discussion in 'General Electronics Discussion' started by Sylithan, Feb 4, 2016.

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  1. Sylithan

    Sylithan

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    Feb 4, 2016
    I'm trying to build an antenna that powers an LED. I want the LED to stay off when the antenna detects no electric field. And turn on when it does detect one. I know the basics but in really confused when it comes down to the exact type of FET transitory I need. And do I need a FET or JFET. What's the difference and how would each of these work in this type of project? Thanks for any help.
     
  2. BobK

    BobK

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    Jan 5, 2010
    Do you mean you want to power the LED from the antenna, or is the LED powered by another source and is only an indicator of the presence of RF.

    And why do you think you need a FET for this?


    Bob
     
  3. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    The circuit for this is on talkingelectronics.com website.
     
  4. Sylithan

    Sylithan

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    Feb 4, 2016
    I want the circuit powered by a battery and the led lights up when RF is detected by the antenna. I say I need a field effect transistor because other diagrams I have looked at say I need it. But if there is a better way that will give the antenna a greater range than that would be nice. I'm very new to electronics so I don't know a lot about this stuff.

    Colin... can you post a link?
     
    Last edited: Feb 5, 2016
  5. Alec_t

    Alec_t

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    AC or DC field?
    If AC, what frequency range?
     
  6. Sylithan

    Sylithan

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    Feb 4, 2016
    Which ever gives the broadest range of detection. Needs to be able to detect emf Hotspots around the house, even the smalest amounts.

    My wife has been experiencing uneasiness around the house and we believe it could emf poisoning. We don't really have the money to buy an expensive emf device so looking to build a cheap and simple circuit that will do the trick.

    Figured if yall knew what it was going to be used for it would help.
     
    Last edited: Feb 5, 2016
  7. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    I have already said: The circuit for this is on talkingelectronics.com website.
     
  8. Sylithan

    Sylithan

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    Feb 4, 2016
    Can you provide a direct link to it? I looked on the website and there are several FET circuits. Like I said I'm new to this stuff and I'd which one will do what I need it to do.
     
  9. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    3 transistor staircase in transistor circuits section
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I think the OP is after something with a bit more "woo".

    Like this. Or even this.

    Of course these circuits contain little theoretical woo, but their practical woo potential is huge.
     
  11. BobK

    BobK

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    Jan 5, 2010
    EMF poisoning does exist, but it comes only from a very strong EMF source, usually the sun or a tanning booth.

    Bob
     
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