Detecting a 10kHz signal

Discussion in 'Homework Help' started by SPSU87, Jan 11, 2009.

  1. SPSU87

    Thread Starter New Member

    Jan 10, 2009
    3
    0
    Hi everyone! I'm new to the forums but there seems to be alot of knowledge and resources here.

    I have a project for school that I'm working on and I am having trouble tackling one part.

    I need to detect a 10kHz frequency that is coming from another device that is transmitting the signal thru a wire about 40ft long.

    My problem is actually detecting the signal. I have tried, with no success, using a condenser microphone fed into an opamp then a bandpass designed to peak at the 10kHz frequency. then I was going to use a frequency to voltage converter to input into the microcontroller.

    does anyone have any other ideas about how to actually pick up the signal? This is where I am really stuck as I don't know much about antennas and signals.

    Thank you for any help you can provide.
     
  2. flat5

    Active Member

    Nov 13, 2008
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    17
    Induction. How far away is the wire? How strong is the signal?
     
  3. SPSU87

    Thread Starter New Member

    Jan 10, 2009
    3
    0
    The wire wont be more than a few inches away. It is actually acting like an invisible fence so I only need to know when it is close to my project. I think the signal is only about 20mW. I only need to know when I am right next to the wire.

    What do you mean by induction?
     
  4. duffy

    Active Member

    Dec 29, 2008
    44
    0
    Use a coil. Look up "inductive loop radio". Tune the coil with a cap so it resonates at 10khz. Check out a 567 pll chip.
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    Might be easier to make a twin-T filter for the detector.
     
  6. SPSU87

    Thread Starter New Member

    Jan 10, 2009
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    0
    I did some looking and can't really understand how the inductive loop works. What will it do when it is over the wire? and how would the loop interface to the 567 chip?

    is there anyway to utilize the condenser microphone? is that capable of picking up the frequency even though there is no sound being emitted from the wire? What about a simple wire for an antenna connected into a bandpass filter?

    Sorry but I am not experienced on this topic. thanks
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
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  8. duffy

    Active Member

    Dec 29, 2008
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    The wire for an antenna won't work as well as a coil. An antenna works on an electric field, this is mainly a magnetic field.

    But you can use a lot of different size coils, or even wind one of your own, and they are easy to hook up to an op-amp, and then you can connect a pair of headphones to the output of the amp so you can hear it and test how it works.
     
  9. bertus

    Administrator

    Apr 5, 2008
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