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idea for creating Touch sensitive wire strip like variable resistor

Discussion in 'General Electronics Discussion' started by Vignesh0025, Aug 23, 2013.

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  1. Vignesh0025

    Vignesh0025

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    Jul 4, 2013
    Hii, I want to create a touch sensitive wire strip... That is .. When i move my hand over a copper wire
     
  2. BobK

    BobK

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    Jan 5, 2010
    Well, there is not much variation in voltage along a copper wire unless it is drawing a LOT of current, so I don't see how.

    Bob
     
  3. davenn

    davenn Moderator

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    Sep 5, 2009
    you could create a capacitive touchpad <--- google it

    you need to understand you need 2 wires

    Dave
     
  4. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    That's partially true. One leg can be commited to ground leaving only one conductor as the capacitive pickup. I think it might be prone to false triggering though.

    Chris
     
  5. Vignesh0025

    Vignesh0025

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    Jul 4, 2013
    I searched for capacitive touchpad but could not find able to find any actual idea to work it out?? Where can i find the details??
     
  6. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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  7. galaxy

    galaxy

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    Nov 3, 2012
  8. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    If you're looking for a simple finger bridging circuit that demonstrates where along a resistive divider your finger has bridged the circuit you can put this together. I show a 9V battery and an Ammeter but a basic Ohmmeter will work just as well. Placing your finger across any of the 4 touch points will give a different Ammeter or Ohmmeter reading.

    Chris
     

    Attached Files:

    Last edited: Aug 25, 2013
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    On a technical note, this applies only if the length of the wire is short compared to the wavelength of the signal.
     
  10. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Are you referring to SWR?

    Chris
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    No, I'm referring to the propagation of a signal through a conductor.

    If the conductor is short compared to the wavelength, you can consider the signal identical throughout the length of the wire, and the signal at both ends are the same.

    If the wire is long, both ends of the wire could be at different potentials.

    As toy realize, an antenna is a perfect example. However, regardless of SWR the effect still happens.
     
  12. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Yes, but this does not hold true for transmission lines properly terminated in it's characteristic impedance at both ends. In this case the only differences from input to output should be dielectric and radiation loss. Usually,the more expensive the transmission line the less one should see in either regard.

    Chris
     
  13. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Steve, brain fart on this end! Yes, you're absolutely correct and so was Toy. My last post I was still stuck on SWR, which is better described and stated as Reflected Power. It has little to do with Toy's theory.

    Yes, that's how antennas work! ;)

    Chris
     
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