project help for cell phone detector

Discussion in 'General Electronics Chat' started by chaithanyatkm, Mar 18, 2013.

  1. chaithanyatkm

    Thread Starter New Member

    Aug 26, 2011
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  2. chaithanyatkm

    Thread Starter New Member

    Aug 26, 2011
    23
    0
    what should be the minimum voltage at base for the transistor BC548(npn) to turn on in this circuit?
     
  3. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    You can't detect an "idle" cellphone as they switch to extremely low power mode and give off no signal you can detect.

    If you get close enough (a few inches) you could detect the cellphone with a metal detector.
     
  4. crutschow

    Expert

    Mar 14, 2008
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    Idle cellphones do periodically send out a "Hello" signal so the cell system knows where it is, but I don't know the period between transmissions. Also the signal is likely to be rather short also making it difficult to detect.
     
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Yeah that's many minutes between "hellos" and the signal lasts for less than a second. You can hear it on nearby audio amps and radios.
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The voltage depends on the LEDYou select. For a normal red indicator LED, the bc548 will need 2.6v. Now, that doesn't mean this circuit will work - see above comments.
     
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