I want to make a key finder. First project, need help!

Discussion in 'The Projects Forum' started by sheffner, Oct 2, 2009.

  1. sheffner

    Thread Starter New Member

    Oct 2, 2009
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    Ok I'm new to this site, as well as electronics. I am attempting to make an electronic key finder. So far I know I will need a piezo buzzer(or its equivalent), 2 transistors, and a 4069(which is some kind of inverter I guess?). What I need to know is what else, and how?!?!?!?! I would really appreciate any help!
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    There is a keys finder project on another website. It does not work but maybe you can fix it. It uses a CD4069, 2 transistors and a piezo transducer used as a microphone and as a beeper. The piezo transducer is sensitive to frequencies higher than anybody can whistle. It might work if a normal microphone is used.
    http://www.electronics-lab.com/projects/misc/002/index.html

    My daughter bought one. She wanted me to fix it because it did nothing when she whistled but it beeped all the time she was talking or when the TV was playing.
    I couldn't fix it because it had a custom IC.
     
  3. sheffner

    Thread Starter New Member

    Oct 2, 2009
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    I know you can buy one, I just want to make one though. I've got a piezo buzzer(do I need the transducer instead?), 2 transistors, and an IC 555. I saw a thread someone posted on here, and there was a schematic for it, but I can't read it! :( I'm hopeless at circuitry! You wouldn't know anything would you?
     
  4. Audioguru

    New Member

    Dec 20, 2007
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    You need a microphone and a mic preamp circuit. A buzzer and a 555 oscillator are different.
     
  5. sheffner

    Thread Starter New Member

    Oct 2, 2009
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    555 oscillator? So I need to get the pieza transducer instead of the buzzer and a mic? Is there a particular model that works best? Thank you for your help! I have absolutely no idea what I'm doing if you haven't noticed yet. :p
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    You can use a transistor to turn on a piezo buzzer or use a 555 oscillator to drive a piezo transducer to make it sound.
    You need a microphone and a mic preamp circuit. An electret mic is common, inexpensive and works well.
    You need a switching circuit so that when the mic preamp receives a signal then the mic is muted when the alarm sounds.
     
  7. sheffner

    Thread Starter New Member

    Oct 2, 2009
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    Ok I have a transistor and a piezo buzzer already. So I just need a mic, a mic preamp circuit, and a switching circuit right? Now what goes where? In what order I suppose. Seriously, thank you so much for your help! This is the first time I've actually posted a thread on here and you've been great!!!!
     
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