Key finder

Discussion in 'General Electronics Chat' started by venigalla, Mar 8, 2010.

  1. venigalla

    Thread Starter New Member

    Mar 8, 2010
    i want the circuit diagram of keychain finder and the components
  2. BMorse

    Senior Member

    Sep 26, 2009
    Sure, and I would like 1 million dollars please while you guys are at it :) ....
  3. jpanhalt

    AAC Fanatic!

    Jan 18, 2008

    Welcome to AAC.

    I am not clear what it is that you want to do. If you want to somehow locate a key with a batteryless transponder, you would need to generate the right code and listen for a response. Those codes are highly guarded secrets, and the range is very limited.

    If you want a fob that has a built-in alarm that you can remotely activate, such aftermarket fobs are made. This is just one example:

    I have no experience with that particular device. It was just the first thing that popped up on a search.

  4. hwy101

    Active Member

    May 23, 2009
    I think I know what he's talking about, those key chains you can find in dollar stores, I have a couple of them, they respond to a whistle if you happen to lose your keys in the house.
    I took one apart and as usual it's just a blob on a circuit board, nothing to look at.
    But it's no big secret, there's schematics all over the net for a similar circuit.
  5. Audioguru

    New Member

    Dec 20, 2007
    There is a keys finder project at . It uses one 4kHz piezo transducer as its microphone and as its beeper. It doesn't work because nobody can whistle as high as 4kHz and it barely responds to lower frequencies.

    My daughter bought a cheap ******* keys finder at The Dollar Store for $1.00. She asked me if I can fix it because it beeped whenever she talked and all the time when the TV was turned on. It had a black blob for its custom-made IC (a microcontroller?) so I couldn't fix it.
  6. retched

    AAC Fanatic!

    Dec 5, 2009
  7. Audioguru

    New Member

    Dec 20, 2007
    My son bought a laser pointer for me at The Dollar Store. It worked for a week then its cheap ******* on-off switch got corroded and doesn't work well anymore.

    Anything I make that uses a low current switch I use gold-plated contacts that cost a couple of cents more. It lasts forever.