i want the circuit diagram of keychain finder and the components

 

Sure, and I would like 1 million dollars please while you guys are at it ....

 

@venigalla

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:
http://en.kioskea.net/guide/50307951-friedland-response-hs3-wirefree-key-fob-security-alarm-remote

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

John

 

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.

http://www.redcircuits.com//Page29.htm

 

There is a keys finder project at www.electronics-lab.com . 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.

 

OP, You can use the clapper circuit for turning on and off lights, and mod it to pulse a piezo for the response.
Try this:
http://www.instructables.com/id/how_773/step1/Clapper-Circuit-Diagram/

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Audioguru, I couldn't imagine you allowing your offspring anywhere near a $1 store.. I must be asleep..

 

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.