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Keys finder circuit


er3na

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Hi Alun,
The project's author is unknown, like me. ;D
I keep my name a secret because sometimes I reveal bad things about my previous employers and manufacturers. I talked about the big skunk under my porch and I don't want more to find out where I live. It dug another hole under there again last week. ;D

I would never design such a lousy circuit. I would use a real microphone and a real opamp for it. I might even include voice-recognition or a counter into it in case you have more than one of these "finder" circuits.

I can find my wireless home phone by pressing a button on the base-station and causing it to ring. I wish my TV remote had one when I misplaced it last night. ::)

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hello,

when i made a whistle the circuit cant be trigger, but then i knock on the table it start buzzing n when i made a loud sound. does that means the piezo i get is not good? becoz when i say piezo tranducer the shop keeper say no idea, so i get the piezo that without oscillator.

after that i made a PCB, but now it cant be trigger even when i manually use the function generator to give signal.

when i tested on the project board, when i knock the table, short circuit of T1's base n emitter or give signal by funtion gen for least then a second, it is trigger then buzzing for a short period of time then it stop.

but after the PCB is done it only trigger when is short circuit of T1's base n emitter
after remove the wire, it will instantly stop (what does this mean?)

as for the name thing, thx for the suggest, Alun, it ok for me to mention this site and the name "audioguru", audioguru?

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when i made a whistle the circuit cant be trigger, but then i knock on the table it start buzzing n when i made a loud sound. does that means the piezo i get is not good?

Hi Lapsap,
Like I said before, the circuit is designed to respond to a fizzle sound, not a whistle sound. I can't make a whistle sound anywhere near as high as the 4kHz resonant frequency of my piezo transducer. I don't know what is a fizzle sound, but it needs to be at the resonant frequency of the piezo.

after that i made a PCB, but now it cant be trigger even when i manually use the function generator to give signal.

when i tested on the project board, when i knock the table, short circuit of T1's base n emitter or give signal by funtion gen for least then a second, it is trigger then buzzing for a short period of time then it stop.

Then there must be something wrong with your pcb.

but after the PCB is done it only trigger when is short circuit of T1's base n emitter
after remove the wire, it will instantly stop (what does this mean?)

After releasing the short of T1's base-emitter, C4 should take a short period of time to charge then T1 can turn-off the oscillator. Since now it happens instantly, then C4 is open and/or R6 is shorted.

as for the name thing, thx for the suggest, Alun, it ok for me to mention this site and the name "audioguru", audioguru?

Sure, you can mention Electronics-Lab and Audioguru. ;D
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after changing the IC, now it is working. but for some reason i will need to use my hand and touch the circuit then only is working. if i didn't do that, when the circuit is trigger, it will buzzing, stop, buzzing, as i mention it before.

some have i mannage to use my whislte to trigger the circuit.

thx, audioguru and others help me out.

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