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i need help extending the keys finder project. can someone help me out????

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Hi Chetan,
Welcome to our forum. ;D
Did you build it and did it work? ???
It is supposed to beep when it hears a fizzle (?) sound. You could have a million of them and they will all beep, maybe continuously. The 2nd one would hear the 1st one beep and it would also beep, and the 3rd one would....., you know.

Maybe you want to transmit a certain pitched sound and want only a single keys finder circuit to be tuned so it responds. Then have others respond to their tuned pitches.
It would be complicated to make stable sharply tuned circuits, maybe you could transmit and receive crystal controlled telephone touch-tones (DTMF) if IC's for them are still available.
The piezo transducer responds only to certain frequencies and would be another problem. :(

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  • 1 month later...

Hi Logan,
Welcome to our forum from that other one. ;D
You got the projects' links and their titles mixed-up.

The Keys Finder project has a serious problem:
It requires that you whistle at a frequency that the piezo transducer is the most efficient, about 4kHz. You nor anybody can whistle at a frequency so high, so its range is reduced since it must detect the lower frequency that you can whistle where it doesn't have much sensitivity. It will also have reduced sensitivity to the harmonics of your whistle.

The Whistle Responder project will have a much farther range since it uses a proper microphone and a bandpass filter for 1.8kHz, a frequency that anyone can whistle.
Its range might be able to be increased even farther by decreasing the value of its R4.
If R4 is decreased too far, the sensitivity might be so high that it keeps responding to its own beep, so maybe a couple of diodes can be added like in the other circuit to cutoff its microphone preamp while it is beeping.

I modified the Whistle Responder to make its beeper as loud as possible.
I have all parts to make one so I will play around with its circuit. I want to see how much its sensitivity can be increased until it responds to common background sounds. ;D 


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the mixing up of the projects only proves that i really need some sleep..

it's really nice of you to modify the circuit.. may you please do it one more time?! i am planning to have a light source to go with the beeping.. so that it can be easier to locate.. and should also include a separate switch for this light so that it can be used as a flashlight when trying to open the front door in a dark porch..

??? about the beeping tone, would it beep continously until you find it?! or it would only beep for a certain amout of time? is it a single beep? how about the light, i am requesting to be added, can u please integrate it to the circuit such that it is blinking..

i hope this is not much work to you.. thank you for the help.. i'll have some rest for now.. hope to hear from yah soon..
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i am planning to have a light source to go with the beeping.. so that it can be easier to locate.. and should also include a separate switch for this light so that it can be used as a flashlight when trying to open the front door in a dark porch..

A white LED needs more than the 3V of the battery, so it will need an additional voltage stepup circuit for its power. Build this circuit 1st then you can build a light circuit later.

??? about the beeping tone, would it beep continously until you find it?! or it would only beep for a certain amout of time? is it a single beep?

From the Whistle Responder article: "This device beeps intermittently for approx. two seconds when a person in a range of about 10 meters emits a whistle."
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i'm not abusing help or being lazy.. but i need your help about some info about the history of sound activated circuits.. i've been searching for days, but i cant really find a site discussing such facts.. maybe, i just dont know the right keywords to search in google... i've tried online encyclopedias, but they require memebrship.. i need some tips of the right way of searching for any information i might need about the whistle responder circuit..

thanks u all!!
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Break down the project into blocks then search in Google for the blocks:
Electret Microphone.
Microphone preamplifier.
Digital Logic.
Cmos Logic Devices.
Cmos oscillators.
Analog Applications for Cmos Digital Devices.
Piezo Transducer.
You can add the keyword Theory following them if you want.

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i was busy preparing for my defense this coming wednesday.. we are about to defend chapters 1(the problem) chapter 2 (Review of related literature and studies and chapter 3 (research design and methodology..  one of my most feared, anticipated question is...

"are you aware that there is already an existing gadget such as this?! how is your proposed prototype different?!"

how am i supposed to answer?! or what if they said like "where did you get the circuit?! what modifications did you add?!

and one more thing.. i titled our project ELECTRONIC ITEM FINDER.. can anybody please suggest a better one?! thnak again for your help..

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1) Build the simple circuit and show that it works!

that's my main objective this coming week!

3) Make it tiny!

during the defence, the panel asked me how small it would be, i said, i would probably use a 3X4 PCB.. i know ist too big but i dont want them to expect too much..

4) Power it with a tiny but powerful 3V lithium coin cell!

assuming none is available, any other alternative?!
any more suggestions how i could make it smaller?! am gonna design the PCB layout later..

how about the light.. i promised them i would put a LED together with the buzzer.. what llight should i use.. they said an LED is too big.. i also need to put a separte switch for the light so that it could be used as a small flashlight..
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Hi Logan,
I purchased bags of tiny LEDs where the LED is about 0.05" in diameter and has flat leads coming out their bottom sides. They fit on a pcb with 0.1" leads spacing. They were red, yellow and green. They weren't bright white nor blue. I use them as low-voltage zener diodes.

For a flashlight, a white LED should be used and are available in 2 sizes. It needs at least 3.5V to work therefore consider using 3 button cells to power the project. The button cells are used in watches and stuff like that. Select alkaline button cells as big as you can because the Whistle Responder project uses much more battery current with 4.5V compared to 3V, and the LED takes a lot of current to be bright.

The Whistle Responder circuit will be less sensitive with 4.5V because a Cmos inverter has higher gain with lower supply voltage. Maybe a couple of diodes should be in series between the circuit and the battery to drop the voltage to about 3.3V, and a resistor in the circuit could be changed to get more gain.

Can you find a piezo beeper from a broken alarm clock or something? Usually an alarm clock uses a transducer and a separate oscillator to drive it. A capacitor and resistor can be changed in the circuit to make an oscillator if you can find just a transducer.

Another transistor can be added to the circuit to make a transducer sound much louder. ;D

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  • 3 months later...

i did a pcb design on the circuit and i needed a second opinion so i asked a friend to make his own version.. the design is similar except for the c2 and c3.. he placed one terminal of r7, r6, and +c2 with pin4.. whereas in my design, i have r7 between pins 3&4 and r6 between pins 4&5.. +c2 is placed in pin5.. i hope i discribed it properly.. i hope you wont have a hard time picturing it out..

i still go with my design..

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Tomorrow I'll be busy working in Canada's national election. All day and half the night.
I'm getting paid pretty well to keep politicians away from the polling station because they bribe folks to vote for them by handing out a bottle of booze!
Also, I'm in charge of 10 people who check-in voters and count the ballots. Lots of fun (boring!)

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ow.. that would be alright.. you could have a look at it as your time permits.. i'Ve also been a poll watcher once.. yah!  its lots of fun alright.. sitting there for hours doing nothing but tally the votes.. you take care of yourself.. here in the Philippines, things like that could get ugly.. some areas are attacked by rebels.. also, watch out for politicians trying to bribe you.. never give in.. hey! have you watched the pacquiao-morales bout! it was awesome, right?! the Philippines is very proud of pacman!!
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the operation of the circuit discussed in the site is very brief. i hope I could get e more thorough explanation about its design. i need to know what's happening in the circuit from the moment someone whistles up to its emission of a beeping tone. i want to know why the parts are wired the way they are. i hope someone (you know who you are.. eheheh) could help me out here..

i have just mounted its parts on a bread board. it didn't work. maybe i didn't whistle at the correct frequency. i tried using my cellphone's ringtone composer, i tried every note i could produce but to no avail. i've checked the connection a dozen times. what could have i done wrong? my bread board is quite small so i have to use lots of wires, could that be the reason?                                      i also used a ceramic capacitor for c2 and c3 instead of polyester. could that be the reason? the mic doesn't have any polarity, right?

i don't know what i did wrong.
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