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


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i have only at least 19 hours before my defense starts. my buzzer got damaged. i can't get a new one in at least 11 hours from now.. i'll just concentrate on my manuscript.. the subject is research methods anyway, and 70% of the grade is given by tour research prof. 30% is from the three-man panel of electronic professors.. even if they will give only 30% of my grade they will do the "interrogation"  all the time during the defense.. and most importantly, they will be the one who decides if you pass or not!

if this thing doesn't work out well tomorrow, i hope you guys have a NEW CIRCUIT for me to work on.. i should've been with the eLab community before i chose a topic. that way, you have recommended the best topic to work on.. anyway, have one ready.. just in case..

Thanks for all the help..  ;D

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Hi Logan, Besides having a broken beeper, your project doesn't work because of your intermittent breadboard.

As we discussed on MSN, the Whistle Responder project's design has some mistakes that can be easily fixed:
1) It uses an unsymmetrical output, high operating current CD4049. That's crazy! It should use a CD4069 instead for its Cmos linear amplifiers.
2) It has a 100k to 220 ohm attenuator following its mic peamp which is also crazy. It should have a trimpot there.
3) The lowpass filter parts in its bandpass filter cutoff frequencies above 49Hz, which is also crazy.
4) It used an emitter-follower to drive the beeper with a voltage loss of about 0.8V, which is 27% of its supply voltage. Crazy! It should use a common-emmiter circuit for the transistor with a voltage loss of only 0.1V or less, like I showed.

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LUCKY BREAK!!
one of our panelist won't be available at our scheduled defense.. meaning we have to re-schedule the defense! everybody is busy the coming days.. the ealiest possible date and time we can defend is next wednesday, meaning i still have 5 days more to make this thing work..

for now i have to concentrate forst on my other subjects.. i missed again another final exam!!


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i have downloaded the pdf files of op amps from Ante's thread.. i missed part3 that is why i cant open the first two..

anyway, i'll study also this file.. my mom referred me to an old friend of hers. He worked in Japan for qiute some time.. he is also concerened if an inverter can be used as an amplifier.. he recommended using op amps.. i will still concentrate on the 4069..

i bought a new buzzer. i had it tested in the store where i bought it.. they used a 6V battery to test it. it beeped. when i got home, and tried it on my AC-DC converter, it is not beeping anymore.. it was beeping though at Rx1 setting of my multitester..

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i've tried your suggestion to make it beep louder... remeber the bottle cap? is that the one from 1.5 liter of coca cola bottles? what is the ideal size of the hole... i've been looking for chassis for the circuit and so far a matchbox is the best  so far.. the piezo buzzer beside the circuit fits perfectly..

i was trying to make a PCB design for the 4069, and i am wondering if i could interchange the inverters..  say for the input, those that are connected to the pin1 will be connected to pin3 instead and for th output, those in pin2 will be in pin4? can you visualize what i want to happen? i hope i explained it properly.. the same with other inverters so that it would be easier to design the PCB layout...

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Hi Logan,
My piezo speaker from an alarm clock is without a housing and its back is exposed. It is much louder when its back is very close but with a small space around it to a big bottle cap like from Coke. A sewing thimble also works well as an acousical resonant chamber.

My piezo buzzer is already mounted in an acousical resonant plastic chamber, it is about 3cm in diameter and is about 3cm deep. The housing's size and shape is designed to resonate at the same frequency that the piezo is loudest. Then its oscillator transistor automatically oscillates at that frequency. Its bottom is sealed with a hard glue but its pcb is there with pins from its transistor.

In an IC, all the inverters are exactly the same. You could use the inverter with pins 1+2 as the 1st inverter, pins 3+4 as the 2nd inverter and pins 5+6 as the 3rd inverter in the circuit if they fit together on a pcb better. Or use the inverter with pins 3+4 as the 1st inverter in the circuit instead as you say.

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alright, i'll see if i it would be easier if i interchange the inverters.. i've been buzy the whole day working on my business policy term paper.. i'll be ready with the questions (ehehehe) about 4069 tomorrow..

i cracked my damaged buzzer open.. i saw what is inside and didn't understand a thing ehehe.. all i recognized was the components, but i never understood why they are there and what they do ;D

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i am logged in for about 6 hours and a half now.. i've been downloading lots of things.. and they takre very very long!! imagine downloading the EAGLE layout editor at 2kbps!! and at some point, say 45% it would suddenly stop!!

i found a lot of useful programs! especially the frequency analyzer which i can (can i?) use in my whistle responder proj. but my pc doesn't have a mic.. and i dont know if it has a sound card..

i've also been to the proejcts section and i came across this: http://www.electronics-lab.com/projects/sensors/005/index.html ..


This sensitive sound operated switch can be used with a dynamic microphone insert as above, or be used with an electret (ECM) microphone. If an ECM is used then R1 (shown dotted) will need to be included. A suitable value would be between 2.2k and 10kohms.

The two BC109C transitors form an audio preamp, the gain of which is controlled by the 10k preset.  The output is further amplified by a BC182B transistor. To prevent instability the preamp is decoupled with a 100u capacitor and 1k resistor. The audio voltage at the collector of the BC182B is rectified by the two 1N4148 diodes and 4.7u capacitor. This dc voltage will
directly drive the BC212B transistor and operate the relay and LED.

It should be noted that this circuit does not "latch". The relay and LED operate momentarily in response to audio peaks.

can i use it to amplify the signal picked up by my Electret mic instead of inverters wired as amplifiers?
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i've been going through my notes in Yahoo Notepad.. i found this: http://www.electronic-circuits-diagrams.com/audioimages/audiockt9.shtml  it uses  LM324, the same opamp audioguru once mentioned.. i know i said that i am not interested in using op amps in my whistle responder proj, but my thesis adviser is persistent.. if ever, can i use it as amplifiers? can i omit the 4027 it also uses.. it's a flipflop.. here's the schematic:

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i came across this: http://www.electronics-lab.com/projects/sensors/005/index.html
can i use it to amplify the signal picked up by my Electret mic instead of inverters wired as amplifiers?

It would need to be re-designed to operate with a 3V supply. Its supply current would quickly kill a small battery.

i found this: http://www.electronic-circuits-diagrams.com/audioimages/audiockt9.shtml

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The lousy old intermittent breadboard stopped the circuit from working.


i will now begin troubleshooting the circuit again using the 4069.. we have tried lots of things on MSN, yet it still continuously beep.. i pointed out that maybe, at some point in that testing, my buzzer got damaged that is why we have to stop working on it? if you will continue help me working on it (i have a pretty good feeling you would, you like working on lousy projects, right? ehehe), would it still be on a breadboard? i think it would be better if we would work on it while it is on the board, because i can't solder/desolder here in the cafe.. besides, that would mean i still have to design and make a PCB of 4069 which is not the one indicated in my PRINTED-and-SUBMITTED-to-the-PANELIST manuscript!! it would be easier on my part to work on it while it is on a bread board..
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Hi Logan,
I think that the gain of the mic preamp is so high that its wiring would pickup mains hum if it was on a breadboard.

Your CD4069 IC was faulty or the breadboard was faulty because when you grounded the inverter's input pin 1, its output pin 2 stayed low instead of going high which would turn off the beeper.

When that is fixed then the DC voltages should be near what I marked on the schematic with pin 2 high because R8 would keep pin 1 low enough for pin 2 to be high.

Then you can try different resistors in the R4-R5 attenuator but a 100k trimpot would be much easier to adjust, with the original wrong value for C3 removed. With the attenuator set correctly, the beeper should beep for a few seconds when you make sound at the mic.

Then you can add a correct value for the C3 lowpass filter which would be about 180pF for a cutoff frequency of 2.7kHz. The dropping high frequency response of the mic preamp would reduce the cutoff frequency further.

Then a value for the highpass filter must be selected for C2 so that it matches the resistors in the circuit.

Then the attenuator can be adjusted for the sensitivity you want.

I have added a 100k trimpot as the attenuator and corrected the wiring of C2: 

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ahh.. audioguru.. i wanted to make the circuit work as much as you do, but i think i need to concentrate on the 4049 since it was the IC used in the manuscript i presented to the panelist.. and during the defense, that is the circuit they are expecting to see.. i know it would be best to show them a working circuit but i really have truckloads and truckloads of things to do.. i have lots of exams this coming week and the projects needed are also due this week.. so i will have very little time working on another circuit.. last week, thought i would have plenty of time working on the circuit but when i went to a classmate this afternoon i found out that we have still lots of things to accomplish..

so, i need first to re-assemble the old, lousy 4049 ciruit.. i have to etch another PCB because the old one that my adviser disassembled was too messy to reuse..

about the flashlight i asked you to integrate with the circuit, i am planning to use this miniflashlight, buit-in a very cheap lighter.. it uses 3 LR41.. do these button sell batteries come in different voltages? or all LR41 are 1.5V? it's pretty bright.. i've asked a lot of electronic shops in our locality and none of them can sell to me the LED it uses.. when go home at midnight i use it.. at a dark spot, it can fairly illuminate as far as 10 meters.. during a power failure, we use this to look for a candle.. it can illuminate the whole living room.. life span is quite long.. besides, this is very very very cheap.. it only costs 10 pesos, and it comes with a lighter! or the other way around. anyhow, point is that it is cheap.. an LED costs 3 pesos.. and a single button cell costs 15pesos each, i think..

I'm going to use this. what would happen to my circuit now? how will i wire this to go with the beeping tone?

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i need first to re-assemble the old, lousy 4049 ciruit.. i have to etch another PCB

As I said before, I don't think a CD4049 will work in this project. It has a very high current and is not symmetrical to be used as linear amplifiers.

about the flashlight i asked you to integrate with the circuit, i am planning to use this miniflashlight, buit-in a very cheap lighter.. it uses 3 LR41.. do these button sell batteries come in different voltages? or all LR41 are 1.5V? it's pretty bright.

The LR41 is 1.5V when new and is guaranteed to produce 1.3V into a 100 ohm resistor (13mA) for only 0.1 second to 2 seconds. It is designed for a 30k load which is only about 42uA. I've seen keychain LED flashlights with them and they last for about 10 or 15 minutes. Here is the datasheet for a substitute LR41 battery cell: http://www.gpbatteries.com.hk/pic/GP192.pdf

I'm going to use this. what would happen to my circuit now? how will i wire this to go with the beeping tone?

A blue or white LED needs more voltage than two cells so three cells must be used. The two linear amps in the project's CD4049 will kill the LR41 cells quickly. The project probably won't work with a CD4049 so you can connect a switch to ground pin 5 of the CD4049 to make the piezo beep. Then connect the blue or white LED in parallel with the piezo to make it flash with the beeping. The internal resistance of the tiny button cells will limit the current to the LED like in a small flashlight.

You could use a 3V lithium battery cell to power the project, and a 2nd transistor and base resistor could turn on the flashlight that has its own battery.
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As I said before, I don't think a CD4049 will work in this project. It has a very high current and is not symmetrical to be used as linear amplifiers.

i really don't have a choice.. i have to make my thesis defense whether the circuit is working or not.


A blue or white LED needs more voltage than two cells so three cells must be used. The two linear amps in the project's CD4049 will kill the LR41 cells quickly.

i doesn't matter. my defense will only take 4 hours at most! ;D

The project probably won't work with a CD4049 so you can connect a switch to ground pin 5 of the CD4049 to make the piezo beep.

grounding pin5 makes it beep? this is to show the the oscillator works, right? i need to make it beep during the defnse to show the range the beeping tone can be heard as stated in my prolem3  in the manuscript

Then connect the blue or white LED in parallel with the piezo to make it flash with the beeping
simple as that? what would be the new schematic then? can you please show me.. please...

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