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

[audioguru2]

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.shtmlView attachment 38486

 

[logan_dslasher]

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..

 

[audioguru2]

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: 

View attachment 38490

 

[logan_dslasher]

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? View attachment 38493

View attachment 38494

 

[audioguru2]

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.

 

[logan_dslasher]

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...

 

[audioguru2]

Hi Logan,
Here is a schematic of the original circuit with its CD4049, with three tiny button battery cells and driving a blue or white LED. You will probably add a switch so that the LED can be turned off and turned on by itself.

View attachment 38501

 

[logan_dslasher]

i appreciate making the schematic for me, but i will use a different supply for the LED.. so there would be a 3V lithium cell for the circuit and 3 button cells for the LED..

 

[logan_dslasher]

what hapens if you fuse the two together such that the the LED will blick together with the beep.. what would the schemtic be?View attachment 38502

View attachment 38503

 

[audioguru2]

Like this:

 

[logan_dslasher]

the circuit is beeping but not blinking.

i knwo there is something wrong on how i wired it.. i tried several times but it is still not blinking. i think it has somehting to do with the LED battery's polarity..
i used a BC337 for Q2..

i just log in on MSn after 3 hours.. you could be awake by then.. pls help me.. thanks..

 

[audioguru2]

Of course the LED won't work if its battery has the wrong polarity.
If you replaced the tiny LR41 button cells battery with your power supply then the LED might be burnt out because it doesn't have a resistor to limit its current.

 

[logan_dslasher]

It's party time!! my LED is blinking together with the beep!! my defense is 13 hours from now!! wish me luck!! i'm gonna need lots of it!! thanks for all the help! it's not yet working though.. i'll work on it again after i finish my hard-bound manuscript!

thanks again..

 

[logan_dslasher]

hi there everybody!

i finished my  defense two  days ago.. it was fine.. i got 91% even if the circuit is not working..

 

[audioguru2]

Congratulations, 91% is wonderful. ;D

Are you going to fix this Whistle Responder project's problems and post a re-design of it that works?

View attachment 38535

View attachment 38536

 

[logan_dslasher]

Congratulations, 91% is wonderful. ;D

during the pre-defense i got  94! eheh.. that's alright..

Are you going to fix this Whistle Responder project's problems and post a re-design of it that works?

i don't want all those components go to waste, of course i'll try to make it work.. but for now, i'm still working on the revision of my manuscript. i have to submit it tomorrow for final editing and printing.. iaudioguru, i  am sorry i left in such a hurry this aftenoon, i have visitors at home that is why i can't stay out for a long time.. there's no windows messenger installed on this PC.

can you please give me some readings about  linear amplifiers or anything that has something to do with my project.. (like about bandpass filters)

tahnks.. a good  website would do..

 

[audioguru2]

Hi Logan,
We have posted two articles about using Cmos inverters as linear amps.
I just looked at Bandpass Filter in Google and found an article with exactly the same bandpass filter ircuit as in the Whistle Responder. I think that the project would have the sharpness of the filter at random since the input and output impedances of the linear inverters aren't known.

 

[logan_dslasher]

i'm sorry,  ive spent two days trying to come up with a good explanation why the circuit didn't work.. i have researched about so many topics.. i have read my saved MSN conversations with audioguru and so far, i still haven't got anything "acceptable" the panelist required me to present an explanation why the circuit was faulty. i have already said things like:

The IC used in the circuit is an old, simple CD4049 CMOS Inverter. Further research revealed that this IC is designed for a fairly high output current and therefore doesn

 

[audioguru2]

Hi Logan,
The CD4069 linear amplifier has been documented as a high gain amplifier when it has a low supply voltage and was easily tested by me.
I have never seen a test of a CD4049 inverter that is used as a linear amp and I have never seen one. Why don't you set-up, test and document the gain of yours?

 

[logan_dslasher]

i have printed the final copy 2 days ago and this morning i had it bounded.. it's a nice feeling to have the finished study.. i just don't know if the explanations i made there are correct..

thank you very much for all the help..  ;D