Electronic Stethoscope

[audioguru]

Hi Greg,
I just finished replying to your duplicated post. Please do not make duplicates of your posts.

[jayshree31]

hi i m new here i want breif discription n working of each component of electronic stethoscope using 741 i ran that ckt 1st i got oscillation at d U1 when i tried 2nd tym it gave me sinewave so also i want 2 know what should output at U1 U2 U3 U4 & U5





thnx

[audioguru]

hi i m new here i want breif discription n working of each component of electronic stethoscope using 741 i ran that ckt 1st i got oscillation at d U1 when i tried 2nd tym it gave me sinewave so also i want 2 know what should output at U1 U2 U3 U4 & U5

Many years ago the project was defective with many errors and did not work. It used five 741 opamps.
I corrected the errors and removed the third opamp which did nothing.
The preamp and lowpass filter opamps are now a low noise dual opamp (TL072), the fourth opamp that blinks the LEDs is a 741 opamp and the 5th amplifier is an LM386 power amplifier.

Here is the corrected circuit:

[jayshree31]

bt last tym it gave me something like squre waves bt they were 2 many n phone jack for wt?

[audioguru]

I cannot understand what you say because you do not talk in English words.
The jack at the output is for over-the-ears headphones. "Open" earphones or a speaker will be heard by the microphone and will cause acoustical feedback howling.

Look at the new project in the Projects section on this site.

[jayshree31]

thnx 2 reply me bt i want working i hav externel on dis project so pls help me

[audioguru]

i want working

If you want a job then you must look for a job. Maybe your friends and family can help you find a good job.

i hav externel on dis project

What is an externel?

Your English and spelling are horrible.

[jayshree31]

oh sorry my english is poor & that was sms language sorry again. pls give me working of that circuit

[audioguru]

The word "working" is not the word that you should say in English.
If you want the circuit description that tells how the circuit functions then it is in the project's text.

[jayshree31]

thank you so much but its not enough for me. I have external oral so i don't know what will they ask on this project so please i want the whole description & also function of each component & also i want to ask you if you're my teacher & taking my oral then what will you ask me on this project? it will me help me for preparation 

[audioguru]

Since you don't know the function of each component in this very simple amplifier circuit then you don't know the basics of electronics.

Your teacher will probably cut the circuit apart:
1) The mic is an electret type that you can read about in Google. It must be powered from a filtered supply. Which components power it and which components are the filter?
2) Opamp IC1a is a very simple preamp that has only 2 resistors. What is the function of the resistors?
3) Opamp IC1b is a Sallen and Key second-order Butterworth Lowpass filter that you can read about in Google. Why is the gain of the opamp set to 1.59, why do R5 and R6 have the same value and why do C3 and C4 have the same value?
4) What is the function of R10 and R12?
5) Read about the components with the LM386 power amp in its datasheet.

[jayshree31]

thank you & right i don't have much knowledge pf function of each component. therotically it is difficult to understand for me