Electronic Stethoscope 2

[mayzry81]

Hi Audioguru...I'm again..I would like to know the advantages of this electronics stethoscope (at least 10) in brief ..because what i can see is just could hear our heartbeat...
Moreover, I would like to know what is the disadvantages of electronics stethoscope?Thank you for your help..

 

[mayzry81]

Hi Audioguru....Actually is it this electronics stethoscope could detect the noise in the car?...I mean is it practical to use it in onother way beside in medical????If yes could you tell me how???..is there any changes that we have to make in our schematic diagram????

 

[audioguru2]

Hi May,
I can think of only a few advantages of an electronic stethoscope:
1) Its output can be viewed on an oscilloscope or computer.
2) Its output can be recorded.
3) Its gain can be turned up to hear faint sounds not heard with a mechanical stethoscope.
4) The cutoff frequency of its low-pass-filter can be raised with a switch to hear breathing sounds or maybe even sounds from joint problems.
You should hear the noises from my ankle that a Chiropractor "adjusted" and sprained. It sounds something like a garbage can being dragged along the street! Sorry, I hope you are not studying to be a Chiro quack.

Disadvantages:
1) Its might be left turned-on then its batteries will go dead.
2) You might lose its headphones.
3) Its mic and/or headphones cables might break or wear-out.

Mechanics use electronic stethoscopes to locate noises in a car engine or general squeaks by moving it around to find where it is the loudest. This project would probably work better for mechanics if the cutoff frequency of its low-pass-filter was raised as explained in the text for the Electronic Stethoscope-2 project for raising the cutoff frequency for doctors to hear breathing sounds. ;D

 

[abhishek k]

we tried makin ur project(Electronic Stethoscope 2) but we r not able to hear anythin also LED  was glowin continously also in between it turns red.
can u suggest me the solution.

 

[audioguru2]

we tried makin ur project(Electronic Stethoscope 2) but we r not able to hear anythin also LED

 

[waqashshah]

can u please give me all information for electronic stehoscope i.e complete circuit etc

 

[audioguru2]

can u please give me all information for electronic stehoscope i.e complete circuit etc

The text in the project for the 2nd version has a complete circuit description:View attachment 38892

 

[Dazza]

;D

View attachment 38895

 

[Dazza]

;D

View attachment 38896

 

[audioguru2]

Hi Dazza,
Welcome back. ;D
Your project looks very well-made.
How does it work?

 

[Dazza]

Hi, audioguru

I don't know about being back, it's more of the case that I've found some time away from taking care of my son Ethan, and my partner and daughter aren't hogging our shared dial-up Internet connection playing neopets ;D.

I think it was about 12 months ago when I made it, it didn't work as well as I had hoped, that is for what I wanted to use it for, but it does work very well for what it was intended to be used for , and with the modifications that you help me with audioguru, it works very well for tuneing into respiratory sounds or heartbeat sounds 8).

The green caps that you can see are not correct, I was just experimenting with different capacitors ;D.

 

[audioguru2]

Hi Dazza,
Your microphone case looks odd. I used a lid from a jar that made some air-space between the mic and the skin.
I also used headphones that completely covered my ears so that the seal made very deep bass sounds.

 

[Dazza]

Hi audioguru

That microphone case is one of many that I made and tested , it's a lid from a deodorant aerosol tin, I used cloth stretched over the bottom that's held in place with a cabletie, I then used a type of rubberised foam to insulate the rest of it, which is held in place with electrical tape.

The cloth almost eliminates friction noises, but in using the cloth the seal is no longer very good, and allows for some outside noises to be heard, but the rubberised foam that encase the rest of it, helps reduce outside noises.  So there is a bit of a trade-off.

I also tried using headphones that completely covered my ears, and Yes it did make a difference.

Dazza .

 

[solycutema]

heyz.. audioguru....

had been working on ur circuit.... i did use a function generator to input some signals.. the output was quite ok.. not much noises.. i cant hear anything using the mic though.. maybe i burned it while soldering... hehe..

anywaes.. do u have the circuit diagram in .ckt format? i need to change it to pcb.. or better maybe straight the pcb diagram..?? =)

dazza... ur box looks cool.. good job..

thanx..

 

[audioguru2]

Hi Soly,
Last year, Con made a nice pcb layout:

View attachment 39671

 

[solycutema]

hi again..

sorry to disturb u... if i wanna connect a speaker to the circuit.. how
do i do it? will the led cont to light up when i turn the swith to off?
its contant blinking when i switch it off.. till i unplugged the batt
connection only it will slowly fade off...

thanx...

 

[audioguru2]

if i wanna connect a speaker to the circuit.. how do i do it?

Plug an 8 ohm speaker into the jack for the headphones. The LM386 power amplifier IC will provide the speaker with 450mW max and probably cause acoustical feedback howling because the microphone will probably hear the speaker.

will the led cont to light up when i turn the swith to off?

For a few seconds while C7 and C8 slowly discharge.

its contant blinking when i switch it off.. till i unplugged the batt
connection

Then your switch is not wired correctly. Look at my schematic with the switch turning both batteries on and off.View attachment 39701

 

[solycutema]

audioguru......the speaker has +ve n -ve.... how do i connect it? the positive to pin 5 of lm386? the negative to ground? im still having trouble connecting the power supply... =(

thanx..

 

[solycutema]

mr audioguru...

Bell (20-200 Hz) - Diaphragm (100-500 Hz) - Extended Range (20-1000 Hz)
these are the ranges that a normal stethoscope can or should detect... can this circuit be likewise? wat changes needed to be done to the circuit to achieve this modes...?? wat is the frequency range of this current circuitry... hope u can reply me asap.. thanks....

 

[audioguru2]

the speaker has +ve n -ve.... how do i connect it? the positive to pin 5 of lm386? the negative to ground?

You never connect a speaker directly to pin 5 of the LM386 because it has a DC voltage. A speaker or headphones must connect to the output of C6 which is the output DC blocking capacitor. The jack for the headphones is where to connect a speaker.

im still having trouble connecting the power supply.

Two batteries and a switch that has 2 poles. I showed you how to connect them.

Bell (20-200 Hz) - Diaphragm (100-500 Hz) - Extended Range (20-1000 Hz)
these are the ranges that a normal stethoscope can or should detect... can this circuit be likewise? wat changes needed to be done to the circuit to achieve this modes...?? wat is the frequency range of this current circuitry?

C2 passes frequencies down to about 2.8Hz. C6 passes frequencies down to 10Hz into stereo 32 ohms headphones (16 ohms total). Therefore the overall low frequency cutoff frequency (-3dB) is about 12.5Hz.
The Sallen and Key Butterworth lowpass filter of U1b provides a highpass cutoff frequency (-3dB) of 103Hz.
The highpass filter will have a cutoff frequency of 212Hz if R5 and R6 are changed to 16k.
The highpass filter will have a cutoff frequency of 1.03kHz if R5 and R6 remain as original and when C3 and C4 are changed to 4.7nF.