Electronic Stethoscope


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Stethoscopes are not only useful for doctors, but home mechanics, exterminators, spying and any number of other uses. Standard stethoscopes provide no amplification which limits their use. This circuit uses op-amps to greatly amplify a standard stethoscope, and includes a low pass filter to remove background noise.

Schematic

Schematic for Electronic Stethoscope

Parts

Part
Total Qty.
Description
Substitutions
R1110K 1/4W Resistor
R212.2K 1/4W Resistor
R4147K 1/4W Resistor
R5, R6, R7333K 1/4W Resistor
R8156K 1/4W Resistor
R1014.7K 1/4W Resistor
R1112.2K to 10K Audio Taper Pot
R121330K 1/4W Resistor
R13, R15, R1631K 1/4W Resistor
R1413.9 Ohm 1/4W Resistor
C1, C82470uF 16V Electrolytic Capacitor
C214.7uF 16V Electrolytic Capacitor
C3, C420.047uF 50V Metalized Plastic Film Capacitor
C510.1uF 50V Ceramic Disc Capacitor
C6, C721000uF 16V Electrolytic Capacitor
U11TL072 Low Noise Dual Op-Amp
U41741 Op-Amp
U51LM386 Audio Power Amp
MIC1Two Wire Electret Microphone
J111/8" Stereo Headphone Jack
Batt1, Batt229V Alkaline Battery
LED1Red/Green Dual Colour Two Wire LED
SW1DPST Switch
MISC1Stethoscope head or jar lid, rubber sleeve for microphone, board, wire, battery clips, knob for R11

Notes

  1. MIC is an assembly made out of a stethoscope head and electret mic. Cut the head off the stethoscope and use a small piece of rubber tube to join the nipple on the head to the mic.
  2. Be careful with the volume, as excess noise levels may damage your ears.
  3. R11 is the volume control.
  4. The circuit marked as optional is not required for the main circuit to function. The optional circuit blinks an LED to the heartbeat as it is heard by the microphone. Even if the optional circuit is not included, sound will still be heard via the headphone jack.

  5. Thanks to audioguru for correcting and improving this original schematic. He has essentially redesigned the circuit as a much improved version. Read about it in this forum topic.

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Comments

muhiti
Didn't u forgot something??
Monday, May 12, 2008 3:07:18 PM
There is no biasing for op-amp u1a. Does it have the same biasing values with u1b??
ernest
Electronic Stethoscope
Wednesday, April 16, 2008 7:45:31 AM
sir, I would like to develop a PCB and make this stethoscope. Sir, could you send me more detail regarding the way it works in details. looking forward to hearing from you soon. Thanks
Varshini.P.R.
Electronic Stethoscope
Wednesday, April 16, 2008 4:39:26 AM
Is this stethoscope just an amplifier of heart beat? Or can it sense small strained vibrations? We are handling a project in which we have to convert strain pulse to voltage. Is this stethoscope identify minute vibrations?
emmanuel michael
Electronic Stethoscope
Saturday, April 12, 2008 10:17:55 AM
I Emmanuel Michael a 400 level physiscist of adamawa state university mubi Nigeria love reading electronics books, and electronics websites during my leasure ours.Iam coming across this website for the first time. I want to build it but afraid of because i dont have TL072 OP AMP, but have JRC4558 and I have studied the pin configurations. I also have LM1872 power OPAMP. I will be glad to be guided.
saurabh
Electronic Stethoscope
Saturday, April 12, 2008 12:31:51 AM
hi . . .can you plz tell me abt the procedure involved in shielding of the condenser microphone.
kehinde
Electronic Stethoscope
Friday, April 11, 2008 9:12:41 PM
Sir, i will appreciate it if u can send a complete analysis on this electronic stethoscope to me. Is it possible to view the heart-beat rate on seven segment display? If so, how? I am presently working on this as my final year project. I will be so much glad if an urgent reply can be given to me. THANK YOU.
Kamardeen
Electronic Stethoscope
Thursday, March 27, 2008 6:15:39 AM
Can you pls send me the complete circuit diagram and the operational write up of the project. i need it for my PGD project next month.
mehak
Electronic Stethoscope
Wednesday, March 12, 2008 11:43:08 AM
sir,i cant fid an electret mic,can u suggest a place,or an alternative!!!plz its urgent!!
anonymous
Electronic Stethoscope
Thursday, February 28, 2008 7:47:10 AM
sir, please give me the complete details of this schematic diagram..we're gonna use for our final defence..tnx..it is very interesting project..
charles
Electronic Stethoscope
Sunday, February 24, 2008 5:21:38 PM
I am interested in getting any more information on the electronic stethoscope you can supply
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