priyank1

Hi all, Hi audioguru... I have tried the modified circuit, but sadly it didnt work for me. I need to clarify one thing in the circuit. IS pin 4 of u5 (lm386) ground or connected to the -9 volt supply. Some of the post in forum have suggested to connnect pin 4 to the -9 volts. why would that be? I went through the datsheet of lm 386 which suugests to ground pin 4. i have built the plastic diaphragm for the microphone insert and have breadboarded the circuit according to the circuit diagram. WIth me i dont get any out put when i connect output from pin 5 of u5 to my a/d converter of the dspace card . i have also used shielded cable for the microphone part. ANy suggestion please....have attached pics of breadboard and the plastic diaphragm for the microphone insert cheers pri [attachment deleted by admin]

Hi audioguru, :) I have made the changes which u had recommended, i have breadboarded the circuit exactly according to ur circuit diagram. My professor at uni has given me a OMNI-DIRECTIONAL ELECTRET MICROPHONE INSERT.. he is suggesting me to insert microphone in the bell of the sthehoscope. The issue i have is the specification of the microphone insert. On the specfication it says its operatin frquency is 50-12,500 hz. My concern is that in order to obeserve korotkoff sounds in branchial artery,frequency of interest is 2- 100 hz. I am not sure if the operating frquency of 50- 12,500 hz will be of any good. i tried search other microphone inserts but coudnt really find one. Audioguru would u recommend any microphone or microphone insert? Following is the link to the microphone insert which my professor has given to me. http://www.maplin.co.uk/SEODynamicPages/module.asp?ModNo=29846 cheers ;D pri

Hey Guys..hi audio guru ;D Iv just completed my tests for this week. last night i was simulating the circuit#2, i have simulated exactly according to ur modified circuit..i.e circuit#2. The only difference was during simulations i have used LM741 instead of lm386. I provided a sinewave signal of 10mv,10hz. The ouput which i got from the circuit(U5 at R15 of ur circuit diagram) was a sqaure wave with a amplitude of around 10-12 volts. I am not sure if that is the output which i should be getting, i feel the output is clipping and thats the reason im getting bit distorted sqaure wave. Following is the picture of my simulated circuit and the output which i get. please find attached screen shots of the simulated circuit and the transient response....(files are *.jpg files)....if u wannt i can also give all the dc opearting points of the simulated circuit. i am intending to start breadboarding the circuit from monday..before i do that i wannt to make sure i get everything correct on the simulations... cheers priyank :)

G'day guys... Hi audioguru, hello everyone... As per ur suggestion i will try with circuit2. I was getting bit confused with so many circuits flying around in this forum..iv got test this week but i am confident that by next monday i should be able to breadboard the circuit ...i will keep u guys posted. Audioguru i appreciate ur help. .. :) pri

Hello Everyone. This is my fist message to the group. I am currently workin on builiding a blood pressure monitor as my final year project. For the first sem i had used oscillometric method to measure the blood pressure. Luckly i was successfull in doing that...and got very good marks for that... :) for my second semester, I am now working on auscultatory method, and task is to capture Korotkoff Sound(Acoustic sounds from radial artery) and display the waveform on PC..project is exactly similar to Electronic Stethoscope... I am currently going through 24 pages of discussion on the forum, trust me there are so many different circuits and suggestions ....well ill have few sleepless nights but ill try figure it out... let me know if anyone wannts my report for oscillometric blood pressure monitor method... ill keep u guys posted...WISH ME LUCK! ;D pri