MD_SHAHRUKH
Advanced Member level 4
- Joined
- Jun 5, 2017
- Messages
- 103
- Helped
- 4
- Reputation
- 8
- Reaction score
- 5
- Trophy points
- 18
- Location
- Bangalore, India
- Activity points
- 1,107
Your headphone is perhaps filtering high frequency noises above the audio range, reason for which heartbeat sounds good and scope seems noisly. Think of making some kind of spectral analysis ( e.g DFT, available on digital osciloscopes ) in order to determine what kind of components are in the noise. In general muscular movements lies in the range of 30-40Hz, so noch filter for this range in addition with 50/60Hz would improve the acquired signal.I get the heartbeat sound very clear to my earphone, but when acquiring that signal to ADC and try to plot the same, I am facing the issue of not so good signal
Of course you have a computer (a laptop or a desktop) and you have a mike input. Piezo transducers are high voltage and you can feed the output of the sensor into the audio in of the sound card and save the audio.I have made many changes to the circuit, it enhances my sound signal but it is not at all improving my plot.
No need to work harder. I´d rather think it´s the other way round.I'll work harder from now on.
Thank you for the circuit you have shared, It is working perfectly fine for heartbeat sound, but it is not giving the sound of breathing, I am placing a sensor to my neck to hear the sound, a very small sound of breathing is coming. Unfortunately, I have few components with me which not include the exact value of cap and resistor. But the I am able hear the heartbeat with values of cpacitor and resistors below in the circuit.Hi,
I usually don´t do others circuit design in the forum....
I did some internet search for heartbeat signals to get a clue about the frequency range.
This absolutely is your first job when doing a design: get the requirements.
Also I don´t know what gain you need. (again your job to get the requirements)
I just guessed a gain of 11 in the frequency range of interest could be suitable.
Gain is set with R1 and R4
I don´t know what information you are interested in or what your application is expected to do. Thus I just tried to reperesent the waveform:
I decided the frequency range of interest to be 1Hz ... 100Hz (while the heartbeat frequency usually is 0.5Hz .. 2Hz I guess you are more interested in it´s overtones.)
Since your mic has an internal series capacitor of 100n ... you need an input resistance of at least 1.5MOhms to get 1Hz lower cutoff. (stage 1)
--> this is made by R5 & R3 which also act as DC bias.
C3 is for DC decoupling. But it´s dominated by the 100n microphone internal cap C5. Don´t use C5 in your circuit.
R2 and C2 are for upper frequency limit ( stage 1)
R1 and C1 are for upper frequency limit (stage 2)
R4 and C4 are for lower frequency limit /stage 2)
C6 is just to protect your earphones from DC.
(Again not knowing any information about your earphones, thus just guessing)
View attachment 169140
****
All this is far from being exact...
Klaus
No, I didn't use it in the circuit. It is only in the simulation.you used C5 = 100n?
No, I didn't use it in the circuit. It is only in the simulation.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?