WEEK 4: The stethoscope

A stethoscope is also the main part of the project. 

Since i'm going to modified the traditional circuit to the electronic one, so we only need the chest piece part as the collector for the input/signal. 

The chest piece of the stethoscope will be cut off from the  tube through the ear tip. 

A microphone will be inserted near the chest piece tube then this part will be connected to the amplifier circuit.

Thus, the chest piece part of the stethoscope will be the place where the input signal of the heart sound is collected.

I have chose this stethoscope to be part of my project. The price is quite reasonable in the market since there are a lot of types and brands out there. So, the stethoscope is like in the picture.
The chest piece is in a good condition, hopefully it will work well with the circuit assemble later.

WEEK 3: Testing the circuit

The circuit was assembled on the breadboard to be tested. 

The pre-amplifier circuit was tested first. To see whether it amplify enough or not.

The input was taken from the trainer and set to 9V. 

Then the circuit was connected to the oscilloscope to see the amplified wave. 

The wave is set to sine wave so that to make it clear to see the change in amplitude of the sine wave that determine the input is amplified.

Below is the circuit assembled with only the pre-amplifier circuit.

Below is the input, and the Pk-pk value is 1.00V.

Below is the output, and the Pk-pk value is 21.60V.

WEEK 2: Designing the Amplifier Circuit

  For the amplifier circuit, there are 2 parts, which are,

 pre-amplifier --> low pass filter. 

Both uses the same IC in order to amplify/filter. Since the op-amp has amplify enough the input sound thus we don't need to apply another circuit which is power amplifier where the sound is power amplify again to make it more audible/clear to be heard.
The circuit is one of the electronic part for this project.

Below is the circuit shows the pre-amplifier circuit and low pass filter.

The input was put in at the pre-amplifier part then the output is taken after the it has been filter in the low pass filter circuit. The gain was calculated and since the pre-amplifier part is inverting amplifier thus it is less input impedance than non-inverting amplifier.

Since, the input is low-noise so the input impedance is need to be low. This is because the noise current can generate large voltage drops otherwise.

WEEK 1 : Choosing the suitable IC for Operational Amplifier

Choosing the suitable OP-amp is one of the most crucial part in this project. Since the sound of the heart is not audible directly to human ear, so we need to amplify the sound so it is suitable and capable to be heard by human ear. Specific operational amplifier is going to be used so that the sound is amplified with the desire amount.

The integrated circuit (IC) that was chosen as the operational amplifier was TL072CN, 
it is a low noise amplifier, since the heart sound is in low noise range which is only 1 - 1.67 Hz.
Choosing  TL072CN as the OP-amp it has low harmonic distortion and low noise making this IC an ideally suited for high-fidelity and audio specifically in amplifying the heart sound that is in low frequency.

 In order to make it audible this project is made so that it will help in amplifying the sound. Most importantly is this electronic part.

Figure 1: The pinout label of the IC of TL072CN