The project aims at designing a electronic stethoscope. We will design a circuit which same as a conventional stethoscope. The circuit is designed on a veroboard. The entire circuit runs on a 9V battery source. By using low cost electronic components like resistors, capacitors and opamps the required design is achieved.
The heart beat sounds are generated will be in low frequency range of 20 t0 30 khz. So it equipment must be designed to detect these low frequency range. The opamp is made to operate low frequency ranges so the gain of the opamp will be in the range of 3.9. The high output impedance of the fet makes the resistor to operate at 12 khz, by which the capacitor allows only low frequency signals. A Butter worth low pass filter with a cutoff frequency of 103hz is produced due to gain of the resistors and by making it to pass through capacitors a sharp butterwoth response is produced. By reducing the capacitor gain values the cut off frequency gets increased to 1khz and this frequency range is used for detecting respiratory sounds.
The entire circuit is placed on a veroboad and the microphone is connected by using a shielded cable. The microphone is connected to the stethoscope by using a isolated rubber sleeve. The stethoscope head can be designed by using thick jar. The microphone must be sealed properly to avoid acoustical noise. To avoid fiction noises the microphone head must be moved while listening heart beats. Thus the stethoscope can be designed by using electronic components.
Download Electronic Stethoscope Project Abstract.