Electronic Stethoscope: Traditional Chinese Circuit Design Guide

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Electronic stethoscope(1)The electronic stethoscope can amplify the sounds of a person's heart, lungs, pulse and other sounds and then play them directly through the speaker. If used with a tape recorder, abnormal sounds can be recorded and saved as medical records.The schematic diagram of the electronic stethoscope circuit is shown in Figure 36-1. The sounds of the heart, lungs, pulse, etc. are converted into electrical signals through the sound probe. After being amplified by the amplifier composed of the transistor VT1, they are adjusted by the potentiometer RP2 and then amplified by the composite tube composed of the transistors VT2 and VT3. The sound is directly emitted by the speaker. Can also be monitored via headphones. Recording can be done via the XJ input recorder input. When listening to rhythmic sounds, such as pulse, the LED can illuminate and flash with the pulse. alt="57.jpg (50890 bytes)">Figure 36-1The sound probe consists of a miniature electret microphone and a stethoscope listening head. During production, cut off the stethoscope's rubber tube, leaving about 10cm, and insert the electret microphone into the cut. It is best to use microphone shielded wire as the lead wire. Since the microphone is encapsulated in a rubber tube, its sensitivity is relatively high and it has almost no reflection on external sounds. The device is shown in Figure 36-2. The output transformer T can be a push-type output transformer used in general transistor radios. …

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