Our first design

We started out with a rectangular box with dimensions 13 cm x 6 cm x 3 cm for our main stethoscope chest piece. The bottom surface bears a circular hole with diameter 2 cm where the diaphragm is placed. An Echo Chamber is formed with the flat diaphragm at its bottom and 0.2 mm-thick walls made from standard thermoplastic polyurethane (TPU) material. The chamber is 2.85 cm in height. At the top of the chamber is a cylindrical neck of diameter 9.7 mm and height 4.5 mm where our electret microphone is inserted.

The microphone is connected to a 70 mm x 50 mm x 1.6 mm printed circuit board (PCB) placed on the right of the echo chamber. Sitting right on top of the PCB is a 61.5 mm x 25 mm x 10 mm Arduino MKR1000. On the left of the echo chamber is a battery with dimensions 22.5 mm x 20 mm x 7.5 mm which powers the Arduino.

Our final design

Our final product is a curved box with dimensions as shown in the diagrams above, with thickness of 1.4mm. By strategically arranging our components, we were able to decrease the size of the box and make it as compact as possible.

 

The diagrams above show the measurements of the echo chamber that will be inserted into our final stethoscope. The base of the echo chamber will be inserted into the hole at the bottom of the box. The horn shaped cone will fit on the base and have a final total height of 27.8mm. The microphone will be fitted on the hole at the top of the cone.