An actual size, single side PCB for the respiration rate meter. The interface assembly simply make use of a nose mask, which is readily available in medical shops and mainly used in hospitals for supply for oxygen to the patients for respiration.

Take a 36cm long transparent glass tube with inner diameter of 5mm. Insert a thermocol ball, commonly used in flower bouquets. Make both the ends of the tube slightly narrow by heating them or putting a rubber tube of a smaller diameter inside. This is done to ensure that the thermocol ball does not come out during the inhale-exhale mechanism of the air.

Take a rubber cork and drill holes on its opposite sides at the center. Pass the glass tube through the center of the cork. Now drill holes on the sides of the cork and fix the transmitter and receiver so that these are placed face to face. Align the transmitter and receiver IR LEDs if required. This adjustment is required is depending upon the type of the glass tube used.

When you inhale and exhale air during respiration, this leads to movement of the ball left and right. Note down the displacement of the ball in the tube and move the cork to the center position of the displacement for more effective measurement.

Such an adjustment of cork postion is required depending upon the age group of the subject whose respiration rate is to be measured. For instance, as the displacement of the ball is less for children, the cork should be moved towards the connected mask.

For a healthy person the displacement of the ball is more, so you have to move the cork away from the mask.