Posted on Feb 5, 2014

Measurement of physiological parameters like heart rate and respiration rate is crucial in the field of medicine. Here is a simple method for respiration rate measurement using a displacement transducer. Its responds fast and is cost effective. By using this, respiration rate can be measured in the range of 0 to 999 respirations/ minute. Digital

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Respiration Rate Meter uses a displacement transducer for sensing the respiration rate using IR transmitter and receiver as shown in the physical assembly. Inhaling and exhaling the air during respiration causes a light ball to move up and down in a capillary glass tube. This movement is sensed with the help of an IR transmitter-receiver assembly of the sensing circuit and converted into pulses through the pulse generator. These pulses are counted for a minute using a counter. The respiration rate is displayed on a 3-digit display through the seven segment decoder/driver. Start switch S1 is used to reset the display to zero and enable the counter for a minute to count the respiration pulse. The gate pulse generator consists of a monostable multivibrator. When triggered by start switch, it generates gating pulse of one minute duration. The IR transmitter LED (IRTX) connected in series with resistor R1 transmits IR signals, which are received by the IR receiver LED (IRRX). The IR receiver is connected to the base of transistor T1 through Resistor R2. When the transmitted IR signal falls directly on the reverse biased IR diode, it produces an electrical signal according to the IR intensity. So transistor T1 conducts and its collector goes low, which makes transistor T2 to cut off. Therefore the collector of transistor T2 becomes high, which represents logic 1`. When the IR signal from the transmitter is interrupted due to...

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