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Microcontroller-Based Heart-Rate Meter

Prof. K. Padmanabhan

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introduction

Heart rate can be measured either by the ECG waveform or by the blood flow into the finger (pulse method). The pulse method is simple and convenient. When blood flows during the systolic stroke of the heart into the body parts, the finger gets its blood via the radial artery on the arm. The blood flow into the finger can be sensed photoelectrically. To count the heart beats, here we use a small light source on one side of the finger (thumb) and observe the change in light intensity on the other side. The blood flow causes variation in light intensity reaching the lightdependent resistor (LDR), which results in change in signal strength due to change in the resistance of the LDR.