Heart Rate Monitor


  • Create a prototype for a heart rate measuring device returning the beats per minute.
  • Determine the accuracy of the device by comparing it to a Fitbit and a chest strap device.


  • Used LED and a light-dependent resistor to determine the amount of reflected light as a fluctuation in the potential difference.
  • Implemented a low-pass filter to remove high-frequency noise and a high-pass filter to eliminate DC offset.
  • Used an Arduino to read the resulting voltage as a function of time.


  • Coded Arduino to determine the elapsed time between the voltage passed above a threshold value.
  • Calculated the beats per minute value from this heartbeat period.
  • Output running graph and beats per minute value on an LCD screen.


  • Designed and 3D printed case.
  • Covered the resistor and LED to minimise background radiation while maintaining user comfort and accessibility.




3D printing

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