Week 3 Iteration - Hasan Berk

 

 Big Heart SETU 

19/02/2024

Week Three Iteration

Reflection

This weeks iteration consisted of semi-auto calibration of heart beat detection, in order to get a more accurate range for our HRV Values. One the pulse sensor was correctly aligned with a user's finger, button A was pressed on the Micro:bit to detect peaks, which was then auto-calibrated. In my own setup, this helped me get the most accurate reading to date.

Setup

The setup for the semi-auto calibration was the same as the previous iteration, with the only difference being the code. The setup consisted of:
  • Micro:bit V2
  • Breakout Board
  • 3.3-5V Pulse Sensor


Code

This is the code Jason provided us with for this weeks iteration:

A quick breakdown :
  • Contains a breathing pacer of 4 in - 6 out.
  • Read and display bar graph of pulse on the local display - very important
  • When button A is pressed it stores the max and min values of heartbeat - for calibration
  • Calculate the time between pulses in ms, delta_t ,also the pulse rate pulse out,
  • and the variation between each heart beat, hrv. Also filter out any noise values above 1000.
  • Finally, serial write the delta_t (time between pulses) and the breathing pacer.

Implementation


https://youtu.be/PA71ct-gFRU

As we can see, I followed the breathing pacer and my HRV started hitting the 'golden' zone. It increased on exhale (heart beat slowing down) and decreased on inhale (heartbeat speeding up). This showed that proper breathing does in fact improve HRV!



Issues

The biggest issue that we are facing is the positioning of the sensor is still too sensitive - it takes a while to get it properly located in order for a good reading. We were brainstorming ways around this in class and we came up with some ideas.

One idea we had was a casing for the sensor so it is in a fixed position on the finger at all times. We found the following design on thingiverse which could be tweaked to fit our own pulse sensors:

https://www.thingiverse.com/thing:3383670



As we can see, it uses a two-piece design in order to 'standardize' the position of the sensor. Its quite similar to the sensors in the hospital.



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