Iteration 2 Conor Gleeson


HRV Monitor Iteration 2 

This week we began the first implementation of a pulse sensor into the MicroBit to record a users heart rate and heart rate variability (HRV)

The pulse sensor is connected to the MicroBit through a breakout board.


 This allowed us to use a premade pulse monitor repository to modify to display the HRV


This allows us to use the "delta_t" value to display the HRV written to the data display 
The display shows the users heart rate and we can also see the HRV rising and falling in time with breathing. 
One of the difficulties with this set up is the need for the if statement values to be adjusted depending on the user and even how hard they are pressing their finger to the pulse sensor. This value needs to be changed based on the values being output to have the if statement trigger correctly, the triggering of this if statement during operation was tested by toggling one of the LEDs in time with the if statement.
One of the issues noticed during the testing of the system was that as the breakouts battery drains it outputs less voltage than is needed by the pulse sensor which greatly affects the values being output requiring further calibration of the if statement or making the triggering of it too unreliable. 

To encourage the user to improve their breathing so that the affects on the HRV can be seen on the screen I added a pacer in the form of changing LEDs on the display, when the bigger square is shown the user should inhale for 4 seconds and then exhale for 4 seconds when the smaller square is shown. The video below shows the system being used


https://youtube.com/shorts/nnqifj_WjPo?feature=share
 
 
Another area to be explored is displaying the feedback to the user without the device connected to a pc, it could be done using the LEDs but this would remove the pacer. Using an external screen or LEDs could be an option. 

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