Blog 2 - HRV

Introduction

For this lab, I learned how a Heart Rate Variability (HRV) sensor works using a Micro:bit and a power supply. The goal was to measure HRV through photoplethysmography (PPG), a technique used in smartwatches and medical devices.

The HRV sensor shines an LED into the skin, and a photodiode detects the reflected light. As blood volume fluctuates with each heartbeat, the amount of reflected light changes, and the sensor captures this data. The Micro:bit processes the signal and transmits it via serial communication for visualisation in charts and such.

Hardware Setup

I used the micro:bit as the microcontroller plugged into a breadboard with a power supply. The HRV sensor was then plugged into pin P0. This let the Micro:bit read analog values from the sensor and convert them into a readable signal.

(SS)

Block Code

The code was setup to read analog values from the HRV sensor and then write the values in real time to the serial monitor.

Results

I collected digital and analog signals from the HRV sensor, which were visualised in a graph. The digital signal showed sharp pulses, while the analog signal displayed smoother variations representing heartbeats.

Digital Output:

(Ss)

Analog Output:

(SS)

Challenges

I ran into issues reading my heartbeat initially. I first troubleshooted my code with no change, but upon changing the HRV sensor it fixed the issue. 

Conclusion

This lab introduced me to micro:bit IoT applications, using a heart rate sensor to collect and analyse HRV data. The experience was interesting, and I now have a better understanding of analog input and digital output.