This project uses an Adafruit Circuit Playground Classic board along with a Pulse Sensor Amped to measure changes in heart rate variability (HRV).  Because fewer changes in heart rate variability are associated with healthy, relaxed states, these measurements can be used as a way to reduce anxiety and increase meditative calm.

What is HRV?

We normally think about our pulse as being a relatively constant value measured in beats per minute, but in reality, the interval between beats (inter-beat interval or IBI) usually fluctuates quite a bit.  This variance between heart beat intervals is known as heart rate variability (HRV).

When breathing is slowed to a rate of ~12 cycles per minute (1 cycle = 1 inhale + 1 exhale), respiratory & cardiac rhythms tend to fall in sync with one another and HRV fluctuations become less erratic and more amplified resembling a sine wave.  This synchronization is considered indicative of a relaxed, healthy state of being where anxiety is reduced and clear, calm thinking is enhanced. 

So, if we measured and graphed the time between heartbeats of a stressed person, it might look something like this:

And the same type of measurement made on a zen master might look something like this:

The goal of this project is to create a device which will help someone achieve a smoother, sinusoidal HRV pattern like the one above.

You can read more about HRV, coherence, and related topics here:

Disclaimer: This is not a medical device and should not be used for any official diagnostic or otherwise life-dependent medical purposes!

What you'll need:

To build the relaxation trainer you'll only need the following:

This guide was first published on Sep 20, 2016. It was last updated on Mar 08, 2024.

This page (Overview) was last updated on Mar 08, 2024.

Text editor powered by tinymce.