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