NEW GUIDE: Make It Pulse using Circuit Playground Express #CircuitPlaygroundExpress #Adafruit #CircuitPython #AdafruitLearningSystem @Adafruit

A new guide in the Adafruit Learning System: Make it Pulse.

Using the Adafruit Circuit Playground Express, the built-in light sensor reads the light modulated by a finger to determine blood flow.

When designing the Circuit Playground Express, Ladyada purposely placed the light sensor near the NeoPixel LEDs so that the light from the LED may illuminate a finger and the sensor measure the minute changes in light signalling someone’s pulse. While not medically accurate, the project is easy to do and demonstrates several concepts without a bunch of specialized materials.

This tutorial will show you how to set up the Circuit Playground Express and will display the heart rate via a NeoPixel using CircuitPython.

The detection of your pulse via your finger via light is called Photoplethysmogram.

Light shines onto the finger and a light detector measures the light that returns.

We use green light, which is absorbed by red blood. The redder the blood, the more green light is absorbed. The blood pumping through one’s finger will change the absorption of the light. Not by much but enough to measure. These variations can be plotted over time to see the changes.

See this guide for how you can use a Circuit Playground Express to do this.