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.
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.
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, or even use Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for MakeCode, CircuitPython, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.