Disclaimer: The Oximeter you make for this activity should not be used for diagnostic purposes. If at any point you are concerned about your heart rhythm or SpO2 readings, you should consult your physician.

What you need for today's activities

The Arduino and Cord
Several Different LEDs
All the Resistor Strips
The Pulse Sensor​
Wires

What is a Pulse Oximeter?

This device checks how well your heart is pumping oxygen through your body.

Oximeters measure oxygen saturation
(SpO2). This represents the extent to which hemoglobin is saturated with oxygen. Hemoglobin is protein in red blood cells (RBCs) that binds with oxygen to carry it from your lungs to the tissues of your body.

Here is a link to more info on Hemoglobin. 
It may be used to monitor conditions that can affect blood oxygen levels.
Some of these conditions include: 

The Visible Color Spectrum

White light is a mix of all primary colors (ROYGBV). Remember prisms from elementary school? See below for how Red, Orange, Yellow, Green, Blue, and Violet (ROYGBV) can be separated from white light! Important point:  Violet does not mean purple. It is the "roses are red, violets are blue" color. 
Wild Violet Flower
Picture source: ​http://blogs.nature.com/ofschemesandmemes/files/2015/02/Week-2-Blog-Dispersive-Prism.jpg

ROYGBV is just the visible light wavelengths! 

​Your Body's Light Penetration

You can see red light penetrate through your finger if you put it in front of a flashlight. You see red on the other side because most of the other colors were absorbed in your finger. Try this at home! Put your phone flashlight, or any white flashlight, on one side of your finger. Then look at what color makes it to the other side! 
www.researchgate.net/publication/316712743/figure/fig13/AS:668385360744448@1536366896067/a-Tissue-penetration-depth-of-light-with-different-wavelengths-NIR-light-penetrates.png
https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip

Red light can be used to see inside your body. 

Well, somethings not right with this finger. Got an x-ray and yep, something is there.
All images below are sourced from: ​http://www.eatonhand.com/img/img00087.htm
Let's shine red light on it. Yep, it's darker where something is sitting. That means there is not good blood flow there, so there is more deoxygenated blood in that spot.  
Click here to see what was taken out after surgery. Warning: somewhat graphic image. 

Seeing your Heartbeat with Light! 

The color of blood

Have you ever heard that blood gets darker if it does not have oxygen in it? Well, that's true. The more oxygen blood has, the more deep red light it absorbs so it reflects less deep red. 
Picture
All sketches for this section come from this source: ​https://www.youtube.com/watch?v=MHPgamGQmDY

Graphing blood's light absorption by wavelength

This is a rough sketch showing how much hemoglobin (Hb) absorbs different light wavelengths  depending on if it is oxygenated.  

Red light at a 660 nm wavelength is used in pulse oximeters. This is because it is the max difference between light absorbance.

Video Lesson about Blood Oxygen

Please watch this video about how the Pulse Ox works. 

Code and directions under development

The inspiration for the SpO2 sensor activity.
https://www.youtube.com/watch?v=cEtyMkubXj4
lesson:

https://surtrtech.com/2019/02/05/measure-heart-pulses-bpm-and-oxygen-saturation-spo%c2%b2-with-max30102-and-arduino/
Code: 
 MAX30102- Heart Rate Pulse Detection-Module  https://electropeak.com/learn/
https://electropeak.com/learn/interfacing-max30102-pulse-oximeter-heart-rate-module-with-arduino/