DIY Pulse Oximeter
Hello all, I Hope you all are safe. I'm here with another project which you can build with very few components. In this writeup, I'm going to tell you, how you can make a Pulse Oximeter by using Arduino and some very basic electronic components, in this pandemic situation of Covid19 most of us probably familiar with oximeter which we use to measure oxygen saturation in blood and the pulse rate. So let's see..
Basic Principle
How An Oximeter works?
Basically Oximeter calculates the percentage oxygen saturation in the blood on basis of amount of different light absorb in it. Oximeter has One photodiode and two LEDs one is Red LED & another one is InfraRed LED, both LEDs are switched one by one on a certain frequency. To take measurements fingertip is placed in between of photodiode and LEDs as shown in the picture. Oxygenated blood absorbs more Infrared Light and passthrough the more red light and Deoxygenated blood absorb more red light and passthrough the more InfraRed Light. Processor calculates the ratio of red light received at photodiode and Infrared light at the different time interval. for more details on Pulse Oximetry Basic Principles and Interpretation visit this or see this pdf on Pulse Oximeter Fundamentals and Design from NXP
Let's Make Our Own Oximeter
Components Used:
Arduino Pro Mini X1 ______________________________ INDIA / Amazon.com
OLED Display X1 ______________________________ INDIA / Amazon.com
Transistor BC547 X2 ______________________________ INDIA / Amazon.com
Photo Diode X1 ______________________________ INDIA / Amazon.com
IR LED X1 ______________________________ INDIA / Amazon.com
Red LED X1 ______________________________ INDIA / Amazon.com
Resistors
10K x1 , 4.7K x2
9V Battery X1 ______________________________ INDIA / Amazon.com
Battery Cap X1 ______________________________ INDIA / Amazon.com
LM7805 X1 ________________________________ INDIA / Amazon.com
Clutcher X1
Just collect all the above Components.
let's see the Circuit Diagram.
Circuit Diagram
The oximeters can also build By using Max30100 Sensor which is specially design for measuring pulse and oxygen saturation in blood. It's not that critical to make an pulse oximeter using it, since It combines two LEDs, a photodetector, optimized optics, low-noise analog signal processing to detect pulse oximetry and heart-rate signals. and I2C interface. But I thought to make one oximeter with it's basic components used in Max30100 sensor i.e. 2 LEDs and Photodetector. I took a general purpose Photo Diode and grind it using grinder to make it flat and thin so that it can receives max light from the source, originally it is in round shape and dark color, these two factors block the more visible light and this is not good for our project, since we are using red visible light as well as the invisible infra red light. Similarly I grinded a red LED and a Infrared LED from one side, and combined them using super glue. Took a hair clutcher and put Photo Diode at one side of it and combined LEDs at another side of it as shown in the picture. After this I connected all the components as shown in the circuit diagram. I didn't used PCB here since there are very few components, so I solder them just around the Arduino board and fix them using hot glue. to power this oximeter I using the 9Volt battery.
After Assembly My Oximeter Is Looking Like This.
Programming
Arduino pro mini dose not comes with any type of USB connector for programming, that's why its hard for beginner to program it. But don't worry here I describing an easy way for uploading the program to Arduino pro mini. Take an arduino uno and remove its main IC i.e. AtMEGA328P. and then wire up it with arduino pro mini as shown in the above picture.
Arduino UNO Arduino Pro Mini
Vcc -------------------------------- Vcc
GND ------------------------------ GND
Rx --------------------------------- Rx
Tx ---------------------------------- Tx
Rst --------------------------------- Rst
After wiring connect Arduino Uno with computer using USB cable. Download the following Arduino code and Open it with Arduino ide. Now goto tool menu and select board Arduino Pro mini, Again goto tool menu and select COM port. And Now click on upload Button. after uploading the program all done and its ready to play.
Downloads
Output
I compare my oximeter with professional one and its showing almost 99% accuracy. to achieve this accuracy I did some calibration settings in code, check this following line in code and make changes in it as per your readings. and upload the program again with new calibrated formula.
//
// SATURTION IS A FUNCTION OF R (calibration)
// Y = k*x + m // change the value of m increase or decrease it as per your reading
// k and m are calculated with another oximeter
SpO2 = -19 * R + 99; // <br>Also check the working video of it on my instagram click here.
Watch Full video on this topic here on my YouTube channel ShubhamSuresh , stay tuned with it, and pleas
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Also the PCB Gerber file will be update soon here.
Also Thank You NextPCB:
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