In this article, I will tell you how to use Arduino and some very basic electronic components to make pulse oximeters in Covid19, most people may be familiar with us to measure blood oxygen. Saturation of blood oxygen permeation blood and pulse.
Step 1: Basic Principles
How does blood oxime work?
Basically, the oxygen system calculates the percentage of oxygen saturation in the blood according to the amount of different light absorbed in the blood. The blood oximeter has a photodiode and two LEDs, one is a red LED, and the other is an infrared LED, and the two LEDs are switched one by one to a specific frequency. As shown, the fingertip is placed between the photodiode and the LEDs. Oxygen-containing blood absorbs more infrared rays and absorbs more red light and through more infrared lines through more red light. The processor calculates the ratio of the red light and infrared light received by the photodiode at different time intervals. For more details on the basic principles and explanations of pulse oxide saturation, please visit this content or view the PDF of the NXP pulse oximeter basics and design.
Step 2: Let us make blood oxygen
Components used:
Arduino Pro Mini X1
OLED display X1
Transistor BC547 X2
Photoelectric diode x1
Infrared LED X1
Red LED X1
Resistor
10k x1, 4.7k x2
9V battery x1
Battery cover x1
Clutch x1
Step 3: Circuit diagram
Blood oximeter can also use the MAX30100 sensor to measure pulse and blood oxygen saturation in the blood. It is not very critical to use it to do pulse oxime, because it combines two LEDs, a photodetector, optimized optical, low noise analog signal processing to detect pulse oximeter and heart rate signals and I2C interfaces. But I want to do an oxygen instrument to use its basic components in the MAX30100 sensor, ie 2 LEDs and photodetectors.
I use the generic photodiode to use the grinder to grind it, let it flat, thin, so that it can receive Max light from the source, which is originally in circular and dark color, these two factors block more visible light, this is not Suitable for our project because we use red visible light and invisible infrared light. Similarly, I have grind a red LED and an infrared LED while combining them with strong glue. Take a hair scratcher, put the photodiode on it, and combine the LED on the other side, as shown. After that, I connected all the components, as shown in the circuit diagram. I didn't use PCB here because I had little components, so I sold them around the Arduino board and then fixed with a heat gum. The blood oximeter is powered by a 9 volt battery.
Step 4: My blood oximeter after assembly
Step 5: Programming
Arduino Pro MINI does not come with any type of USB connector for programming, which is why beginners have difficulty programming. But don't worry, I describe a simple way to upload procedures to Arduino Pro MINI. Take an Arduino UNO and remove its main IC, that is, Atmega328p. Then connect it with the Arduino Pro Mini, as shown in the figure above.
Arduino Uno Arduino Pro Mini
VCC ------------------------------- VCC
Ground -----------------------------
Receive -------------------------------- Receive
Send ---------------------------------- Send
RST -------------------------------- RST
After wiring, use the USB cable to connect Arduino Uno with your computer. Download the following Arduino code and open it with Arduino IDE. Go to the Tools menu and select the board Arduino Pro MINI, go to the Tool menu again and select the COM port. Now click on the upload button. The uploader is all completed and ready to play.
Pulse oximeter .ino
Step 6: Output is completed
I compared my oximeter with professional oxoxia, and the accuracy reached 99%. In order to achieve this accuracy, I made some calibration settings in the code, check the following line code and make changes according to your reading. And upload the program again using the new calibration formula.
//
// SATURTION IS A FUNCTION OF R (CALIBRATION)
// y = k * x + m // change the value of m increase or decreaase it aspe ready
// k And m Are Calculated with another oximeter
SPO2 = -19 * R + 99; //
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