Pulse Oximeter Using Microcontroller
Volumn 2

Pulse Oximeter Using Microcontroller

Sanjivani Barde#1

#1Mtech Scholar & VLSI Department RTMNU




Pulse oximetry is one of the most commonly employed monitoring modalities in critical care setting. This review describes the latest technological advances in the field of pulse oximetry. Accuracy of pulse oximeter and their limitations are critically examined. Finally, existing data regarding the clinical application and cost effectiveness of pulse oximeter are discussed.

Non-invasive, measurement of arterial oxygen saturation (SpO2) by pulse oximetry is widely acknowledged to be one of the most important technological advances in monitoring clinical patients. Pulse oximeter compute (SpO2) by measuring differences in the visible and near infrared absorbance of fully oxygenated and deoxygenated arterial blood. Unlike clinical blood gas analyzers, which require a sample of blood from the patient and can provide only intermittent measurement of patient oxygenation, pulse oximeter provides continuous, safe and instantaneous measurement of blood oxygenation. Here, I review the theoretical background behind this advanced technology, instrument requirements, practical instrument calibration, common features of commercial pulse oximeter, specific clinical application and performance limitation of pulse oximation.

Keywords— Oxidation,Analyzers,Oximeter,°kelvin,


In the recent decades, health related issues are becoming more and more important. In conventional health monitoring systems, mobility of patient is hindered. Also, emergency cannot be handled immediately solution to this is real time monitoring. The remote health care is a useful solution to achieve continuous monitoring of patients effectively. Oxygen gas is integral for countless biological process.

The transport of oxygen throughout the human body is performed by the circulatory system, and more specifically, haemoglobin in red cells. Critical medical information can be  obtained by measuring the amount of oxygen in blood, as a percentage of maximum capacity. Pulse oximeter by using microcontroller is a medical instrument that is used to measure amount of oxygen in the blood. Pulse oximetry shortens the time passed before the detection of hypoxemia that is deficiency of oxygen which has been documented in the critically ill people during invasive or diagnostic procedures.


The objective of this project is to monitor the oxygen saturation of patients blood and heart rate. It also measures the temperature of patient’s body. When the finger is kept in the photo- sensor used in this device the infrared led transmits the light through the finger which is absorbed by the blood and absorbed light is then transmitted to the microcontroller through which the blood saturation is calculated. The temperature is calculated through temperature sensor. Here, we have used LCD display which displays the calculated heartbeat, temperature and the blood saturation.


A blood oxygen monitor displays the percentage of blood that is loaded with oxygen. More specifically, it measures what percentage of haemoglobin, the protein in blood that carries oxygen is loaded. Acceptable normal ranges for patients without pulmonary pathology are from 95-99 percent. For a patient breathing room air at or near sea level an estimate of arterial pO2 can be made from the blood oxygen monitor “saturation  peripheral oxygen” SpO2 reading.

Process Description

Pulse oximetry is a particularly convenient non invasive measurement method. Typically it utilizes a processor and a pair of small light emitting diode facing a photo diode through a translucent part of the patients body, usually of finger tip or an earlobe. This chapter give a explanation of the various processes taking place in a complete pulse oximeter system using microcontroller. The motive of this system is to monitor the oxygen saturation of patient’s blood and heart rate as well as measurementof temperature of patient’s body.

Fig1 Basic Pulse Oximeter
  1. ATMEGA8

The AVR core combines a rich instruction set with 32 general purpose working registers. All the 32 registers are directly connected to the ALU, allowing two independent registers to be accessed in one single instruction executed in one clock cycle.

The devices manufactured using ATMELs high density non-volatile memory technology. The flash program memory can be reprogrammed in system through an SPI serial interface, by a conventional non-volatile memory programmer, or by an on chip boot program running on the AVR core. The boot program can use any interface to download the application program in the flash memory. Software in the boot flash section will continue to run while the application flash section is updated, providing true read while write operation.


A DC jack is a component used in many electronic devices that allows a steady power source to be plugged in. Through electronics require direct current power, alternating current is the type of electricity supplied to and available in household wall sockets, mainly because of its ability to be delivered over long distances without losing strength. Therefore with most electronics, an AC adapter connected to a DC jack is necessary to supply power in a usable way.

3. HD44780U( LCD 16X2)

The HD44780U dot-matrix liquid crystal display controller and driver LSI displays alphanumerics,Japanese kana characters, and symbols. It can be configured to drive a dot matrix liquid crystal display under the control of a 4bit or 8bit microprocessor. Since all the functions such as display RAM, character generator and liquid crystal driver required for driving a dot matrix liquid crystal display are internally provided on 1 chip, a minimal system can interfaced with this controller or driver. A single HD44780U can display upto one 8character line or two 8 character lines.

 4. LM78XX/LM78XXA

The LM78XX series of three terminal positive regulators are available in the TO-220 package and with several fixed output voltages, making them useful in a wide range of applications. Each type employs internal current limiting, thermal shutdown and safe operating area protection, making it essentially indestructible. If adequate heat sinking is provided they can deliver over 1A output current. Although designed primarily as fixed voltage regulators, devices can be used with external components to obtain adjustable voltages and currents.


This heartbeat sensor is designed to give output of heartbeat when a finger is placed inside it. When the heart detector is working, the top most LED flashes in unison with each heartbeat. This digital output can be connected to microcontroller directly to measure the beats per minute. It works on the principle of light modulation by blood flow through finger at each pulse. 

6. LM35

These series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius temperature. Thus it has an advantage over linear temperature sensors calibrated in °kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient centigrade scaling. Its low output impedance, linear output and precise inherent calibration make interfacing to readout or control circuitry especially easy.

Fig2 Pulse Oximeter Diagram


The work on the proposed system has been concluded. The device stands to be working. This project presents a wearable portable pulse oximeter device.

It is portable and suitable for people’s daily life. In our project, in order to make the device portable, the dimensions of all wearable electronics was carefully chosen, making them as small as possible. The device has a high performance and low power 8 bit microcontroller which calculates heart rate and oxygen saturation of patients blood.


  1. WIRELESS PULSE OXIMETER Joseph Bailey  Michael Fecteau  Noah L. Pendleton
  2. Larid 2009, Thermoelectric Assembly Modules for Industrial Application, Application  Note, Larid Technologies.
  3. Marlow Industries, Thermoelectric Cooling systems Design Guide, pp -11, Dallas, Texas.
  4. Mee-controlled car-seat system utilizing thermoelectric device, Applied Thermal Engineering, pp 2841-2849.
  5. Bulat, L & Nekhoroshev, Y 2003, Thermoelectric cooling-heating unit for thermostatic body of pickup refrigerated trucks, 22nd international conference on thermoelectricslcor 2010, Thermoelectric Handbook, Laird Technologies.
  6. Hyeung,SC, Sangkook, Y & Kwang-il, W 2007, Development of a temperatur

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