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Electronics Instrumentation Final Project, University Carlos lll of Madrid (Sep-Dec 2020)
The objective of this project was to develop the electronics and hardware design needed to operate a pulse-oximeter, a widely-used medical device that measures both heartbeat and blood oxygen saturation.
To compute these values, light from two different LEDs is passed through human tissue and received by a photodetector. By analyzing the different levels of light absorption in the tissue, we can determine the bloodstream and therefore the heartbeat and oxygen percentage present.
Polarization Board to switch the direction of the signal current
Customized circuitry: Multisim simulation (left), hardware board implementation (right)
The hardware was comprised of four main components: a finger clip with two LEDs and a photodetector, a trans-impedance amplifier PCB to amplify the raw signal captured, a polarization PCB that allows switching the current direction, and an NI Data Acquisition Board that connects the circuitry to the computer.
My responsibility in this individual project was to design the circuitry that amplifies and filters the signal coming from the finger clip so that it can later be analyzed on the acquisition board. To characterize the circuitry, I generated a program in Matlab to compute the required values for the resistors and capacitors conforming the filtering and amplification stages. In addition, the circuitry was simulated using NI Multisim, where a sinusoid was generated, passed through the designed circuitry, and plotted on an oscilloscope to determine whether the setup had been properly developed.
Once the hardware was assembled, the Data Acquisition Board was connected to a LabView VI, where the numerical computation of the pulse and oxygen saturation is programmed and shown in a simple GUI.
This project provided me with a valuable learning experience in several electronics design principles, as well as in LabView programming and general engineering practices. I had to familiarize myself with the bioengineering background to develop a solution system that met the project requirements.
Diagram of connections between the signal conditioning stages with the NI Data Acquisition Board
List of main Software utilized
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