ENGR337 Lab 2020 Spring
Lab 4: An Oximeter
Name: Audra Benally
Email: albenally1@fortlewis.edu

1. Title: An Oximeter

2. Introduction: The purpose of this lab was to use an IR sensor and 1NA 128P instrumentation amplifiers to build an oximeter. This oximeter measures reflected IR light and outputs a voltage.

3. Materials and Methods:
       Materials:
          - Oscilloscope
          - Function Generator
          - TCRT5000 IR
          - Capacitors: 4.7µF and 470nF
          - Resistors: 100k-ohm x3, 68k-ohm, 10k-ohm x2
          - 741 Op Amp
          - 1NA 128 PA Instrument Amp x2
          - 1N4370 Zener Diode
          - Multimeter
          - 3.3-5V DC module
          - Arduino UNO board

       Methods:
    In this lab, an oximeter is made using an IR sensor connected to a high-pass filter, a low-pass filter, a zener diode, and a led to show our heartbeat. When the IR is pushed against our finger the blood is the absorber of light and so the output voltage corresponds to our pumping blood. The voltage pulses can then be comparable to our heartbeat rate.

4. Results:

   
             Figure 1. Final working oximeter circuit connected to an Arduino UNO board.

   
             Figure 2. My oximeter heartbeat readings.

   
             Figure 3. My lab partner's oximeter heartbeat readings.

    I wasn't sure how to put a video in here so here is a link and back-up link of my video:

    Audra's Oximeter video
    Oximeter Video on Youtube


5. Discussion
    In this lab, we had a lot of issues trying to get the circuit to work. Our circuit was rewired three times on three different breadboards before the oximeter was outputting desirable voltages. Faulty breadboard connections may be the reason the first two circuits were not working. This conclusion is because our circuit was looked over and checked on multiple occasions for human error and none was found. After a couple weeks we were finally able to get a successful working oximeter to show our heartbeat readings in the above results section.