1. Measure 2 (Post Exercise)
In A Heartbeat
1Bella Fishman
2Ava Hedayatipour
1Knoxville Catholic High School, 2The University of Tennessee, Knoxville
OBJECTIVES
Research, build, and design a heart rate monitoring system using Arduinos.
Test this heart rate monitor to find its accuracy compared to other heart monitors
BACKGROUND
Pulse oximetry is a method that measures the oxygen saturation in one’s blood by shining red and infrared light through the skin of a finger, toe, or earlobe. Oxygenated hemoglobin absorbs more infrared light than deoxygenated hemoglobin. Therefore, the amount of infralight reflected by the finger to the detector reveals the heart rate.
The TCRT1000 sensor in the monitor emits and detects light in the finished board
The light source gives off light which is reflected to the phototransistor.
METHODS
Learning about each component of the heart monitor is vital to constructing the monitor. Arduino is the circuit and programming for each project. Eagle is the program used to design the Printed Circuit Board (PCB).
Transmitters and Receivers
Step 1: Learn about circuitry
Voltmeter
Transmitters and receivers send and amplify signals.
The voltmeter was built and tested using the Arduino program. The voltmeter is a key part as it displays the heart rate.
Step 2:
Design the PCB
Printed Circuit Board (PCB) Design
The program, Eagle was used to design the PCB. The schematic for the PCB was made and then it was converted to board mode in Eagle. After completing the design of the PCB in Eagle, it was built.
Original PCB model layout.
PCB in Eagle Schematic
Routed PCB in Eagle Board Layout
Step 3:
Test the Monitor
Testing the Accuracy of the Heart Rate Monitor
The completed PCB was connected to the LCD and various machines, so it could display a pulse. Then, it was tested based on accuracy compared to aa commercial pulse oximeter which was compared to a heart rate monitoring app.
RESULTS
Measure 1 (Resting)
Phone App 76 67 66 69
Pulse oximeter 68 64 61
The lab-made heart monitor accuracy was proven by the commercial pulse oximeter equaling its readings. The lab-made system’s analog to digital converter has 5 volts divided by 1024 (10 bits) while commercial pulse oximeters have at least 12 to 16 bits, so the commercial pulse oximeter is more accurate than a lab-made one.
The commercial heart monitor was compared to the app, “Heart Rate Monitor,” which uses the flashlight and camera of the phone to emit and detect light as a pulse oximeter would. However in most of the tests, the commercial and phone monitors did not give the same heart rate. While the commercial monitor constantly updates the heart rate, the phone app gives only one reading, so they were difficult to compare.
Measure 2 (Post Exercise)
Phone App 97
107
130 89
Pulse oximeter 95
109 84
CONCLUSION
The tests suggest that pulse oximeters, specifically commercial pulse oximeters are very accurate compared to other heart rate monitoring apps because of their advanced technology. The tests show how much improvement is still left to be made for phone heart monitors.