Brad Breinholt, Electrical & Computer Engineering
Thank you for your support of the Wireless Heartbeat Monitor project. This has been an exciting project that has given me experience in wireless communications and in medical instrumentation. It has introduced me to microprocessor control and given me training in project planning and followthrough. The Wireless Heartbeat Monitor senses a person’s heartbeat by passing light through the individual’s finger or earlobe. Blood circulating though the body, moving in pulses as the heart and the muscles surrounding the veins and arteries contract, filters this light. Creating a varying electrical signal, a photo resistor senses the slight fluctuations in light leaving the body. The electrical signal is amplified and shaped to provide a usable signal.
The signal from the sensor controls an audio tone that is fed into a frequency modulator and transmitted at radio frequencies. Allowing for easy adaption to a mobile sensor/transmitter unit, the transmitter is small and requires few parts.
Compact and portable, the receiver easily receives the transmitter’s signal at distances of over fifty feet. The receiver moves the radio-frequency signal to two intermediate frequencies, amplifying and filtering the signal at each stage. Then the signal is demodulated. The two intermediate stages provide for sharp selectivity from nearby channels.
Due to time constraints on the project, the proposed display unit was not completed; however, I did obtain microcontroller chips and investigated a preliminary design. I hope to continue work on the display unit in the future.
The Wireless Heartbeat Monitor works well; however, improvements do need to be made before the project can be considered manufacturable. Because the sensor relies on detecting fluctuations in the amount of light reaching the photo resistor, the Wireless Heartbeat Monitor is susceptible to interference created by natural light and by body movement. Thus the monitor works well for monitaring individuals who are stationary but requires further work if it is to be used by athletes.
I demonstrated the project during a formal presentation on Apri16, 1994 to my faculty advisor, Dr. David Comer. A report describing the project in more detail was submitted to the Electrical Engineering department at BYU.
The Wireless Heartbeat Monitor has given valuable experience in project planning and research and has increased my knowledge in technical areas. I saw several principles demonstrated (such as frequency translation) that I had only learned about in theory in my studies at BYU. I kept the number of required parts low so that manufacturing of the product would be inexpensive and easily done. I hope to continue work on the project in the future.