2016-03-10 (Th) Cyborg Heart Rate Sensor

A new transistor was taken from stock to replace the burnt transistor that was “smoked” yesterday. Another 3904 was used although consideration was given to using a 3906 in a different configuration. The choice was probably arbitrary but replacing the broken component meant breaking fewer solder joints.

 Replacement transistor and board

The new transistor was mounted vertically unlike last time. This made no difference in performance but was just an easier was to arrange the component. From this position it was easier to bend the legs into position and solder them to the desired the terminals. One leg was able to snake over to the GND terminal while the other leg was temporarily left open for testing.

 New transistor vertically mounted

An LED and resistor combo, the one built before, was bridged between the 5V terminal and the transistor leg. A simple program was used to intermittently activate the pin which caused the LED to blink according to the program. This showed that the new transistor was working as expected.

 LED blinking by the transistor output

The same program, which actually pulsed the output at a low duty cycle, was tried with the vibrator motor. This lead to very poor performance with the motor but the blink program was modified to pulse the motor for 60milliseconds twice per second, actually 60mS ON and 400mS OFF. Using this program caused the vibrator to turn on for a period of time that was easy to recognize and fast enough to keep up with a heart beat.

Vibrator motor working with blink program

To do:
  • Record set of analog input data showing heart sensor readings. 2mS readings
  • Rerecord at same location with vibrator motor activating periodically and observe any discrepancies in signal due to motor use
  • If the motor activation causes a problem the project may not work without a second voltage regulator
  • If there is no problem
    • Take second reading at different body location
    • Take third reading at different body location
    • Compare data
    • Write pseudo code for extracting heart rate
    • Program with Arduino UNO

The rest of the posts for this project have been arranged by date.

First time here?

Completed projects from year 1.
Completed projects from year 2

This disclaimer must be intact and whole. This disclaimer must be included if a project is distributed.

All information in this blog, or linked by this blog, are not to be taken as advice or solicitation. Anyone attempting to replicate, in whole or in part, is responsible for the outcome and procedure. Any loss of functionality, money, property or similar, is the responsibility of those involved in the replication.

All digital communication regarding the email address 24hourengineer@gmail.com becomes the intellectual property of Brian McEvoy. Any information contained within these messages may be distributed or retained at the discretion of Brian McEvoy. Any email sent to this address, or any email account owned by Brian McEvoy, cannot be used to claim property or assets.

Comments to the blog may be utilized or erased at the discretion of the owner. No one posting may claim claim property or assets based on their post.

This blog, including pictures and text, is copyright to Brian McEvoy.

2016-03-07 (M)