Date: 20-06-08, present: Danielle & Richard van Bemmelen
I asked my friend Richard to look at the instability of our current heart rate sensor. Richard is a programmer and engineer so exactly the right man for the job 🙂 It was kind of hard to analyze the current device as everything was soldered together. But Richard discovered that there was a flaw in the design with caused the device generating random measurements.
We had to totally reconstruct the sensor. Using an extra potmeter to stabilize the measurements. This will later be substituted by a resistor. We also used a new light sensor which has a range of 2 – 20 k.
For testing we used a make shift setting with an LED connected to the laptop USB port 🙂 We did three tests: no exertion, heavy exertion and a blank test to look for deviations. The latter appeared to be almost none existing. For this test we wrote a processing script which captures the data from the arduino and writes the results to a csv file (text file). With Excel we can easily visualize this data in a line.
If I find out how I’ll post the Scheme heart-rate sensor and processing pde code .