Adventures with an Arduino

I got an Arduino to play with Christmas 2011, but barely played with it. During 2012 I have become more interested in medical research, well health generally, especially after watching some of the research shown at TEDMED. So I decided last summer to put the two together, buy a Pulse Sensor and do some experiments. Well I never bought one, I had issues sourcing one in the UK at the time. After reading various documents I also had reservations about the project using a green LED, most documents say red or infrared should be used. I have no idea which is best, the team there say they tried several and found green was the best and I have seen other commercial products using green.

Hence I thought it would be interesting to build a heart rate monitor myselft that would let me experiment.  What I would like to end up with is a Pulse Oximeter. This measures the heart rate and the oxygen in the blood at the same time. The idea would be to allow me to experiment with different colours for the light sources and different sensors.

Thus I have purchased several parts from SKPang (first rate service), digital RGB LEDs, LDR, IR LED with a matching IR photodiode and TSL2561 digital light meter. Rather than do this in one hit and fail, I plan to do a few steps at a time, document each step and put the results on this blog. The steps I plan, and these may well change, are:

  • Pulse Meter (no Oxygen sampling)
    1. Connect a single RGB LED and control it.
    2. Connect two RGB LEDs and control independently.
    3. Connect the TSL2561 sensor and take readings (IR and vis).
    4. Try different sampling rates for light sensor.
    5. Connect sensor and LED at same time, next to each other.
    6. See if placing a finger between the LED and sensor will result in usable data (record it to a file).
    7. Only do the following if 6 worked…otherwise rethink...
    8. Adapt the PulseSensor code for use with this setup.
    9. Try recording with different colours at the source (RGB LED).
    10. Replace the TSL2561 with an LDR.
    11. If results are unusable look at using op-amps to improve the signal.
    12. Replace all parts with an IR emitter and photodetector.
    13. Compare all results, both in terms of quality and complexity. So will get Red, Green, Blue (and so on) with IR as light sources and then also shown with each type of sensor.
  • An oximeter (as above but measures heart rate and oxygen content)
    1. See how sensitive the LDR is to IR light.
    2. See how sensitive IR photodiode is to visible light
    3. Depending on above results
    4. Use an IR emitter and RGB LED with (LDR & IR photodiode).
    5. Get results and plot.
    6. Calculate heart rate and oxygen.
    7. Use TSL2561 for sensor (Both IR and Visible if fast enough).

Now assuming it all works as planned, what I would like to then do is create a PCB with everything on. Ambitious, may well be and I won't hold my breath on any of it working or getting done, but the ideas and plans are there and I have already made the first, albeit simple, steps. Will document the LED set-up and TSL2561 sensor later in the week, in part 2!